Assessment of contrast sensitivity Part II: The relationship between objective lens opacity and laser interferometric contrast sensitivity in the cataract patient

Abstract

The laser interferometer can effectively bypass the optics of the eye and measure retinal function in patients with immature cataracts. However, it is not known how much laser interferometric measurements are impaired by cataract density. In this study we compared objective lens opacity using the IntraOptics opacity lensmeter with contrast sensitivity (CS) measured by a Randwal He-Ne laser interferometer. Comparison of lens opacity with CS in the cataract population revealed an inverse linear relationship between objective lens opacity and retinal contrast sensitivity. Separation by cataract type showed correlation coefficients as high as -0.91 for nuclear sclerotic predominant cataracts and as low as no significant correlation for posterior subcapsular predominant cataracts. Comparisons of before and after implantation surgery contrast sensitivities (as measured by the laser interferometer) with preoperative lens opacities (as measured by the IntraOptics opacity lensmeter) quantified the extent to which laser interferometric measurements underestimated potential retinal function. We found that for all cataracts, other than posterior subcapsular predominant cataracts, potential contrast sensitivity (in decibels) was underestimated by about 0.2 to 0.3 times the opacity measured by this technique.