Design of a novel smartphone-based photostress recovery time test for detecting abnormalities in the macula. A cross-sectional study.

Background: The study aims to present a new smartphone-based photostress recovery time test (K-PSRT test) that measures the stimulus-specific loss of visual sensitivity, as well as the differentiation between normal from abnormal macular function. This novel test defines a new standardized photostress application as an alternative tool for incorporation into clinical practice. Materials and methods: A total of 48 visually impaired eyes and 47 normal sighted age-matched controls eyes were enrolled in the study. The median age in subjects with impairment was 71.0 years, while the median age in normal subjects was 70.0 years. A light produced by the smartphone camera at approximately 5 cm distance, perpendicular to the eye up 10 s filled the pupil. The photostress recovery time was assessed immediately after the exposure by asking the subjects to read correctly at least three successive letters of size corresponding to the previous line of the BCVA line at a distance of 40 cm. The digital photostress testing was performed with the best-corrected visual acuity (BCVA). The patients were examined twice within 2 weeks. Correlations among the recovery times, the visual acuity, and the contrast sensitivity function as well as correlations concerning each specific ocular disease were also performed. Furthermore, correlations among technology, usability, and ease of performance in both groups were analyzed. Results: The initial median photostress recovery time in patients with impaired eyes was 83.5 (68.5, 126.0), while in the normal individuals was 39.0 (14.0, 43.0). The median visual acuity in individuals with impairment was 0.59 logMAR (0.40, 0.90), whereas in the normal individuals was -0,06 logMAR. Test-retest reliability study was performed on 26 eyes (16 males, 10 females) for visually impaired eyes as well as on 35 normal eyes (19 males, 16 females). Concerning the reliability, the average Intraclass Correlation Coefficients (with 95% confidence intervals) ICC (95% CI) = 0,99 (0,98-1,00), indicating significant correlation between them (p < 0.01). The coefficient of repeatability for eye measurements reaches clinically acceptable levels, which is demonstrated with increased repeatability and consistency. The recovery time in patients with diabetic retinopathy was statistically significantly lower than in those with dry age-related macular degeneration (p = 0.027) and those with wet age-related macular degeneration (p = 0.032). The patient group has lower scores concerning technology, usability, and ease of performance compared to the normal. Conclusions: This new testing modality (K-Photostress Recovery time test), is designed to be an easily implemented measurement in ophthalmic practice, and it can expand our understanding of macular function. The above findings support the usefulness of a novel reproducible photostress application as an indicator of macular pathology.