VISUAL FUNCTION MEASURES IN EARLY AND INTERMEDIATE AGE-RELATED MACULAR DEGENERATION

Abstract

Purpose: The objectives of this study were to evaluate 1) the feasibility of performing computerized tests of low luminance visual acuity (LLVA), cone-specific contrast (Cone Contrast Test [CCT]), contrast sensitivity, and microperimetry and 2) the test-retest repeatability of these outcomes in dry age-related macular degeneration (AMD).

Methods: This prospective study enrolled 30 subjects at a single site (8 controls, 8 early AMD, and 12 intermediate AMD). Subjects underwent LLVA, contrast sensitivity, CCT, and microperimetry with eye tracking. Low luminance deficit was defined as best-corrected visual acuity minus LLVA in EDTRS letters. Follow-up testing was administered at approximately 1 month.

Results: There was high test-retest repeatability at one month for all visual function metrics (intraclass correlations >0.7) except log contrast sensitivity (intraclass correlations 0.6). Compared with controls, patients with intermediate AMD showed significant deficits on best-corrected visual acuity, LLVA, low luminance deficit, percent-reduced threshold on microperimetry, and red CCT (P < 0.05), but not on contrast sensitivity, green and blue CCT.

Conclusion: This pilot study supports the feasibility and reliability of using LLVA, microperimetry, and CCT in early dry AMD. Our data suggest these measures can be used as alternative future clinical trial endpoints. A larger, prospective natural history study of alternative visual function measures in dry AMD is warranted.

Conflict of interest statement

No authors have a proprietary interest in this publication.

Figures

Figure 1

Boxplots showing (A) best-corrected visual acuity (BCVA), (B) low-luminance visual acuity (LLVA), (C) low-luminance deficit (LLD), (D) Red Cone Contrast Test (CCT), and (E) Percent Reduced Threshold on microperimetry testing for control and each age-related macular degeneration (AMD) AREDS clinical group. Each boxplot demonstrates outliers along with the maximum, upper quartile, median, lower quartile, and minimum values. (A) displays values collected during visit 1 only, while (B)-(E) show values from visits 1 and 2 in light and dark gray respectively. Black dots represent outliers while one asterisk denotes significance at the P D. Both early and intermediate groups had differing performance compared to controls on the Red CCT test during the second visit. E. The intermediate AMD group was characterized by a significantly higher percent reduced threshold as compared to the control group. BCVA and LLD are reported as aggregate letters; Percent Reduced Threshold and Red CCT are both measured as percent.

Figure 2

A-C Retinal sensitivity on microperimetry testing of participants from each of the three groups (control, early AMD and intermediate AMD). Color scale bar on the bottom of the image represents retinal sensitivity value range for microperimetry. Note the difference in retinal sensitivity between the 3 subjects with increasing AMD pathology. The corresponding values for BCVA, LLVA, LLD (all expressed in ETDRS letters), CCT red (%), and PRT are shown for each subject.

Figure 3

Scatterplots examining the relationship between functional measures amongst all subjects. A, B show correlations indicating worse BCVA is associated with worse low light visual function. C, D, E demonstrate strong relationships between LLVA and LLD (reported in letters) and MAIA measures PRT (%) and central foveal sensitivity (dB).