High-Pass Visual Acuity Loss and Macular Structure-Function Relationship in Patients With Primary Open-Angle Glaucoma

Abstract

Purpose: The Logarithm of the Minimum Angle of Resolution (logMAR) chart is the most common clinical test for assessing central visual function in glaucoma. However, based on the use of these charts, visual acuity (VA) often remains normal even when severe macular damage exists. Here, we aim to investigate the potential advantages of high-pass VA in detecting glaucoma compared with conventional VA.

Methods: Monocular best-corrected VA measurements were compared for a novel high-pass electronic VA chart (e-chart) and a conventional e-chart in 113 primary open-angle glaucoma (POAG) patients with normal logMAR VA and 65 age-similar healthy controls. One hundred thirty-nine POAG patients underwent spectral-domain optical coherence tomography (SD-OCT) for measurement of macular ganglion cell layer plus inner plexiform layer (GCL+IPL) thickness. Structure-function relationships between OCT measurements and the two VAs were compared. The enrolled eyes were divided into two groups for further analyses according to macular visual field (MVF) defects, specifically two or more adjacent abnormal points within the 12 central sites of 30-2 VF.

Results: The mean deviation (MD) of 30-2 VF test was -12.77 ± 7.47 dB for glaucoma group and -1.70 ± 1.12 dB for control group. The mean difference of the two VAs was slightly larger in glaucoma group (0.29 logMAR) than in control group (0.22 logMAR). The area under the receiver operating characteristic curve of the high-pass e-chart was larger than that of conventional e-chart (0.917 vs. 0.757, P < 0.001). Significant correlations between high-pass VA and GCL+IPL thickness were found only in the MVF-damaged group. Compared with conventional VA, high-pass VA demonstrates stronger correlations with nasal-side macular GCL+IPL thickness (Fisher's Z-test, two-tailed, P2mmin diameter = 0.033 and P3mmin diameter = 0.005).

Conclusions: Compared with conventional VA, high-pass VA displays slightly higher sensitivity to visual loss in glaucoma and has a stronger correlation with the nasal-side macular GCL+IPL thickness.

Translational relevance: The high-pass acuity test has the potential to be used as an ancillary tool to monitor glaucoma over time.

Figure 1.

Illustrations of the two optotypes: (A) High-pass designed letter “E” with average luminance of the strokes equaling to the luminance of the gray background. (B) Black-on-white style conventional letter.

Figure 2.

OCT imaging in this study: (A) Sectoral heat map of the GCL thickness. The average GCL thickness (in 1, 2, and 3 mm diameters) are shown for each of the nine sectors. The thickness of the inner plexiform layer was generated in the same manner. (B) The GCL+IPL thickness for evaluating structure-function relationships.

Figure 3.

(A) Bland-Altman plots for test-retest reliability for (a) the conventional e-chart (first test versus second test) and (b) the high-pass e-chart (first test versus second test) with data for the healthy controls plotted in green (dots) and the glaucomatous eyes in red (squares). The horizontal lines represent the bias of the tests and 95% Limits of Agreements. (B) Bland-Altman plots display the differences between the two VAs in the (a) healthy controls and (b) the glaucoma group.

Figure 4.

The ROC curves for the two acuity tests, conventional e-chart acuity test in blue (area under the ROC curve [AUC]: 0.757, P < 0.001) and high-pass e-chart test in green (AUC: 0.917, P < 0.001).

Figure 5.

Bland-Altman plots display the differences between the two VAs in the (A) MVF-preserved group and the (B) MVF-damaged group, respectively.

Figure 6.

The scatterplots show the correlations between the sectoral GCL+IPL thickness (nasal side and superior side) and high-pass VA. A regression line of each diagram was generated mathematically and shows the structure-function relationships between the sectoral GCL+IPL thickness and high-pass VA. (A) The plots for OCT data from 2mm-diameter macular area versus high-pass VA. (B) The plots for OCT data from 3 mm-diameter macular area versus high-pass VA.