Abstract
Purpose :
Photostress and photobleach have been studied as potential endpoints for evaluating novel therapeutics for maculopathies. Key to an effective endpoint is the ability to clearly distinguish study populations. The OraLux SystemTM and the Eger Macular Stressometer were compared to determine their relative ability to distinguish potential age differences in recovery of best corrected visual acuity (BCVA) after photobleach in a normal population.
Methods :
A group of 8 normal subjects (mean age 39.3 ± 16) (16 eyes) were subjected to macular photostress using the Eger Macular Stressometer and the OraLux System. Photobleach using the Stressometer was by means of a thyristor photo flash held at a distance of 6 inches. The OraLux System provided a diffuse light source of 40,000 cd/m2 viewed for 90 seconds from a distance of 12 inches (~84% cone photopigment bleach). Bleaching was performed in random order. At least 30 minutes were allowed for recovery from the OraLux bleach, and 10 minutes for the Stressometer, per protocol for that device. After photobleaching by each method, subjects were instructed to read an eye chart at 40 cm under two ambient light levels: 700 lux and 90 lux. The recovery time needed to read one line above BCVA was measured.
Results :
Mean VA recovery time (seconds) for the OraLux System increased with subject age (sec/year) at (1.24 OD, p=0.001; 1.07 OS, p=0.025) at 90 lux and (0.39 OD, p=0.45; 0.42 OS, p=0.26) at 700 lux. Mean recovery time at 90 lux was significantly greater for subjects over 40 years (98.2 sec) than for younger (61.4 sec) p=0.02. Mean VA recovery time (seconds) for the Stressometer did not trend consistently with subject age (-0.17 OD, p=0.31; -0.24 OS, p=0.094) at 90 lux and (-0.029 OD, p=0.26; 0.105 OS, p=0.22) at 700 lux. No mean comparisons were significant (p>0.11).
Conclusions :
The OraLux System showed a consistently better correlation than the Eger Macular Stressometer with regard to recovery of visual acuity and age over a range of ambient light levels, possibly due to a greater impact on cones during photostress. This system offers a potential new instrument for studying maculopathies and differentiating the impact of therapies in future clinical trials.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.