Examination of Cone Photoreceptor Packing and Foveal Architecture in Eyes of Children and Adults

Purpose: The fovea is a specialized retinal region that plays an integral role in vision. The goal of this dissertation was to better understand whether axial elongation impacts (a) overall foveal geometry in adults and children, and (b) parafoveal microvascular geometry in adults. Methods: (1) Foveal pit parameters were quantified from volume scans acquired in healthy adult eyes using spectral domain optical coherence tomography. Cone density, cone spacing, and foveal avascular zone (FAZ) geometry were quantified from adaptive optics scanning laser ophthalmoscope (AOSLO) images of cone photoreceptors and foveal capillaries. Metrics were compared between eyes with short and long axial lengths (ALs). (2) Cone density and spacing, foveal pit, and FAZ metrics were quantified in healthy children and examined as a function of age and refractive status. (3) AOSLO images of FAZ microvasculature were used to quantify metrics of parafoveal intercapillary regions (PICRs) within 3 zones in healthy adults. Metrics were examined as a function of axial length and FAZ geometry. Results: (1) Adult eyes with long ALs had lower cone densities and increased cone spacing (increased farthest neighbor, nearest neighbor, and intercell distances) (P<0.02). In the long AL group, eyes with larger FAZ areas had larger foveal pit volumes (P=0.004), areas (P=0.004), and diameters (P=0.003). Cone density was not related to FAZ area or foveal pit volume. (2) Foveal pit and FAZ metrics were not related to the age, axial length, or refractive status of healthy children. Cone density was lower in myopic versus non-myopic children at eccentricities of 0.2 and 0.3 mm (P<0.001). Age and cone density were not related after controlling for AL. (3) PICR minor axis was not related to axial length or FAZ area. However, eyes with smaller FAZ areas had more circularly-shaped PICRs, as evidenced by increased values of PICR circularity (P<0.05 for all zones). Conclusions: This dissertation increases understanding of the role of axial elongation on foveal features in healthy adults and children. Results suggest that the morphometry of the FAZ, parafoveal microvasculature, and foveal pit are not related to eye’s axial length, whereas cone density and spacing are affected by axial elongation.