Persistent Dark Cones in Oligocone Trichromacy Revealed by Multimodal Adaptive Optics Ophthalmoscopy

Joanne Li; Tao Liu; Oliver J Flynn; Amy Turriff; Zhuolin Liu; Ehsan Ullah; Jianfei Liu; Alfredo Dubra; Mary A Johnson; Brian P Brooks; Robert B Hufnagel; Daniel X Hammer; Laryssa A Huryn; Brett G Jeffrey; Johnny Tam

doi:10.3389/fnagi.2021.629214

Persistent Dark Cones in Oligocone Trichromacy Revealed by Multimodal Adaptive Optics Ophthalmoscopy

Front Aging Neurosci. 2021 Mar 9:13:629214. doi: 10.3389/fnagi.2021.629214. eCollection 2021.

Authors

Affiliations

¹ National Eye Institute, National Institutes of Health, Bethesda, MD, United States.
² Center for Devices and Radiological Health, U.S. Food and Drug Administration, Silver Spring, MD, United States.
³ Department of Ophthalmology, Stanford University, Palo Alto, CA, Unites States.
⁴ Ophthalmology and Visual Sciences, University of Maryland School of Medicine, Baltimore, MD, United States.

Abstract

Dark cone photoreceptors, defined as those with diminished or absent reflectivity when observed with adaptive optics (AO) ophthalmoscopy, are increasingly reported in retinal disorders. However, their structural and functional impact remain unclear. Here, we report a 3-year longitudinal study on a patient with oligocone trichromacy (OT) who presented with persistent, widespread dark cones within and near the macula. Diminished electroretinogram (ERG) cone but normal ERG rod responses together with normal color vision confirmed the OT diagnosis. In addition, the patient had normal to near normal visual acuity and retinal sensitivity. Occasional dark gaps in the photoreceptor layer were observed on optical coherence tomography, in agreement with reflectance AO scanning light ophthalmoscopy, which revealed that over 50% of the cones in the fovea were dark, increasing to 74% at 10° eccentricity. In addition, the cone density was 78% lower than normal histologic value at the fovea, and 20-40% lower at eccentricities of 5-15°. Interestingly, color vision testing was near normal at locations where cones were predominantly dark. These findings illustrate how a retina with predominant dark cones that persist over at least 3 years can support near normal central retinal function. Furthermore, this study adds to the growing evidence that cones can continue to survive under non-ideal conditions.

Keywords: adaptive optics; color vision; dark cones; oligocone trichromacy; optical coherence tomography; pde6h; scanning laser ophthalmoscopy; visual function.