PubMed · 14886563
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R J FLETCHER. 1951. Astigmatic accommodation.. https://pubmed.ncbi.nlm.nih.gov/14886563/
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A dynamic model of ocular accommodation is used to simulate the stability and dynamic performance of accommodating intraocular lenses (A-IOLs) that replace the hardened natural ocular lens that is unable to change focus. Accommodation simulations of an older eye with A-IOL materials having biomechanical properties of a younger eye illustrate overshoots and oscillations resulting from decreased visco-elasticity of the A-IOL. Stable dynamics of an A-IOL are restored by adaptation of phasic and tonic neural-control properties of accommodation. Simulations indicate that neural control must be recalibrated to avoid unstable dynamic accommodation with A-IOLs. An interactive web-model of A-IOL illustrating these properties is available at http://schorlab.berkeley.edu.
Although blur adaptation in myopia has been investigated, knowledge regarding its effect on blur sensitivity remains unknown. In the present study, changes in three blur thresholds (i.e., noticeable, bothersome, and non-resolvable blur) were assessed monocularly after 1h of blur adaptation in myopes. A Badal optical system was used to present either an isolated 20/50 Snellen E or 20/50 lines of text, with the full text field used in the latter condition for all blur judgments. Eight visually normal adult myopes were tested with paralyzed accommodation. All subjects exhibited blur adaptation, with a significant improvement in group mean visual acuity of -0.16 LogMAR. There was a consistent and concurrent significant decrease of 0.15-0.19 D in all blur thresholds for the isolated 20/50 E. However, there was no significant effect of blur adaptation on blur thresholds for the 20/50 text, with large intersubject variability evident. The enhanced blur sensitivity for the isolated E target may in part be attributed to the increased visual resolution following blur adaptation. Differences found in the blur thresholds for the two targets may be related to a variety of neuroperceptual phenomena, in particular lateral masking.
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