Assessment of Multiple Visual Functions Important in Patients with iAMD

Karl G. Csaky, MD, PhD

The use of low luminance area under the log quantitative contrast sensitivity function (LL AULCSF) and other features of fundus autofluorescence (FAF) should be considered in clinical trials of intermediate age-related macular degeneration (iAMD), according to new cross-sectional findings.

The study data report that low luminance contrast sensitivity was significantly more reduced in eyes with non foveal nascent geographic atrophy (nGA) than in eyes with drusen alone, but other cone functions showed no differences between the two groups with normal luminance CS or low luminance visual acuity (LLVA).

“In the present study no correlation was found between normal luminance VA and LL AULCSF but only in eyes with nonfoveal nGA,” wrote study author Karl G. Csaky, MD, PhD, Retina Foundation of the Southwest. “Therefore, it may be important to understand that various cone visual function assessments reflect different aspects of cone function.”

Current investigators have studied vision function assessments of progression of intermediate AMD (iAMD) as an alternative or adjuncts to optical coherence tomography (OCT), but visual acuity (VA) may be unaffected through various stages of iAMD. Thus, to better stratify disease severity and risk of progression to more advanced stages, there is an unmet need to address additional functional markers.

The current cross-sectional study compared various measures of cone function in subjects with drusen alone and in subjects with drusen associated with non foveal nascent geographic atrophy (nGA). The measures included low luminance visual acuity (LLVA), the area under the log quantitative contrast sensitivity function (AULCSF), and LL AULCSF.

Csaky’s underlying hypothesis was that eyes with non foveal nGA represented more advanced iAMD and thus may have more widespread photoreceptor and retinal pigment epithelium (RPE) dysfunction. The study was performed as a single-site cross-sectional clinical trial of 60 eyes of 33 subjects aged ≥55 years with iAMD.

The study included 30 eyes with drusen only and 30 with non foveal nGA, determined by spectral-domain OCT and FAF, which underwent testing for best-corrected visual acuity (BCVA), LLVA, and the area under the log qCSF under both standard photopic and low luminance conditions.

In the drusen only group, the mean age was 76 years and 53% of the subjects were female. Data show the BCVA was 81 letters ± 3 (mean ± standard deviation [SD]), the LLVA was 65 letters ± 4, the AULCSF was 0.99 ± 0.0.5, and the LL AULCSF was 0.38 ± 0.04.

Then, in the nGA group, the mean age was 80 years and 66% of the subjects were female. The findings indicate the BCVA was 77 letters ± 4, LLVA was 61 letter mean ± 4, AULCSF was 0.87 ± 0.09, and LL AULCSF was 0.28 ± 0.06.

Meanwhile, the multivariate analysis of variance (ANOVA) examining the overall differences between the functional assessments of cone function demonstrated no significant difference between subjects when LLVA, AULCSF, and LL AULCSF are grouped together (P = .167).

Investigators noted a significant difference between the two groups in LL AULCSF (P = .037) when individual ANOVA tests were run for each of the three visual functions.

The linear regressions demonstrated significant relationships between normal luminance visual acuity and AULCSF under both normal and low luminance conditions in the drusen only group (r = .83 [P <10-9];  r = .68 [P <10-5]). Moreover, a significant but lower relationship was observed between normal visual acuity and AULCSF in the nGA group (r = .61 [P = .0004]).

However, normal luminance visual acuity did not correlate with AULCSF under low luminance conditions (r = 2.9 [P = .13]) in patients with non foveal nGA.

The study, “Cross-Sectional Study of Cone Function in Age-Related Macular Degeneration Subjects with Non-Foveal Nascent Geographic Atrophy,” was published in the American Journal of Ophthalmology.