Change in contrast sensitivity functions with Corning CPF filters in patients with age related macular degeneration

Abstract

Do Corning CPF filters change contrast sensitivity in patients with age related macular degeneration (AMD)? A retrospective review was conducted of 54 charts of veterans with AMD receiving comprehensive low vision services at VICTORS (VA Chicago West Side). CSF measurements with the VISTECH 6500 test system were compared before and after introduction of Corning CPF filters. Veterans were asked if filters made a noticeable change in contrast. Pre/post-filter CSF data was obtained for 63 trials at 1 m test distance and 60 trials at the 3 m test distance. To evaluate the data we used an analytic function to fit the contrast sensitivity data previously described by Lakshminarayanan [Optom. Vis. Sci. 72 511 (1995)]. An index was used to compare pre- and post-filter information. Veterans were prescribed filters if improvement in contrast was noted, or a subjective improvement was made. Patients were then contacted post-filter during this retrospective study to determine if the filters still enhanced daily activities. Mean improvement in the contrast sensitivity for each spatial frequency ranged from +0.344 to +0.422 patches with the filters at 1 m and +0.183 to +0.548 patches at 3 m. 87.5% of patients reported improvement in contrast while performing activities of daily living with Corning filters. Paired t test are t = −3.8298 (p = 0.003) at 1 m and t = −4.957 (p = 0.000 01) at 3 m test distance. While the changes in the CSF with filters are statistically significant and consistent with report of self-improvement by patients, the change in the number of patches on the VISTECH 6500 chart is not clinically significant. Clinical implications are that the chart in its current format is not useful for the prescription of filters leaving patient perception of change as a better guideline.