Assessing Ganglion Cell Layer Topography in Human Albinism Using Optical Coherence Tomography

Abstract

Purpose To test whether ganglion cell layer (GCL) and inner plexiform layer (IPL) topography is altered in albinism. Methods Optical coherence tomography scans were analyzed in 30 participants with albinism and 25 control participants. Horizontal and vertical line scans were acquired at the fovea, then strip registered and averaged. The Duke Optical Coherence Tomography Retinal Analysis Program was used to automatically segment the combined GCL and IPL and total retinal thickness, followed by program-assisted manual segmentation of the boundary between the GCL and IPL. Layer thickness and area under the curve (AUC) were calculated within 2.5 mm of the fovea. Nasal-temporal and superior-inferior asymmetry were calculated as an AUC ratio in each quadrant. Results GCL and IPL topography varied between participants. The summed AUC in all quadrants was similar between groups for both the GCL ( P = 0.84) and IPL ( P = 0.08). Both groups showed nasal-temporal asymmetry in the GCL, but only participants with albinism had nasal-temporal asymmetry in the IPL. Nasal-temporal asymmetry was greater in albinism for both the GCL ( P < 0.0001) and the IPL ( P = 0.0006). The GCL usually comprised a greater percentage of the combined GCL and IPL in controls than in albinism. Conclusions The GCL and IPL have greater structural variability than previously reported. GCL and IPL topography are significantly altered in albinism, which suggests differences in the spatial distribution of retinal ganglion cells. This finding provides insight into foveal development and structure-function relationships in foveal hypoplasia.

The Influence of Axial Length Upon the Retinal Ganglion Cell Layer of the Human Eye

“…Raza and Hood (2015) 15 presented the average, segmented, two-dimensional GCL profile from macular volume scans in 36 healthy participants. Woertz and colleagues (2020) 41 measured the thickness of the segmented GCL along the horizontal and vertical meridians in 25 control participants. All of these measurements identify a peak thickness of approximately 60 microns in the nasal parafoveal region, and a slightly lower peak thickness on the temporal side.…”

“…[56][57][58] As the morphology of the foveal pit is influenced by multiple retinal layers, the GCL thickness profiles we report here cannot be directly related to these prior studies. Indeed, we note that Woertz and colleagues (2020) 41 found that the GCL and IPL had quite variable relative thicknesses across individuals, leading us to be cautious in attempting to relate our measurements of a single retinal layer to larger properties of retinal morphology.…”

Characterization of Retinal Thickness in Individuals with Albinism: Baseline Data for a Black South African Population

“… 14 , 25 , 27 Studies using OCT devices have shown that individuals with albinism have anomalous foveal morphology owing to foveal hypoplasia whereby the foveal depression is either missing or shallow and there is continuity of the inner retinal layers across the fovea. 4–6 , 12 , 14 , 18 , 31 To this extent, Meyer et al 5 and Holmström et al 14 reported that OCT images in albinism show a widespread thickening of the macular region with no differentiation of the central fovea from the rest of the retina because the ganglion cell and nerve fibre layers extend across the central fovea without thinning. 4 , 17 However, other studies have noted that there is significant variability in the fovea of individuals with albinism whereby some individuals have low-grade foveal hypoplasia and some of the features associated with normal foveal development.…”

“… 15 , 18 Consequently, foveal hypoplasia, which refers to the fovea being absent or partially developed, is a common clinical characteristic in individuals with albinism. 12 , 19 …”

“…10,11 The macular is one of the landmark structures on the retina and at its centre, referred to as the fovea, contains only cone photoreceptors that are responsible for high spatial resolution acuity. 10,12 With the introduction of optical coherence tomography (OCT), it is possible to non-invasively measure retinal thickness and document the retinal layers particularly at the fovea. 10,[13][14][15] In healthy individuals scanned using OCT technology, the fovea shows a distinctive morphology characterised by a depression that is formed by the peripheral displacement of the inner retinal layers (ganglion cell layer, inner plexiform layer and inner nuclear layer) and densely packed cone photoreceptors.…”