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Wang J, Liu T, Li S, He M, Wang X, Wang N, Zhang Y. Associations of static and dynamic iris parameters in healthy Chinese individuals: the Handan Eye Study. Eye (Lond) 2024:10.1038/s41433-024-03345-1. [PMID: 39294231 DOI: 10.1038/s41433-024-03345-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 08/02/2024] [Accepted: 09/12/2024] [Indexed: 09/20/2024] Open
Abstract
PURPOSE To determine the associations between the demographic factors (age and sex) and physiological dynamic iris changes and explore the associated factors for iris cross-sectional area (IA) change in healthy Chinese individuals. METHODS This cross-sectional study included individuals aged ≥40 years with an open angle and underwent anterior segment optical coherence tomography under light and dark conditions from the follow-up cohort of the Handan Eye Study. Ocular data from the right eye were analyzed. The Pearson correlation coefficient was used to assess the relationship between age and iris parameters, including iris thickness (IT), IA, and iris curvature (IC), as well as the pupil diameter (PD) in the dark, and their changes from light to dark conditions. Linear regression analysis was performed to identify the potential factors associated with IA change. RESULTS The final analysis included 465 healthy individuals. PD in dark, IA change and PD change decreased with age (P < 0.001), whereas IC increased with age (P < 0.001). IT and IT change were smaller, and IC was larger in women than that in men (P = 0.021, 0.007, and 0.010, respectively). Older age (P = 0.041), larger lens thickness (P = 0.013), larger IC change (P < 0.001), and smaller PD change (P < 0.001) were significantly associated with a smaller IA change. CONCLUSIONS Our study demonstrated the associations of static and dynamic iris parameters in healthy Chinese individuals. The findings provided a possible explanation for the higher prevalence of primary angle closure disease in elderly and female populations.
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Affiliation(s)
- Jin Wang
- Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Tongren Hospital, Capital Medical University, Beijing, China
- Beijing Institute of Ophthalmology, Beijing, China
| | - Tingting Liu
- Key Laboratory for Biomechanics and Mechanobiology of Ministry for Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Sizhen Li
- Nanjing Tongren Hospital, Jiangsu, China
| | - Mingguang He
- Experimental Ophthalmology, The Hong Kong Polytechnic University, Hong Kong, China
| | - Xiaofei Wang
- Key Laboratory for Biomechanics and Mechanobiology of Ministry for Education, Beijing Advanced Innovation Center for Biomedical Engineering, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Ningli Wang
- Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
- Beijing Institute of Ophthalmology, Beijing, China.
| | - Ye Zhang
- Beijing Tongren Eye Center, Beijing Key Laboratory of Ophthalmology and Visual Science, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
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Soh ZD, Tan M, Nongpiur ME, Yu M, Qian C, Tham YC, Koh V, Aung T, Xu X, Liu Y, Cheng CY. Deep Learning-based Quantification of Anterior Segment OCT Parameters. OPHTHALMOLOGY SCIENCE 2024; 4:100360. [PMID: 37869016 PMCID: PMC10587633 DOI: 10.1016/j.xops.2023.100360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Revised: 06/22/2023] [Accepted: 06/26/2023] [Indexed: 10/24/2023]
Abstract
Objective To develop and validate a deep learning algorithm that could automate the annotation of scleral spur (SS) and segmentation of anterior chamber (AC) structures for measurements of AC, iris, and angle width parameters in anterior segment OCT (ASOCT) scans. Design Cross-sectional study. Subjects Data from 2 population-based studies (i.e., the Singapore Chinese Eye Study and Singapore Malay Eye Study) and 1 clinical study on angle-closure disease were included in algorithm development. A separate clinical study on angle-closure disease was used for external validation. Method Image contrast of ASOCT scans were first enhanced with CycleGAN. We utilized a heat map regression approach with coarse-to-fine framework for SS annotation. Then, an ensemble network of U-Net, full resolution residual network, and full resolution U-Net was used for structure segmentation. Measurements obtained from predicted SSs and structure segmentation were measured and compared with measurements obtained from manual SS annotation and structure segmentation (i.e., ground truth). Main Outcome Measures We measured Euclidean distance and intraclass correlation coefficients (ICC) to evaluate SS annotation and Dice similarity coefficient for structure segmentation. The ICC, Bland-Altman plot, and repeatability coefficient were used to evaluate agreement and precision of measurements. Results For SS annotation, our algorithm achieved a Euclidean distance of 124.7 μm, ICC ≥ 0.95, and a 3.3% error rate. For structure segmentation, we obtained Dice similarity coefficient ≥ 0.91 for cornea, iris, and AC segmentation. For angle width measurements, ≥ 95% of data points were within the 95% limits-of-agreement in Bland-Altman plot with insignificant systematic bias (all P > 0.12). The ICC ranged from 0.71-0.87 for angle width measurements, 0.54 for IT750, 0.83-0.85 for other iris measurements, and 0.89-0.99 for AC measurements. Using the same SS coordinates from a human expert, measurements obtained from our algorithm were generally less variable than measurements obtained from a semiautomated angle assessment program. Conclusion We developed a deep learning algorithm that could automate SS annotation and structure segmentation in ASOCT scans like human experts, in both open-angle and angle-closure eyes. This algorithm reduces the time needed and subjectivity in obtaining ASOCT measurements. Financial Disclosures The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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Affiliation(s)
- Zhi Da Soh
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Mingrui Tan
- Institute of High Performance Computing, Agency for Science, Technology and Research, Singapore
| | - Monisha Esther Nongpiur
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Ophthalmology & Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
| | - Marco Yu
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Ophthalmology & Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
| | - Chaoxu Qian
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
| | - Yih Chung Tham
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Centre for Innovation and Precision Eye Health, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Victor Koh
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Centre for Innovation and Precision Eye Health, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Tin Aung
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Ophthalmology & Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
| | - Xinxing Xu
- Institute of High Performance Computing, Agency for Science, Technology and Research, Singapore
| | - Yong Liu
- Institute of High Performance Computing, Agency for Science, Technology and Research, Singapore
| | - Ching-Yu Cheng
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Ophthalmology & Visual Sciences Academic Clinical Program, Duke-NUS Medical School, Singapore
- Centre for Innovation and Precision Eye Health, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Tan RKY, Panda SK, Braeu FA, Muralidharan AR, Nongpiur ME, Chan ASY, Aung T, Najjar RP, Girard MJA. The Structural Layers of the Porcine Iris Exhibit Inherently Different Biomechanical Properties. Invest Ophthalmol Vis Sci 2023; 64:11. [PMID: 37796489 PMCID: PMC10561784 DOI: 10.1167/iovs.64.13.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Accepted: 08/09/2023] [Indexed: 10/06/2023] Open
Abstract
Purpose The purpose of this study was to isolate the structural components of the ex vivo porcine iris tissue and to determine their biomechanical properties. Methods The porcine stroma and dilator tissues were separated, and their dimensions were assessed using optical coherence tomography (OCT). The stroma underwent flow test (n = 32) to evaluate for permeability using Darcy's Law (ΔP = 2000 Pa, A = 0.0391 mm2), and both tissues underwent stress relaxation experiments (ε = 0.5 with initial ramp of δε = 0.1) to evaluate for their viscoelastic behaviours (n = 28). Viscoelasticity was characterized by the parameters β (half width of the Gaussian distribution), τm (mean relaxation time constant), E0 (instantaneous modulus), and E∞ (equilibrium modulus). Results For the stroma, the hydraulic permeability was 9.49 ± 3.05 × 10-6 mm2/Pa · s, and the viscoelastic parameters were β = 2.50 ± 1.40, and τm = 7.43 ± 4.96 s, with the 2 moduli calculated to be E0 = 14.14 ± 6.44 kPa and E∞ = 6.08 ± 2.74 kPa. For the dilator tissue, the viscoelastic parameters were β = 2.06 ± 1.33 and τm = 1.28 ± 1.27 seconds, with the 2 moduli calculated to be E0 = 9.16 ± 3.03 kPa and E∞ = 5.54 ± 1.98 kPa. Conclusions We have established a new protocol to evaluate the biomechanical properties of the structural layers of the iris. Overall, the stroma was permeable and exhibited smaller moduli than those of the dilator muscle. An improved characterization of iris biomechanics may form the basis to further our understanding of angle closure glaucoma.
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Affiliation(s)
- Royston K. Y. Tan
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
| | - Satish K. Panda
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Department of Mechanical Engineering, Indian Institute of Technology, Bhubaneswar, India
| | - Fabian A. Braeu
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
- Critical Analytics for Manufacturing Personalized-Medicine, Singapore-MIT Alliance for Research and Technology, Singapore
| | - Arumugam R. Muralidharan
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
| | - Monisha E. Nongpiur
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
| | - Anita S. Y. Chan
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
| | - Tin Aung
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore
| | - Raymond P. Najjar
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore
- Centre for Innovation & Precision Eye Health, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Michaël J. A. Girard
- Ophthalmic Engineering & Innovation Laboratory, Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore
- Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland
- Department of Biomedical Engineering, NUS College of Design and Engineering, National University of Singapore, Singapore
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Analysis of color vision and cognitive function in first-episode schizophrenia before and after antipsychotic treatment. J Psychiatr Res 2022; 152:278-288. [PMID: 35759980 DOI: 10.1016/j.jpsychires.2022.06.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 05/31/2022] [Accepted: 06/07/2022] [Indexed: 11/20/2022]
Abstract
BACKGROUND A large body of recent research has demonstrated that patients with schizophrenia exhibit significant changes in visual function and ocular tissue structure in the early stages of onset. It is therefore possible to explore a novel scientific breakthrough in the etiology of schizophrenia by transforming the traditional study of brain structure and function with a view to examining the potential field of eye tissue and function. However, few studies have investigated the correlation between iris characteristics and schizophrenia, and evidence is lacking in this regard. Thus, further exploration is needed. PURPOSE This study was designed to analyze the characteristics of iris structure, color vision function and cognitive function, as well as the changes therein in patients with the first-episode drug-free schizophrenia before and after antipsychotic treatment. It aimed to preliminarily identify easily-measurable biomarkers for early clinical screening and diagnosis of schizophrenia. METHODS This study recruited 61 patients (22 males) with first-episode schizophrenia. Prior to the commencement of treatment with antipsychotic drugs, the Montreal Cognitive Assessment (MoCA) and Farnsworth-Munsell Dichotomous (D-15 Hue Test) were used as assessment tools to evaluate cognitive function and color vision function, respectively. Over a 6-week period, patients received a second-generation antipsychotic treatment (all converted to olanzapine equivalent dose) as prescribed by the doctor, and the Positive and Negative Syndrome Scale (PANSS) was applied to evaluate the clinical treatment effects before treatment (baseline), as well as at the 2nd, 4th, and 6th weeks after drug treatment. On the basis of iris characteristics, the patients were divided into groups. The observed differences in drug treatment effects between the groups were then compared and analyzed to further clarify the relationship between treatment efficacy and iris characteristics. Finally, changes in the cognitive function and color vision function of patients at baseline and at the 6th week after drug treatment were compared, and the effects of antipsychotic drug treatment on the above-mentioned functions were analyzed. RESULTS On the basis of structural iris characteristics, 61 patients were classified as follows: 28 patients without iris crypts and 33 with iris crypts; 35 without iris pigment dots and 26 with iris pigment dots; 42 without iris wrinkles and 19 with iris wrinkles. No significant difference was observed in the PANSS scores of all of the patients at baseline; however, significant differences were found in patients with iris crypts and iris pigment dots at each follow-up timepoint (i.e., at the 2nd, 4th, and 6th week). Moreover, it is noteworthy that, compared with other patients, the PANSS scores of patients without specific iris structure characteristics (iris crypts and pigment dots) decreased significantly (P<0.05), which indicated that the drug therapy was highly effective. Excluding the interference of drug factors, a significant correlation was found between the results of the D-15 (color vision function) and MoCA (cognitive function) in first-episode untreated patients (r = -0.401, P < 0.05). In addition, the MoCA scores (mean difference = 2.36, t = 10.05, P ˂ 0.01) were significantly higher after 6 weeks of antipsychotic drug treatment compared to conditions at baseline. CONCLUSIONS The findings of this study demonstrated that color vision function of patients with schizophrenia improved with the improvement of cognitive function. The structural characteristics of the iris with crypts and pigment dots could have a significant impact on the drug treatment effect of schizophrenia and could be considered as a potential biomarker for detecting and recognizing schizophrenia.
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Meng J, Han X, Wang W, Gong X, Li W, Xiong K, Li Y, Zhang X, Liang X, Huang J, Huang W. Analysis of Iris volume using swept-source optical coherence tomography in patients with type 2 diabetes mellitus. Acta Ophthalmol 2022; 100:e553-e559. [PMID: 34137171 DOI: 10.1111/aos.14931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 02/22/2021] [Accepted: 05/20/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE To evaluate iris volume before and after pupil dilation using swept-source anterior segment optical coherence tomography (SS-ASOCT) and investigate the associated factors of iris volume and iris volume change after pupil dilation in patients with type 2 diabetes mellitus (T2DM). METHODS A cross-sectional study was conducted in Zhongshan Ophthalmic Center among T2DM registered patients in the community of Guangzhou, China. Anterior chamber volume (ACV), iris volume, anterior chamber depth (ACD), angle opening distance at 500 μm (AOD 500) and pupil diameter were estimated using SS-ASOCT (CASIA; Tomey, Nagoya, Japan). Venous blood was taken for the measurement of glycosylated haemoglobin A1c (HbAlc). All biometric measurements were performed before and after pharmacologic pupil dilation. RESULTS A total of 117 subjects were included in the analysis. The mean age (±SD) was 64.96 ± 7.75 years, and 62.4% were females. After pupil dilation, iris volume decreased in all eyes. Shorter duration of diabetes (p = 0.035), longer axial length (p < 0.001) and smaller pupil diameter (p < 0.001) were associated with larger iris volume. The change in iris volume per millimetre change in pupil diameter was 1.35mm3 /mm. Smaller baseline iris volume (p = 0.002) and higher HbA1c level (p = 0.010) were associated with smaller change in iris volume per millimetre change in pupil diameter, after adjusting for other factors. CONCLUSION Iris volume can be estimated by SS-ASOCT. Diabetic duration was associated with static anatomy of iris volume, while HbA1c level indicated the dynamic response of iris volume. It is likely that diabetic duration and HbA1c level could affect the macroscopic and microscopic composition of the iris in the diabetic population.
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Affiliation(s)
- Jie Meng
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Xiao Han
- Seventh Affiliated Hospital Sun Yat‐sen University Shenzhen China
| | - Wei Wang
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Xia Gong
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Wangting Li
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Kun Xiong
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Yuting Li
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Xiulan Zhang
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Xiaoling Liang
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Jingjing Huang
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
| | - Wenyong Huang
- State Key Laboratory of Ophthalmology Zhongshan Ophthalmic Center Sun Yat‐sen University Guangzhou China
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Association between Iris Biological Features and Corneal Biomechanics in Myopic Eyes. DISEASE MARKERS 2021; 2021:5866267. [PMID: 34840631 PMCID: PMC8616650 DOI: 10.1155/2021/5866267] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 11/05/2021] [Indexed: 01/16/2023]
Abstract
Purpose Iris biological features such as surface features and profile characteristics reflected the development of iris stroma and microvessels. Iris vessels and microcirculation are still lack of effective detection methods, and we can directly observe only the iris surface biological characteristics. This cross-sectional study evaluated the association between iris surface biological features and corneal biomechanics in young adults with myopia. Methods We recruited 152 patients with myopia aged ≥18 years, from the Eye Hospital of Wenzhou Medical University, who had complete Corneal Visualization Scheimpflug Technology (Corvis ST) data and graded iris surface features. Iris surface features included crypts, furrows, and color measured from digital slit lamp images. The biomechanical properties of the cornea were assessed using Corvis ST. Only 1 eye of each participant was randomly selected for analysis. Associations between the iris surface features and corneal biomechanics were analyzed using linear regression models. The grade of iris crypts, furrows, and color and corneal biomechanical parameters measured with Corvis ST was the main outcome measures. Results The iris crypts were significantly associated with deflection amplitude at the first applanation (A1 DLA, β = 0.001, P = 0.013), A1 delta arc length (A1 dArcL) (β = −0.001, P = 0.01), maximum delta arc length (dArcLM) (β = −0.004, P = 0.03), and stiffness at the first applanation (SP-A1) (β = −2.092, P = 0.016). The iris furrows were only associated with integrated radius (β = −0.212, P = 0.025). Iris color was found not related with corneal biomechanical parameters measured via Corvis ST. Conclusions Iris surface features were associated with corneal biomechanical properties in myopic eyes; more iris crypts were associated with lower corneal stiffness while more extensive furrows were related with higher corneal stiffness. Iris crypts and furrows may provide useful information on corneal biomechanical properties in myopic eyes.
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Panda SK, Tan RKY, Tun TA, Buist ML, Nongpiur M, Baskaran M, Aung T, Girard MJA. Changes in Iris Stiffness and Permeability in Primary Angle Closure Glaucoma. Invest Ophthalmol Vis Sci 2021; 62:29. [PMID: 34714323 PMCID: PMC8558521 DOI: 10.1167/iovs.62.13.29] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Purpose To evaluate the biomechanical properties of the iris by evaluating iris movement during pupil constriction and to compare such properties between healthy and primary angle-closure glaucoma (PACG) subjects. Methods A total of 140 subjects were recruited for this study. In a dark room, the anterior segments of one eye per subject were scanned using anterior segment optical coherence tomography imaging during induced pupil constriction with an external white light source of 1700 lux. Using a custom segmentation code, we automatically isolated the iris segments from the AS-OCT images, which were then discretized and transformed into a three-dimensional point cloud. For each iris, a finite element (FE) mesh was constructed from the point cloud, and an inverse FE simulation was performed to match the clinically observed iris constriction in the AS-OCT images. Through this optimization process, we were able to identify the elastic modulus and permeability of each iris. Results For all 140 subjects (95 healthy and 45 PACG of Indian/Chinese ethnicity; age 60.2 ± 8.7 for PACG subjects and 57.7 ± 10.1 for healthy subjects), the simulated deformation pattern of the iris during pupil constriction matched well with OCT images. We found that the iris stiffness was higher in PACG than in healthy controls (24.5 ± 8.4 kPa vs. 17.1 ± 6.6 kPa with 40 kPa of active stress specified in the sphincter region; P < 0.001), whereas iris permeability was lower (0.41 ± 0.2 mm2/kPa s vs. 0.55 ± 0.2 mm2/kPa s; p = 0.142). Conclusions This study suggests that the biomechanical properties of the iris in PACG are different from those in healthy controls. An improved understanding of the biomechanical behavior of the iris may have implications for the understanding and management of angle-closure glaucoma.
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Affiliation(s)
- Satish K Panda
- Ophthalmic Engineering & Innovation Laboratory (OEIL), Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.,Department of Biomedical Engineering, National University of Singapore, Singapore
| | - Royston K Y Tan
- Ophthalmic Engineering & Innovation Laboratory (OEIL), Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.,Department of Biomedical Engineering, National University of Singapore, Singapore
| | - Tin A Tun
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
| | - Martin L Buist
- Department of Biomedical Engineering, National University of Singapore, Singapore
| | - Monisha Nongpiur
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
| | - Mani Baskaran
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.,Sankara Nethralaya, Chennai, India
| | - Tin Aung
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.,Duke-NUS Medical School, Singapore.,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Michaël J A Girard
- Ophthalmic Engineering & Innovation Laboratory (OEIL), Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.,Duke-NUS Medical School, Singapore.,Institute of Molecular & Clinical Ophthalmology, Basel, Switzerland
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Tun TA, Sawicki A, Wilkos-Kuc A, Aung T, Zarnowski T. Circumferential Assessment of Changes in Anterior Segment Characteristics and Baseline Predictors of Angle Widening After Laser Iridotomy in Caucasian Eyes. J Glaucoma 2021; 30:839-845. [PMID: 33927153 DOI: 10.1097/ijg.0000000000001866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Accepted: 03/28/2021] [Indexed: 11/26/2022]
Abstract
PRCIS Laser peripheral iridotomy (LPI) widened the iridocorneal angle and flattened the iris circumferentially in Caucasian eyes and baseline refractive error, lens vault, and iris volume play a significant role in the angle widening. PURPOSE The purpose of this study was to investigate circumferential angle widening and iris changes after LPI using swept-source optical coherence tomography (SS-OCT) in Caucasian eyes with the use of novel anterior segment parameters. MATERIALS AND METHODS A total of 130 eyes (68 primary angle-closure suspect, 34 primary angle closure, and 28 primary angle-closure glaucoma eyes) of 66 subjects underwent 360-degree SS-OCT (SS-1000 CASIA) angle imaging and gonioscopy in the dark before and 7, 30, 90 days after LPI. For each eye, 16 frames (11.25 degree apart) were selected for analysis from 128 cross-sectional images, and novel 2-dimensional and 3-dimensional anterior segment parameters namely angle opening distance area (AODA) and the trabecular-iris space volume (TISV) 750 µm from the scleral spur, as well as iris parameters such as iris thickness (IT750 and IT2000), iris curvature, and iris curvature area were measured for each image. RESULTS AODA and TISV were significantly increased and the iris curvature and iris curvature area were significantly decreased at days 7, 30, and 90 after LPI when compared with their baseline (all P<0.001) but there was no significant change in the IT750 and IT2000 (all P>0.05). The multivariable linear regression model showed a significant association of ΔAODA with refractive error (β=-0.23, P=0.013), lens vault (β=2.8, P=0.007), and iris volume (β=-0.11, P=0.027) after adjusting for age and sex. CONCLUSIONS LPI widened the iridocorneal angle and flattened the iris circumferentially in Caucasian eyes in this study. Baseline refractive error, lens vault, and iris volume play a significant role in the circumferential angle widening by LPI.
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Affiliation(s)
- Tin A Tun
- Singapore Eye Research Institute and Singapore National Eye Centre
| | - Andrzej Sawicki
- Department of Diagnostics and Microsurgery of Glaucoma, Medical University of Lublin, Lublin, Poland
| | - Agnieszka Wilkos-Kuc
- Department of Diagnostics and Microsurgery of Glaucoma, Medical University of Lublin, Lublin, Poland
| | - Tin Aung
- Singapore Eye Research Institute and Singapore National Eye Centre
- Duke-NUS Medical School
- Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Tomasz Zarnowski
- Department of Diagnostics and Microsurgery of Glaucoma, Medical University of Lublin, Lublin, Poland
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Measurement of Iris Thickness at Different Regions in Healthy Chinese Adults. J Ophthalmol 2021; 2021:2653564. [PMID: 34055394 PMCID: PMC8131156 DOI: 10.1155/2021/2653564] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 04/28/2021] [Indexed: 11/17/2022] Open
Abstract
Purpose To study the variation of iris thicknesses in different regions and explore the possible correlations with age and gender. Methods Healthy Chinese adults were recruited; the anterior segment of their eyes was imaged by swept-source optical coherence tomography (SS-OCT). The horizontal scan of the right eye was selected, and the thicknesses of both the nasal and temporal irises were measured at 199 evenly spaced points. Results A total of 233 subjects with an average age of 36.79 ± 10.04 years (range 19 to 62) were included in the final analysis. The mean iris thicknesses of the temporal and nasal sides were 364.79 ± 47.58 μm and 372.44 ± 43.75 μm, respectively. The mean nasal iris thickness was positively correlated with age (β = 0.9 μm/year; P = 0.002), but the temporal one was not (β = 0.077 μm/year; P = 0.806). At 139 points of the nasal iris and 146 points of the temporal iris, the iris thickness was significantly correlated with age (P < 0.05). The thicknesses of the peripheral and pupillary parts were positively correlated with age, while the middle part was negatively correlated with age. No significant difference was observed in the mean iris thickness between genders (temporal: t = 1.597, P = 0.112; nasal: t = 1.870, P = 0.063), but females had a thicker iris than males at 50 points in the temporal side and 49 points in the nasal side (P < 0.05); no point in males was observed to have thicker iris compared to females. Conclusion Using SS-OCT and the novel method, thicknesses of the iris at different regions were measured. The thicknesses of the peripheral and pupillary irises increase with age, while the thicknesses of the middle part decrease.
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Lu Q, He W, Lu Y, Zhu X. Morphological features of anterior segment: factors influencing intraocular pressure after cataract surgery in nanophthalmos. EYE AND VISION 2020; 7:47. [PMID: 32974413 PMCID: PMC7495875 DOI: 10.1186/s40662-020-00212-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 08/19/2020] [Indexed: 11/30/2022]
Abstract
Purpose To investigate the anterior segment in nanophthalmic eyes and their association with intraocular pressure after cataract surgery. Methods Thirty-two nanophthalmic eyes (axial length [AL] < 18.5 mm) in 18 patients and 35 normal eyes (21 ≤ AL ≤ 24.5 mm) in 35 controls who had undergone uneventful cataract surgery were included. Swept-source optical coherence tomography was used to compare the anterior segment structures between the two groups. The associations between the anterior segment characteristics of nanophthalmic eyes and postoperative intraocular pressure (IOP) were also investigated. Results The IOP-lowering effect of cataract surgery was remarkably insufficient in nanophthalmic eyes. Peripheral anterior synechiae (PAS) were observed in 56% (18/32) of nanophthalmic eyes, and a characteristic boomerang-shaped iris was observed in 28% (9/32). The anterior surface of the iris seemed “smoother” in nanophthalmic eyes than in normal eyes. Schlemm’s canal (SC) diameter, SC area, trabecular meshwork (TM) thickness, TM width, and TM area were generally smaller in the nanophthalmic eyes. Younger age, higher preoperative IOP, broader PAS, and smaller SC area were main contributors to higher postoperative IOP. AL and SC diameter may also be of great importance in IOP prediction in patients without glaucoma surgery and PAS. Conclusions The morphological features of the anterior segment in nanophthalmic eyes are significantly different from those of normal eyes. Influencing factors such as age, AL, preoperative IOP, extent of PAS, SC and TM size could all be prognostic for IOP after cataract surgery in nanophthalmic eyes. Trial registration ClinicalTrails.gov, Trial registration number: NCT02182921, Registered 8 July 2014.
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Affiliation(s)
- Qiang Lu
- Department of Ophthalmology, Eye and Ear, Nose, and Throat Hospital, Fudan University, 83 Fenyang Road, Shanghai, 200031 People's Republic of China.,Eye Institute, Eye and Ear, Nose, and Throat Hospital of Fudan University, Shanghai, 200031 People's Republic of China.,Key Laboratory of Myopia, Ministry of Health, Shanghai, 200031 People's Republic of China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, 200031 People's Republic of China
| | - Wenwen He
- Department of Ophthalmology, Eye and Ear, Nose, and Throat Hospital, Fudan University, 83 Fenyang Road, Shanghai, 200031 People's Republic of China.,Eye Institute, Eye and Ear, Nose, and Throat Hospital of Fudan University, Shanghai, 200031 People's Republic of China.,Key Laboratory of Myopia, Ministry of Health, Shanghai, 200031 People's Republic of China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, 200031 People's Republic of China
| | - Yi Lu
- Department of Ophthalmology, Eye and Ear, Nose, and Throat Hospital, Fudan University, 83 Fenyang Road, Shanghai, 200031 People's Republic of China.,Eye Institute, Eye and Ear, Nose, and Throat Hospital of Fudan University, Shanghai, 200031 People's Republic of China.,Key Laboratory of Myopia, Ministry of Health, Shanghai, 200031 People's Republic of China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, 200031 People's Republic of China
| | - Xiangjia Zhu
- Department of Ophthalmology, Eye and Ear, Nose, and Throat Hospital, Fudan University, 83 Fenyang Road, Shanghai, 200031 People's Republic of China.,Eye Institute, Eye and Ear, Nose, and Throat Hospital of Fudan University, Shanghai, 200031 People's Republic of China.,Key Laboratory of Myopia, Ministry of Health, Shanghai, 200031 People's Republic of China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, 200031 People's Republic of China
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11
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Voronin GV, Petrov SY, Volzhanin AV, El-Sangahawi AA, Avetisov KS. [Iris shape change and risk of anterior chamber angle closure]. Vestn Oftalmol 2020; 136:93-98. [PMID: 32366076 DOI: 10.17116/oftalma202013602193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Potential obstruction of the anterior chamber angle by iris root is a key factor of the pathogenesis of angle-closure glaucoma. Development and adoption of ultrasound biomicroscopy and optical coherence tomography in clinical practice have significantly expanded the capabilities of studying the structures of the anterior eye segment in terms of angle closure risk factors through improving visualization depth and quality of examination, including different variants of iris structure and potential changes of its shape in mydriasis. The article reviews various studies dedicated to the progression of primary angle-closure glaucoma and its dependence on the biometric parameters of the eye and changes in pupil size.
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Affiliation(s)
- G V Voronin
- I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia.,Research Institute of Eye Diseases, Moscow, Russia
| | - S Yu Petrov
- Research Institute of Eye Diseases, Moscow, Russia
| | | | - A A El-Sangahawi
- I.M. Sechenov First Moscow State Medical University (Sechenov University), Moscow, Russia
| | - K S Avetisov
- Research Institute of Eye Diseases, Moscow, Russia
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12
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Soh ZD, Thakur S, Majithia S, Nongpiur ME, Cheng CY. Iris and its relevance to angle closure disease: a review. Br J Ophthalmol 2020; 105:3-8. [PMID: 32193222 DOI: 10.1136/bjophthalmol-2020-316075] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 03/04/2020] [Indexed: 12/18/2022]
Abstract
Glaucoma is a leading cause of irreversible visual impairment, and primary angle closure glaucoma (PACG) affects Asians disproportionately. Whereas advances in ocular imaging have identified several anatomical risk factors, our ability to predict PACG still requires considerable improvement. The iris plays a crucial role in the pathophysiology of angle closure disease, either through a mechanical or vascular mechanism. Irises of closed-angle eyes inhibit vastly different structural constituents as compared with those of open-angle eyes, thereby effecting variations in biomechanical properties and iris fluid conductivity. The clinical consequences include a smaller change in iris volume on pupil dilation in closed-angle eyes, thereby bringing the iris and trabecular meshwork closer in apposition. In this review, we summarise the potential role of the iris in the pathogenesis of angle closure disease.
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Affiliation(s)
- Zhi Da Soh
- Ocular Epidemiology Research Group, Singapore Eye Research Institute, Singapore
| | - Sahil Thakur
- Ocular Epidemiology Research Group, Singapore Eye Research Institute, Singapore
| | - Shivani Majithia
- Ocular Epidemiology Research Group, Singapore Eye Research Institute, Singapore
| | - Monisha Esther Nongpiur
- Glaucoma, Singapore Eye Research Institute, Singapore.,Ophthalmology & Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore
| | - Ching-Yu Cheng
- Ocular Epidemiology Research Group, Singapore Eye Research Institute, Singapore .,Ophthalmology & Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore.,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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13
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Birla S, Gupta D, Somarajan BI, Gupta S, Chaurasia AK, Kishan A, Gupta V. Classifying juvenile onset primary open angle glaucoma using cluster analysis. Br J Ophthalmol 2019; 104:827-835. [DOI: 10.1136/bjophthalmol-2019-314660] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 08/24/2019] [Accepted: 09/09/2019] [Indexed: 12/24/2022]
Abstract
AimTo classify unrelated patients with juvenile onset primary open angle glaucoma (JOAG) into clinically useful phenotypes using cluster analysis.MethodsOut of the 527 unrelated patients with JOAG, the study included 414 patients who had all the phenotypic characteristics required for the study. A cluster analysis was performed to classify the patients based on their iris and angle morphology, age of onset, highest untreated intraocular pressure (IOP), worst mean deviation and greatest vertical cup disc ratio of the worst eye. The iris features were broadly classified into three groups: those with normal iris crypts (NIC), those with prominent iris crypts (PIC) and those with absence of iris crypts. The gonio photographs were graded as normal appearing angle or those with angle dysgenesis in the form of a featureless angle, one with a high iris insertion and an angle with prominent iris processes. Using a hierarchical clustering model and a two-way cluster analysis, the distribution of clusters of JOAG was analysed to obtain a classification of JOAG subtypes.ResultsThe four major clusters identified were: Cluster 1 with NIC and normal angles had the lowest untreated IOP and higher age of onset among all clusters. Cluster 2 with NIC and featureless angle was found to be associated with earliest age of onset. Cluster 3 had NIC and either a high iris insertion or prominent iris processes. Cluster 4 was a heterogeneous cluster with maximum number of patients in a group comprising of those with PIC and high iris insertion.ConclusionsCluster analysis extracted four subgroups of the JOAG phenotype that have clinical and prognostic significance and can potentially be helpful while evaluating these patients in the clinics.
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14
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Wang Q, Perez CI, Masis M, Feinstein M, Mora M, Lin SC, Hsia YC. Post-phacoemulsification iris changes in eyes with glaucoma or glaucoma suspect status. PLoS One 2018; 13:e0208776. [PMID: 30543659 PMCID: PMC6292659 DOI: 10.1371/journal.pone.0208776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2018] [Accepted: 11/21/2018] [Indexed: 12/29/2022] Open
Abstract
Purpose This prospective study used anterior segment optical coherence tomography (AS-OCT) to determine how phacoemulsification (phaco) changes iris parameters in eyes with glaucoma or glaucoma suspect status. Methods Using Visante AS-OCT (Carl Zeiss Meditec AG), the following pre- and post-phaco parameters were measured: IT750 = iris thickness at 750 μm from the scleral spur; IT2000 = iris thickness 2000 μm from the scleral spur; ITCM = the maximum iris thickness at the middle one third of the iris; ICURV = iris curvature; IAREA = iris area; and pupil size = pupil diameter (mm). Only high-quality images with an identifiable scleral spur were included, and only the nasal quadrant was analyzed. A single glaucoma specialist analyzed the parameters according to the Zhongshan Angle Assessment Program (ZAAP, Guangzhou, China). Multivariate analysis was performed using mixed effects regression correcting for age, gender, and ethnicity. Results 89 subjects and 110 eyes were included in this study. The mean age of subjects was 74.83 {+/-} 8.69 years old. Most common diagnoses were POAG and glaucoma suspect (23% and 52%, respectively), and 16% of subjects had an LPI. In multivariate analysis of AS-OCT parameters, decreases in IT750, IT2000, ITCM, ICURV, and pupil size were statistically significant (p<0.05). Conclusions After phacoemulsification, eyes with glaucoma as well as glaucoma suspect eyes have thinner irises and smaller pupils. This may lead to less iris-mediated aqueous outflow obstruction, providing support for early phacoemulsification glaucoma treatment. Translational relevance Our AS-OCT imaging findings may guide clinical practice as iris parameters become increasingly relevant in preoperative phaco planning.
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Affiliation(s)
- Qinyun Wang
- University of California at San Francisco, Department of Ophthalmology, San Francisco, California, United States of America
- * E-mail:
| | - Claudio I. Perez
- University of California at San Francisco, Department of Ophthalmology, San Francisco, California, United States of America
- Fundación Oftalmológica los Andes, Universidad los Andes, Santiago, Chile
| | - Marissé Masis
- University of California at San Francisco, Department of Ophthalmology, San Francisco, California, United States of America
| | - Max Feinstein
- University of California at San Francisco, Department of Ophthalmology, San Francisco, California, United States of America
| | - Marta Mora
- University of California at San Francisco, Department of Ophthalmology, San Francisco, California, United States of America
| | - Shan C. Lin
- University of California at San Francisco, Department of Ophthalmology, San Francisco, California, United States of America
| | - Yen C. Hsia
- University of California at San Francisco, Department of Ophthalmology, San Francisco, California, United States of America
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15
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Chua J, Thakku SG, Pham TH, Lee R, Tun TA, Nongpiur ME, Tan MCL, Wong TY, Quah JHM, Aung T, Girard MJA, Cheng CY. Automated Detection of Iris Furrows and their Influence on Dynamic Iris Volume Change. Sci Rep 2017; 7:17894. [PMID: 29263345 PMCID: PMC5738384 DOI: 10.1038/s41598-017-18039-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 12/05/2017] [Indexed: 11/09/2022] Open
Abstract
We introduced a new method for detecting iris surface furrows and identify its associations with dynamic changes in iris volume in healthy eyes. Swept-source optical coherence tomography was performed on 65 subjects with open angle under light and dark conditions. Iris boundaries were identified and a reconstruction of the anterior iris surface was obtained. Furrows were detected by identifying locally deep (minima) points on the iris surface and reported as furrow length in millimetres. Iris volume was quantified. Associations between furrow length and dynamic changes in iris volume were assessed using linear regression model. With pupil dilation, furrow length increased (15.84 mm) whereas iris volume decreased (−1.19 ± 0.66 mm3). Longer furrow length was associated with larger static iris volume, as well as smaller loss of iris volume with pupil dilation (β = −0.10, representing 0.1 mm3 less loss in iris volume per 10 mm increase in iris furrow length; P = 0.002, adjusted for age, gender and changes in pupil size). Our iris furrow length measurements are robust and intuitive. Eyes with longer furrows have larger iris volume and lose less volume during physiological pupil dilation. These findings highlight the potential for iris surface features as indicators of iris morphological behavior.
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Affiliation(s)
- Jacqueline Chua
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,Ophthalmology & Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore, Singapore
| | - Sri Gowtham Thakku
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore
| | - Tan Hung Pham
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore
| | - Ryan Lee
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore
| | - Tin A Tun
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore
| | - Monisha E Nongpiur
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,Ophthalmology & Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore, Singapore
| | - Marcus Chiang Lee Tan
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore
| | - Tien Yin Wong
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,Ophthalmology & Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore, Singapore.,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore
| | | | - Tin Aung
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,Ophthalmology & Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore, Singapore.,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore
| | - Michael J A Girard
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore.,Department of Biomedical Engineering, National University of Singapore, Singapore, Singapore
| | - Ching-Yu Cheng
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore. .,Ophthalmology & Visual Sciences Academic Clinical Program (Eye ACP), Duke-NUS Medical School, Singapore, Singapore. .,Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore and National University Health System, Singapore, Singapore.
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16
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Koh V, Chua J, Shi Y, Thakku SG, Lee R, Nongpiur ME, Baskaran M, Kumar RS, Perera S, Aung T, Cheng CY. Association of iris crypts with acute primary angle closure. Br J Ophthalmol 2017; 101:1318-1322. [DOI: 10.1136/bjophthalmol-2016-309842] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 01/16/2017] [Accepted: 01/30/2017] [Indexed: 11/03/2022]
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