Microperimetry Features of Geographic Atrophy Identified With En Face Optical Coherence Tomography

Progressive geographic atrophy (GA) of the retinal pigment epithelium leads to loss of central vision. To identify GA in age-related macular degeneration and assess treatment, correlation of function observed on microperimetry with structure observed on optical coherence tomographic (OCT) images may be of value.

To characterize the microperimetric function of GA as identified from en face OCT imaging.

In a case-series study, 20 patients (22 eyes) entered the study at the University of Padova according to preplanned conditions. From March 1 to July 30, 2014, en face OCT images were obtained at the outer retinal layer and choroidal layer levels. The microperimetry sensitivity map was superimposed on the en face OCT images, which had been used to measure GA areas. Relative and dense scotoma rates were calculated in the GA areas. After data collection, the study eyes were divided into 3 groups according to the macular residual mean sensitivity.

Retinal sensitivity measured by microperimetry within areas of GA identified by en face OCT images.

Twenty patients (5 men and 15 women) were included in the study, with a mean (SD) age of 79.5 (7.0) years (range, 69-98 years). Macular residual mean retinal sensitivity was less than 5 dB in 7 eyes (group 1), 5 to 10 dB in 9 eyes (group 2), and greater than 10 dB in 6 eyes (group 3). Mean (SD) GA area differed among the groups at the outer retinal (13.13 [5.03] mm2 [range, 5.75-21.04 mm2] in group 1; 7.80 [3.25] mm2 [range, 3.31-13.52 mm2] in group 2; and 3.94 [2.35] mm2 [range, 1.46-7.90 mm2] in group 3; P = .001) and choroidal (11.83 [5.55] mm2 [range, 4.55-22.14 mm2] in group 1; 7.00 [4.29] mm2 [range, 0.90-13.83 mm2] in group 2; and 3.27 [2.29] mm2 [range, 0.91-7.23 mm2] in group 3; P = .007) layer levels. Mean (SD) GA area imaged at the outer retinal layer level was significantly larger than that imaged at the choroidal level in group 3 (difference, 0.67 mm2; 95% CI, 0.31-1.03 mm2; P = .005), but not in groups 1 or 2. Mean (SD) rate of relative scotoma was significantly higher in the GA area imaged at the outer retinal layer level than at the choroidal level in group 3 (47.70% [31.30%] [range, 13.60%-100%] vs 34.00% [37.30%] [range, 0%-100%]; difference, 13.74%; 95% CI, 3.84%-23.63%; P = .02), but not in groups 1 or 2.

In the early stage of GA, when retinal sensitivity is relatively good, these data suggest that the GA area imaged on en face OCT at the outer retinal level correctly detects the wide functional degenerative involvement of the photoreceptors. These findings provide novel data that correlate function and structure, which may be of value when assessing treatments that might prevent or reduce the rate of growth of GA.