Abstract
Abstract: :
Purpose: To validate a new model addressing functional near reading capability with monofocal pseudophakes. Methods: The literature shows that a simple "blur–spot" model accounts for visual acuity (VA) loss with defocus and pupil size for individual subjects. [Reference: G. Smith, "Relation between spherical refractive error and visual acuity", Optom Vision Science, Vol 68, No 8, pp. 591–598.] Coupling the "individual–subject" VA behavior with populations of best–corrected visual acuity, realistic cumulative visual acuity distributions can be generated to investigate the near visual capabilities of pseudophakic subjects with monofocal IOLs. The method assumes that the visual acuity (VA) for each subject in a distribution of best corrected visual acuities is governed by: VA^2 = Vo^2 + (k Dp Rx)^n, where Vo is best correct visual acuity, k the model constant, Dp the pupil diameter, Rx the refractive error and n a model constant approximately equal to 2. Results: Cumulative visual acuity distributions were generated to quantify the percentages of subject with various levels of near visual acuity. Comparing these to distance–corrected near VA data demonstrated that the predictions are accurate only if reasonable variations in near test distance and population–specific pupil size are included using a Monte Carlo statistical method. Conclusions: This model addresses the controversy of functional near reading capability with monofocal pseudophakes, elucidating the effects of shifts in mean pupil size (e.g. age), myopic defocus and mean best corrected VA. The model was also extended to include the effects of pseudoaccommodation with multifocal IOLs, demonstrating reasonable agreement between prediction and measurement.
Keywords: aging: visual performance • visual acuity