Changes in retinal sensitivity in geographic atrophy progression as measured by microperimetry

Abstract

Purpose: To characterize changes in macular sensitivity during geographic atrophy (GA) progression using microperimetry.

Methods: Retinal sensitivity in the macular area was evaluated by microperimetry in 10 patients with bilateral GA, with adequate data obtained in 9 of 10 patients (n = 18 eyes). Patients had been enrolled in an interventional trial in which one eye had been randomized to treatment and the other eye observed. No treatment effect with regard to GA growth and microperimetric measurements was detected, and all eyes were analyzed. Microperimetric assessments of the central 20° of the macula were performed every 6 months over 24 months. Parameters analyzed included number of scotomatous points, mean retinal sensitivity of responding points, and fixation stability. Autofluorescence imaging and fundus photography were also obtained.

Results: Microperimetric parameters demonstrated statistically significant changes as a function of time. Mean number of scotomatous points increased significantly with time (P = 0.004) at a rate of 4.4 points/year. Mean retinal sensitivities of all points, all responding points, and all perilesional points all decreased significantly with time (P < 0.003), as did fixation quality within the 2° and 4° circles (P < 0.002). The growth of GA lesion area was associated with the changes in the number of scotomatous points (P = 0.01) but not with changes in the other microperimetric parameters.

Conclusions: Macular sensitivity and fixation quality undergo progressive change during the GA progression, reflecting alterations in macular function extending beyond the GA lesion proper. Microperimetric measurements may provide useful functional outcome measures for the clinical study of GA.

Trial registration: ClinicalTrials.gov NCT00306488.

Figure 1.

Changes in functional scotoma in GA progression on microperimetry testing. Interpolated map demonstrating a progressive expansion in the functional scotoma corresponding to the GA lesion as shown at (A) baseline, (B) 12 months, and (C) 24 months for a representative eye with GA. Areas in red indicate nonresponding points with an absolute scotoma. (D) The mean number of scotomatous points for all study eyes increased steadily as a function of follow-up time, reflecting a progressive increase in the area of functional scotoma with time (n = 18 eyes for time points 0, 6, 12, and 18 months; n = 16 for time point 24 months).

Figure 2.

Changes in overall macular sensitivity in GA progression on microperimetry testing. Interpolated map demonstrating progressive changes in macular sensitivity at (A) baseline, (B) 12 months and (C) 24 months in a representative eye with GA. Color coding in maps and their temporal progression illustrate overall decreases in areas of higher sensitivity (green and yellow) and increases in areas of lower sensitivity (orange and red). (D) Graph of the mean change in macular sensitivity of all tested points as a function of time. Error bars, SE.

Figure 3.

Changes in sensitivity of responding points at baseline after 1 and 2 years on microperimetry testing. Responding points at baseline were identified and scored at 1 and 2 years of follow-up as to whether they had decreased in sensitivity by at least 10, 6, or 4 dB or transitioned to a nonresponding/scotomatous point. Error bars, SE.

Figure 4.

Location of macular sensitivity change with time outside the GA lesion on microperimetry testing. (A) Symbolic microperimetric map in a representative eye with GA. (B) Corresponding map showing the segmentation of tested points into scotomatous or nonresponding points (pink), perilesional points (i.e., points immediately adjacent to scotomatous points, blue), and extralesional points (i.e., all remaining points, gray). (C) Comparison of the mean sensitivity of perilesional and extralesional points in all study eyes (n = 18) demonstrate a significantly greater sensitivity in extralesional points. (D) Graph of mean change in sensitivity from baseline for perilesional and extralesional points as a function of time demonstrates a more marked decline in perilesional compared with extralesional points. Error bars, SE.

Figure 5.

Changes in fixation quality with time on microperimetry testing. Representative study eye at baseline (A) with recordings of eye position (blue points) around a fixation cross. Fixation was quantified by calculating the percentage of eye positions during fixation assessment that fall within circle of either 2° or 4° diameter centered on fixation (inset). (B) Fixation measurement of the same eye at 24 months. Changes in fixation quality with time were followed by calculating the percentage of fixation points falling within the (C) 2° circle or (D) 4° circle. Reduction in fixation quality as a function of time was evident in both measures. Error bars, SE.