Abstract
Purpose :
The amount of light absorbed by photoreceptors likely drops at early stages of retinal diseases (e.g., age-related macular degeneration) although basic visual functions like visual acuity (VA) and contrast sensitivity (CS) remain normal. The current study adapted a psychophysical paradigm to create a novel psychophysical test (photon noise test) presumably sensitive to the amount of light absorbed by photoreceptors. This experimental study tested the hypothesis that the photon noise test is better at detecting a reduction in the amount of light absorbed by photoreceptors compared to current standard functional tests: ETDRS (VA), Pelli-Robson (CS) and MARS (CS).
Methods :
Twenty-one young healthy adults participated in this study comparing the capability of the photon noise test and three standard clinical tests (ETDRS, Pelli-Robson, MARS) to discriminate the baseline viewing condition from a reduction of light absorbed by photoreceptors. To simulate a reduction of light absorbed by photoreceptors, neutral density (ND) filters of 0.5, 1.0 and 1.5 reducing the amount of light by a factor of 3.1, 10 and 31, respectively were used. The capability of each test to detect a reduced absorption of light was quantified by measuring the area under the ROC curve (AUC). Then, the capability of the photon noise test was compared to the capability of each clinical test using a chi-square test.
Results :
The figure shows the AUC for the four tests and three levels of light reduction. Even for the smallest amount of simulated reduction in absorption rate tested (ND filter=0.5), the capability of the photon noise test was outstanding (AUC=.95) and significantly higher (p<.015) than the three clinical tests, which were poor or acceptable (AUC of .66, .75 and .73 for ETDRS, Pelli-Robson and MARS tests, respectively).
Conclusions :
The photon noise test is better at detecting a small decline in light absorption than standard functional tests. The photon noise test may be useful to detect early signs of retinal diseases affecting the photoreceptors.
This is a 2021 ARVO Annual Meeting abstract.