There is more to accommodation of the eye than simply minimizing retinal blur

Abstract

Eyes of children and young adults change their optical power to focus nearby objects at the retina. But does accommodation function by trial and error to minimize blur and maximize contrast as is generally accepted? Three experiments in monocular and monochromatic vision were performed under two conditions while aberrations were being corrected. In the first condition, feedback was available to the eye from both optical vergence and optical blur. In the second, feedback was only available from target blur. Accommodation was less precise for the second condition, suggesting that it is more than a trial-and-error function. Optical vergence itself seems to be an important cue for accommodation.

Aberrations and accommodation

“…Recent work by Del Águila‐Carrasco et al suggests that accommodation responds to the actual changes in target vergence, and not changes in blur alone. A similar experiment to that of Phillips and Stark agreed somewhat with their results; nevertheless, when target blur was changed quickly, some participants’ accommodation was worse or even absent. An interesting conclusion of this work is that accommodation works much better when changes in light vergence were present than when there were only changes in target blur.…”

“…Knowledge of how aberrations vary with static accommodation provides information about the shape of the surface of the lens as well as information about its internal structure . Dynamic accommodation studies usually shed light on fundamental questions such as which cues trigger the accommodation system to accurately change the power of the lens and accommodate in the right direction, which is of particular interest concerning myopia development . From an applied science perspective, knowledge of how aberrations change with accommodation can lead to improved designs of multifocal and accommodative intraocular lenses, which imitate the profile of ocular aberrations during accommodation.…”

Amplitude, Latency, and Peak Velocity in Accommodation and Disaccommodation Dynamics

“…Accommodation dynamics have been extensively studied [ 2 – 9 ]. Two typical accommodation demand patterns have been used for this purpose in the past: sinusoidal [ 10 – 14 ] and pulse changes [ 7 , 15 – 17 ]. However, sinusoidal changes in demand are not suitable to properly evaluate first- or second-order dynamics of accommodation, that is, velocity and acceleration.…”

Predictability of Sinusoidal Stimulus Movement in Accommodative Demand Does Not Improve Accommodation

“…The analysis reported here differed from that of Marín-Franch et al 10 in that amplitude and temporal phase was calculated over time in each trial, using a loess-like approach locally fitting a sine function. Nevertheless, the results obtained with this new and more sophisticated analysis are consistent with the ones obtained with the original analysis.…”