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Affiliation(s)
- Thomas H. Dohlman
- Schepens Eye Research Institute/Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Jia Yin
- Schepens Eye Research Institute/Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
| | - Reza Dana
- Schepens Eye Research Institute/Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA, USA
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Corneal structure, transparency, thickness and optical density (densitometry), especially as relevant to contact lens wear—a review. Cont Lens Anterior Eye 2019; 42:238-245. [DOI: 10.1016/j.clae.2018.11.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 11/21/2018] [Accepted: 11/23/2018] [Indexed: 11/18/2022]
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Hilmi MR, Che Azemin MZ, Mohd Kamal K, Mohd Tamrin MI, Abdul Gaffur N, Tengku Sembok TM. Prediction of Changes in Visual Acuity and Contrast Sensitivity Function by Tissue Redness after Pterygium Surgery. Curr Eye Res 2017; 42:852-856. [PMID: 28118054 DOI: 10.1080/02713683.2016.1250277] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE The goal of this study was to predict visual acuity (VA) and contrast sensitivity function (CSF) with tissue redness grading after pterygium surgery. MATERIALS AND METHODS A total of 67 primary pterygium participants were selected from patients who visited an ophthalmology clinic. We developed a semi-automated computer program to measure the pterygium fibrovascular redness from digital pterygium images. The final outcome of this software is a continuous scale grading of 1 (minimum redness) to 3 (maximum redness). The region of interest (ROI) was selected manually using the software. Reliability was determined by repeat grading of all 67 images, and its association with CSF and VA was examined. RESULTS The mean and standard deviation of redness of the pterygium fibrovascular images was 1.88 ± 0.55. Intra-grader and inter-grader reliability estimates were high with intraclass correlation ranging from 0.97 to 0.98. The new grading was positively associated with CSF (p < 0.01) and VA (p < 0.01). The redness grading was able to predict 25% and 23% of the variance in the CSF and the VA, respectively. CONCLUSIONS The new grading of pterygium fibrovascular redness can be reliably measured from digital images and showed a good correlation with CSF and VA. The redness grading can be used in addition to the existing pterygium grading.
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Affiliation(s)
- Mohd Radzi Hilmi
- a Department of Optometry and Visual Science , Kulliyyah of Allied Health Sciences, International Islamic University Malaysia (IIUM) , Kuantan , Pahang , Malaysia
| | - Mohd Zulfaezal Che Azemin
- a Department of Optometry and Visual Science , Kulliyyah of Allied Health Sciences, International Islamic University Malaysia (IIUM) , Kuantan , Pahang , Malaysia
| | - Khairidzan Mohd Kamal
- b Department of Ophthalmology , Kulliyyah of Medicine, International Islamic University Malaysia (IIUM) , Kuantan , Pahang , Malaysia
| | - Mohd Izzuddin Mohd Tamrin
- c Kulliyyah of Information and Communication Technology , International Islamic University Malaysia (IIUM) , Gombak , Malaysia
| | - Norfazrina Abdul Gaffur
- a Department of Optometry and Visual Science , Kulliyyah of Allied Health Sciences, International Islamic University Malaysia (IIUM) , Kuantan , Pahang , Malaysia
| | - Tengku Mohd Tengku Sembok
- d Department of Computer Science, Faculty of Defence Science and Technology , National Defence University of Malaysia , Kuala Lumpur , Malaysia
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Rodriguez JD, Johnston PR, Ousler GW, Smith LM, Abelson MB. Automated grading system for evaluation of ocular redness associated with dry eye. Clin Ophthalmol 2013; 7:1197-1204. [PMID: 23814457 PMCID: PMC3693861 DOI: 10.2147/opth.s39703] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background We have observed that dry eye redness is characterized by a prominence of fine horizontal conjunctival vessels in the exposed ocular surface of the interpalpebral fissure, and have incorporated this feature into the grading of redness in clinical studies of dry eye. Aim To develop an automated method of grading dry eye-associated ocular redness in order to expand on the clinical grading system currently used. Methods Ninety nine images from 26 dry eye subjects were evaluated by five graders using a 0–4 (in 0.5 increments) dry eye redness (Ora Calibra™ Dry Eye Redness Scale [OCDER]) scale. For the automated method, the Opencv computer vision library was used to develop software for calculating redness and horizontal conjunctival vessels (noted as “horizontality”). From original photograph, the region of interest (ROI) was selected manually using the open source ImageJ software. Total average redness intensity (Com-Red) was calculated as a single channel 8-bit image as R – 0.83G – 0.17B, where R, G and B were the respective intensities of the red, green and blue channels. The location of vessels was detected by normalizing the blue channel and selecting pixels with an intensity of less than 97% of the mean. The horizontal component (Com-Hor) was calculated by the first order Sobel derivative in the vertical direction and the score was calculated as the average blue channel image intensity of this vertical derivative. Pearson correlation coefficients, accuracy and concordance correlation coefficients (CCC) were calculated after regression and standardized regression of the dataset. Results The agreement (both Pearson’s and CCC) among investigators using the OCDER scale was 0.67, while the agreement of investigator to computer was 0.76. A multiple regression using both redness and horizontality improved the agreement CCC from 0.66 and 0.69 to 0.76, demonstrating the contribution of vessel geometry to the overall grade. Computer analysis of a given image has 100% repeatability and zero variability from session to session. Conclusion This objective means of grading ocular redness in a unified fashion has potential significance as a new clinical endpoint. In comparisons between computer and investigator, computer grading proved to be more reliable than another investigator using the OCDER scale. The best fitting model based on the present sample, and usable for future studies, was
C4=−12.24+2.12C2HOR+0.88C2RED:C4 is the predicted investigator grade, and
C2HOR and
C2RED are logarithmic transformations of the computer calculated parameters COM-Hor and COM-Red. Considering the superior repeatability, computer automated grading might be preferable to investigator grading in multicentered dry eye studies in which the subtle differences in redness incurred by treatment have been historically difficult to define.
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Automated hyperemia analysis software: reliability and reproducibility in healthy subjects. Jpn J Ophthalmol 2011; 56:1-7. [PMID: 22130522 DOI: 10.1007/s10384-011-0107-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Accepted: 10/05/2011] [Indexed: 10/15/2022]
Abstract
PURPOSE To evaluate the reliability and reproducibility of automated software to analyze human bulbar hyperemia. METHODS We enrolled 89 healthy volunteers in this study. A slit lamp was used to take pictures of the conjunctiva on the temporal side of each subject's right eye. Photographic conditions were standardized by using a single photographer. Images were transferred to software for automatic pixel value calculation in the green channel of the region of interest (ROI). We investigated optimal ROI size, mean ROI pixel frequency, percentage ROI blood vessel coverage, and data reproducibility. We also used this software to evaluate bimatoprost-induced hyperemia and hyperemia in allergic conjunctival diseases. RESULTS The optimal ROI was found to be 400 vertical pixels by 300 horizontal pixels. Mean ROI pixel frequency was 5305 and % coverage was 4.4%. We confirmed the reproducibility of the analysis by comparing two images (r (2) = 0.7, P < 0.0001). Percentage blood vessel coverage increased in images of bimatoprost-induced hyperemia and hyperemia in allergic conjunctival diseases compared to the data from healthy volunteers. CONCLUSIONS The software was simple to use and provided reproducible data. We established standard settings for the operation of the software. The use of our software will improve hyperemia evaluation, which is presently done using nonquantitative methods.
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López-Miguel A, Nieto JC, Díez-Cuenca M, Piñero DP, Maldonado MJ. Agreement of non-contact pachymetry after LASIK: comparison of combined scanning-slit/Placido disc topography and specular microscopy. Eye (Lond) 2009; 24:1064-70. [PMID: 19786958 DOI: 10.1038/eye.2009.233] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To assess the interchangeability of central corneal thickness (CCT) measurements between combined scanning-slit/Placido disc topography (Orbscan-II) and specular microscopy (Topcon SP-2000P) in patients who underwent laser in situ keratomileusis (LASIK) for myopia. PATIENTS AND METHODS We recruited 118 consecutive patients who underwent LASIK for myopia. The CCT was measured using Orbscan-II and Topcon SP-2000P randomly. Orbscan-II and Topcon SP-2000P CCT data were analysed using the paired-sample t-test and the limits of agreement (LoA) were calculated with the method described by Bland-Altman. RESULTS The average CCT measurements by Orbscan-II and Topcon SP-2000P were 447.55+/-49.78 microm and 461.38+/-35.35 microm, respectively (P<0.0001; mean difference, 13.83+/-22.31 microm; 95% confidence interval, 9.77-17.09 microm). The Bland-Altman plot showed an inverse association between the average and the difference between the devices: Topcon-Orbscan-II=174.23 -0.353xAverage (P<0.01). The widths of the crude and regression-based 95% limits of agreement were 87.45 and 63.72 microm, respectively. CONCLUSIONS Orbscan-II measurements of CCT after myopic LASIK were significantly lower than those obtained using Topcon SP-2000P. The limits of agreement between the two devices were too broad and, therefore, both pachymetric values cannot be used interchangeably. Further, the tendency towards comparably Orbscan-II readings in thinner corneas precludes that one technique can directly replace the other. This is important for the adequate medium- and long-term follow-up of the growing LASIK patient population.
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Affiliation(s)
- A López-Miguel
- Departamento de Oftalmología, Clínica Universitaria, Universidad de Navarra, Pamplona, Spain.
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Abstract
Perhaps no diagnostic technology has emerged as rapidly in ophthalmology as optical coherence tomography (OCT). A single clinical device for this noninvasive imaging technique was first released in 1996, and now at least ten clinical devices are available. Although the first clinical anterior segment OCT was marketed only 2 years ago, a substantial amount of work has been done using modified retinal imagers or prototype laboratory-based imagers. In this review, we discuss OCT imaging primarily of the cornea. We also highlight previous and current publications on nonclinical and clinical uses of the device to illustrate how anterior segment OCT can be used to understand corneal structure and function in health and disease.
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Affiliation(s)
- Trefford Simpson
- Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada
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Maldonado MJ, Nieto JC, Piñero DP. Advances in technologies for laser-assisted in situ keratomileusis (LASIK) surgery. Expert Rev Med Devices 2008; 5:209-29. [PMID: 18331182 DOI: 10.1586/17434440.5.2.209] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Laser-assisted in situ keratomileusis (LASIK) has become the most widely used form of refractive surgery today. The objective of this surgical technique is to modify the anterior corneal shape by ablating tissue from the stroma by means of the excimer laser after creating a hinged corneal flap. This way, we are able to change the refractive status of the patient, providing better unaided vision. Continuous improvements in the original technique have made the surgical procedure safer, more accurate and repeatable. These progressions are due to the development of novel technologies that are the responsible for new surgical instrumentation, which makes the surgical procedure easier for the surgeon, and better excimer laser ablation algorithms, which increase the optical quality of the ablation and thus the safety of the vision correction procedure. This article aims to describe the more relevant advances in LASIK that have played an important role in the spread and popularity of this technique.
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Affiliation(s)
- Miguel J Maldonado
- Department of Ophthalmology, Clínica Universitaria, University of Navarra, Avda Pio XII, 36, 31080, Pamplona, Spain.
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Sorbara L, Simpson T, Duench S, Schulze M, Fonn D. Comparison of an objective method of measuring bulbar redness to the use of traditional grading scales. Cont Lens Anterior Eye 2007; 30:53-9. [PMID: 17254834 DOI: 10.1016/j.clae.2006.12.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2006] [Revised: 11/21/2006] [Accepted: 12/04/2006] [Indexed: 11/23/2022]
Abstract
PURPOSE The primary objective was to compare measures of bulbar redness objectively using a photometric method with standard grading methods. Measures of redness were made on 24 participants wearing a silicone hydrogel contact lens in one eye for overnight wear. This report compares hyperaemia after 1 week of daily wear (baseline) with redness measured after 6 months of overnight wear. METHOD A new method of objectively measuring bulbar conjunctival redness was performed using the Spectrascan650 Photometer by Photo Research under fixed illumination. Photometric measures in CIEu(*) chromaticity values involve the measurement of chromaticity, a physical analogue of redness, greenness and blueness in the image. This method was validated in Part 1 of the study using repeated measurements on the photographic CCLRU scale. In Part 2 of the study, the photographic grading scale (CCLRU) from 0 (none) to 100 (extreme) was used to make the comparison. RESULTS Part 1 indicated that the photometer provides a repeatable and reliable measure of bulbar redness (CCC=0.989). A moderately strong and significant correlation was found between the CIEu(*) chromaticity values and the analogue data (R=0.795, p=0.000) at each measurement session (from baseline to 1 day, 1 week, and 1, 3 and 6 months of overnight wear). CONCLUSIONS This new standardized and objective method of measuring bulbar redness has great potential to replace subjective grading scales, especially with multi-centre studies, where variability between investigators occurs. This method may also detect smaller changes between visits or between eyes.
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Affiliation(s)
- Luigina Sorbara
- Centre for Contact Lens Research, School of Optometry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
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Maldonado MJ, Nieto JC, Díez-Cuenca M, Piñero DP. Repeatability and Reproducibility of Posterior Corneal Curvature Measurements by Combined Scanning-Slit and Placido-Disc Topography after LASIK. Ophthalmology 2006; 113:1918-26. [PMID: 16935339 DOI: 10.1016/j.ophtha.2006.05.053] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2005] [Revised: 05/20/2006] [Accepted: 05/20/2006] [Indexed: 10/24/2022] Open
Abstract
OBJECTIVE To assess the repeatability and reproducibility of posterior corneal curvature (PCC) measurements made by combined scanning-slit/Placido-disc topography (Orbscan II) after LASIK. DESIGN Experimental instrument validation study. PARTICIPANTS We recruited 22 consecutive postmyopic LASIK patients for the repeatability study and another 50 consecutive postmyopic LASIK patients for the reproducibility study. METHODS To analyze intrasession repeatability, 1 examiner measured 22 postmyopic LASIK eyes 10 times successively in the shortest time possible. To study intersession reproducibility, the same operator obtained measurements from another 50 eyes with stable refraction in 2 consecutive visits at the same time of the day between 6 and 9 months after myopic LASIK. We explored any association between residual stromal bed thickness and measurement variability. MAIN OUTCOME MEASURES Orbscan II scanning-slit PCC data, precision, within-subject coefficient of variation (CV(w)), limits of agreement (LoA), and intraclass correlation coefficient (ICC). RESULTS For intrasession repeatability, precision was 0.067 mm (best-fit sphere [BFS]), 0.110 diopters (D; power within 5 mm), 0.158 D (power within 3 mm), and 0.46 (eccentricity). Repeatability was high for PCC BFS and power measurements within 3-mm and 5-mm zones (CV(w) ranged from 0.5%-1.2%) but poor for eccentricity data (CV(w), 31.6%). Correspondingly, ICCs ranged from 0.89 to 0.98 for PCC BFS and power, and the ICC was 0.20 for PCC eccentricity values. For intersession reproducibility, on average, no difference in PCC measurements could be found, indicating that when there is variability, it is due to random factors. The width of the 95% LoA between sessions was clinically acceptable for BFS (0.25 mm) and power (0.4 D [within 5 mm] and 0.6 D [within 3 mm]). Similarly, ICCs indicated good intersession reliability for BFS and power (0.98, 0.96, and 0.85 for BFS, power within 5 mm, and power within 3 mm, respectively) but poor reliability for eccentricity (0.59). Repeatability and reproducibility were unrelated to stromal bed thickness. CONCLUSIONS Orbscan II provides reliable post-LASIK PCC data for symmetrical parameters (BFS and power), independent of the residual stromal bed thickness, but is unreliable for measurements that are radially asymmetrical (eccentricity). Orbscan II is useful for monitoring the PCC after LASIK once the early postoperative period is over.
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Affiliation(s)
- Miguel J Maldonado
- Department of Ophthalmology, University Clinic, University of Navarra, Pamplona, Spain
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Maldonado MJ, Nieto JC, Díez-Cuenca M, Piñero DP. Posterior Corneal Curvature Changes after Undersurface Ablation of the Flap and In-the-Bed LASIK Retreatment. Ophthalmology 2006; 113:1125-33. [PMID: 16713626 DOI: 10.1016/j.ophtha.2006.01.065] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2005] [Revised: 12/30/2005] [Accepted: 01/03/2006] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE To analyze LASIK retreatment-induced changes in the posterior corneal curvature (PCC) with undersurface ablation of the flap (UAF) and in-the-bed techniques. DESIGN Nonrandomized, comparative, interventional study. PARTICIPANTS Forty-six eyes with a residual spherical equivalent refraction between -0.37 and -2.75 diopters (D) and astigmatism between 0.0 and -1.25 D were included prospectively. In 23 eyes, the calculated postenhancement flap thickness exceeded 150 microm using micropachymetric optical coherence tomography, whereas with further ablation of the bed, the residual bed thickness (RBT) would have been <250 microm, or <55% of the pre-LASIK central pachymetry. In another 23 eyes, RBT allowed the planned ablation for a calculated post-retreatment RBT exceeding 250 microm, >55% of the pre-LASIK central pachymetry. INTERVENTION Eyes with insufficient RBT for further ablation underwent UAF retreatment, whereas those with adequate RBT received conventional in-the-bed LASIK retreatment. Examinations were performed before retreatment and 3 and 6 months postoperatively. No eye was lost to follow-up. MAIN OUTCOME MEASURES Micropachymetry, Orbscan II scanning-slit PCC data, and visual acuity (VA). RESULTS The groups did not differ in age, intraocular pressure, or retreatment ablation depth, but the UAF eyes had a lower mean pre-retreatment RBT (270.7+/-25.4 microm) than conventional enhancement eyes (353.0+/-41.5 microm) (P = 0.001). Eyes undergoing UAF had no significant change in PCC, whereas eyes undergoing conventional retreatment had an increase in the posterior corneal power within the central 3-mm zone (P = 0.008) 3 months after retreatment. No significant changes occurred thereafter. The amount of change in posterior corneal power within the 3-mm central zone from before to after retreatment differed significantly between the groups (mean difference, 0.135 D; 95% confidence interval, 0.022-0.248 D; P = 0.02). No keratectasia developed clinically, and no retreated eye lost or gained > or =2 lines of best-corrected VA. Six months after retreatment, the efficacy and safety indices for the UAF procedure were 0.96 and 1.01, respectively, and 1 and 1.06 for conventional LASIK enhancement. CONCLUSION Undersurface ablation of the flap retreatment appears to have less potential for changing the posterior corneal surface than conventional LASIK enhancement and can help reduce the likelihood of retreatment-induced keratectasia.
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Affiliation(s)
- Miguel J Maldonado
- Department of Ophthalmology, University Clinic, University of Navarra, Pamplona, Spain.
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Abstract
AIM To examine the academic literature on the grading of corneal transparency and to assess the potential use of objective image analysis. METHOD Reference databases of academic literature were searched and relevant manuscripts reviewed. Annunziato, Efron (Millennium Edition) and Vistakon-Synoptik corneal oedema grading scale images were analysed objectively for relative intensity, edges detected, variation in intensity and maximum intensity. In addition, corneal oedema was induced in one subject using a low oxygen transmissibility (Dk/t) hydrogel contact lens worn for 3h under a light eye patch. Recovery from oedema was monitored over time using ultrasound pachymetry, high and low contrast visual acuity measures, bulbar hyperaemia grading and transparency image analysis of the test and control eyes. RESULTS Several methods for assessing corneal transparency are described in the academic literature, but none have gained widespread use in clinical practice. The change in objective image analysis with printed scale grade was best described by quadratic parametric or sigmoid 3-parameter functions. 'Pupil image scales' (Annunziato and Vistakon-Synoptik) were best correlated to average intensity; however, the corneal section scale (Efron) was strongly correlated to variations in intensity. As expected, patching an eye wearing a low Dk/t hydrogel contact lens caused a significant (F = 119.2, p < 0.001) 14.3% increase in corneal thickness, which gradually recovered under open eye conditions. Corneal section image analysis was the most affected parameter and intensity variation across the slit width, in isolation, was the strongest correlate, accounting for 85.8% of the variance with time following patching, and 88.7% of the variance with corneal thickness. CONCLUSION Corneal oedema is best determined objectively by the intensity variation across the width of a corneal section. This can be easily measured using a slit-lamp camera connected to a computer. Oedema due to soft contact lens wear is not easily determined over the pupil area by sclerotic scatter illumination techniques.
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Affiliation(s)
- Clare O'Donnell
- Department of Optometry and Neuroscience, UMIST, PO Box 88, Manchester M60 1QD, UK.
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Wolffsohn JS. Incremental nature of anterior eye grading scales determined by objective image analysis. Br J Ophthalmol 2004; 88:1434-8. [PMID: 15489489 PMCID: PMC1772388 DOI: 10.1136/bjo.2004.045534] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIM To use previously validated image analysis techniques to determine the incremental nature of printed subjective anterior eye grading scales. METHODS A purpose designed computer program was written to detect edges using a 3 x 3 kernal and to extract colour planes in the selected area of an image. Annunziato and Efron pictorial, and CCLRU and Vistakon-Synoptik photographic grades of bulbar hyperaemia, palpebral hyperaemia roughness, and corneal staining were analysed. RESULTS The increments of the grading scales were best described by a quadratic rather than a linear function. Edge detection and colour extraction image analysis for bulbar hyperaemia (r2 = 0.35-0.99), palpebral hyperaemia (r2 = 0.71-0.99), palpebral roughness (r2 = 0.30-0.94), and corneal staining (r2 = 0.57-0.99) correlated well with scale grades, although the increments varied in magnitude and direction between different scales. Repeated image analysis measures had a 95% confidence interval of between 0.02 (colour extraction) and 0.10 (edge detection) scale units (on a 0-4 scale). CONCLUSION The printed grading scales were more sensitive for grading features of low severity, but grades were not comparable between grading scales. Palpebral hyperaemia and staining grading is complicated by the variable presentations possible. Image analysis techniques are 6-35 times more repeatable than subjective grading, with a sensitivity of 1.2-2.8% of the scale.
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Affiliation(s)
- J S Wolffsohn
- Neurosciences Research Institute, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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Møller-Pedersen T. On the structural origin of refractive instability and corneal haze after excimer laser keratectomy for myopia. ACTA ACUST UNITED AC 2003. [DOI: 10.1034/j.1600-0420.81.s237.1.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Lamminen H, Voipio V, Ruohonen K, Uusitalo H. Telemedicine in ophthalmology. ACTA OPHTHALMOLOGICA SCANDINAVICA 2003; 81:105-9. [PMID: 12752046 DOI: 10.1034/j.1600-0420.2003.00045.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
OBJECTIVES To give an overview of telemedical applications in ophthalmology and to provide background information on new tele-ophthalmological applications. METHODS We carried out a literature review, a database search and an Internet search. RESULTS According to published research, the cost-efficiency of telemedicine in ophthalmology has not been established. It has been found to have educational benefits and patients have been satisfied with the possibility of obtaining specialist care without having to travel. CONCLUSIONS Most studies have been pilot studies and telemedicine is still seldom the primary mode of operation. Technical problems have not been significant, but many open questions about organizational and operational issues remain. Further studies should be directed towards solving these problems and establishing technical standards.
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Affiliation(s)
- Heikki Lamminen
- Department of Ophthalmology, Tampere University Hospital, Finland Primary Health Care Centre, Ikaalinen, Finland.
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Wolffsohn JS, Purslow C. Clinical monitoring of ocular physiology using digital image analysis. Cont Lens Anterior Eye 2003; 26:27-35. [PMID: 16303494 DOI: 10.1016/s1367-0484(02)00062-0] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
AIM To examine the use of image analysis to quantify changes in ocular physiology. METHOD A purpose designed computer program was written to objectively quantify bulbar hyperaemia, tarsal redness, corneal staining and tarsal staining. Thresholding, colour extraction and edge detection paradigms were investigated. The repeatability (stability) of each technique to changes in image luminance was assessed. A clinical pictorial grading scale was analysed to examine the repeatability and validity of the chosen image analysis technique. RESULTS Edge detection using a 3 x 3 kernel was found to be the most stable to changes in image luminance (2.6% over a +60 to -90% luminance range) and correlated well with the CCLRU scale images of bulbar hyperaemia (r=0.96), corneal staining (r=0.85) and the staining of palpebral roughness (r=0.96). Extraction of the red colour plane demonstrated the best correlation-sensitivity combination for palpebral hyperaemia (r=0.96). Repeatability variability was <0.5%. CONCLUSIONS Digital imaging, in conjunction with computerised image analysis, allows objective, clinically valid and repeatable quantification of ocular features. It offers the possibility of improved diagnosis and monitoring of changes in ocular physiology in clinical practice.
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Affiliation(s)
- James S Wolffsohn
- Neurosciences Research Institute, School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK.
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Abstract
OBJECTIVE To develop a novel technique, undersurface ablation of the flap (UAF), for laser in situ keratomileusis (LASIK) retreatment in eyes with insufficient posterior stroma. DESIGN Noncomparative, interventional case series. PARTICIPANTS From 30 eyes examined, 25 eyes with a spherical equivalent residual refraction between -0.75 and -3.25 diopters (D) and astigmatism between 0.0 and -1.5 D were prospectively included in the study. In these eyes, calculated postenhancement flap thickness was >150 micro m using micropachymetric optical coherence tomography (OCT), whereas with further ablation of the bed, posterior stromal thickness would have been <250 micro m. Primary LASIK procedures had been performed with the Hansatome microkeratome. INTERVENTION The flap was lifted and the eye deviated downward, so that the corneal visual axis mark aligned with the laser beam. Mirror pattern ablations with an optical zone of 5 mm were performed on the flap stroma using either the Summit Apex Plus excimer laser or the Technolas Keracor 217 spot-scanning excimer laser. New axis orientation for toric ablations was calculated with the formula: beta = 180 degrees - alpha. MAIN OUTCOME MEASURES Refraction, visual acuity, OCT pachymetry, tangential videokeratography, and patient satisfaction. RESULTS The average follow-up was 6.36 +/- 2.64 months (range, 3-12 months). Mean preenhancement spherical equivalent (-2.05 +/- 0.75 D) was reduced to -0.19 +/- 0.38 D at the last visit (P = 0.001). Mean cylinder decreased from -0.48 +/- 0.53 D before retreatment to -0.23 +/- 0.28 D at the last follow-up (P = 0.003). Best-corrected visual acuity worsened by 1 line in two eyes (8%), and no eye lost 2 or more lines. Satisfactory globe stabilization and stromal smoothness during ablation were more difficult to achieve than with conventional LASIK enhancements. The average central flap thickness before UAF, 187 +/- 13 micro m, decreased to 164 +/- 12 micro m after 1 month (P = 0.001). No keratectasia developed. Finally, 92% of cases were satisfied with surgery compared with 48% before UAF retreatment (P = 0.001). CONCLUSIONS UAF retreatment for low residual refractive errors after LASIK in eyes with sufficient flap stroma seems to be effective and may prevent future keratectasia.
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Affiliation(s)
- Miguel J Maldonado
- Department of Ophthalmology, University Clinic, University of Navarra, Pamplona, Spain
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Abstract
Medicine has to balance between the advantages and costs of new technology. As the significance of technical aids has increased, medicine has become more tightly bound to technology. Telemedicine is one of the fastest developing fields, as its development is connected to the development of telecommunication and information technology. Technology sets the ultimate restrictions to telemedicine. However, most challenges are nontechnical. Fast development makes it difficult to perform generalizable studies on the field, and the lack of practical, applicable standardization hinders telemedical system design. The cost of technology is quickly falling compared with the cost of human labour. Because of these factors the efficient use of telemedicine requires strategic decisions at the level of the organization as well as more research concerning the effects of telemedicine on medical practice. This article describes the telemedical frame of reference by using dermatology and ophthalmology as examples.
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Affiliation(s)
- H Lamminen
- Department of Ophthalmology, Tampere University Hospital, Finland.
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Abstract
Technology to create and move multimedia medical information is creating alternatives to physically transporting patients and health care professionals. Teletechnology is a physician extender, both supplementing and reinventing traditional health care delivery systems. The potential of comprehensive teleophthalmology is compelling. This article provides a historical perspective of telemedicine, describes various teleophthalmology systems, and surveys teleophthalmology in clinical consultation, research, and education programs around the world. It also discusses basic issues in applying teleophthalmology to public health.
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Affiliation(s)
- H K Li
- Department of Ophthalmology and Visual Sciences, University of Texas Medical Branch, Galveston 77555-0787, USA
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Seitz B, Moreira L, Baktanian E, Sanchez D, Gray B, Gordon EM, Anderson WF, McDonnell PJ. Retroviral vector-mediated gene transfer into keratocytes in vitro and in vivo. Am J Ophthalmol 1998; 126:630-9. [PMID: 9822226 DOI: 10.1016/s0002-9394(98)00205-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PURPOSE To determine the potential of somatic gene transfer as a technique for modulating corneal wound healing after superficial keratectomy. METHODS The transduction of human and rabbit keratocytes with beta-galactosidase and herpes simplex virus thymidine kinase genes was performed. In vitro, human and rabbit keratocytes were transduced with retroviral vectors bearing beta-galactosidase or HStk (herpes simplex virus thymidine kinase) genes. In vivo, rabbit keratocytes were transduced by topical application of vector supernatant after a superficial keratectomy. In vitro and in vivo, expression of the beta-galactosidase gene was examined with histochemical staining. In vitro, ganciclovir cytotoxicity in HStk gene-transduced keratocytes and bystander effect in co-cultures of HStk(+) and HStk(-) keratocytes were measured by determining the degree of confluency of cells in 6-well plates after 10 days of incubation. Corneal haze in rabbits was measured after transduction with Hstk and subsequent treatment with topical ganciclovir. RESULTS In vitro, both human and rabbit keratocytes were transduced successfully with both beta-galactosidase and HStk genes. Transduction efficiency was greater with human (22%) than with rabbit (16%) cells, and both HStk-transduced cell lines showed dose-dependent ganciclovir cytotoxicity and a significant bystander effect. In vivo, expression of beta-galactosidase within vimentin-positive corneal stromal cells confirmed transduction of keratocytes in the rabbit after superficial stromal keratectomy with an efficiency of 25% to 40%. Postoperative application of topical ganciclovir reduced corneal stromal haze in rabbits. CONCLUSIONS The ability to genetically transduce stromal keratocytes provides a new strategy for understanding the important cellular and molecular events that influence corneal wound healing, thus offering a potential approach to decrease or prevent corneal haze and scarring after superficial keratectomy.
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Affiliation(s)
- B Seitz
- Doheny Eye Institute and the Department of Ophthalmology, University of Southern California School of Medicine, Los Angeles 90033, USA
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