Visual field deficits in early age-related macular degeneration

Patients with early age-related macular degeneration (AMD) may retain good visual acuity but experience distortion and other qualitative visual changes. The purpose of the present study was to determine whether deficits of form recognition, as well as of light sensitivity, were related to retinal pigment epithelial (RPE) atrophy and/or drusen. We assessed form recognition deficits by the Amsler grid and by a perimetric test of letter recognition and sensitivity deficits by the macular threshold test of the Humphrey Field Analyzer in 59 patients with AMD and visual acuities of 20/40 or better. The number of defects on each test was compared with the area of RPE atrophy and with the area of drusen determined from fundus photographs. Multiple regression analyses based on ordinal data revealed that the number of visual field defects by each test was significantly correlated with the area of atrophy, but not with the area of drusen. There was also no significant tendency for a patient with a regional preponderance of drusen to have more impairment in the corresponding visual field. These results suggest that deficits of form recognition, as well as of sensitivity, in patients with early stages of AMD can be attributed to alteration of photoreceptor function associated with RPE atrophy, but not with drusen.