Faculty Collaboration Database

Evaluating outer segment length as a surrogate measure of peak foveal cone density. Vision Res 2017 Jan;130:57-66

Date

11/27/2016

Pubmed ID

27887888

Pubmed Central ID

PMC5186335

DOI

10.1016/j.visres.2016.10.012

Scopus ID

2-s2.0-85010217268 (requires institutional sign-in at Scopus site)   47 Citations

Abstract

Adaptive optics (AO) imaging tools enable direct visualization of the cone photoreceptor mosaic, which facilitates quantitative measurements such as cone density. However, in many individuals, low image quality or excessive eye movements precludes making such measures. As foveal cone specialization is associated with both increased density and outer segment (OS) elongation, we sought to examine whether OS length could be used as a surrogate measure of foveal cone density. The retinas of 43 subjects (23 normal and 20 albinism; aged 6-67years) were examined. Peak foveal cone density was measured using confocal adaptive optics scanning light ophthalmoscopy (AOSLO), and OS length was measured using optical coherence tomography (OCT) and longitudinal reflectivity profile-based approach. Peak cone density ranged from 29,200 to 214,000cones/mm² (111,700±46,300cones/mm²); OS length ranged from 26.3 to 54.5μm (40.5±7.7μm). Density was significantly correlated with OS length in albinism (p<0.0001), but not normals (p=0.99). A cubic model of density as a function of OS length was created based on histology and optimized to fit the albinism data. The model includes triangular cone packing, a cylindrical OS with a fixed volume of 136.6μm³, and a ratio of OS to inner segment width that increased linearly with increasing OS length (R²=0.72). Normal subjects showed no apparent relationship between cone density and OS length. In the absence of adequate AOSLO imagery, OS length may be used to estimate cone density in patients with albinism. Whether this relationship exists in other patient populations with foveal hypoplasia (e.g., premature birth, aniridia, isolated foveal hypoplasia) remains to be seen.

Author List

Wilk MA, Wilk BM, Langlo CS, Cooper RF, Carroll J

Authors

Joseph J. Carroll PhD Director, Professor in the Ophthalmology and Visual Sciences department at Medical College of Wisconsin
Robert F. Cooper Ph.D Assistant Professor in the Biomedical Engineering department at Marquette University

MESH terms used to index this publication - Major topics in bold

Adolescent
Adult
Aged
Albinism, Ocular
Case-Control Studies
Child
Female
Fovea Centralis
Humans
Male
Middle Aged
Ophthalmoscopy
Optics and Photonics
Retinal Cone Photoreceptor Cells
Retinal Photoreceptor Cell Outer Segment
Tomography, Optical Coherence
Young Adult