Dark adaptation measurement using a smartphone

Abstract

Purpose : Dark adaptation (DA) measurement is important for detecting retinal diseases. We developed a smartphone app for DA measurement and performed its preliminary evaluation in normal vision (NV) and visually impaired subjects.

Methods : Testing was done by placing a Samsung Galaxy S8 smartphone in front of the subject sitting in a dark room (40 cm from the test eye). After bleaching, a series of blue stimuli of size 1° between luminance range of -1.5 to -4 log Cd/m² were presented 8° inferior to the fixation on the smartphone display. The subject tapped the screen whenever the stimulus was visible, and the time and stimulus threshold were logged. Test duration was capped at 15 minutes. Evaluation of the app was primarily based on examination of age effect on DA characteristics in NV subjects (n=10), between 24 to 82 years of age (mean 45, std. 20) with visual acuity (VA) 20/25 or better, and without diagnosis of any vitreoretinal conditions. Additionally, we tested 1 patient with retinal damage due to myopic degeneration (MRD) (VA 20/100, age 62) and 1 patient with optic nerve atrophy (ONA) (VA: 20/500, age 40) to verify whether the effect of pathology can be detected by the app. Outcome measures were time to reach the minimum test threshold luminance, TMAX (15 minutes if the test ended before that), and the area under the time-luminance threshold curve (AUC). AUC was normalized using the preset bounds on test duration and luminance thresholds of the device. Regression analysis was used for determining age effect on outcome measures.

Results : TMAX and AUC increased with age in NV subjects (TMAX: R² = 0.48, p = 0.016; AUC: R² = 0.51, p = 0.012). The 95% confidence interval (CI) for within-subject differences for TMAX and AUC was ±2 min. and 6%, respectively. As expected, DA was greatly prolonged in the MRD subject with the final luminance threshold 1.2 log Cd/m² higher than the minimum test threshold at the termination of the test. The AUC was outside the 95% CI of regression of age and 52% greater than the NV mean. On the other hand, for the ONA subject, TMAX (12.8 min.) was not significantly different than the NV subjects (within the interquartile range of the regression of age), and the AUC was 21% larger than the NV mean, but still within the 95% CI of regression of age.

Conclusions : The smartphone app might be able to detect the effects of age and retinal pathology on DA characteristics. Further investigation is warranted.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.