Mosaad Alhassan

Purpose Reading is a critical visual task that depends on the resolution of fine character features, and how these features are affected by display variables under degraded viewing conditions remains an important question in clinical psychophysics. While contrast polarity effects on reading have been documented in Latin scripts, evidence from non-Latin orthographies is limited. This study investigated the effect of contrast polarity on Arabic reading performance under simulated visual impairment. Methods Reading acuity (RA), maximum reading speed (MRS) and critical print size (CPS) were assessed in 47 normally sighted adults using the Balsam Alabdulkader–Leat (BAL) reading chart. Testing was conducted under baseline and simulated visual impairment using a Bangerter filter, with both black-on-white and white-on-black charts. Results The simulation significantly degraded all reading measures (MRS, p = 0.001; RA, p < 0.0001; CPS, p < 0.0001). A significant simulation × polarity interaction was found for RA (p < 0.0001), with black-on-white charts producing better visual acuity at baseline and white-on-black producing better visual acuity under simulated impairment. Chart polarity did not affect MRS (p = 0.38) or CPS (p = 0.82) significantly. Conclusion Arabic relies on small, high-spatial-frequency features such as dots for letter discrimination, which appear to modulate how contrast polarity interacts with optical degradation at threshold. These findings provide preliminary evidence that may guide future studies of reading performance in Arabic-speaking patients with visual impairment.

Background: Dry eye disease (DED) and refractive errors are increasingly prevalent among young adults, particularly in populations with prolonged digital device use. However, the relationship between refractive error, axial length (AL), and dry eye parameters remains incompletely understood. Methods: A cross-sectional observational study was conducted among 114 young Saudi adults attending the optometry clinic of King Saud University. Participants underwent comprehensive ocular examination including refractive assessment, AL measurement, Ocular Surface Disease Index (OSDI), non-invasive tear breakup time (NI-TBUT) and tear breakup time (TBUT). Refractive error was classified into hyperopia and myopia, with further stratification by severity. Continuous variables are presented as mean ± standard deviation (SD), while categorical variables are summarized as frequencies and percentages. One-way ANOVA was performed among refractive error groups, whereas the Kruskal–Wallis H test was used for dry eye severity. Pearson’s correlation, Spearman’s correlation, Bonferroni-adjusted post-hoc analysis, and linear regression analysis were performed, keeping the p-value < 0.05. The study got IRB approval and adhered to the tenets of the declaration of Helsinki. Results: The mean age of participants was 23.95 ± 3.73 years, with 64.9% females. Mean daily screen-time was 9.40 ± 2.93 h. Axial length demonstrated a weak positive correlation with OSDI scores; however, it did not reach statistical significance (r = 0.174, p = 0.065). Similarly, AL was not significantly correlated with TBUT (r = −0.134, p = 0.157) or NI-TBUT (r = −0.147, p = 0.120). In contrast, screen time showed significant correlations with the OSDI scores (r = 0.650, p < 0.001), TBUT (r = −0.585, p < 0.001), and NI-TBUT (r = −0.509, p < 0.001). Dry eye severity differed significantly across refractive error groups (Kruskal–Wallis H = 18.762, p = 0.002), showing higher refractive error associated with greater dry eye severity. Multivariable regression analyses demonstrated that greater screen time was significantly associated with higher OSDI scores and shorter TBUT and NI-TBUT, whereas spherical equivalent (SE) was not independently associated with any of these dry eye outcomes after adjusting for demographic variables. Additionally, greater screen time was significantly associated with composite dry eye severity (Spearman’s ρ = 0.639, p < 0.001). Conclusions: Prolonged digital screen exposure showed the most consistent association with greater dry eye severity, whereas refractive error and axial length were not independently associated with dry eye outcomes after adjustment for screen time and demographic factors. Although unadjusted differences exist across certain refractive subgroups, behavioral factors such as screen time may contribute to dry eyes. These findings support comprehensive dry eye evaluation in individuals with refractive error and prolonged digital device use.

Normal binocular vision depends on the precise alignment and coordination of the eyes; any disruption in this process can result in binocular vision anomalies.1 The near point of convergence (NPC) ...

Background/Objectives: This study aimed to examine how interpupillary distance (IPD) influences motor and sensory binocular vision functions at distance and near, and to examine associations between different motor and sensory binocular vision functions. Methods: A descriptive cross-sectional study was performed involving 100 random participants of both genders, aged 20 to 38 years. Optically corrected and non-strabismic participants were selected from King Saud University, Riyadh, Saudi Arabia between June 2024 and June 2025. Distance and near IPD were assessed with a pupillometer. Motor binocular functions included horizontal phoria using the von Graefe technique and near point of convergence (NPC). Sensory binocular vision was assessed using crossed and uncrossed TNO and Random-dot E stereopsis tests at near and distance respectively. Statistical analysis was conducted using SPSS version 26 (p ≤ 0.05). Results: IPD and phoria were not significantly associated at distance or near. However, moderate and significant correlations were found between IPD (distance and near) and NPC. Significant correlations were also found between IPD and both crossed and uncrossed stereopsis at distance, but correlations were weak or non-significant at near. A strong correlation was observed between NPC and stereopsis at distance. Conclusions: As interpupillary distance (IPD)increases, near point of convergence (NPC) receded, and stereopsis at distance declined, suggesting that anatomical variation influences binocular vision primarily at distance.

Background/Objectives: Hydroxychloroquine (HCQ) is used to manage various autoimmune diseases, including systemic lupus erythematosus. The prolonged use of HCQ is associated with retinopathy and irreversible visual loss due to retinal toxicity. Despite adherence to dosage regimens, patients may develop functional rather than structural changes, without detectable abnormalities on routine examination using visual acuity and optical coherence tomography (OCT). The study aimed to detect early signs of retinopathy in patients with autoimmune diseases treated with HCQ. Methods: This cross-sectional study included patients (n = 36) with autoimmune diseases who were treated with HCQ. The control group (n = 35) comprised healthy volunteers matched for age and sex. All participants were screened using colour vision tests (Ishihara, Konan ColourDX high definition [HD]), and retinal thickness was evaluated using OCT. Results: Our findings suggest a significant reduction in the contrast threshold of the L and M-cone photoreceptors compared with that of the control using Konan ColourDX HD. The OCT measurements revealed no statistically significant difference in retinal thickness between patients and controls; however, the contrast sensitivity test showed a significant reduction at all spatial frequencies (p < 0.0001). Conclusions: The current study suggests that the Konan ColourDX cone contrast test HD and contrast sensitivity testing may be valuable for periodic monitoring of patients receiving HCQ, potentially enabling earlier detection of toxicity. However, longitudinal studies with larger cohorts are needed to confirm these findings and to further establish the clinical value of these functional visual tests.

AIM: To evaluate the efficacy of the total computer vision syndrome questionnaire (CVS-Q) score as a predictive tool for identifying individuals with symptomatic binocular vision anomalies and refractive errors. METHODS: A total of 141 healthy computer users underwent comprehensive clinical visual function assessments, including evaluations of refractive errors, accommodation (amplitude of accommodation, positive relative accommodation, negative relative accommodation, accommodative accuracy, and accommodative facility), and vergence (phoria, positive and negative fusional vergence, near point of convergence, and vergence facility). Total CVS-Q scores were recorded to explore potential associations between symptom scores and the aforementioned clinical visual function parameters. RESULTS: The cohort included 54 males (38.3%) with a mean age of 23.9±0.58y and 87 age-matched females (61.7%) with a mean age of 23.9±0.53y. The multiple regression model was statistically significant [R²=0.60, F=13.28, degrees of freedom (DF=17 122, P0.001]. This indicates that 60% of the variance in total CVS-Q scores (reflecting reported symptoms) could be explained by four clinical measurements: amplitude of accommodation, positive relative accommodation, exophoria at distance and near, and positive fusional vergence at near. CONCLUSION: The total CVS-Q score is a valid and reliable tool for predicting the presence of various non-strabismic binocular vision anomalies and refractive errors in symptomatic computer users.

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.

Background: Measuring contrast sensitivity for each of the three cone types separately allows for a more precise and clinically valuable assessment of color vision. This study examined how pupil size affects cone contrast sensitivity (CCS). Methods: This study included 50 participants of equal gender. The mean age was 20.88 (±1.8) years. Using the ColorDx, a Landolt C stimulus of various sizes in an adaptive screening mode, we sequentially determined contrast sensitivity for long-, medium-, and short-wavelength stimuli. Two consecutive measurements were performed on participants, one with their natural pupil size (range 4–5 mm diameter) and, subsequently, with six artificial eye pupils (1 mm to 6 mm). Results: Generally, the 1 mm pupil size caused the greatest reduction in contrast sensitivity for two of the three cones. There was no significant main effect of sex (F = 0.96, df = 1, p = 0.32) on the log cone contrast sensitivity of the L-cone. However, pupil size had a significant main effect (F = 116.1, df = 6, p < 0.001). Within each sex, the log CCS was significantly reduced as the pupil size decreased compared with the normal pupil size. Conclusions: New technologies that assess individual cone pathway functions could potentially assist in identifying early or progressive conditions that may impact color vision pathways from the retina to the brain. Standardized protocols—such as controlled retinal illumination—are critical to avoid misinterpretation.

This study compared the reading performance for Arabic text defined by chromatic and achromatic contrast to understand better how chromatic contrast affects reading of normally sighted individuals and to establish a baseline for determining whether patients have a selective red–green chromatic sensitivity loss. Reading performance for Arabic text was accessed by examining maximum reading speed (MRS), reading acuity (RA), critical print size (CPS), and the Reading Accessibility Index (ACC) using three near-point charts. The charts were the black-on-white Balsam Alabdulkader–Leat (BAL) chart, a red-on-green chart, and a gray-on-gray chart with a background luminance equal to the chromatic chart. The MRSs were significantly different (P = 0.03), with the red-on-green chart having a slightly higher value than the BAL chart. The ACC was lower for the BAL chart than the red-on-green and gray charts (P = 0.003). However, RA for the BAL chart was better, and the CPS was smaller relative to the red-on-green chart (P < 0.05) and gray chart (P < 0.001). Individuals with red–green color vision deficiencies had poorer RA and larger CPS on the red-on-green chart relative to the achromatic charts. Although the MRS and ACC of the chromatic chart were significantly higher, the difference was not clinically important. The result that the MRS was similar for all three charts confirmed earlier findings that MRS is similar if text contrast is sufficiently above threshold. The lower RA and corresponding larger CPS for the red-on-green and gray charts were due to their lower background luminance and lower contrast.