Cone mosaic characteristics in red-green colour deficiency: a comparative study

Rebika Dhiman; Vinay Gupta; Rohan Chawla; Atul Kumar; Rohit Saxena

doi:10.1016/j.jcjo.2019.11.007

Cone mosaic characteristics in red-green colour deficiency: a comparative study

Can J Ophthalmol. 2020 Jun;55(3):232-238. doi: 10.1016/j.jcjo.2019.11.007. Epub 2020 Jan 11.

Authors

Rebika Dhiman¹, Vinay Gupta¹, Rohan Chawla², Atul Kumar², Rohit Saxena³

Affiliations

¹ Neuro-Ophthalmology and Strabismus Services, Dr. R. P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
² Retina Services, Dr. R. P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.
³ Neuro-Ophthalmology and Strabismus Services, Dr. R. P. Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India. Electronic address: rohitsaxena80@yahoo.com.

PMID: 31937413
DOI: 10.1016/j.jcjo.2019.11.007

Abstract

Objective: To compare photoreceptor cone characteristics using adaptive optics (AO) technology between congenital colour blind patients and healthy age-matched controls.

Design: Cross-sectional.

Participants: 21 eyes (21 cases) with congenital red-green colour blindness and 21 eyes of age-matched controls (21 controls), all having a best-corrected visual acuity of 20/20 and normal ophthalmological examination, were recruited.

Methods: Colour vision testing was done using the Farnsworth-Munsell 100-Hue test and Nagel anomaloscope. Imaging of fovea was done using rtx1 AO retinal camera with a sampling window size of 4° × 4°. Peak cone density, intercone spacing, cone regularity, and cone dispersion were determined using AOdetect Mosaic software.

Results: Overall, mean cone characteristics at 2° off fixation in cases and controls, respectively, were density 26 587 ± 1328/26 448 ± 687 cells/mm² (p = 0.67), spacing 6.69 ± 0.17/6.75 ± 0.11 μm (p = 0.19), regularity 94.36 ± 2.56/94.83 ± 1.28% (p = 0.46), dispersion 10.22 ± 1.21/11.68 ± 0.79% (p = 0.0001), and hexagonality 50.62 ± 4.21/49.52 ± 2.45% (p = 0.31). No significant difference was noted in various cone metrics except dispersion, which was markedly decreased in colour-deficient individuals. At 4° off fixation, the cone characteristics were not significantly different between cases and controls: density 16 521 ± 1230/16 930 ± 678 cells/mm² (p = 0.37), spacing 8.60 ± 0.29/8.46 ± 0.17 μm (p = 0.19), regularity 92.68 ± 2.83/92.6 ± 3.05% (p = 0.95), dispersion 13.43 ± 3.48/13.65 ± 2.38% (p = 0.87), and hexagonality 45.22 ± 3.8/45.21 ± 5.5% (p = 0.99). A significant reduction in cone density, regularity, and hexagonality was associated with corresponding increase in spacing and dispersion as we moved from 2° to 4° off fixation in both cases and controls.

Conclusion: Cone photoreceptor characteristics are anatomically well preserved in young colour-deficient individuals except cone dispersion.

MeSH terms

Color
Color Vision Defects
Cross-Sectional Studies
Humans
Retinal Cone Photoreceptor Cells*
Software*
Visual Acuity