Visual acuity and X-linked color blindness

  • Herbert Jägle
  • Emanuela de Luca
  • Ludwig Serey
  • Michael Bach
  • Lindsay T. Sharpe
Clinical Investigation

Abstract

Purpose

Optimal sampling for visual acuity requires a fine array of cones with identical sensitivity. Thus, dichromats, whose inner fovea is made up of cones having the same spectral sensitivity, may have better than normal visual acuity. We investigated this by comparing the visual acuities of trichromats and X-linked dichromats, while taking into account the different molecular genetics underlying the disorder.

Methods

Our subjects were age- and refraction-matched groups of normals (n=8) and X-linked dichromats (n=13). The dichromats (four protanopes and nine deuteranopes) were genotyped and classified according to whether they carried a single (n=6) or multiple (n=7) visual pigment genes on their X-chromosome. Visual acuity was measured in both eyes with the Freiburger Visual Acuity Test.

Results

Normal trichromats and ungenotyped dichromats do not significantly differ in visual acuity, nor do ungenotyped protanopes and deuteranopes. However, multi-gene dichromats, who possess more than one photopigment gene in the array, all of which encode for the same long- or middle-wavelength sensitive photopigment, have significantly higher visual acuity than either normal trichromats or dichromats who have only a single-gene.

Conclusions

Multi-gene dichromats may benefit from a reduction in chromatic aberration and chromatic noise in the high acuity channel, normally a consequence of combining signals from different cone photoreceptor types and of cone-specific patterns of retinal image defocus and blur. Single-gene dichromats may not share in the advantage because of other molecular differences that influence the development of the retinal mosaic and/or its visual pathways.

Keywords

Visual acuity Color vision Pigment genes 

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  • Herbert Jägle
    • 1
  • Emanuela de Luca
    • 1
  • Ludwig Serey
    • 1
  • Michael Bach
    • 2
  • Lindsay T. Sharpe
    • 1
    • 3
  1. 1.University Eye ClinicTübingenGermany
  2. 2.University Eye ClinicFreiburg im BreisgauGermany
  3. 3.Institute of OphthalmologyLondonUK

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