Natural History of Visual Function Changes Over Three Years in Normal Aging and in Early and Intermediate Age-Related...

The purpose of this study was to evaluate change in visual functions over 3 years in normal macular health, and early and intermediate age-related macular degeneration (AMD) including tests of rod-, cone-, and mixed rod-cone-mediated visions; and to evaluate whether visual function change over 3 years meets the minimal clinically important difference (MCID), defined as meaningful to patients in everyday life.

Eight visual functions were evaluated at baseline and 3-year follow-up (acuity, low luminance acuity, photopic and mesopic contrast sensitivity, mesopic and scotopic light sensitivity, and rod-mediated dark adaptation [RMDA] at 5 degrees and 12 degrees). The Age-Related Eye Disease Study (AREDS) 9-step classification system defined AMD severity.

In normal aging and intermediate AMD, 6 of 8 visual functions had statistically significant worsening over 3 years; mesopic contrast sensitivity and mesopic light sensitivity, respectively, showed no change. In early AMD, five of eight visual functions showed worsening over time, with photopic and mesopic contrast sensitivity and scotopic sensitivity unchanged. The largest percentage of eyes in each group meeting MCID was RMDA at 5 degrees or 12 degrees (38%-55%). The lowest percentage of eyes meeting MCID was visual acuity and photopic contrast sensitivity (0%-10%).

Whereas most visual functions evaluated have statistically significant worsening over 3 years in normal aging to intermediate eyes, the percentage of eyes reaching MCID was low for most visual functions except RMDA, which met MCID for almost half the eyes.

The natural history of change in visual function over time in normal aging to intermediate AMD should be characterized in terms of MCID, not only statistical significance.