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15 pages, 4029 KB

Open AccessArticle

Diurnal Variations in Anterior and Posterior Corneal Thickness and Curvature in Healthy Eyes: Global and Sector-Based Metrics and Lifestyle Associations

by Laura Barberán-Bernardos, Miguel Angel Ariza-Gracia, Philippe Büchler and David P. Piñero

Life 2026, 16(5), 711; https://doi.org/10.3390/life16050711 - 22 Apr 2026

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Abstract

This study aims to characterize diurnal changes in corneal geometry of the anterior and posterior cornea in healthy eyes using global and sector-based metrics, and to explore their associations with lifestyle-related factors. A prospective observational study of 109 eyes was conducted, measuring intraocular [...] Read more.

This study aims to characterize diurnal changes in corneal geometry of the anterior and posterior cornea in healthy eyes using global and sector-based metrics, and to explore their associations with lifestyle-related factors. A prospective observational study of 109 eyes was conducted, measuring intraocular pressure (IOP), corneal thickness, volume, and global/sector-based keratometry at five time points over a 10 h period, alongside a lifestyle questionnaire. Results revealed significant diurnal decreases in IOP, central and minimum corneal thickness, and corneal volume (p ≤ 0.031). While posterior keratometry remained stable, anterior keratometry showed statistically significant but clinically negligible changes (amplitude of change ≤ 0.29 D), primarily within the central 4 mm and inferotemporal regions. Weak to moderate positive correlations were found between water and coffee intake, smoking, and changes in corneal thickness and volume, with no relevant effects on keratometric parameters. Overall, corneal thickness and volume exhibit significant diurnal reductions, whereas anterior keratometric changes are minimal and clinically irrelevant globally. These findings underscore the importance of considering the time of day when interpreting corneal measurements, as lifestyle factors appear to modulate corneal thickness but not curvature in healthy eyes. Full article

(This article belongs to the Special Issue Vision Science and Optometry: 2nd Edition)

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13 pages, 592 KB

Open AccessArticle

Agreement Between Non-Cycloplegic Photorefraction and Retinoscopy in Pediatric Refraction

by Ana Roque, Amélia Fernandes Nunes, Henrique Nascimento, NIAOO Group and Clara Martinez-Perez

Life 2026, 16(4), 678; https://doi.org/10.3390/life16040678 - 16 Apr 2026

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Abstract

Accurate assessment of refractive error in children is essential for clinical decision-making, yet agreement between non-cycloplegic techniques remains uncertain, particularly due to differences in accommodative demand. This study evaluated the agreement between static retinoscopy and handheld photorefraction for measuring spherical power, cylindrical power, [...] Read more.

Accurate assessment of refractive error in children is essential for clinical decision-making, yet agreement between non-cycloplegic techniques remains uncertain, particularly due to differences in accommodative demand. This study evaluated the agreement between static retinoscopy and handheld photorefraction for measuring spherical power, cylindrical power, and spherical equivalent in children aged 4–16 years and assessed whether agreement varied by refractive status. In this cross-sectional observational study, 193 children underwent objective refraction during a single visit using non-cycloplegic static retinoscopy (distance fixation) and handheld infrared photorefraction (~1 m fixation). Inter-method differences were analyzed using Bland–Altman plots, intraclass correlation coefficients (ICCs), mean absolute error (MAE), and non-parametric tests. Photorefraction showed a statistically significant myopic shift compared with retinoscopy for spherical power (−0.16 D), cylindrical power (−0.24 D), and spherical equivalent (−0.28 D). Agreement was moderate in statistical terms for spherical equivalent (ICC = 0.73) and spherical power (0.71), and lower for cylindrical power (0.46); however, wide limits of agreement indicate clinically relevant variability. MAE for spherical equivalent was 0.80 D overall, with 45.1% of measurements within ±0.50 D, and varied by refractive status, being lowest in emmetropic eyes and higher in hyperopic and myopic eyes. These findings indicate that, under non-cycloplegic conditions, photorefraction shows modest mean differences but substantial individual variability, likely influenced by differences in accommodative demand between techniques. While suitable for pediatric vision screening, photorefraction should not be considered interchangeable with retinoscopy for individual refractive assessment. Full article

(This article belongs to the Special Issue Vision Science and Optometry: 2nd Edition)

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15 pages, 1771 KB

Open AccessArticle

Deep Learning-Based Generation of Retinal Nerve Fibre Layer Thickness Maps from Fundus Photographs: A Comparative Analysis of U-Net Architectures for Accessible Glaucoma Assessment

by Kyoung Ohn, Harin Jun, Yong-Sik Kim and Woong-Joo Whang

Life 2026, 16(4), 559; https://doi.org/10.3390/life16040559 - 29 Mar 2026

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Abstract

Introduction: Optical coherence tomography (OCT) is the gold standard for retinal nerve fibre layer (RNFL) assessment; its high cost and limited accessibility hinder widespread use. This study aims to develop deep learning models that generate RNFL thickness maps from fundus images, providing a [...] Read more.

Introduction: Optical coherence tomography (OCT) is the gold standard for retinal nerve fibre layer (RNFL) assessment; its high cost and limited accessibility hinder widespread use. This study aims to develop deep learning models that generate RNFL thickness maps from fundus images, providing a cost-effective alternative to OCT. Methods: A dataset of 5000 fundus-OCT image pairs from 5000 unique glaucoma patients was used to train and compare the following four U-Net-based deep learning models: ResU-Net, R2U-Net, Nested U-Net, and Dense U-Net. All models were trained for up to 1000 epochs with early stopping (patience = 50 epochs). Performance was evaluated using Mean Squared Error (MSE), Mean Absolute Error (MAE), Peak Signal-to-Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM), and Fréchet Inception Distance (FID). Results: ResU-Net demonstrated the best performance, achieving MSE = 0.00061, MAE = 0.01877, SSIM = 0.9163, PSNR = 32.19 dB, and FID = 30.08. These results represent a 108% improvement in SSIM and a 67% improvement in PSNR compared to previously published benchmark for this task. Conclusions: This study demonstrates that deep learning models, particularly ResU-Net, can generate high-fidelity RNFL thickness maps from fundus photographs, substantially outperforming prior published benchmarks. This approach represents a potential contribution toward accessible glaucoma assessment, contingent upon prospective clinical validation and regulatory evaluation. Full article

(This article belongs to the Special Issue Vision Science and Optometry: 2nd Edition)

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18 pages, 5551 KB

Open AccessArticle

Isolation and Characterization of Integrin α9 Positive Extracellular Vesicles Derived from Human Corneoscleral Rings

by Hung-Yin Lai, Ming-Chieh Hsieh, Hao-Hsiang Wu, Chien-Wei Lee, Shih-Hua Liu, Hsing-Yu Lin, Yi-Wen Chen, Chun-Chi Chiang, Yi-Ching Hsieh, Ying-Hsuen Wu, You-Ling Li, Hsiao-Fan Tung, Jennifer Hui-Chun Ho and Yi-Yu Tsai

Life 2025, 15(11), 1780; https://doi.org/10.3390/life15111780 - 20 Nov 2025

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Abstract

Corneoscleral-ring-derived extracellular vesicles represent a potential therapeutic strategy for promoting in vitro corneal wound healing. In this study, we successfully isolated and characterized extracellular vesicles from human corneolimbal tissue obtained from 42 donors, with a mean age of 51.62 ± 15.56 years. Donor-related [...] Read more.

Corneoscleral-ring-derived extracellular vesicles represent a potential therapeutic strategy for promoting in vitro corneal wound healing. In this study, we successfully isolated and characterized extracellular vesicles from human corneolimbal tissue obtained from 42 donors, with a mean age of 51.62 ± 15.56 years. Donor-related factors such as age, corneal endothelial cell density, and underlying systemic conditions did not confound extracellular vesicle size and concentration with mean peak size of 99.52 ± 13.00 nm by nanoparticle tracking analysis. Western blotting analysis revealed positive Alix, stable expression of CD9 and CD81, and variable expression of CD63. Limbal stem cell (LSC)-associated markers, i.e., ABCG2, p63, Notch-1, and Integrin α9 were positively detected in the isolated extracellular vesicles. Notably, Integrin α9 showed stable and relatively strong expression in all samples serving a specific marker of LSC-derived extracellular vesicles. Functional assays demonstrated that LSC-derived extracellular vesicles exhibited better wound healing potency compared to extracellular vesicles derived from mesenchymal stem cells (MSCs). These findings suggest that corneoscleral-ring-derived extracellular vesicles express distinct LSC markers, including Integrin α9, and hold significant potential for application in corneal wound healing and ocular surface regeneration. Full article

(This article belongs to the Special Issue Vision Science and Optometry: 2nd Edition)

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10 pages, 364 KB

Open AccessArticle

Visual Function in Athletes from Different Team Sports and Non-Athlete Controls

by Henrique Nascimento, Ana Roque and Clara Martinez-Perez

Life 2025, 15(10), 1619; https://doi.org/10.3390/life15101619 - 16 Oct 2025

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Abstract

Visual skills are increasingly recognized as critical to athletic performance, yet it remains unclear whether participation in specific team sports is associated with enhanced visual function. This cross-sectional study compared visual acuity, peripheral vision, stereoacuity, ocular alignment, and refractive error among 52 participants [...] Read more.

Visual skills are increasingly recognized as critical to athletic performance, yet it remains unclear whether participation in specific team sports is associated with enhanced visual function. This cross-sectional study compared visual acuity, peripheral vision, stereoacuity, ocular alignment, and refractive error among 52 participants aged 15–56 years: basketball (n = 10), futsal (n = 9), hockey (n = 12), roller derby (n = 9), and non-athlete controls (n = 12). Standardized assessments included best-corrected visual acuity (logMAR), Hirschberg shift, peripheral perception using a tachistoscope, stereoacuity with the Randot^® test, and non-cycloplegic autorefraction. Group comparisons were conducted using ANOVA, post hoc analyses, and regression models adjusted for age. Significant differences were observed only for visual acuity (F(4, 47) = 4.46, p = 0.003, η² = 0.275): non-athlete controls (0.00 ± 0.08 logMAR) and basketball players (0.02 ± 0.05) showed the best performance, while roller derby athletes demonstrated the poorest (0.16 ± 0.12). No significant group differences were found for peripheral vision, stereoacuity, Hirschberg deviation, or refractive error, and the poorer acuity in roller derby remained after adjustment for age. These findings suggest that participation in team sports does not universally confer superior visual function and that static clinical measures may overlook the dynamic visual–motor strategies that underlie athletic performance. Full article

(This article belongs to the Special Issue Vision Science and Optometry: 2nd Edition)

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12 pages, 692 KB

Open AccessArticle

Age-Related Effects on the Color Discrimination Threshold

by Ali Almustanyir, Mohammed Alhazmi, Amal Aldarwesh, Meznah S. Almutairi, Mohammed Almahubi, Ansam Alateeq, Tahani Alqahtani, Muteb Alanazi, Sultan Alotaibi, Mansour Alghamdi, Essam Almutleb, Basal H. Altoaimi, Balsam Alabdulkader and Mosaad Alhassan

Life 2025, 15(7), 1074; https://doi.org/10.3390/life15071074 - 5 Jul 2025

Cited by 5 | Viewed by 2348 | Correction

Abstract

Traditional color vision tests lack the sensitivity to detect subtle differences in individuals with normal color vision. The Konan ColorDx Cone Contrast Threshold (CCT) HD test allows the quantitative measurement of color discrimination thresholds for each cone type. This cross-sectional study established normative [...] Read more.

Traditional color vision tests lack the sensitivity to detect subtle differences in individuals with normal color vision. The Konan ColorDx Cone Contrast Threshold (CCT) HD test allows the quantitative measurement of color discrimination thresholds for each cone type. This cross-sectional study established normative values for L-, M-, and S-cone contrast sensitivities and evaluated the effects of age and sex on color discrimination thresholds. Participants aged 15–79 years with normal color vision were included (n = 216; 55% female). CCTs were measured monocularly using the Konan ColorDx CCT HD test under standardized conditions, and the influences of age and sex on L-, M-, and S-cone sensitivities were evaluated. In all groups, L-cone sensitivity was the highest, followed by the M- and S-cone sensitivities. Overall contrast sensitivity was significantly higher in females than in males (mean difference = −0.041), especially for adolescents and young adults (20–24 years). Young adults outperformed middle-aged and older adults, with age-related decline most pronounced for S-cone sensitivity in those over 60. The right and left eye sensitivities did not differ. This study provides age- and sex-stratified normative data for the Konan Color Dx CCT HD test, supporting its use for clinical and occupational assessments. Full article

(This article belongs to the Special Issue Vision Science and Optometry: 2nd Edition)

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Open AccessCorrection

Correction: Almustanyir et al. Age-Related Effects on the Color Discrimination Threshold. Life 2025, 15, 1074

by Ali Almustanyir, Mohammed Alhazmi, Amal Aldarwesh, Meznah S. Almutairi, Mohammed Almahubi, Ansam Alateeq, Tahani Alqahtani, Muteb Alanazi, Sultan Alotaibi, Mansour Alghamdi, Essam Almutleb, Basal H. Altoaimi, Balsam Alabdulkader and Mosaad Alhassan

Life 2025, 15(11), 1771; https://doi.org/10.3390/life15111771 - 19 Nov 2025

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In the published publication [...] Full article

(This article belongs to the Special Issue Vision Science and Optometry: 2nd Edition)

15 pages, 926 KB

Open AccessSystematic Review

Refractive Outcomes in Keratoconus Patients Following Toric Lens Implantation: A Systematic Review and Single-Group Meta-Analysis

by Tun Giap Tan, Kieran O’Kane and Harry W. Roberts

Life 2025, 15(9), 1362; https://doi.org/10.3390/life15091362 - 27 Aug 2025

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Abstract

This systematic review and meta-analysis evaluated refractive outcomes, particularly astigmatic correction, in keratoconus following toric intraocular lens (tIOL) implantation. A systematic search identified eligible studies reporting pre- and postoperative refractive cylinder, spherical equivalent (SE), uncorrected distance visual acuity (UDVA), and corrected distance visual [...] Read more.

This systematic review and meta-analysis evaluated refractive outcomes, particularly astigmatic correction, in keratoconus following toric intraocular lens (tIOL) implantation. A systematic search identified eligible studies reporting pre- and postoperative refractive cylinder, spherical equivalent (SE), uncorrected distance visual acuity (UDVA), and corrected distance visual acuity (CDVA). Eight studies, comprising 135 eyes, were included. Outcomes were pooled using a random-effects model with restricted maximum likelihood as the estimator for tau². Methodological quality was assessed using the MINORS tool for non-comparative studies and the JBI checklist for case series. Postoperative refractive cylinder and SE improved by 2.28 dioptres (95% CI, 1.60–2.96) and 4.17 dioptres (95% CI, 2.32–6.01), respectively. UDVA and CDVA also improved substantially, with pooled gains of 0.87 logMAR (95% CI, 0.71–1.03) and 0.19 logMAR (95% CI, 0.12–0.26), respectively. Most tIOL rotations did not exceed 10 degrees, with only one case requiring realignment surgery. Complications were infrequent and mostly minor. tIOL implantation is effective in reducing astigmatism and improving vision in stable keratoconus patients. However, limitations in vector analysis and methodology heterogeneity underscore the need for standardised reporting to optimise outcomes. Full article

(This article belongs to the Special Issue Vision Science and Optometry: 2nd Edition)

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