Vision, Volume 10, Issue 3 (August 2026) – 16 articles

Patient-reported outcome measures (PROMs) in vision science are commonly evaluated using Cronbach’s alpha, yet Rasch-based statistics may provide different information about their reliability. This study compared Cronbach’s alpha, a Classical Test Theory (CTT) index, with Rasch person reliability and the person separation ratio across three vision-related questionnaires: the Symptom Questionnaire for Visual Dysfunctions (SQVD; n = 434), the Ocular Surface Disease Index (OSDI; n = 294), and the Quality of Vision questionnaire (QoV; n = 288), using retrospective data from unselected clinical populations. Cronbach’s alpha indicated acceptable internal consistency across all questionnaires (α = 0.80–0.87), whereas Rasch person reliability was lower (0.62–0.80) and person separation ratios ranged from 1.29 to 2.00, indicating more limited discrimination. Item reliability was generally high (0.90–0.97) overall but declined in subgroups with restricted score variability. Discrepancies were most pronounced in the OSDI, where estimates approached their theoretical floor when subgroups were defined by the questionnaire’s own scores. Cronbach’s alpha and Rasch-based statistics are not interchangeable and capture different aspects of measurement precision: alpha may overestimate internal consistency, whereas person reliability and the separation ratio provide complementary information about discriminatory capacity. These findings support reporting both CTT and Rasch-based reliability statistics when evaluating vision-related PROMs in clinical populations. Full article

Studies suggest that anticipation in sports-related tasks is better if the task maintains the coupling of perception and action required in competition. Study 1 addressed the question of whether gaze tracking varies between coupled tasks in baseball and softball batters. Fifteen subjects executed either a coupled task (partially swinging a bat at an approaching ball) or an uncoupled task (predicting the passing height of an approaching ball). The ball was stopped by a net 8 feet (2.44 m) in front of the subject. Rapid gaze shifts occurred for 53.0% of the pitches in the uncoupled task, and for 39.7% of the pitches in the coupled task (p = 0.039). The number of predictive gaze shifts toward the terminal ball location in each condition (i.e., the expected location of bat–ball contact in the coupled condition, and the observer in the uncoupled condition) did not vary between the conditions (p = 0.388). Study 2 examined whether gaze fixations on the net found in Study 1 occurred because passing height judgments could not be improved at distances closer than 8 feet from the observer. Passing height judgments were lower when the ball was allowed to pass by the observer, suggesting that subjects processed trajectory information within 8 feet. Full article

Alzheimer’s disease (AD) extends beyond the brain to the visual system, offering a promising window for pathology, monitoring, and intervention. This review synthesizes evidence on AD-related visual impairments across molecular, cellular, circuit, and cortical levels. We examine the eye–brain pathological relationship as a working framework, noting experimental evidence for brain-to-eye amyloid-β (Aβ) transport in mouse models and associations between retinal and cerebral pathology in humans, while emphasizing that bidirectional pathological transport has not been established. Structural and functional changes in the retina, optic nerve, and visual cortex are reviewed, alongside white matter damage and posterior cortical atrophy patterns. We evaluate emerging multimodal tools (OCTA, ERG, and hyperspectral imaging) that shift diagnosis toward an integrated “structure–vessel–function” assessment. We critically examine non-pharmacological interventions, including 40 Hz gamma stimulation and photobiomodulation, discussing their mechanisms, translational challenges, and the dissociation between structural and cognitive outcomes. We propose the visual system as a candidate pathological window, a quantitative monitoring platform, and an investigational intervention entry point in Alzheimer’s disease. However, clinical translation of these applications requires standardized acquisition protocols, prospective longitudinal validation, and robust mechanistic evidence. To advance this agenda, we identify three priorities: multimodal data integration, closed-loop neuromodulation strategies, and methodologically rigorous validation frameworks. Full article

Purpose: Keratoconus is a progressive corneal ectatic disorder that causes visual impairment, particularly in adolescents and young adults. Evidence on its epidemiology in Latin America and the Caribbean remains limited. This study aimed to estimate the prevalence of keratoconus and evaluate associated factors, including eye rubbing, sex, family history, and allergy history, in the region. Methods: A systematic search of PubMed, Scopus, PsycINFO, and Google Scholar was conducted on 15 December 2025 for observational studies published up to December 2025. Study selection and data extraction were performed independently by two reviewers, with disagreements resolved by consensus. Study quality was assessed using the Newcastle–Ottawa Scale. Pooled prevalence estimates and odds ratios (ORs) were calculated using a random-effects model with variance-stabilizing transformation. Heterogeneity was assessed using the I² statistic, and publication bias was explored using funnel plots and Egger’s test. Results: Seven prevalence studies were included in the primary meta-analysis following exclusion of three studies from the previous version of the review, with no additional eligible prevalence studies identified in the updated search. One additional nationwide registry-based study from Colombia was identified but excluded from the primary prevalence synthesis because it reported incidence derived from administrative diagnostic coding rather than clinically assessed prevalence. Among the seven prevalence studies, reported prevalence ranged from 0.50% to 2.88%. The pooled prevalence of keratoconus was 2.07% (95% CI: 1.53–2.79), with substantial heterogeneity (I² = 71.9%). Subgroup analyses suggested that prevalence estimates varied by study design, with lower estimates observed in community- and school-based studies and higher estimates in clinic-based studies. No statistically significant associations were identified for eye rubbing, sex, family history, or allergy history; however, these analyses should be interpreted cautiously due to small sample sizes, heterogeneous exposure definitions, and wide confidence intervals. Conclusions: Keratoconus prevalence estimates in Latin America and the Caribbean remain variable and should be interpreted cautiously due to substantial heterogeneity, differences in study design, variability in diagnostic criteria, and differences in case ascertainment. The findings highlight important evidence gaps and support the need for well-designed population-based studies using standardized diagnostic criteria to inform screening strategies, early detection, and eye-care planning in the region. Full article

Despite the widespread use of orthokeratology (ortho-k), the diurnal behavior of corneal geometry after lens removal remains unclear. This prospective observational study evaluated diurnal variations in corneal geometry, refractive error, and visual performance in ortho-k wearers using global and sector-based corneal analyses. Nineteen eyes from ten ortho-k wearers were examined at five time points over a 10-h period following overnight lens wear. Corneal thickness, anterior and posterior corneal curvature, corneal asphericity, autorefractometry, and visual acuity were assessed. Corneal elevation data were reconstructed using Zernike polynomial expansions, and regional analyses were performed using concentric annular sectors. Diurnal amplitudes were compared with a healthy control cohort evaluated using the same protocol. Corneal thickness progressively decreased throughout the day (p < 0.001). Anterior corneal curvature showed progressive steepening (p ≤ 0.011), whereas posterior corneal curvature exhibited significant flattening (p ≤ 0.018). A progressive myopic refractive shift was also observed, with a spherical equivalent amplitude of −1.03 D (p = 0.002). Despite these changes, visual acuity remained stable (p = 0.248). Compared with healthy controls, ortho-k wearers showed greater amplitudes of central corneal thickness and anterior corneal curvature changes. These findings indicate that ortho-k may enhance normal diurnal corneal changes while maintaining visual acuity. Full article

The magnitude and short-term recovery of residual objective myopic bias after a brief, clinically plausible over-minus exposure during distance refraction remain insufficiently quantified. This study quantified the short-term residual objective myopic shift following 10 s of transient myopic overcorrection of 0.50 D or 1.00 D in young adults with myopia. Twenty healthy young adults with myopia and low astigmatism underwent open-field automated objective over-refraction (OR) while viewing a high-contrast 5 m target. After trial lenses induced a moderate myopic state, each participant completed three randomized 10 s lens conditions: 0.50 D undercorrection, 0.50 D overcorrection, and 1.00 D overcorrection. The primary endpoint was OR at 5 s after restoration of the objective neutral correction. Both overcorrection conditions produced significantly more negative OR than undercorrection at 5 s; exploratory analyses showed the same pattern at 10 s. The shift was evident at 5 and 10 s after restoration of the objective neutral correction and, by 30 s, was no longer statistically significant and appeared clinically negligible. This bias should be considered when OR measurements obtained shortly after over-minus lens exposure are used to inform subsequent subjective refinement. Full article

Dry Eye Disease (DED) is a multifactorial condition increasingly affecting young populations, including medical students, due to intensive screen use, prolonged near work, and demanding academic environments. This study aimed to estimate the prevalence of DED-related outcomes among medical students and to examine how estimates vary according to diagnostic methods, methodological characteristics, and publication period. A systematic review with meta-analysis was conducted. PubMed, Scopus, Web of Science (including SciELO), and EMBASE were searched from January 2000 to March 2026. A random-effects model was applied, and subgroup, sensitivity, and exploratory meta-regression analyses were performed. Twenty-seven studies were included, comprising 12,501 participants. The pooled prevalence of DED-related outcomes was 47.4% (95% CI: 38.4–56.4%); however, between-study heterogeneity was extreme (I² = 99%). Therefore, this estimate should be interpreted as an approximate summary of a highly heterogeneous evidence base rather than as a definitive global epidemiological value. Prevalence estimates varied according to diagnostic approach, particularly between self-report, symptom questionnaires, and clinical tests. Exploratory meta-regression suggested a positive association with publication year, but these analyses did not meaningfully resolve heterogeneity and should not be interpreted as causal evidence of a temporal increase. Standardized diagnostic approaches combining symptoms and ocular surface signs are needed to improve comparability across studies and inform preventive visual-health strategies in medical education. Full article

Background/Objectives: High astigmatism remains challenging in keratorefractive lenticule extraction because small errors in centration or cyclotorsion may affect astigmatic correction. This study evaluated early refractive and astigmatic vector outcomes after small-incision lenticule extraction (SMILE) Pro using the VISUMAX 800 in eyes with high astigmatism. Methods: This prospective interventional cohort study was conducted at Cung Hong Son International Eye Hospital, Hanoi, Vietnam. Refractive outcomes, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, astigmatic vector analysis, and intraoperative and postoperative complications, were evaluated up to 3 months postoperatively. Results: A total of 160 eyes from 102 patients were included in the final analysis. The mean age was 23.7 ± 4.7 years, and 63.7% of participants were female. The mean preoperative spherical equivalent (SEQ) was −7.21 ± 2.03 D, and the mean preoperative refractive cylinder was −2.51 ± 0.56 D. Mean postoperative SEQ was −0.10 ± 0.38 D at 1 month and 0.02 ± 0.31 D at 3 months. At 3 months, 99% and 84% of eyes achieved UDVA of 0.8 decimal or better and 0.9 decimal or better, respectively. The mean residual refractive cylinder was −0.52 ± 0.28 D, with 69% and 98% of eyes achieving a residual cylinder ≤0.50 D and ≤1.00 D, respectively. All eyes had an angle of error within ±15°. The safety index was 1.01, and no eyes lost two or more lines of CDVA. Conclusions: SMILE Pro performed with the VISUMAX 800 provided favorable early 3-month refractive and astigmatic vector outcomes with a satisfactory safety profile in eyes with high astigmatism. Full article

Spatial working memory (SWM) has been characterised as a flexible resource that determines the precision with which memoranda are stored. The ‘cortical map’ proposal predicts that resource allocation, and therefore mnemonic precision, is limited by the availability of cortical space to represent memoranda. This hypothesis was tested using a continuous spatial localisation task in which memory items were presented at three eccentricities and set sizes of 1–8. Localisation error increased systematically with eccentricity, as predicted by the cortical maps hypothesis. Mixture-modelling analyses indicated that the eccentricity effect was primarily driven by increases in imprecision at small set sizes (set sizes 1–5). In contrast, when set size exceeded five items, guessing made an increasingly important contribution to localisation error, suggesting that representations of peripheral locations become more vulnerable to memory failure under high memory loads. Misbinding errors were most prominent for locations nearest fixation, likely reflecting reduced inter-item spacing at small eccentricities. Stimuli were not scaled to compensate for cortical magnification, but the observed increase in imprecision closely matched predictions derived from a cortical magnification function. Together, these findings support the cortical maps hypothesis and indicate that spatial working memory representations compete for limited representational resources within the spatial maps that guide action. Full article

Myopia is an increasingly common refractive disorder in children, with growing concern regarding the potential role of screen time and digital device use in its development and progression. This systematic review assessed the association between screen-related behaviours and myopia in European children and adolescents. A systematic search of Ovid Embase, Ovid MEDLINE, Scopus, Web of Science and Cochrane/CENTRAL was conducted in accordance with PRISMA guidance. Original English-language studies published within the last 10 years were included if they involved participants aged <18 years, were conducted in Europe, and investigated screen time, digital device use, near-work behaviour or related lifestyle exposures in relation to myopia-related outcomes. A total of 1196 records were identified across the databases. After duplicate removal, title and abstract screening, and full-text assessment, 14 studies were included. Overall, the evidence suggested an association between screen-related behaviours, prolonged near work, reduced outdoor exposure and myopia-related outcomes in European children. However, findings were heterogeneous, and screen exposure was often measured using broad or proxy variables, including total screen time, smartphone use, internet data consumption, computer use, handheld near-screen use and COVID-19-related lifestyle change. Outdoor activity appeared to be a protective factor, while parental myopia was an important risk factor and confounder. Most included studies were observational, many were cross-sectional, and several relied on self- or parent-reported exposure measures, limiting causal inference and introducing potential recall bias. Overall, the certainty of evidence was low to very low. Practical advice should therefore be framed around balanced digital device use, regular breaks from prolonged near work, appropriate viewing distances and increased outdoor activity, while further longitudinal studies using objective screen-use measures, cycloplegic refraction and axial length outcomes are needed to clarify causality. Full article

Combined intrastromal corneal ring segment implantation with corneal collagen cross-linking (CXL) aims to improve optical regularity and reduce the risk of ectatic progression in selected eyes with keratoconus. In this retrospective, single-center, complete-case longitudinal series, 58 eyes from 40 patients treated at OCULENS Ophthalmology Clinic between 2019 and 2022 were analyzed after same-session KeraRing implantation and conventional epithelium-off CXL, with baseline and 6-, 12-, 24-, and 36-month follow-up data. Outcomes included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), thinnest pachymetry, maximum keratometry (Kmax), the Belin/Ambrosio enhanced ectasia total deviation index (BAD-D), the C and D components of the ABCD classification, and Corvis ST-derived dynamic deformation parameters. Longitudinal continuous outcomes were analyzed as eye-level repeated-measures estimates with Holm-adjusted paired comparisons, and stage distributions were analyzed with the Friedman test. At 36 months, UDVA improved from 0.560 ± 0.151 to 0.469 ± 0.136 logMAR and CDVA from 0.350 ± 0.109 to 0.287 ± 0.092 logMAR (both p < 0.001). Kmax decreased from 56.11 ± 3.17 D to 54.87 ± 2.86 D, BAD-D improved from 5.62 ± 1.89 to 4.70 ± 1.75, and thinnest pachymetry measured 440.7 ± 21.9 µm at 36 months, corresponding to 97.0% of baseline thickness. Corvis ST-derived deformation behavior shifted toward lower deformation amplitude and higher stiffness parameter at first applanation (SP-A1), but these device-derived parameters should be interpreted as indirect deformation response metrics rather than as direct tissue stiffness measurements. Two clinically significant complications were recorded (2/58 eyes, 3.4%): one sterile corneal infiltrate requiring ring explantation and one case of corneal melting requiring ring explantation and referral for keratoplasty. The findings support sustained 36-month visual, tomographic, and Corvis ST-derived changes after combined treatment, while interpretation remains limited by the retrospective complete-case design, unavailable denominator for cases excluded because of incomplete follow-up, eye-level analysis with bilateral cases, lack of a control group, and indirect nature of Corvis ST-derived biomechanical assessment. Full article

Keratoconus is a progressive corneal ectasia that results in substantial visual impairment and imposes a significant functional and psychosocial burden on affected individuals. Despite evidence suggesting earlier onset and a potentially more aggressive disease course of keratoconus in Saudi populations, there is a significant lack of region-specific data evaluating vision-related quality of life (VRQoL) in Riyadh. This cross-sectional study conducted in Riyadh, Saudi Arabia, evaluated VRQoL in individuals with keratoconus using the 25-item National Eye Institute Visual Function Questionnaire (NEI-VFQ-25). Data were obtained from January to March 2025 through an online, structured, self-administered questionnaire. A total of 1007 participants were included, of whom 299 (29.7%) reported a diagnosis of keratoconus. The mean composite NEI-VFQ-25 score among participants with keratoconus was 61.0 ± 15.8, reflecting moderate impairment in VRQoL. Reduced VRQoL was significantly associated with eye-rubbing behavior, including both frequency (p = 0.027) and method (p = 0.026). The results highlight the importance of early detection and the relevance of eye-rubbing behavior in relation to reduced VRQoL, while supporting the need for longitudinal research to further clarify these associations. Full article

Physical activity levels, hallucination experiences, sleep quality, and perceived stress were assessed using a survey administered to 57 adults with a confirmed diagnosis of Charles Bonnet Syndrome (CBS). Physical activity demonstrated a significant negative correlation with hallucination severity (r = –0.335, p = 0.011, two-tailed). A significant negative correlation was also observed between physical activity and perceived stress (r = –0.497, p < 0.001, two-tailed). In contrast, no significant association was identified between hallucination frequency and sleep disruption or insomnia. These findings suggest that engaging in appropriate levels of physical activity may help reduce the severity of hallucinations and mitigate stress among individuals with CBS. The observation that higher levels of physical activity are associated with reduced hallucination burden may help the development of evidence-based management strategies for CBS. Additionally, the finding that physical activity was significantly related to hallucination severity, whereas sleep disruption was not, merits deeper exploration in future research. Full article

This study aims to address whether a new visual–motor-based learning paradigm with music can potentially promote neuroplasticity and create new interventional tools, building upon prior research that shows behavioral and putative neural changes following dance-based neurorehabilitation in people with Parkinson’s disease (PD). Eye movements of 10 healthy adult participants, aged 20–25, were tracked using the Eyelink 1000 Plus system during a 68 s eye dance sequence. The experiment consisted of a learning phase, where participants observed the sequence five times with 30 s breaks, and a performance phase, where they performed the sequence five times from memory on a gray screen without visual cues. Results showed a significant improvement in percentage of total movements performed correctly between the first session (g1; M = 40%, SD = 7.2%) and the last session (g5; M = 69.7%, SD = 22.8%). Similarly, there was significant improvement in the average time on beat from the intended choreography timing, between the first session (g1; M = 0.29, SD = 0.06) and the fifth session (g5; M = 0.46, SD = 0.12). These findings suggest that eye movement choreography has the potential to be learned within healthy adults. Full article

Background: Visio-spatial skills (VSS) are fundamental perceptual–cognitive capacities that enable athletes to process dynamic visual information, interpret spatial relationships, and execute precise motor responses under competitive conditions. In taekwondo, where scoring actions are executed within milliseconds and success depends on the rapid detection and anticipation of an opponent’s movements, well-developed VSS are considered a functional prerequisite for performance. Method: This cross-sectional observational study examined differences in VSS between amateur taekwondo athletes (n = 50) and non-athletes (n = 50) recruited from the King Cetshwayo Municipality District, KwaZulu-Natal, South Africa. Six VSS were assessed using standardized, validated instruments: accommodation facility (AF), saccadic eye movement (SEM), speed of recognition (SR), hand–eye coordination (HEC), peripheral awareness (PA), and visual memory (VM). Between-group comparisons were performed using the Mann–Whitney U test, with effect sizes reported as rank-biserial correlations (r). Results: Taekwondo athletes demonstrated significantly superior performance across all VSS domains (all p ≤ 0.05), with a large effect observed for SR (r = 0.91), HEC (r = 0,87), SEM (r = 0.78), and AF (r = 0.74), and moderate effect for VM (r = 0.58) and PA (r = 031). The largest between-group percentage differences were observed for SR (79.43%), HEC (48.13%), and SEM (33.33%), with smaller but significant differences in AF (31.05%), VM (14.92%), and PA (4.23%). Pearson correlation analysis revealed a dense, globally integrated VSS network in non-athletes anchored by AF, contrasting with a sparse pattern in taekwondo athletes, in which SEM showed the greatest number of moderate or stronger associations with other variables. These within-group correlation structures are presented as preliminary and descriptive observations only. Intraclass correlation coefficients were excellent for five of the six VSS (ICC ≥ 0.963), with PA yielding a point estimate of ICC = 0.853, characterized by a wide confidence interval. Conclusions: These findings indicate that amateur taekwondo athletes show superior perceptual, oculomotor, and visuo-motor performance compared to non-athletes. Within-group VSS correlation pattern differs descriptively between the groups. The cross-sectional design cannot determine whether these differences reflect training-associated perceptual adaptation, pre-existing trait-based self-selection into taekwondo, or a combination of both mechanisms. Both interpretations carry applied implications for talent identification and vision training program design. A longitudinal investigation is required to establish causal directionality. SEM and AF are proposed as the most diagnostically informative VSS markers for taekwondo screening, under either interpretation. Full article

Purpose: This study was conducted to assess retinal responses in myopic and non-myopic participants after exposure to repeated low-level red-light therapy (RLRT) of 3 min and 1 min duration to see if response differs with exposure time and refractive status using global flash multifocal electroretinogram (gf-mfERG). Methods: This was a prospective exploratory pilot study with a convenient sample of 20 participants of mean age of 25.5 years (18 to 39 years) who underwent 3 min therapy, followed by, 1 week after, 1 min therapy in each participant between February to May 2025. However, four participants who did not appear in 1 min therapy for measurements were excluded from the between-group comparison analysis. We measured retinal responses using gf-mfERG ring-wise implicit time (DCT, ICT) and amplitude (DCA, ICA), baseline, post-first and post-second RLRT. Data analysis included descriptives, repeated measures ANOVA, post hoc test, Bonferroni adjusted correction, and correlation with axial length (AL) and choroidal thickness (CT) in each group. The study was conducted at CEORLab, University of Minho, Portugal, and adhered to Ethical Committee approval and the tenets of the Declaration of Helsinki. Results: In 3 min RLRT exposure, no significant within-subject changes were observed across direct (DC) and induced (IC) gf-mfERG components across all rings (p > 0.05). Statistically significant between-group differences in DC implicit time were noted in Ring 2 (p = 0.029) and Ring 3 (p = 0.012). IC amplitude showed significant within-subject changes in myopes (Ring 1: p = 0.030; Ring 4: p = 0.035) and non-myopes (Ring 1: p = 0.042; Ring 3: p = 0.001; Ring 4: p < 0.001; Ring 5: p = 0.034), with no significant between-group differences (p > 0.05). In contrast, 1 min RLRT showed no significant changes in DC, IC time or amplitudes ICA, DCA (all p > 0.05). Correlation analysis after 3 min RLRT showed that in myopes, DCT positively correlated with AL in Ring 3 (r = 0.591, p = 0.006) and Ring 4 (r = 0.615, p = 0.004), ICT positively correlated with CT in Ring 2 (r = 0.601, p = 0.005) and Ring 3 (r = 0.573, p = 0.008), and ICA negatively correlated with AL in Rings 3–5 (all p < 0.01). Non-myopes demonstrated limited correlations, including a negative association between ICT and axial length in Ring 4 (r = −0.619, p = 0.004). Similar but weaker patterns were observed following 1 min RLRT. Conclusions: 3-min RLRT induces localized inner retinal functional changes without significantly altering outer retinal responses, while 1-min exposure shows no measurable effect. Retinal ERG responses are primarily influenced by axial length, particularly in myopic eyes, highlighting a structure–function relationship rather than a robust short-term therapeutic effect of RLRT. Full article