1
|
Kling S, Frigelli M, Aydemir ME, Tahsini V, Torres-Netto EA, Kollros L, Hafezi F. Optical coherence tomography quantifies gradient refractive index and mechanical stiffness gradient across the human lens. COMMUNICATIONS MEDICINE 2024; 4:162. [PMID: 39134623 PMCID: PMC11319654 DOI: 10.1038/s43856-024-00578-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 07/18/2024] [Indexed: 08/15/2024] Open
Abstract
BACKGROUND As a key element of ocular accommodation, the inherent mechanical stiffness gradient and the gradient refractive index (GRIN) of the crystalline lens determine its deformability and optical functionality. Quantifying the GRIN profile and deformation characteristics in the lens has the potential to improve the diagnosis and follow-up of lenticular disorders and guide refractive interventions in the future. METHODS Here, we present a type of optical coherence elastography able to examine the mechanical characteristics of the human crystalline lens and the GRIN distribution in vivo. The concept is demonstrated in a case series of 12 persons through lens displacement and strain measurements in an age-mixed group of human subjects in response to an external (ambient pressure modulation) and an intrinsic (micro-fluctuations of accommodation) mechanical deformation stimulus. RESULTS Here we show an excellent agreement between the high-resolution strain map retrieved during steady-state micro-fluctuations and earlier reports on lens stiffness in the cortex and nucleus suggesting a 2.0 to 2.3 times stiffer cortex than the nucleus in young lenses and a 1.0 to 7.0 times stiffer nucleus than the cortex in the old lenses. CONCLUSIONS Optical coherence tomography is suitable to quantify the internal stiffness and refractive index distribution of the crystalline lens in vivo and thus might contribute to reveal its inner working mechanism. Our methodology provides new routes for ophthalmic pre-surgical examinations and basic research.
Collapse
Affiliation(s)
- Sabine Kling
- Institute for Biomedical Engineering, ITET Department, ETH Zurich, Zurich, Switzerland.
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland.
| | - Matteo Frigelli
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | | | - Vahoora Tahsini
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Emilio A Torres-Netto
- ELZA Institute AG, Dietikon, Switzerland
- CABMM, University of Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | | | - Farhad Hafezi
- ELZA Institute AG, Dietikon, Switzerland
- CABMM, University of Zurich, Zurich, Switzerland
- Faculty of Medicine, University of Geneva, Geneva, Switzerland
| |
Collapse
|
2
|
Hughes RPJ, Read SA, Collins MJ, Vincent SJ. Axial Elongation During Short-Term Accommodation in Myopic and Nonmyopic Children. Invest Ophthalmol Vis Sci 2022; 63:12. [PMID: 35275173 PMCID: PMC8934556 DOI: 10.1167/iovs.63.3.12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Purpose Axial length increases during accommodation in adults and children; however, refractive error group differences are conflicting and have not been explored in pediatric populations. This study aimed to evaluate differences in accommodation-induced axial elongation between myopic and nonmyopic children. Methods A range of ocular biometric measurements were captured during brief accommodation tasks (0, 3, 6, and 9 D) using a Badal optometer mounted to a noncontact optical biometer (Zeiss IOLMaster 700). Reliable measurements were captured for 15 myopic and 15 age- and sex-matched nonmyopic children. The average central corneal thickness (CCT), anterior chamber depth (ACD), crystalline lens thickness (LT), anterior segment length (ASL), vitreous chamber depth (VCD), and axial length (AL) were determined for each accommodation stimulus. Raw measurements of AL and VCD were corrected for the estimated error associated with LT increases during accommodation. Results All biometric parameters, except CCT, changed significantly during accommodation (all P < 0.001). Myopic children exhibited significantly greater accommodation-induced axial elongation than nonmyopic children (P = 0.002) at the 3, 6, and 9 D accommodation stimuli, with a mean difference of 7, 10, and 16 µm, respectively (all pairwise comparisons, P ≤ 0.03). The changes in all other biometric parameters were not different between the refractive error groups (P ≥ 0.23). Conclusions Accommodation-induced axial elongation was greater in myopic than nonmyopic children. This finding could support a potential mechanism linking near work, axial elongation, and myopia development in children or may reflect greater susceptibility to accommodation-induced axial elongation in children with established myopia.
Collapse
Affiliation(s)
- Rohan P J Hughes
- Queensland University of Technology, Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Brisbane, Queensland, Australia
| | - Scott A Read
- Queensland University of Technology, Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Brisbane, Queensland, Australia
| | - Michael J Collins
- Queensland University of Technology, Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Brisbane, Queensland, Australia
| | - Stephen J Vincent
- Queensland University of Technology, Contact Lens and Visual Optics Laboratory, Centre for Vision and Eye Research, School of Optometry and Vision Science, Brisbane, Queensland, Australia
| |
Collapse
|
3
|
Short-Term Effect of Wearing of Extended Depth-of-Focus Contact Lenses in Myopic Children: A Pilot Study. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12010431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
This pseudo-experimental, prospective, and longitudinal pilot study was conducted to characterize the optical and visual changes occurring in the short-term wear of a hydrophilic contact lens (CL) based on extended focus technology (EDOF). A total of 30 eyes of 15 children (age, 6–16 years) were fitted with the EDOF CL Mylo (Mark’ennovy Care SL), performing an exhaustive follow-up for one month evaluating changes in visual acuity (VA), accommodation, binocularity, ocular aberrometry, visual quality, pupillometry, keratometry and biometry. Far and near VA with the CL improved progressively (p < 0.001), obtaining mean final binocular values of −0.08 ± 0.01 and −0.07 ± 0.01 LogMAR, respectively. There was a mean reduction in the accommodative LAG of 0.30 D (p < 0.001), without associated alterations in the magnitude of the phoria and fusional vergences (p ≥ 0.066). A controlled but statistically significant increase (p ≤ 0.005) of ocular high order aberration (HOA) root mean square (RMS), primary coma RMS, primary spherical aberration Zernike term and secondary astigmatism RMS was found with the CL wear. In conclusion, the EDOF CL evaluated provides adequate visual acuity and quality, with associated increased of several HOAs and a trend to reduction in the accommodative LAG that should be confirmed in future studies.
Collapse
|
4
|
She Z, Hung LF, Beach KM, Arumugam B, Smith EL, Ostrin LA. Comparing low-coherence interferometry and A-scan ultrasonography in measuring ocular axial dimensions in young rhesus monkeys. Exp Eye Res 2022; 217:108937. [PMID: 35074342 PMCID: PMC8957592 DOI: 10.1016/j.exer.2022.108937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 12/28/2021] [Accepted: 01/06/2022] [Indexed: 11/04/2022]
Abstract
We investigated a commercial low-coherence interferometer (LenStar LS 900 optical biometer) in measuring young rhesus monkey ocular dimensions. Ocular biometry data obtained using a LenStar and an A-scan ultrasound instrument (OPT-scan 1000) from 163 rhesus monkeys during 20-348 days of age were compared by means of coefficients of concordance and 95% limits of agreement. Linear regression was employed to examine and analyze the inter-instrument discrepancies. In young rhesus monkeys, the test-retest reliability of the LenStar was equal to or exceeded that of A-scan ultrasound (intraclass correlation = 0.86 to 0.93). The inter-instrument agreement was strong for vitreous chamber depth and axial length (coefficient of concordance = 0.95 and 0.86, respectively) and moderate for anterior chamber depth and lens thickness (coefficient of concordance = 0.74 and 0.63, respectively). The LenStar systematically underestimated ocular dimensions when compared to A-scan ultrasound (mean magnitude of difference = 0.11-0.57 mm). This difference could be minimized using linear calibration functions to equate LenStar data with ultrasound data. When this method was applied, the values between instruments were in excellent absolute agreement (mean magnitude of difference = 0.004-0.01 mm). In conclusion, the LenStar reliably measured ocular dimensions in young monkeys. When an appropriate calibration function is applied, the LenStar can be used as a substitute for A-scan ultrasonography.
Collapse
|
5
|
Waring GO, Chang DH, Rocha KM, Gouvea L, Penatti R. Correlation of Intraoperative Optical Coherence Tomography of Crystalline Lens Diameter, Thickness, and Volume with Biometry and Age. Am J Ophthalmol 2021; 225:147-156. [PMID: 33385370 DOI: 10.1016/j.ajo.2020.12.021] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Revised: 09/30/2020] [Accepted: 12/17/2020] [Indexed: 12/12/2022]
Abstract
PURPOSE To characterize crystalline lens dimensions derived from in vivo spectral-domain optical coherence tomography (SD-OCT) and identify associations among these parameters, ocular biometry, and age. METHODS In this retrospective study, lens thickness (LT), lens diameter (LD), and lens volume (LV) were measured intraoperatively using SD-OCT in 293 eyes undergoing lens surgery. Correlations among LT, LD, LV, age, axial length (AL), and anterior chamber depth (ACD) were analyzed. Multiple regression analysis was performed to determine whether a combination of biometric data could predict LD and LV. RESULTS Wide variations were observed in LT (3.6-5.7 mm), LD (7.5-11.9 mm), and LV (119.9-312.4 mm3) of aging eyes. Correlations among the 3 lens dimensions were statistically significant (LV-LT: r = 0.785; P < .001; LV-LD: r = 0.696; P < .001; and LT-LD: r = 0.121; P = .039). With age, the correlation coefficients of LT, LD, and LV were 0.526, 0.326, and 0.573, respectively (P < .001). Although there was significant correlation of AL with LT (r = -0.137; P = .002) and LD (r = 0.268; P < .001), it was not significant with LV (r = 0.084; P = .15). Subgroup analysis revealed that 19.8% of long eyes had LD >1 standard deviation (SD) above and that 5.2% had LD <1 SD below the mean LD. CONCLUSIONS Dimensions of the aging lens vary considerably and are most accurately characterized by direct measurement of LT, LD, and LV, rather than making assumptions based on AL. These findings challenge historically proposed relationships between LD and AL and represent a normative dataset of contemporary geometric features of the aging lens, possibly aiding in surgical decision making and future developments in lens surgery.
Collapse
Affiliation(s)
| | - Daniel H Chang
- Empire Eye and Laser Center, Bakersfield, California, USA
| | - Karolinne Maia Rocha
- Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Larissa Gouvea
- Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada
| | | |
Collapse
|
6
|
Logan NS, Radhakrishnan H, Cruickshank FE, Allen PM, Bandela PK, Davies LN, Hasebe S, Khanal S, Schmid KL, Vera-Diaz FA, Wolffsohn JS. IMI Accommodation and Binocular Vision in Myopia Development and Progression. Invest Ophthalmol Vis Sci 2021; 62:4. [PMID: 33909034 PMCID: PMC8083074 DOI: 10.1167/iovs.62.5.4] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression. Convergence is synergistically linked with accommodation and the impact of this on myopia has also been critiqued. Specific topics reviewed included accommodation and myopia, role of spatial frequency, and contrast of the task of objects in the near environment, color cues to accommodation, lag of accommodation, accommodative-convergence ratio, and near phoria status. Aspects of retinal blur from the lag of accommodation, the impact of spatial frequency at near and a short working distance may all be implicated in myopia development and progression. The response of the ciliary body and its links with changes in the choroid remain to be explored. Further research is critical to understanding the factors underlying accommodative and binocular mechanisms for myopia development and its progression and to guide recommendations for targeted interventions to slow myopia progression.
Collapse
Affiliation(s)
- Nicola S Logan
- School of Optometry, Aston University, Birmingham, United Kingdom
| | - Hema Radhakrishnan
- Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
| | - Fiona E Cruickshank
- Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
| | - Peter M Allen
- Vision and Hearing Sciences Research Centre, School of Psychology and Sports Sciences, Anglia Ruskin University, Cambridge, United Kingdom
| | - Praveen K Bandela
- Brien Holden Vision Institute, Sydney, New South Wales, Australia.,School of Optometry and Vision Science, University of New South Wales, Sydney, New South Wales, Australia
| | - Leon N Davies
- School of Optometry, Aston University, Birmingham, United Kingdom
| | - Satoshi Hasebe
- Department of Ophthalmology, Kawasaki Medical School, Kurashiki, Okayama, Japan
| | - Safal Khanal
- School of Optometry, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Katrina L Schmid
- School of Optometry and Vision Science, Queensland University of Technology, Brisbane, Australia
| | | | | |
Collapse
|
7
|
Affiliation(s)
- W Neil Charman
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
E‐mail:
| |
Collapse
|
8
|
Hughes RPJ, Read SA, Collins MJ, Vincent SJ. Changes in ocular biometry during short‐term accommodation in children. Ophthalmic Physiol Opt 2020; 40:584-594. [DOI: 10.1111/opo.12711] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 05/29/2020] [Indexed: 12/14/2022]
Affiliation(s)
- Rohan P J Hughes
- Contact Lens and Visual Optics Laboratory School of Optometry and Vision Science Queensland University of Technology (QUT) Brisbane Queensland Australia
| | - Scott A Read
- Contact Lens and Visual Optics Laboratory School of Optometry and Vision Science Queensland University of Technology (QUT) Brisbane Queensland Australia
| | - Michael J Collins
- Contact Lens and Visual Optics Laboratory School of Optometry and Vision Science Queensland University of Technology (QUT) Brisbane Queensland Australia
| | - Stephen J Vincent
- Contact Lens and Visual Optics Laboratory School of Optometry and Vision Science Queensland University of Technology (QUT) Brisbane Queensland Australia
| |
Collapse
|
9
|
Aksoy M, Asena L, Gungor SG, Soy EHA, Akman A, Haberal M. Changes in ocular biometric parameters after renal transplantation. Int Ophthalmol 2020; 40:2283-2289. [DOI: 10.1007/s10792-020-01411-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 05/02/2020] [Indexed: 10/24/2022]
|
10
|
de Jong PT. The quest for the human ocular accommodation mechanism. Acta Ophthalmol 2020; 98:98-104. [PMID: 31347276 PMCID: PMC7004159 DOI: 10.1111/aos.14194] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2019] [Accepted: 06/29/2019] [Indexed: 01/14/2023]
Abstract
We have known the accommodation phenomenon since 400 BC. Hypotheses about its mechanisms varied widely for two millennia. Early in the 17th century, when people became more aware of ophthalmic optics, Scheiner and Descartes were close to solving that accommodation worked by changes in the lens. Others rejected their idea, and people even denied the existence of accommodation because there was no clear proof. In the early 19th century, evidence accumulated for accommodation mechanisms studying bird, fish, insect, mammal and human eyes. On the discovery of muscle fibres in the ciliary body, attention shifted to its role in accommodation. Around 1850, came the proof that accommodation occurs by a change in the anterior lens curvature. Still for another 50 years, controversies remained about the exact changes in the lens and the precise accommodation mechanism. On looking back, this is not surprising because only late in the 20th century did it become clear that one cannot extrapolate from the multitude of accommodation mechanisms in the animal kingdom to human eyes.
Collapse
Affiliation(s)
- Paulus T.V.M. de Jong
- Department of Retinal Signal ProcessingThe Netherlands Institute for NeuroscienceKNAWAmsterdamThe Netherlands,Department of OphthalmologyAmsterdam University Medical CenterAmsterdamThe Netherlands,Department of OphthalmologyLeiden University Medical CenterLeidenThe Netherlands
| |
Collapse
|
11
|
Optical Coherence Tomography Reveals Sigmoidal Crystalline Lens Changes during Accommodation. Vision (Basel) 2018; 2:vision2030033. [PMID: 31735896 PMCID: PMC6835499 DOI: 10.3390/vision2030033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 08/15/2018] [Accepted: 08/17/2018] [Indexed: 12/02/2022] Open
Abstract
This study aimed to quantify biometric modifications of the anterior segment (AS) during accommodation and to compare them against changes in both accommodative demand and response. Thirty adults, aged 18–25 years were rendered functionally emmetropic with contact lenses. AS optical coherence tomography (AS-OCT) images were captured along the 180° meridian (Visante, Zeiss Meditec, Jena, Germany) under stimulated accommodative demands (0–4 D). Images were analysed and lens thickness (LT) was measured, applying a refractive index correction of 1.00. Accommodative responses were also measured sequentially through a Badal optical system fitted to an autorefractor (Shin Nippon NVision-K 5001, Rexxam, Japan). Data were compared with Dubbelman schematic eye calculations. Significant changes occurred in LT, anterior chamber depth (ACD), lens centroid (i.e., ACD + LT/2), and AS length (ASL = ACD + LT) with accommodation (all p < 0.01). There was no significant change in CT with accommodation (p = 0.81). Measured CT, ACD, and lens centroid values were similar to Dubbelman modelled parameters, however AS-OCT overestimated LT and ASL. As expected, the accommodative response was less than the demand. Interestingly, up until approximately 1.5 D of response (2.0 D demand), the anterior crystalline lens surface appears to be the primary correlate. Beyond this point, the posterior lens surface moves posteriorly resulting in an over-all sigmoidal trajectory. he posterior crystalline lens surface demonstrates a sigmoidal response with increasing accommodative effort.
Collapse
|
12
|
Dong J, Zhang Y, Zhang H, Jia Z, Zhang S, Wang X. Comparison of axial length, anterior chamber depth and intraocular lens power between IOLMaster and ultrasound in normal, long and short eyes. PLoS One 2018; 13:e0194273. [PMID: 29543854 PMCID: PMC5854401 DOI: 10.1371/journal.pone.0194273] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 02/28/2018] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To compare the axial length (AL), anterior chamber depth (ACD) and intraocular lens power (IOLP) of IOLMaster and Ultrasound in normal, long and short eyes. METHODS Seventy-four normal eyes (≥ 22 mm and ≤ 25 mm), 74 long eyes (> 25 mm) and 78 short eyes (< 22 mm) underwent AL and ACD measurements with both devices in the order of IOLMaster followed by Ultrasound. The IOLP were calculated using a free online LADAS IOL formula calculator. RESULTS The difference in AL and IOLP between IOLMaster and Ultrasound was statistically significant when all three groups were combined. The difference in ACD between IOLMaster and Ultrasound was statistically significant in the normal group (P<0.001) and short eye group (P<0.001) but not the long eye group (P = 0.465). For the IOLP difference between IOLMaster and Ultrasound in the normal group, the percentage of IOLP differences <|0.5|D, ≥|0.5|D<|0.75|D, ≥|0.75|D<|1.0|D, and ≥|1.0|D were 90.5%, 8.1%, 1.4% and 0%, respectively. For the long eye group, they were 90.5%, 5.4%, 4.1% and 0%, respectively. For the short eye group, they were 61.5%, 23.1%, 10.3%, and 5.1%, respectively. CONCLUSIONS IOLMaster and Ultrasound have statistically significant differences in AL measurements and IOLP (using LADAS formula) for normal, long eye and short eye. The two instruments agree regarding ACD measurements for the long eye group, but differ for the normal and short eye groups. Moreover, the high percentage of IOLP differences greater than |0.5|D in the short eye group is noteworthy.
Collapse
Affiliation(s)
- Jing Dong
- Department of Ophthalmology, The First Hospital of Shanxi Medical University, Shanxi, P.R. China
| | | | | | | | | | | |
Collapse
|
13
|
Kaluzny BJ. Anterior Movement of the Crystalline Lens in the Process of Accommodation in Children. Eur J Ophthalmol 2018; 17:515-20. [PMID: 17671924 DOI: 10.1177/112067210701700406] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Purpose To investigate changes of crystalline lens position during accommodation in children with emmetropia, myopia, and hyperopia. Methods A total of 188 children (372 eyes) from 4 to 19 years old (mean age 11.3±4.43) with cycloplegic refractive error within a range +9.00 D to −9.00 D were enrolled. After a general ophthalmic examination, ultrasound biometry was performed, with the eye at a maximal accommodative effort. Cycloplegia was induced by triple installation of 1% tropicamide drops and 30 minutes later the biometric examination was repeated. Results In emmetropic eyes in the process of accommodation, the anterior pole of the crystalline lens moved forward by 0.144±0.14 mm (p ≤ 0.001); the position of the posterior pole did not change. In myopic eyes, the anterior pole moved forward by 0.071±0.13 mm (p≤0.001) and the posterior pole moved backward by 0.039±0.10 mm (p=0.003). In hyperopic eyes, the whole lens translocated anteriorly: anterior pole moved forward by 0.242±0.16 mm (p≤ 0.001) and posterior pole moved forward by 0.036±0.09 mm (p≤0.001). Differences among emmetropia, myopia, and hyperopia were statistically significant. Forward movement of the posterior pole correlated with a low axial length of the eye, and also with plus refractive error and with a smaller accommodative increase of lens thickness. Conclusions In children, accommodative changes of the crystalline lens position depend on refractive status.
Collapse
Affiliation(s)
- B J Kaluzny
- Department of Ophthalmology, Collegium Medicum, Nicolaus Copernicus University, Curie-Skłodowskiej 9, 85-094 Bydgoszcz, Poland.
| |
Collapse
|
14
|
Hitzenberger CK. Adolf Friedrich Fercher: a pioneer of biomedical optics. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:1-8. [PMID: 29148272 DOI: 10.1117/1.jbo.22.12.121704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2017] [Accepted: 10/26/2017] [Indexed: 06/07/2023]
Abstract
Adolf Friedrich Fercher, an outstanding pioneer of biomedical optics, passed away earlier this year. He was a brilliant and visionary researcher who pioneered various fields of biomedical optics, such as laser speckle flowgraphy, tissue interferometry, and optical coherence tomography (OCT). On the occasion of the 25th anniversary of OCT, this paper reviews and commemorates Fercher's pioneering work.
Collapse
Affiliation(s)
- Christoph K Hitzenberger
- Medical University of Vienna, Center for Medical Physics and Biomedical Engineering, Vienna, Austria
| |
Collapse
|
15
|
Scleral changes with accommodation. Ophthalmic Physiol Opt 2017; 37:263-274. [DOI: 10.1111/opo.12377] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 02/21/2017] [Indexed: 11/26/2022]
|
16
|
Li Z, Zeng J, Jin W, Long W, Lan W, Yang X. Time-Course of Changes in Choroidal Thickness after Complete Mydriasis Induced by Compound Tropicamide in Children. PLoS One 2016; 11:e0162468. [PMID: 27622495 PMCID: PMC5021335 DOI: 10.1371/journal.pone.0162468] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 08/22/2016] [Indexed: 12/11/2022] Open
Abstract
PURPOSE The aim of this study was to investigate the time-course of changes in choroidal thickness (ChT) following complete mydriasis induced by compound tropicamide. METHODS ChT was measured by OCT with the enhanced-depth imaging technique (Spectralis HRA+OCT, Heidelberg Engineering, Germany) at nine locations of the fundus: subfoveal ChT (SFChT) and ChT at 1 mm and 3 mm from the fovea in four quadrants. Mydriasis was induced with compound tropicamide (0.5% tropicamide plus 0.5% phenylephrine hydrochloride, three doses at 5-minute intervals). Measurements were conducted prior to the instillation and at 0, 30, and 60 min following complete mydriasis. Results at different time-points were compared using repeated-measures ANOVA to investigate the time-course of the changes. RESULTS Thirty-nine subjects (mean age 11.9±2 years; 16 males and 23 females) were enrolled in the study. Compound tropicamide resulted in a statistically significant decrease in SFChT at 0, 30, and 60 min after complete mydriasis, as compared to baseline (-5±4 μm, -12±4 μm, and -13±4 μm, respectively; all P<0.0001). No significant changes were detected in the parafoveal choroid except at 1 mm temporal (T1mm) and nasal (N1mm) to the fovea at 30 and 60 min (T1mm: -6±4 μm and -7±5 μm at 30 and 60 min; N1mm: -6±4 μm and -7±5 μm at 30 and 60 min, respectively; all P<0.0001). Repeated-measures ANOVA showed a significant interaction between the time after complete mydriasis and the effect of the mydriasis agent. CONCLUSIONS Complete mydriasis induced by compound tropicamide led to choroidal thinning, and the magnitude varied over time.
Collapse
Affiliation(s)
- Zhouyue Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Junwen Zeng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Wei Jin
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Wen Long
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Weizhong Lan
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
- Optometry and Visual Science Institute, Aier Eye Hospital Group, Changsha, Hunan Province, China
| | - Xiao Yang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| |
Collapse
|
17
|
Sisó-Fuertes I, Domínguez-Vicent A, del Águila-Carrasco A, Ferrer-Blasco T, Montés-Micó R. Corneal changes with accommodation using dual Scheimpflug photography. J Cataract Refract Surg 2015; 41:981-9. [DOI: 10.1016/j.jcrs.2014.08.038] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 08/12/2014] [Accepted: 08/14/2014] [Indexed: 11/15/2022]
|
18
|
Ramasubramanian V, Glasser A. Can Ultrasound Biomicroscopy Be Used to Predict Accommodation Accurately? J Refract Surg 2015; 31:266-73. [DOI: 10.3928/1081597x-20150319-06] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 01/30/2015] [Indexed: 11/20/2022]
|
19
|
Domínguez-Vicent A, Monsálvez-Romín D, Del Águila-Carrasco AJ, Ferrer-Blasco T, Montés-Micó R. Changes in the anterior chamber during accommodation assessed with a Scheimpflug system. J Cataract Refract Surg 2014; 40:1790-7. [DOI: 10.1016/j.jcrs.2014.02.043] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2013] [Revised: 10/14/2013] [Accepted: 02/06/2014] [Indexed: 11/29/2022]
|
20
|
|
21
|
Sander BP, Collins MJ, Read SA. The effect of topical adrenergic and anticholinergic agents on the choroidal thickness of young healthy adults. Exp Eye Res 2014; 128:181-9. [PMID: 25304219 DOI: 10.1016/j.exer.2014.10.003] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 09/30/2014] [Accepted: 10/06/2014] [Indexed: 01/30/2023]
Abstract
The human choroid is capable of rapidly changing its thickness in response to a variety of stimuli. However little is known about the role of the autonomic nervous system in the regulation of the thickness of the choroid. Therefore, we investigated the effect of topical parasympatholytic and sympathomimetic agents upon the choroidal thickness and ocular biometrics of young healthy adult subjects. Fourteen subjects (mean age 27.9 ± 4 years) participated in this randomized, single-masked, placebo-controlled study. Each subject had measurements of choroidal thickness (ChT) and ocular biometrics of their right eye taken before, and then 30 and 60 min following the administration of topical pharmacological agents. Three different drugs: 2% homatropine hydrobromide, 2.5% phenylephrine hydrochloride and a placebo (0.3% hydroxypropyl methylcellulose) were tested in all subjects; each on different days (at the same time of the day) in randomized order. Participants were masked to the pharmacological agent being used at each testing session. The instillation of 2% homatropine resulted in a small but significant increase in subfoveal ChT at 30 and 60 min after drug instillation (mean change 7 ± 3 μm and 14 ± 2 μm respectively; both p < 0.0001). The parafoveal choroid also exhibited a similar magnitude, significant increase in thickness with time after 2% homatropine (p < 0.001), with a mean change of 7 ± 0.3 μm and 13 ± 1 μm (in the region located 0.5 mm from the fovea center), 6 ± 1 μm and 12.5 ± 1 μm (1 mm from the fovea center) and 6 ± 2 μm and 12 ± 2 μm (1.5 mm from the fovea center) after 30 and 60 min respectively. Axial length decreased significantly 60 min after homatropine (p < 0.01). There were also significant changes in lens thickness (LT) and anterior chamber depth (ACD) (p < 0.05) associated with homatropine instillation. No significant changes in choroidal thickness, or ocular biometrics were found after 2.5% phenylephrine or placebo at any examination points (p > 0.05). In human subjects, significant increases in subfoveal and parafoveal choroidal thickness occurred after administration of 2% homatropine and this implies an involvement of the parasympathetic system in the control of choroidal thickness in humans.
Collapse
Affiliation(s)
- Beata P Sander
- Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Queensland University of Technology, Room B562, O Block, Victoria Park Road, Kelvin Grove, 4059 Brisbane, Queensland, Australia.
| | - Michael J Collins
- Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Queensland University of Technology, Room B562, O Block, Victoria Park Road, Kelvin Grove, 4059 Brisbane, Queensland, Australia
| | - Scott A Read
- Contact Lens and Visual Optics Laboratory, School of Optometry and Vision Science, Queensland University of Technology, Room B562, O Block, Victoria Park Road, Kelvin Grove, 4059 Brisbane, Queensland, Australia
| |
Collapse
|
22
|
Yan L, Huibin L, Xuemin L. Accommodation-induced intraocular pressure changes in progressing myopes and emmetropes. Eye (Lond) 2014; 28:1334-40. [PMID: 25190534 DOI: 10.1038/eye.2014.208] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Accepted: 07/17/2014] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To investigate the changes of intraocular pressure (IOP) and anterior eye segment biometric parameters under different accommodative statuses in progressing myopes and emmetropes. METHODS Forty-six progressing myopes and 40 emmetropes participated in this study. All the subjects had their IOP and anterior eye segment biometric parameters (including corneal thickness, anterior chamber depth, anterior chamber angle width, and lens thickness) measured using iCare rebound tonometer and VisanteTM anterior segment-optical coherence tomography while accommodative stimuli of 0, 3, and 6D were presented. RESULTS There was no significant difference in IOP between progressing myopes and emmetropes when no accommodation was induced (16.22±4.11 vs 17.01±3.72, respectively, t=-0.93, P>0.05). However, IOP significantly increased with accommodation in progressing myopes (mean change +1.02±2.07 mm Hg from 0D to 6D, F=5.35, P<0.01), but remained unchanged (mean change -0.76±3.22 mm Hg from 0D to 6D, F=1.46, P>0.05) in emmetropes. Meanwhile, we found that their anterior chamber depth decreased (P<0.01), anterior chamber angle narrowed (P<0.01), and lens thickened (P<0.01) significantly with accommodation, both in progressing myopes and emmetropes. CONCLUSIONS Although no difference was detected between the IOPs of progressing myopes and emmetropes without accommodation, accommodation could induce transient IOP elevation in progressing myopes. Simultaneously, we found that their anterior chamber depth decreased, anterior chamber angle narrowed, and lens thickened with accommodation. Although emmetropes showed the similar anterior eye segment structure changes, their IOPs did not increase with accommodation. Our study indicated that IOP elevation with accommodation in progressing myopes might be related to myopia progression.
Collapse
Affiliation(s)
- L Yan
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China
| | - L Huibin
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China
| | - L Xuemin
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China
| |
Collapse
|
23
|
Zhong J, Tao A, Xu Z, Jiang H, Shao Y, Zhang H, Liu C, Wang J. Whole eye axial biometry during accommodation using ultra-long scan depth optical coherence tomography. Am J Ophthalmol 2014; 157:1064-69. [PMID: 24487051 DOI: 10.1016/j.ajo.2014.01.016] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 01/15/2014] [Accepted: 01/17/2014] [Indexed: 12/17/2022]
Abstract
PURPOSE To investigate changes of whole eye axial biometry during accommodation using ultra-long scan depth optical coherence tomography (UL-OCT). DESIGN Prospective, observational case series. METHODS Twenty-one adult subjects were enrolled. Using UL-OCT, the left eye of each subject was imaged with relaxed diopters (0 D) and accommodative stimuli (+6 D). Full eye biometry included central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness, vitreous length, and axial length (AL). RESULTS During accommodation (+6 D), the axial biometry of the whole eye changed significantly. Compared to the rest state, ACD at the accommodative state decreased significantly from 3.128 ± 0.305 mm to 2.961 ± 0.298 mm (paired t test, P < .001). The lens thickness increased significantly from 3.723 ± 0.237 mm to 3.963 ± 0.234 mm (P < .001). The vitreous length decreased significantly from 17.129 ± 0.864 mm to 17.057 ± 0.848 mm (P < .001). AL was 24.519 ± 0.917 mm at the rest state and increased to 24.545 ± 0.915 mm with +6 D accommodation stimulus. The elongated AL of 26.1 ± 13.4 μm between the rest and accommodative states was significant (P < .001). CONCLUSIONS During accommodation, whole eye axial biometry changed, including a decrease in ACD and vitreous length and an increase in lens thickness and AL. UL-OCT provides an alternative method that is suitable for full eye biometry during accommodation.
Collapse
Affiliation(s)
- Jianguang Zhong
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; Hangzhou First People's Hospital, Zhejiang, China
| | - Aizhu Tao
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, China
| | - Zhe Xu
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, China
| | - Hong Jiang
- Hangzhou First People's Hospital, Zhejiang, China
| | - Yilei Shao
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida; School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, China
| | | | - Che Liu
- Department of Biomedical Engineering, University of Miami, Miami, Florida
| | - Jianhua Wang
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida.
| |
Collapse
|
24
|
Abstract
PURPOSE To investigate the changes occurring in the axial length, choroidal thickness, and anterior biometrics of the eye during a 10-minute near task performed in downward gaze. METHODS Twenty young adult subjects (10 emmetropes and 10 myopes) participated in this study. To measure ocular biometrics in downward gaze, an optical biometer was inclined on a custom-built height- and tilt-adjustable table. Baseline measures were collected after each subject performed a distance primary gaze control task for 10 minutes to provide washout period for previous visual tasks before each of three different accommodation/gaze conditions. These other three conditions included a near task (2.5 diopters [D]) in primary gaze and a near (2.5 D) and a far (0 D) accommodative task in downward gaze (25 degrees), all for 10 minutes' duration. Immediately after and then 5 and 10 minutes from the commencement of each trial, measurements of ocular biometrics (e.g., anterior biometrics, axial length, choroidal thickness, and retinal thickness) were obtained. RESULTS Axial length increased with accommodation and was significantly greater for downward gaze with accommodation (mean ± SD change, 23 ± 13 μm at 10 minutes) compared with primary gaze with accommodation (8 ± 15 μm at 10 minutes) (p < 0.05). A small amount of choroidal thinning was also found during accommodation that was statistically significant in downward gaze (13 ± 14 μm at 10 minutes; p < 0.05). Accommodation in downward gaze also caused greater changes in anterior chamber depth and lens thickness compared with accommodation in primary gaze. CONCLUSIONS Axial length, choroidal thickness, and anterior eye biometrics change significantly during accommodation in downward gaze as a function of time. These changes seem to be caused by the combined influence of biomechanical factors (i.e., extraocular muscle forces, ciliary muscle contraction) associated with near tasks in downward gaze.
Collapse
|
25
|
Abstract
PURPOSE To investigate crystalline lens thickness (LT) across a range of ages and accommodative demands and to evaluate the repeatability of LT measurements using the Visante Anterior Segment Optical Coherence Tomographer (AS-OCT) (Zeiss Meditec, Germany) under non-cycloplegic conditions. METHODS Participants were 98 visually normal adults aged 18-75 years, stratified into age groups of 18-29, 30-39, 40-49, 50-59, and 60-75 years of age. Images of the crystalline lens were taken using the Visante AS-OCT during stimulation of accommodation at demands of 0, 1, 2, 3, 4, 5, and 8 D with accommodative response measured in a subgroup of participants. Images were analyzed and LT measured assuming a refractive index of 1.42. Repeat measures were taken from 86 participants for each accommodative demand at a second visit. RESULTS The mean unaccommodated LT for all participants was 4.07 ± 0.40 mm. An average increase in LT of 20 μm per year was calculated (linear regression, R² = 0.61, F(1,89) = 143.92, p < 0.00001). Increase in LT with accommodation was shown to be significant in the 18- to 29-year-olds (repeated measures ANOVA, F(6,105) = 96.31, p < 0.00001), 30- to 39-year-olds (F(6,93) = 71.25, p < 0.00001), and 40- to 49-year-olds (F(6,90) = 12.60, p < 0.01) with little or no measureable change in the older age groups. Eighty-six participants returned for a second visit. The mean difference in LT in the unaccommodated state for all participants between visit 1 and visit 2 was 0.0006 mm (95% limits of agreement of -0.07 to 0.07 mm). The 95% limits of agreement were widest for youngest age groups and narrowest for the oldest participants. CONCLUSIONS This study is the first to report the repeatability of LT measures using the Visante AS-OCT in the non-cyclopleged eye. It has also demonstrated the ability of the Visante AS-OCT to detect small changes in lens thickness with accommodation.
Collapse
|
26
|
Comment on ‘Diminished ciliary muscle movement on accommodation in myopia’ by S. Joen, W.K. Lee, L. Lee and N.J. Moon [Exp. Eye Res. 105 (2012) 9–14]. Exp Eye Res 2013; 115:276-7. [DOI: 10.1016/j.exer.2012.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Accepted: 12/06/2012] [Indexed: 11/17/2022]
|
27
|
Yoon S, Aglyamov S, Karpiouk A, Emelianov S. The mechanical properties of ex vivo bovine and porcine crystalline lenses: age-related changes and location-dependent variations. ULTRASOUND IN MEDICINE & BIOLOGY 2013; 39:1120-7. [PMID: 23453376 PMCID: PMC3646975 DOI: 10.1016/j.ultrasmedbio.2012.12.010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 11/01/2012] [Accepted: 12/15/2012] [Indexed: 05/03/2023]
Abstract
The mechanical properties of ex vivo animal lenses from three groups were evaluated: old bovine (25-30 mo old, n = 4), young bovine (6 mo old, n = 4) and young porcine (6 mo old, n = 4) eye globes. We measured the dynamics of laser-induced microbubbles created at different locations within the crystalline lenses. An impulsive acoustic radiation force was applied to the microbubble, and the microbubble displacements were measured using a custom-built high pulse repetition frequency ultrasound system. Based on the measured dynamics of the microbubbles, Young's moduli of bovine and porcine lens tissue in the vicinity of the microbubbles were reconstructed. Age-related changes and location-dependent variations in the Young's modulus of the lenses were observed. Near the center, the old bovine lenses had a Young's modulus approximately fivefold higher than that of young bovine and porcine lenses. The gradient of Young's modulus with respect to radial distance was observed in the lenses from three groups.
Collapse
Affiliation(s)
- Sangpil Yoon
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Salavat Aglyamov
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Andrei Karpiouk
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
| | - Stanislav Emelianov
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX 78712
- Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712
- Corresponding Author: 107 W. Dean Keeton St. Austin, TX 78712; ; +1-512-471-1733
| |
Collapse
|
28
|
Abstract
PURPOSE To objectively measure changes in the human ciliary muscle dimensions in vivo after instillation of topical phenylephrine, a mydriatic and vasodilating agent. METHODS A cross-sectional study of 25 healthy young adults was conducted. Measurements of pupil size, accommodation, and ciliary muscle thickness were made both before and 30 min after instillation of 1% proparacaine and 2.5% phenylephrine. Accommodation was measured in three ways: subjectively using a push-up technique and Royal Air Force (RAF) rule, and objectively using both the Grand Seiko autorefractor and PowerRefractor. Images of the temporal ciliary muscle were acquired using the Visante Anterior Segment Optical Coherence Tomographer (OCT). Ciliary muscle images were objectively analyzed using a computer-based segmentation technique. RESULTS Amplitude of accommodation using the push-up test was reduced by about 1 D with phenylephrine (p < 0.001). Phenylephrine did not change the accommodative response to a 4 D Badal target as measured by either autorefraction or photorefraction (p > 0.30). There was statistically significant thickening of the anterior region and thinning of the posterior region of the ciliary muscle with accommodation (p < 0.001, all locations). Phenylephrine did not affect either baseline ciliary muscle thickness or the accommodative contraction of the muscle (p > 0.09). CONCLUSIONS Low-dose phenylephrine does not affect ciliary muscle dimensions, ciliary muscle contractility, or accommodative response to a 4 D near target.
Collapse
|
29
|
Eppig T, Gillner M, Zoric K, Jäger J, Löffler A, Langenbucher A. Biomechanical eye model and measurement setup for investigating accommodating intraocular lenses. Z Med Phys 2013; 23:144-52. [PMID: 23474131 DOI: 10.1016/j.zemedi.2013.02.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2012] [Revised: 02/13/2013] [Accepted: 02/13/2013] [Indexed: 11/17/2022]
Abstract
We present a biomechanical eye model to induce pseudophakic accommodative movement for evaluation of the focal shift of accommodative intraocular lenses. Therefore, an accommodative intraocular lens (IOL) was implanted into freshly enucleated porcine eyes. The eyes were glued into a mechanical apparatus to expand the ciliar body effectuating mechanical accommodation. An optical coherence tomographer was used to measure positional and geometrical changes of the IOL for different levels of expansion. The expansion unit allowed stretching of the globe of several millimeters. With the biomechanical eye model we were able to simulate the mechanical functionality of accommodation as well as to measure the lens vault and change in geometry. Accommodative vault could only be measured with an intact vitreous, indicating that the vitreous plays an important role for the functionality of accommodative IOLs.
Collapse
Affiliation(s)
- Timo Eppig
- Experimental Ophthalmology, Saarland University, Kirrberger Straße 100, Bldg. 22, 66421 Homburg, Germany.
| | | | | | | | | | | |
Collapse
|
30
|
Ruggeri M, Uhlhorn SR, De Freitas C, Ho A, Manns F, Parel JM. Imaging and full-length biometry of the eye during accommodation using spectral domain OCT with an optical switch. BIOMEDICAL OPTICS EXPRESS 2012; 3:1506-20. [PMID: 22808424 PMCID: PMC3395477 DOI: 10.1364/boe.3.001506] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Revised: 05/21/2012] [Accepted: 06/01/2012] [Indexed: 05/20/2023]
Abstract
An optical switch was implemented in the reference arm of an extended depth SD-OCT system to sequentially acquire OCT images at different depths into the eye ranging from the cornea to the retina. A custom-made accommodation module was coupled with the delivery of the OCT system to provide controlled step stimuli of accommodation and disaccommodation that preserve ocular alignment. The changes in the lens shape were imaged and ocular distances were dynamically measured during accommodation and disaccommodation. The system is capable of dynamic in vivo imaging of the entire anterior segment and eye-length measurement during accommodation in real-time.
Collapse
Affiliation(s)
- Marco Ruggeri
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute,
University of Miami Miller School of Medicine, 1638 NW 10th Ave. Miami, FL 33136,
USA
- Biomedical Optics and Laser Laboratory, Department of Biomedical
Engineering, University of Miami, College of Engineering, Coral Gables, FL,33146
USA
| | - Stephen R. Uhlhorn
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute,
University of Miami Miller School of Medicine, 1638 NW 10th Ave. Miami, FL 33136,
USA
| | - Carolina De Freitas
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute,
University of Miami Miller School of Medicine, 1638 NW 10th Ave. Miami, FL 33136,
USA
| | - Arthur Ho
- Brien Holden Vision Institute, Sydney, NSW,
Australia
- Vision Cooperative Research Centre, Sydney, NSW,
Australia
- School of Optometry & Vision Science, University of New South
Wales, Australia
| | - Fabrice Manns
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute,
University of Miami Miller School of Medicine, 1638 NW 10th Ave. Miami, FL 33136,
USA
- Biomedical Optics and Laser Laboratory, Department of Biomedical
Engineering, University of Miami, College of Engineering, Coral Gables, FL,33146
USA
| | - Jean-Marie Parel
- Ophthalmic Biophysics Center, Bascom Palmer Eye Institute,
University of Miami Miller School of Medicine, 1638 NW 10th Ave. Miami, FL 33136,
USA
- Biomedical Optics and Laser Laboratory, Department of Biomedical
Engineering, University of Miami, College of Engineering, Coral Gables, FL,33146
USA
- Vision Cooperative Research Centre, Sydney, NSW,
Australia
| |
Collapse
|
31
|
Davies LN, Dunne MCM, Gibson GA, Wolffsohn JS. Vergence analysis reveals the influence of axial distances on accommodation with age and axial ametropia. Ophthalmic Physiol Opt 2011; 30:371-8. [PMID: 20629959 DOI: 10.1111/j.1475-1313.2010.00749.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Despite numerous investigations, the aetiology and mechanism of accommodation and presbyopia remains equivocal. Using Gaussian first-order ray tracing calculations, we examine the contribution that ocular axial distances make to the accommodation response. Further, the influence of age and ametropia are also considered. The data show that all changes in axial distances during accommodation reduce the accommodation response, with the reduction in anterior chamber depth contributing most to this overall attenuation. Although the total power loss due to the changes in axial distances remained constant with increasing age, hyperopes exhibited less accommodation than myopes. The study, therefore, enhances our understanding of biometric accommodative changes and demonstrates the utility of vergence analysis in the assessment of accommodation.
Collapse
Affiliation(s)
- Leon N Davies
- Ophthalmic Research Group, School of Life and Health Sciences, Aston University, Birmingham, B4 7ET, UK.
| | | | | | | |
Collapse
|
32
|
Abstract
PURPOSE To investigate the influence of accommodation on axial length (AXL) and a comprehensive range of ocular biometric parameters) in populations of young adult myopic and emmetropic subjects. METHODS Forty young adult subjects had ocular biometry measured using a noncontact optical biometer (Lenstar LS 900) based on the principle of optical low coherence reflectometry under 3 different accommodation demands (0 D, 3 D, and 6 D). Subjects were classified as emmetropes (n = 19) or myopes (n = 21) based on their spherical equivalent refraction (mean emmetropic refraction -0.05 +/- 0.27 D and mean myopic refraction -1.82 +/- 0.84 D). RESULTS AXL changed significantly with accommodation, with a mean increase of 11.9 +/- 12.3 mum and 24.1 +/- 22.7 mum for the 3 D and 6 D accommodation stimuli, respectively. A significant axial elongation associated with accommodation was still evident even after correction of the AXL data for potential error because of lens thickness change. The mean "corrected" increase in AXL was 5.2 +/- 11.2 mum and 7.4 +/- 18.9 mum for the 3 D and 6 D stimuli, respectively. There was no significant difference between the myopic and emmetropic populations in terms of the magnitude of change in AXL with accommodation, regardless of whether the data were corrected or not. A number of other ocular biometric parameters, such as anterior chamber depth, lens thickness, and vitreous chamber depth also exhibited significant change with accommodation. The myopic and emmetropic populations also exhibited no significant difference in the magnitude of change in these parameters with accommodation. CONCLUSIONS The eye undergoes a significant axial elongation associated with a brief period of accommodation, and the magnitude of this change in eye length increases for larger accommodation demands, however, there is no significant difference in the magnitude of eye elongation in myopic and emmetropic subjects.
Collapse
|
33
|
Wendt M, Glasser A. Topical and intravenous pilocarpine stimulated accommodation in anesthetized rhesus monkeys. Exp Eye Res 2010; 90:605-16. [PMID: 20159011 DOI: 10.1016/j.exer.2010.02.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 02/09/2010] [Accepted: 02/10/2010] [Indexed: 10/19/2022]
Abstract
Many studies have used pilocarpine to stimulate accommodation in both humans and monkeys. However, the concentrations of pilocarpine used and the methods of administration vary. In this study, three different methods of pilocarpine administration are evaluated for their effectiveness in stimulating accommodation in rhesus monkeys. Experiments were performed in 17 iridectomized, anesthetized rhesus monkeys aged 4-16 years. Maximum accommodation was stimulated in all these monkeys with a 2% pilocarpine solution maintained on the cornea for at least 30 min in a specially designed perfusion lens. In subsequent topical pilocarpine experiments, baseline refraction was measured with a Hartinger coincidence refractometer and then while the monkeys were upright and facing forward, commercially available pilocarpine (2, 4, or 6%) was applied topically to the cornea as 2 or 4 drops in two applications or 6 drops in three applications over a five minute period with the eyelids closed between applications. Alternatively, while supine, 10-12 drops of pilocarpine were maintained on the cornea in a scleral cup for 5 min. Refraction measurements were begun 5 min after the second application of pilocarpine and continued for at least 30 min after initial administration until no further change in refraction occurred. In intravenous experiments, pilocarpine was given either as boluses ranging from 0.1mg/kg to 2mg/kg or boluses followed by a constant infusion at rates between 3.06 mg/kg/h and 11.6 mg/kg/h. Constant 2% pilocarpine solution on the eye in the perfusion lens produced 10.88+/-2.73 D (mean+/-SD) of accommodation. Topically applied pilocarpine produced 3.81 D+/-2.41, 5.49 D+/-4.08, and 5.55 D+/-3.27 using 2%, 4%, and 6% solutions respectively. When expressed as a percentage of the accommodative response amplitude obtained in the same monkey with constant 2% pilocarpine solution on the eye, the responses were 34.7% for 2% pilocarpine, 48.4% for 4% pilocarpine, and 44.6% for 6% pilocarpine. Topical 4% and 6% pilocarpine achieved similar, variable accommodative responses, but neither achieved maximum accommodation. IV boluses of pilocarpine achieved near maximal levels of accommodation at least ten times faster than topical methods. Doses effective for producing maximum accommodation ranged from 0.25mg/kg to 1.0mg/kg. IV pilocarpine boluses caused an anterior movement of the anterior lens surface, a posterior movement of the posterior lens surface, and a slight net anterior movement of the entire lens. Considerable variability in response amplitude occurred and maximum accommodative amplitude was rarely achieved with topical application of a variety of concentrations of commercially available pilocarpine. Intravenous infusion of pilocarpine was a rapid and reliable method of producing a nearly maximal accommodative response and maintaining accommodation when desired.
Collapse
Affiliation(s)
- Mark Wendt
- College of Optometry, University of Houston, 505 J. Davis Armistead Building, Houston, TX 77204, USA.
| | | |
Collapse
|
34
|
Fercher AF. Optical coherence tomography - development, principles, applications. Z Med Phys 2009; 20:251-76. [PMID: 21134630 DOI: 10.1016/j.zemedi.2009.11.002] [Citation(s) in RCA: 156] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 10/09/2009] [Accepted: 11/18/2009] [Indexed: 12/17/2022]
Abstract
This paper presents a review of the development of optical coherence tomography (OCT), its principles and important applications. Basic OCT systems are described and the physical foundations of OCT signal properties and signal recording systems are reviewed. Recent examples of OCT applications in ophthalmology, cardiology, gastroenterology and dermatology outline the relevance of this advanced imaging modality in the medical field.
Collapse
Affiliation(s)
- Adolf Friedrich Fercher
- ZBMTP - Medizinische Physik, Medizinische Universität Wien, Währinger Straße 13, A-1090 Wien.
| |
Collapse
|
35
|
Richdale K, Bullimore MA, Zadnik K. Lens thickness with age and accommodation by optical coherence tomography. Ophthalmic Physiol Opt 2008; 28:441-7. [PMID: 18761481 PMCID: PMC2857534 DOI: 10.1111/j.1475-1313.2008.00594.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE To utilize time-domain optical coherence tomography (OCT) to measure changes in the crystalline lens with age and accommodation. METHODS A cross-sectional study of pre-presbyopic and presbyopic subjects was conducted. Amplitude of accommodation was measured with the push-up test. Objective accommodation was measured with the Grand Seiko auto-refractor and a Badal lens system. Lens thickness was measured with the Zeiss Visante OCT and an internal optometer. The data were analysed using correlation coefficients, linear regression, and by calculating the average change in lens thickness per diopter change in objective accommodation. RESULTS Twenty-two subjects between the ages of 36 and 50 years completed the study. Subjective amplitude of accommodation ranged from 2.17 to 6.38 D. Objective accommodation ranged from 0.22 to 4.56 D. The mean lens thickness was 4.05+/-0.20 mm. The mean change in lens thickness for up to a 5-D accommodative stimulus ranged from 0.01 to 0.26 mm. The correlation coefficients were: age and subjective accommodation, r= -0.74; age and objective accommodation, r= -0.84; change in lens thickness and age, r= -0.65; change in lens thickness and subjective accommodation, r=0.74; change in lens thickness and objective accommodation, r=0.64; objective and subjective accommodation, r=0.82 (all p<0.01). An increase in lens thickness of 21 microm per year of age was determined by linear regression. For the subjects who showed at least 1 D of accommodative response on the Grand Seiko auto-refractor, there was an increase of 51+/-19 microm per dioptre of accommodation. CONCLUSIONS Optical coherence tomography is a non-invasive technique that can be used to quantify changes in the thickness of the crystalline lens. Subjective and objective measurements of accommodation, as well as age, were robustly correlated with the measured changes in lens thickness. Lens thickness changes with age and accommodation as measured with the Visante OCT compare well with previous findings using Scheimpflug photography and ultrasound.
Collapse
Affiliation(s)
- Kathryn Richdale
- The Ohio State University College of Optometry, 338 West 10th Avenue, Columbus, OH 43210, USA.
| | | | | |
Collapse
|
36
|
|
37
|
Ehrmann K, Ho A, Parel JM. Biomechanical analysis of the accommodative apparatus in primates. Clin Exp Optom 2008; 91:302-12. [PMID: 18279413 DOI: 10.1111/j.1444-0938.2008.00247.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND The restoration of natural accommodation in the presbyopic and cataract affected eye is a subject of intense research effort. A new instrument has been developed to test the viability and efficacy of procedures and methods to restore accommodation ex vivo in animal or human eyes. METHODS A section of the globe containing the crystalline lens, zonules, ciliary muscle and sclera is bonded into eight curved shoes. After dissecting the sclera between the shoes, even radial load is applied to stretch the zonules and capsular bag to simulate the natural accommodative process. The associated change in optical power is measured using a modified Scheiner's disk method. Changes in the diameter of the lens and ciliary processes are recorded, as well as zonular load. RESULTS No effective change in power was observed for the three presbyopic human eyes under four millimetres diameter stretching; the diameter of the ciliary aperture increased by between 1.8 mm and 2.3 mm, while the maximum increase in lens diameter was 0.19 mm. For the three younger monkey eyes, the diameter of the ciliary aperture increased by 1.4 mm with a corresponding increase in the lens diameter of between 0.50 mm and 0.65 mm. Stretching forces were generally higher for the human than for the monkey eyes, reaching maxima of 35 mN and 52 mN, respectively. The monkey eyes changed power by between 9.1 and 10.1 dioptres. An almost identical, progressive increase for lens diameter, power and stretching force versus stretch distance was found for all three monkey eyes. CONCLUSION The better understanding of the mechanisms and forces involved in the primate accommodative apparatus will assist with the development of accommodating IOLs and other methods to restore accommodation.
Collapse
Affiliation(s)
- Klaus Ehrmann
- Institute for Eye Research and the Vision Cooperative Research Centre, University of New South Wales, Sydney, Australia.
| | | | | |
Collapse
|
38
|
Tsorbatzoglou A, Németh G, Széll N, Biró Z, Berta A. Anterior segment changes with age and during accommodation measured with partial coherence interferometry. J Cataract Refract Surg 2007; 33:1597-601. [PMID: 17720076 DOI: 10.1016/j.jcrs.2007.05.021] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Accepted: 05/25/2007] [Indexed: 11/24/2022]
Abstract
PURPOSE To evaluate anterior segment alterations with age and during accommodation in different age groups. SETTING Department of Ophthalmology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary. METHODS Fifty-three subjects (101 normal eyes) were enrolled in this study and divided into 3 age groups: younger than 30 years (Group 1), between 31 years and 44 years (Group 2), and older than 45 years (Group 3). The total amplitude of accommodation was determined with a defocusing technique, and anterior segment measurements were performed by partial coherence interferometry. RESULTS Group 1 comprised 32 eyes; Group 2, 37 eyes; and Group 3, 32 eyes. The total amplitude of accommodation decreased with age (P<.0001). With the target position at infinity, the lens thickness (LT) and anterior segment length (ASL) increased and the anterior chamber depth (ACD) decreased significantly with age (P<.0001). During accommodation in the youngest group, the mean change in LT was 36.3 mum/diopter (D) and in ACD, -26.7 mum/D. The mean accommodation-induced ACD change was -0.08 mm +/- 0.06 (SD) in Group 1, -0.064 +/- 0.087 mm in Group 2, and -0.03 +/- 0.06 mm in Group 3 (P = .0004). The mean LT change during near fixation was 0.109 +/- 0.063 mm in Group 1, 0.103 +/- 0.136 mm in Group 2, and 0.006 +/- 0.05 mm in Group 3 (P<.0001). The mean ASL change during accommodation was 0.029 +/- 0.037 mm, 0.039 +/- 0.114 mm, and -0.023 +/- 0.051, respectively (P<.0001). CONCLUSIONS In addition to forward movement of the anterior lens surface with age, the posterior surface moved backward. Alterations in LT and ACD sufficient for a unit of refractive power change during accommodation might be smaller than previously thought. Anterior shifting of the lens may also participate in the accommodative response.
Collapse
Affiliation(s)
- Alexis Tsorbatzoglou
- Department of Ophthalmology, Medical and Health Science Center, University of Debrecen, Debrecen, Hungary.
| | | | | | | | | |
Collapse
|
39
|
Ljubimova D, Eriksson A, Bauer S. Aspects of eye accommodation evaluated by finite elements. Biomech Model Mechanobiol 2007; 7:139-50. [PMID: 17457627 DOI: 10.1007/s10237-007-0081-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2005] [Accepted: 02/20/2007] [Indexed: 11/29/2022]
Abstract
Axisymmetric nonlinear finite models of accommodation incorporating the posteriorly sloped force and vitreous effects have been studied by means of their effectiveness in mechanical and optical performances. All materials were assumed to be linearly elastic, vitreous and lens matrices were incompressible. The present model is subjected to certain indicated shortcomings, however, the behavior of the model is predictable, reasonable and favourably consistent with different published data, supporting the Helmholtz theory of accommodation.
Collapse
Affiliation(s)
- Darja Ljubimova
- Department of Mechanics, Royal Institute of Technology, 100 44, Stockholm, Sweden.
| | | | | |
Collapse
|
40
|
Abolmaali A, Schachar RA, Le T. Sensitivity study of human crystalline lens accommodation. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2007; 85:77-90. [PMID: 17005291 DOI: 10.1016/j.cmpb.2006.08.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 08/22/2006] [Accepted: 08/24/2006] [Indexed: 05/12/2023]
Abstract
A nonlinear axisymmetric finite element method (FEM) analysis was employed to determine the critical geometric and material properties that affect human accommodation. In this model, commencing at zero, zonular traction on all lens profiles resulted in central lenticular surface steepening and peripheral surface flattening, with a simultaneous increase in central lens thickness and central optical power. An age-related decline in maximum zonular tension appears to be the most likely etiology for the decrease in accommodative amplitude with age.
Collapse
Affiliation(s)
- A Abolmaali
- Department of Civil and Environmental Engineering, University of Texas at Arlington, TX 76019, USA
| | | | | |
Collapse
|
41
|
Bolz M, Prinz A, Drexler W, Findl O. Linear relationship of refractive and biometric lenticular changes during accommodation in emmetropic and myopic eyes. Br J Ophthalmol 2006; 91:360-5. [PMID: 17050582 PMCID: PMC1857649 DOI: 10.1136/bjo.2006.099879] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIM Aim of this study was to investigate the relationship between refractive changes in the eye and biometric changes of the human crystalline lens during accommodation. Furthermore, differences in these relationships between young, healthy emmetropic and myopic subjects were analyzed. METHODS Mean relative change in anterior chamber depth (ACD), lens thickness (LT), anterior segment length (ASL = ACD + LT) and in objective refraction were simultaneously assessed during near-point-induced accommodation in 10 emmetropic and 10 myopic subjects. Via a beam splitter, measurements were performed simultaneously using partial coherence interferometry (PCI) and infrared (IR) photorefraction. RESULTS On average, for each diopter of accommodation LT increased by 0.063 mm in emmetropic and by 0.072 mm in myopic eyes, and ACD decreased by 0.047 mm and 0.057 mm, respectively. Mean ASL, indicating the position of the posterior lens pole, increased by 0.009 mm in emmetropic and by 0.013 mm in myopic eyes. The correlation between refractive and biometric changes was found to be essentially linear in both subgroups. Differences in ACD between emmetropic and myopic eyes were statistically significant at an accommodative stimulus of -1 D (p<0.04) and -2 D (p<0.02). CONCLUSION The biometric and refractive changes of the human lens are highly correlated and linear in function in both emmetropic and myopic eyes.
Collapse
Affiliation(s)
- Matthias Bolz
- Department of Ophthalmology, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
| | | | | | | |
Collapse
|
42
|
Kriechbaum K, Leydolt C, Findl O, Bolz M, Drexler W. Comparison of Partial Coherence Interferometers: ACMaster Versus Laboratory Prototype. J Refract Surg 2006; 22:811-6. [PMID: 17061719 DOI: 10.3928/1081-597x-20061001-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate anterior segment biometry using the ACMaster (Carl Zeiss Meditec AG, Jena, Germany) in regard to precision of measurement and clinical performance compared to the original laboratory prototype of the partial coherence interferometry technique. METHODS Ten phakic (20 eyes) and 27 pseudophakic (44 eyes) patients were included in this study. Anterior segment biometry of phakic and pseudophakic study eyes was performed using the ACMaster and the laboratory prototype of the partial coherence interferometry technique. The ACMaster is a commercially available device based on the partial coherence interferometry technique, which provides high precision anterior segment measurements in a quick and user-friendly fashion. Examination included measurement of central corneal thickness, anterior chamber depth, and lens thickness, the latter only in the phakic eyes. RESULTS The consistency of anterior segment measurements performed with both units was excellent in phakic as well as in pseudophakic eyes. In pseudophakic eyes, the measurement of anterior chamber thickness and lens thickness with the ACMaster produced several (typical) measurement artifacts in some cases, which partially aggravated the identification of the A-scan peak representing the anterior intraocular lens surface. CONCLUSIONS The ACMaster is a user-friendly device that enables axial anterior segment biometry using the partial coherence interferometry technique with a reproducibility similar to that of the original laboratory prototype.
Collapse
|
43
|
Bolz M, Sacu S, Drexler W, Findl O. Local corneal thickness changes after small-incision cataract surgery. J Cataract Refract Surg 2006; 32:1667-71. [PMID: 17010865 DOI: 10.1016/j.jcrs.2006.05.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Accepted: 05/17/2006] [Indexed: 11/15/2022]
Abstract
PURPOSE To assess whether a temporal limbal-corneal incision approach for phacoemulsification cataract surgery induces a gradient in corneal thickening along the horizontal meridian. SETTING Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. METHODS Corneal thickness in 21 eyes of 21 patients was measured preoperatively as well as 1 day, 1 week, and 1 and 3 months after phacoemulsification through a temporal limbal-corneal incision. Measurements were performed using partial coherence interferometry (PCI) with a commercial instrument, the ACMaster (Carl Zeiss Meditec, Jena). Measurements were taken along the horizontal meridian centrally along the visual axis at 1.5 mm, 3.0 mm, and 4.5 mm eccentricity. RESULTS Preoperatively, there were slight nasal-temporal differences in corneal thickness at all eccentricities. The mean thickness was 522 microm +/- 34 (SD) at 1.5 mm nasally and 513 +/- 36 microm at 1.5 mm temporally (P<.01). On day 1, there was a significant mean increase in corneal thickness (38 +/- 43 microm) along all locations. The thickening was slightly more pronounced in the periphery than in the center, a difference not reaching statistical significance. At 1 week, corneal thickness returned almost to baseline at all locations except for 3.0 mm temporally, where it was slightly, but not significantly, thicker (mean 8 +/- 14 mum). At 1 month, corneal thickness at the 3.0 mm temporal location returned to baseline. CONCLUSIONS A nasal-temporal difference in corneal thickness was found preoperatively in all patients. Phacoemulsification through a temporal limbal-corneal incision caused an increase in corneal thickness along the horizontal meridian 1 day after surgery. The prolonged corneal thickening at 3.0 mm eccentricity temporally could be a result of the proximity to the incision site.
Collapse
Affiliation(s)
- Matthias Bolz
- Department of Ophthalmology, Medical University of Vienna, Vienna, Austria
| | | | | | | |
Collapse
|
44
|
Schachar RA, Abolmaali A, Le T. Insights into the age-related decline in the amplitude of accommodation of the human lens using a non-linear finite-element model. Br J Ophthalmol 2006; 90:1304-9. [PMID: 16854823 PMCID: PMC1857424 DOI: 10.1136/bjo.2006.100347] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/05/2006] [Indexed: 11/04/2022]
Abstract
AIM To understand the effect of the geometric and material properties of the lens on the age-related decline in accommodative amplitude. METHODS Using a non-linear finite-element model, a parametric assessment was carried out to determine the effect of stiffness of the cortex, nucleus, capsule and zonules, and that of thickness of the capsule and lens, on the change in central optical power (COP) associated with zonular traction. Convergence was required for all solutions. RESULTS Increasing either capsular stiffness or capsular thickness was associated with an increase in the change in COP for any specific amount of zonular traction. Weakening the attachment between the capsule and its underlying cortex increased the magnitude of the change in COP. When the hardness of the total lens stroma, cortex or nucleus was increased, there was a reduction in the amount of change in COP associated with a fixed amount of zonular traction. CONCLUSIONS Increasing lens hardness reduces accommodative amplitude; however, as hardness of the lens does not occur until after the fourth decade of life, the age-related decline in accommodative amplitude must be due to another mechanism. One explanation is a progressive decline in the magnitude of the maximum force exerted by the zonules with ageing.
Collapse
MESH Headings
- Accommodation, Ocular/physiology
- Adult
- Aging/pathology
- Aging/physiology
- Elasticity
- Finite Element Analysis
- Humans
- Lens Capsule, Crystalline/anatomy & histology
- Lens Capsule, Crystalline/physiology
- Lens Cortex, Crystalline/anatomy & histology
- Lens Cortex, Crystalline/physiology
- Lens Nucleus, Crystalline/anatomy & histology
- Lens Nucleus, Crystalline/physiology
- Lens, Crystalline/anatomy & histology
- Lens, Crystalline/physiology
- Middle Aged
- Models, Biological
Collapse
Affiliation(s)
- R A Schachar
- Department of Physics, University of Texas at Arlington, Arlington, TX, USA.
| | | | | |
Collapse
|
45
|
Ostrin L, Kasthurirangan S, Win-Hall D, Glasser A. Simultaneous Measurements of Refraction and A-Scan Biometry During Accommodation in Humans. Optom Vis Sci 2006; 83:657-65. [PMID: 16971844 DOI: 10.1097/01.opx.0000232810.61191.02] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Accommodation is a dioptric change in power of the crystalline lens resulting from ciliary muscle contraction that leads to an increase in lens surface curvatures and thickness and changes in the position of lens surfaces. Previous studies have used A-scan ultrasound to measure changes in the position of lens surfaces with voluntary accommodation, but have not simultaneously measured the change in refraction. The goal of this study is to simultaneously measure and correlate refractive and biometric changes in the lens during voluntary accommodation in humans. METHODS Refraction was measured off-axis in the right eye and biometry on-axis in the left eye simultaneously during voluntary accommodation in 22 human subjects between the ages of 21 and 30 years (mean +/- standard deviation: 25.8 +/- 2.3 years). Subjects viewed a distant target and four near targets spanning the full accommodative range available to evaluate refraction and lens surface position at each accommodative state. RESULTS Maximum objectively measured accommodative amplitude of all subjects was 5.64 +/- 0.21 D (mean +/- standard error of mean). Biometric and refractive changes during accommodation were linearly correlated. The mean +/- standard error of mean decrease in anterior chamber depth was 0.051 +/- 0.008 mm/D, increase in lens thickness was 0.067 +/- 0.008 mm/D, and increase in anterior segment length was 0.017 +/- 0.005 mm/D during accommodation. There was a net anterior movement of the lens center of 0.017 +/- 0.005 mm/D. CONCLUSION Anterior chamber depth, lens thickness, and anterior segment length change linearly with refraction during accommodation. Per-diopter changes in the lens were greater in the current study compared with previous studies in which only accommodative demand was measured, which overestimates the accommodative response.
Collapse
Affiliation(s)
- Lisa Ostrin
- University of Houston College of Optometry, Houston, Texas 77004, USA
| | | | | | | |
Collapse
|
46
|
Zhu M, Collins MJ, Iskander DR. The contribution of accommodation and the ocular surface to the microfluctuations of wavefront aberrations of the eye. Ophthalmic Physiol Opt 2006; 26:439-46. [PMID: 16918767 DOI: 10.1111/j.1475-1313.2006.00373.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We have used videokeratoscopy and wavefront sensing to investigate the contribution of the ocular surface and the effect of stimulus vergence on the microfluctuations of the wavefront aberrations of the eye. The fluctuations of the wavefront aberrations were quantified by their variations around the mean and by using power spectrum analysis. Integrated power was determined in two regions: 0.1-0.7 Hz (low frequencies) and 0.8-1.8 Hz (high frequencies). Changes in the ocular surface topography were measured using high-speed videokeratoscopy and variations in the ocular wavefront aberrations were measured with a wavefront sensor. The microfluctuations of wavefront aberrations of the ocular surface were found to be considerably smaller than the microfluctuations of the wavefront aberrations of the total eye. The fluctuations in defocus while viewing a closer target at 2 or 4 D were found to be significantly greater than fluctuations in defocus when viewing a far target. This increase in defocus fluctuations (p < or = 0.001) occurred in both the low- and high-frequency regions of the power spectra.
Collapse
Affiliation(s)
- Mingxia Zhu
- Contact Lens and Visual Optics Laboratory, School of Optometry, Queensland University of Technology, Victoria Park Road, Kelvin Grove 4059, Queensland, Australia.
| | | | | |
Collapse
|
47
|
Schachar RA, Kamangar F. Computer image analysis of ultrasound biomicroscopy of primate accommodation. Eye (Lond) 2006; 20:226-33. [PMID: 15818391 DOI: 10.1038/sj.eye.6701838] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
PURPOSE To assess and correct images of the eye for movements that can confound the evaluation of the presence, direction, and magnitude of intraocular movement of the crystalline lens equator during centrally induced ciliary muscle contraction (accommodation). METHOD Ultrasound biomicroscopic (UBM) video images of a cynomologus monkey crystalline lens were obtained from an independent source. The images, prior to, during, and following electrical stimulation of the Edinger-Westphal (EW) nucleus were compared for evidence of movement of the crystalline lens equator. Extraocular eye movements were assessed by use of objective computer imaging analysis techniques. RESULTS Extraocular eye movements were identified and reduced by using objective computer imaging analysis techniques to register and realign the corneal images. Highly significant corrections are required to effect corneal realignment. Analysis of paired and registered images from this data source indicates that any movements of the primate lens equator are not detectable when maximum accommodation was induced by EW stimulation. CONCLUSION The displacement of the edge of the primate crystalline lens equator during electrically induced contraction of the ciliary muscle is a small displacement phenomenon, only analysable after confounding extraocular movements are removed from the compared images.
Collapse
Affiliation(s)
- R A Schachar
- Department of Physics, University of Texas at Arlington, Arlington, TX, USA.
| | | |
Collapse
|
48
|
Chien CHM, Huang T, Schachar RA. Analysis of human crystalline lens accommodation. J Biomech 2006; 39:672-80. [PMID: 16023655 DOI: 10.1016/j.jbiomech.2005.01.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2004] [Accepted: 01/10/2005] [Indexed: 11/18/2022]
Abstract
The behavior of the human crystalline lens during accommodation is analytically studied. The lens is modeled as a closed axisymmetrical membrane shell of varying thickness enclosing an incompressible liquid. To simulate zonular tension associated with lenticular accommodation, an axisymmetrical radial force or displacement is imposed around the shell equator. Two second-order, simultaneous, nonlinear governing differential equations are derived. Numerical results, obtained from the investigation of human lens profiles of three independently published MRI images and a drawing of a microphotograph, demonstrate that when zonular traction within the physiological force range of the ciliary muscle is exerted, both central lens thickness and central optical power increase. Qualitatively, these increases are independent of lens shape. However, the magnitude of these changes is dependent on the initial profile of the lens and is enhanced by the "natural" variation in capsular thickness. Only when a pulling force significantly exceeds the force capacity of the ciliary muscle does the lens flatten and its central thickness and optical power decrease.
Collapse
Affiliation(s)
- Chang-Hai M Chien
- Department of Civil and Environmental Engineering, University of Texas at Arlington, Arlington, TX 76019, USA
| | | | | |
Collapse
|
49
|
Lege BAM, Haigis W, Neuhann TF, Bauer MH. Age-related behavior of posterior chamber lenses in myopic phakic eyes during accommodation measured by anterior segment partial coherence interferometry. J Cataract Refract Surg 2006; 32:999-1006. [PMID: 16814059 DOI: 10.1016/j.jcrs.2006.02.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Accepted: 12/01/2005] [Indexed: 10/24/2022]
Abstract
PURPOSE To evaluate age-related position shifts of the crystalline lens and the implantable contact lens (ICL, Staar Surgical) by a new, commercially available, anterior segment partial coherence interferometer, the ACMaster (Carl Zeiss Meditec), during accommodation in myopic eyes. SETTING ALZ Augenklinik, Munich, Germany. METHODS Fifty-three eyes of 29 consecutive patients were measured after myopic ICL implantation before and during subjective accommodation to a stimulus of 3 diopters (D) by anterior segment partial coherence interferometry (PCI). Nine eyes were also measured with a 5.00 diopters (D) stimulus; 14 eyes were measured repeatedly at different visits. The mean patient age was 33 years +/- 9 (SD) (range 21 to 59 years). The preoperative mean sphere was -7.6 +/- 1.9 D (range -5.0 to -11.5 D) and the cylinder, -1.4 +/- 1.1 D (range 0 to -4.25 D). RESULTS Older patients had a tendency toward smaller vaults on desaccommodation between the ICL and the crystalline lens compared to younger individuals. In younger patients, there was a decrease of the vault on accommodation, whereas it increased in older persons (P = .005). During accommodation, the more the anterior lens surface shifted forward, the more the ICL bulged (P = .005). The change in vaulting was significantly larger at 5.00 D than at 3.00 D accommodation stimulus (P = .012). CONCLUSIONS The behavior of ICLs in relation to the crystalline lens during accommodation varied with age and could be shown by PCI. The position shift of the ICL depended on the initial vault at desaccommodation and the ability of the anterior lens surface to bulge forward. Even though the crystalline lens stiffened, and therefore accommodation deteriorated with age, there was still a movement of the ICL, pointing to the role of the ciliary muscle movement in accommodation.
Collapse
|
50
|
Ho A, Manns F, Parel JM. Predicting the performance of accommodating intraocular lenses using ray tracing. J Cataract Refract Surg 2006; 32:129-36. [PMID: 16516791 DOI: 10.1016/j.jcrs.2005.07.047] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/05/2005] [Indexed: 10/24/2022]
Abstract
PURPOSE To predict and compare the amount of accommodation achievable by pseudophakic accommodating intraocular lenses (IOLs) using optical ray-tracing analysis. SETTING Computational laboratory. METHODS Two-element IOLs (2E-IOL, with mobile front or back optical elements) were compared with single-element IOLs (1E-IOL). Modeling using computer-assisted ray tracing of both IOL types assumed lens elements were equiconvex/equiconcave. The 4 possible combinations of configurations representing a wide range of varying positive and negative power (up to +40 diopters [D]) of front and back optical elements were evaluated. RESULTS The 1E-IOLs offered limited amplitude of accommodation with axial shift (approximately 1.2 D/mm). For 2E-IOLs, configurations with high positive-power front elements returned the best amplitude of accommodation (up to approximately 3.0 D/mm when the front element power was +40 D). CONCLUSIONS Considering the maximum potential amounts of axial shifts available, 1E-IOLs were predicted to provide 1.0 D of accommodation or less and 2E-IOLs were predicted to provide up to 3.0 D to 4.0 D depending on design configuration and amount of axial shift achievable. Potential issues relating to accommodative aniseikonia and spherical aberration have been identified.
Collapse
Affiliation(s)
- Arthur Ho
- Vision Cooperative Research Centre, Sydney, NSW, Australia.
| | | | | |
Collapse
|