Faculty Collaboration Database

Integrity of the cone photoreceptor mosaic in oligocone trichromacy. Invest Ophthalmol Vis Sci 2011 Jul 01;52(7):4757-64

Date

03/26/2011

Pubmed ID

21436275

Pubmed Central ID

PMC3175968

DOI

10.1167/iovs.10-6659

Scopus ID

2-s2.0-80052348348 (requires institutional sign-in at Scopus site)   32 Citations

Abstract

PURPOSE: Oligocone trichromacy (OT) is an unusual cone dysfunction syndrome characterized by reduced visual acuity, mild photophobia, reduced amplitude of the cone electroretinogram with normal rod responses, normal fundus appearance, and normal or near-normal color vision. It has been proposed that these patients have a reduced number of normal functioning cones (oligocone). This paper has sought to evaluate the integrity of the cone photoreceptor mosaic in four patients previously described as having OT.

METHODS: Retinal images were obtained from two brothers (13 and 15 years) and two unrelated subjects, one male (47 years) and one female (24 years). High-resolution images of the cone mosaic were obtained using high-speed adaptive optics (AO) fundus cameras. Visible structures were analyzed for density using custom software. Additional retinal images were obtained using spectral domain optical coherence tomography (SD-OCT), and the four layers of the photoreceptor-retinal pigment epithelium complex (ELM, IS/OS, RPE1, RPE2) were evaluated. Cone photoreceptor length and the thickness of intraretinal layers were measured and compared to previously published normative data.

RESULTS: The adult male subject had infantile onset nystagmus while the three other patients did not. In the adult male patient, a normal appearing cone mosaic was observed. However, the three other subjects had a sparse mosaic of cones remaining at the fovea, with no structure visible outside the central fovea. On SD-OCT, the adult male subject had a very shallow foveal pit, with all major retinal layers being visible, and both inner segment (IS) and outer segment (OS) length were within normal limits. In the other three patients, while all four layers were visible in the central fovea and IS length was within normal limits, the OS length was significantly decreased. Peripherally the IS/OS layer decreased in intensity, and the RPE1 layer was no longer discernable, in keeping with the lack of cone structure observed on AO imaging outside the central fovea.

CONCLUSIONS: Findings are consistent with the visual deficits being caused by a reduced number of healthy cones in the two brothers and the adult female. In the unrelated adult subject, no structural basis for the disorder was found. These data suggest two distinct groups on the basis of structural imaging. It is proposed that the former group with evidence of a reduction in cone numbers is more in keeping with typical OT, with the latter group representing an OT-like phenotype. These two groups may be difficult to readily discern on the basis of phenotypic features alone, and high-resolution imaging may be an effective way to distinguish between these phenotypes.

Author List

Michaelides M, Rha J, Dees EW, Baraas RC, Wagner-Schuman ML, Mollon JD, Dubis AM, Andersen MK, Rosenberg T, Larsen M, Moore AT, Carroll J

Author

Joseph J. Carroll PhD Director, Professor in the Ophthalmology and Visual Sciences department at Medical College of Wisconsin

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

Adolescent
Adult
Cell Count
Color Vision
Electroretinography
Female
Fluorescein Angiography
Fundus Oculi
Humans
Male
Middle Aged
Phenotype
Retina
Retinal Cone Photoreceptor Cells
Retinal Diseases
Tomography, Optical Coherence
Visual Acuity
Young Adult