Visual Tasks Dependence of the Neural Compensation for the Keratoconic Eye's Optical Aberrations

Purpose: To investigate whether “normal” eyes viewing through keratoconic (KC) eye aberrations can achieve a similar visual performance (VP) to that of KC eyes. Method: We measured the high-contrast visual acuity (VA) and the 10, 15 and 20 c/deg contrast sensitivity (CS) of 6 KC eyes and 6 “normal” eyes while dynamically correcting their monochromatic aberrations. The VP of both populations was also measured when viewing through the usual sphero-cylindrical correction (i.e. spectacle correction) of each KC eye. In both cases, the desired wavefront was simulated thanks to a deformable mirror. Results: During dynamic correction, both KC and “normal” eyes showed similar (P>0.10) amounts of higher-order aberrations (in average, 0.10 μm of RMS for a 5.5 mm pupil). The difference between KC and “normal” eyes’ VP was 0.24 log units and 0.12 log-MAR in terms of CS and VA, respectively. When viewing through KC eye aberrations, “normal” eyes showed comparable or slightly better CS (difference of 0.05 log units) but lower VA (difference of 0.13 logMAR) than KC eyes. Conclusions: KC subjects are adapted to their poor retinal image quality. However, this neural adaptation might only occur for usual “real life” visual tasks (i.e., VA-related tasks)