First Author: S.Peixoto-de-Matos PORTUGAL
Co Author(s): H. Neves J. Gonzalez Meijome N. Lopez Gil
Purpose:
There is an interest in methods to improve night vision disturbances. Furthermore, the benefit of correcting certain optical imperfections of the eye such as spherical aberration is not always well understood and cannot be predicted with the desired confidence. To evaluate the effect of a soft contact lens that corrects positive spherical aberration on reducing the negative over-refraction to optimize the visualization of a punctual light under a dark environment.
Setting:
Clinical & Experimental Optometry Research Lab (CEORLab), Center of Physics, University of Minho, Braga, Portugal.
Methods:
Twenty-eight right eyes from 28 patients were fitted with a silicone hydrogel soft contact lens that compensates for the spherical aberration of the eye. The patients were allowed to wear the lenses for 15 days and were evaluated at different intervals during this period (Baseline, 7 and 15 days). In the presence of positive spherical aberration when looking to a small punctual stimulus, the eye tends to accommodate to naturally reduce the spherical aberration by changing the shape of the crystalline lens (Lopez-Gil et al. ARVO Meeting 2012 1360/A32). As a result, the ove-refraction to optimize the visualization of such a stimulus is more myopic. The effectiveness of the correction of the spherical aberration with the Purevision HD2 (Bausch + Lomb, Rochester, NY) was assessed by over-refracting the eye with and without the contact lens while the patient was looking at the punctual stimulus in a dark room. A small light emitting diode (LED) of 1 mm was used as fixation stimulus.
Results:
The contact lenses reduced the spherical aberration of the eye from an average of 0.13±0.16 microns to -0.03±0.20 microns for a 6 mm pupil size (p<0.05, paired sample T-test) after 15 days of lens wear. The mean over-refraction obtained without lenses was of -0.81±0.54 D for a punctual LED before lens fitting and -0.22±0.22 D after contact lens fitting (p<0.05, paired sample T-test). The over-refraction under daylight conditions did not change significantly with the lens compared to the values obtained without the lenses suggesting that changes obtained in dark environment are not due to refractive errors induced by the lens itself. Visual acuity under photopic conditions was also unchanged between the best spectacle corrected visual acuity and best contact lens corrected visual acuity (p>0.05).
Conclusions:
Silicone hydrogel soft contact lenses that reduce the positive spherical aberration of the eye are effective in improving the visual quality of the ey while viewing a punctual stimulus under dark environment. These findings open new directions to the improvement of night vision disturbances. The effectiveness of correcting positive spherical aberration with contact lenses might also indicate with greater confidence which patients must benefit from such a correction with some surgical solutions such as apheric IOLs or custom corneal treatments, but this might be further studied in future clinical trials. FINANCIAL DISCLOSURE?: No
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