Ganglion Cell Complex Thickness and Visual Function in Chronic Leber Hereditary Optic Neuropathy

Abstract

Purpose: To evaluate the correlation between the macular ganglion cell complex (GCC) thickness measured with manually corrected segmentation and visual function in individuals with chronic Leber hereditary optic neuropathy (LHON).

Methods: Twenty-six chronic LHON subjects (60% treated with idebenone or Q10) from the Swedish LHON registry were enrolled. Best-corrected visual acuity (BCVA), visual field tests, and optical coherence tomography (OCT) were performed. Visual field was evaluated with the Haag-Streit Octopus 900 with the Esterman test and a custom 30° test. Canon OCT-HS100 scans were exported to the Iowa Reference Algorithm. GCC thickness was obtained after the segmentation was corrected manually in nine macular sectors.

Results: The GCC thickness was overestimated by 16 to 30 µm in different macular sectors with the automated segmentation compared with the corrected (P < 0.001). GCC thickness in all sectors showed significant correlation with all functional parameters. The strongest correlation was seen for the external temporal sector (BCVA: r = 0.604, P < 0.001; mean defect: r = 0.457, P = 0.001; Esterman score: r = 0.421, P = 0.003). No differences were seen between treated and untreated subjects with regard to GCC and visual field scores (P > 0.05), but BCVA was better among treated subjects (P = 0.017).

Conclusions: The corrected GCC thickness showed correlation with visual function in chronic LHON subjects. The frequently occurring segmentation errors in OCT measurements related to chronic LHON can potentially be misleading in monitoring of disease progression and in evaluating the treatment effects. Precise measurements of GCC could serve as a sensitive tool to monitor structural changes in LHON. We therefore emphasize the importance of careful evaluation of the accuracy of OCT segmentation.

Figure 1.

Schematic representation of the macula sectors overlapped on scanning laser ophthalmoscopy images from the OCT. Macula scan, 10 × 10 mm; 1024 × 128 B-scans. The yellow grid represents the ETDRS grid defined by three concentric rings with diameters of 1, 3, and 6 mm. CC, central circle; IR, internal ring; IS, internal superior; IN, internal nasal; II, internal inferior; IT, internal temporal; ER, external ring; ES, external superior; EN, external nasal; EI, external inferior; ET, external temporal.

Figure 2.

Points of stimuli at 10°, 15°, 20°, 25°, and 30°. The test was designed with the following protocol: custom, dynamic, low vision, white-on-white, Goldmann size V stimulus.

Figure 3.

Automatic segmentation of the GCL–IPL by the OCT instrument built-in automated segmentation algorithm of a foveal B-scan of a chronic LHON subject. (A) Foveal B-scan from Canon OCT-HS100 (purple and yellow lines represent GCL–IPL segmentation). (B) Foveal B-scan from the ZEISS CIRRUS 5000 (orange and cyan lines represent GCL–IPL segmentation). In A, segmentation error can be seen on the temporal side, and in B on the nasal side.