Monday, February 24, 2014 11:00am – 12:30pm, in 489 Minor Hall

Retinal Image Quality in the Accommodating Eye

presented by

Larry N. Thibos, Ph.D.,
Professor Emeritus of Optometry, Indiana University

 

According to classical models of static accommodation, the human eye typically accommodates too much for distant targets (‘accommodative lead’) and too little for near targets (‘accommodative lag’). This classical model implies that the retinal image is typically defocused except for a singular accommodative state where lead transitions to lag. If habitual focusing errors are small enough to be functionally insignificant (i.e within the eye’s depth-of-focus) then they are of little consequence, but if they are large and functionally significant then it becomes important to understand why the visual system would tolerate a focusing error that is within its power to correct.

Our theoretical and empirical approach to this question is to quantify retinal image quality during accommodation while simultaneously monitoring visual performance and the wavefront aberrations of the eye. Our results show that focusing errors of the accommodating eye do not necessarily produce a measurable loss of image quality or clinically significant loss of visual performance, especially when accommodation is accompanied by pupil constriction that increases depth-of-focus. When retinal image quality is close to maximum achievable (given the eye’s higher-order aberrations), acuity is also near maximum. Conversely, when image quality is compromised by accommodative errors, acuity suffers as well. This latter case is more likely for mononcular viewing than for binocular viewing, which has implications for the visual control of accommodation.

 

Host: Austin Roorda

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