Effect of defocus and spherical aberration on light disturbances measured with a new psychophysical method

Session Details

Session Title: Investigations and Complications Management

Session Date/Time: Tuesday 13/09/2016 | 13:30-15:15

Paper Time: 13:48

Venue: Hall C3

First Author: : J.González-Méijome PORTUGAL

Co Author(s): :    R. Araujo-de-Macedo   H. Ferreira-Neves   L. Rico-del-Viejo   S. Peixoto-de-Matos   J. Salgado-Borges        

Abstract Details

Purpose:

To evaluate the effect of spherical defocus, cylinder defocus and spherical aberration on the measurement the light disturbances surrounding bright sources of light under dim light conditions.

Setting:

CEORLab - Center of Physics, University of Minho, Braga, Portugal

Methods:

Twenty subjects were involved in the study. Light distortion has been measured using an experimental prototype (Light Distortion Analyzer, CEORLab, University of Minho, Portugal) comprising 24 LED arrays panel at 2 meters. Measurements were obtained under induction of +0.50, +1.00 and +1.50 D of spherical defocus, +2.00 and +4.00 D of cylinder and negative and positive spherical aberration (up to +/-0.300 microns for 5 mm pupil diameter). Size, shape, location and irregularity parameters have been obtained.

Results:

Size and shape of the light disturbance area increased linearly with the amount of spherical and astigmatic defocus induced (p<0.001). When negative spherical aberration was induced, the average size of the light disturbance tended to decrease (p>0.05) while the opposite occurred when positive spherical aberration was induced (p<0.05). The disturbance index increased from 14.86±6.12% to 57.98±36.20% (p<0.05) with the +0.300 microns plate. Graphical representations of the dysphotopic phenomena were rendered using customized software to exemplify their clinical significance and serve as demonstrations of the expected results in different clinical situations (undercorrection, overcorrection, residual astigmatism, side effects of refractive surgery).

Conclusions:

Measurements of light disturbance were fast and repeatable. Even small ammounts of spherical and astigmatic defocus can induce significant increases in light disturbances. While negative spherical aberration decreases light disturbances in the average eye, positive spherical aberration induces a dramatic increase in such photic phenomena. This results might have implications in our understanding of the dysphotoptic complains experience by some patients after refractive surgical procedures.

Financial Disclosure:

... is employed by a for-profit company with an interest in the subject of the presentation