Assessing the Relationship between Foveal Cone Density, Outer Nuclear Layer Thickness and Foveal Morphology

To assess the relationship between foveal cone topography, foveal outer nuclear layer (ONL) thickness, foveal morphology, and foveal avascular zone (FAZ) area in individuals with normal vision.

Retrospective cross-sectional study.

A total of 68 participants with normal vision were included (49 female; 19 male).

Directional OCT images were used to derive ONL thickness measurements. Images of the foveal cone mosaic were obtained using adaptive optics scanning light ophthalmoscopy, from which peak cone density (PCD) was measured. Foveal avascular zone area and foveal pit morphology were estimated using OCT angiography images and OCT macular thickness maps, respectively.

Foveal cone density metrics, foveal ONL thickness, foveal pit diameter and volume, and FAZ area.

There was a weak positive correlation between maximum ONL thickness and PCD in individuals with normal vision (r = 0.23; P = 0.06), and PCD was significantly negatively correlated with both foveal pit diameter (r = -0.54; P < 0.0001) and foveal pit volume (r = -0.39; P = 0.0011).

Findings suggest that foveal ONL thickness should be used with caution as a clinical biomarker of foveal cone density, at least when measured using current OCT technology. The relationship between foveal pit size and foveal cone density supports possible mechanistic links between the processes that establish these important features of foveal specialization.

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