Effects of refractive corrections on contrast sensitivity under mesopic conditions

ANÍBAL DE PAUL; LUIS ISSOLIO; SILVIANA COMASTRI; JUAN ANTONIO APARICIO; ELISA COLOMBO

Benasque

Congreso; Engineering the Eye III; 2011

We have previously described a model that accounts for the influence of refractive correction on the parameters that determine the veiling luminance produced by a glare source: illuminance and angle. In this work we study the effect of a glare source on contrast sensitivity in mesopic lighting conditions when a subject wears glasses, adding to the study the effect of blur caused by an inappropriate refractive compensation. We measured contrast sensitivity for sinusoidal gratings with spatial frequencies of 2 and 8 c/deg, and an adaptation luminance of 0.5 cd/m2 in emmetropics subjects. We used contact lenses (-5D, -2D, +2D and +5D) in order to induce different degrees of ametropia in these subjects. In all cases the induced ametropia was corrected with ophthalmic lenses for the best visual acuity. Results are expressed as loss of sensitivity by means of the ratio of the contrast sensitivity measured with glare and without glare. The highest ratios were obtained for the condition of emmetropia, being reduced in cases of induced ametropia for both myopia and hyperopia. The measurements with ±0.25D additions produced a much greater loss of sensitivity than those can be explained by the effect of changes in the veiling luminance. In addition to parameters, such as illuminance and angle of the source in the model tested, should be included other factors such as the blur. These results warn about the importance of adequate compensation of ammetropia to prevent the effects of glare.