Selective cone dystrophy with protan genotype

Invest Ophthalmol Vis Sci. 1995 Nov;36(12):2381-7.


Purpose: To determine the functional defects in two male patients with progressive cone dystrophy and hybrid L-M cone pigment genes.

Methods: Clinical evaluation, standard electroretinography, and electrooculography were performed in two affected patients and two family members. Measurements of spectral sensitivity and transient tritanopia were made in both patients.

Results: In the patients, visual acuity varied between 20/50 and 20/100. The electroretinogram showed reduced flicker responses. When light adapted, a-wave amplitudes were borderline, but b-wave amplitudes were reduced severely. Electroretinography with chromatic stimuli showed a difference between well-preserved responses to green and markedly reduced responses to red stimuli. Spectral sensitivity measurement revealed a lack of L (long-wavelength sensitive; red) cone function and normal function of the S (short-wavelength sensitive; blue) and M (middle-wavelength sensitive; green) cones. Transient tritanopia was abnormal, indicating a severe disturbance of cone-cone interaction.

Conclusions: Progressive cone dystrophy with predominant dysfunction of L cones exists in both patients. The cone dystrophy may be caused by a rearrangement of the X-chromosome pigment gene array that is associated with the deletion of L-cone sequences and the formation of hybrid L-M cone pigment genes. It cannot be excluded, however, that both patients have protanopia and that cone dystrophy developed because of other causes.

MeSH terms

  • Adult
  • Aged
  • Color Perception / physiology
  • Color Vision Defects / genetics
  • Color Vision Defects / physiopathology*
  • DNA / analysis
  • Dark Adaptation
  • Electrooculography
  • Electroretinography
  • Female
  • Genotype
  • Humans
  • Male
  • Retinal Cone Photoreceptor Cells / physiopathology*
  • Retinal Degeneration / physiopathology*
  • Retinal Pigments / genetics*
  • Sensory Thresholds / physiology
  • Visual Acuity


  • Retinal Pigments
  • DNA