Clinical features of achromatopsia in Swedish patients with defined genotypes

Ophthalmic Genet. 2002 Jun;23(2):109-20. doi: 10.1076/opge.


Purpose: To describe the clinical phenotype, with emphasis on the electrophysiological findings, of patients with autosomal recessive rod monochromacy (RM) and defined mutations in the CNGA3/CNGB3 genes.

Methods: RM patients from eight different families were included in the study. Their genotypes were determined by DNA sequencing and/or RFLP analysis of PCR-amplified genomic segments of the CNGA3 and CNGB3 genes. For comparison, we investigated one patient with blue-cone monochromacy (BCM). The clinical examination included best-corrected visual acuity, fundus examination, and full-field ERG. In six patients, the examination was complemented by multifocal ERG (MERG).

Results: Three patients had three different CNG3A genotypes. Five patients were homozygous and one patient compound heterozygous for a 1-bp deletion (1148delC) in the CNGB3 gene. All patients examined presented with a visual acuity of 0.1-0.15. Small residual cone responses were noted in four young RM patients. The oldest patient examined (age 47 years) presented with pigmentary changes in the mid-peripheral retina and concentric constrictions of the visual fields.

Conclusions: Patients with RM and mutations in the CNGA3/CNGB3 genes presented a similar clinical phenotype, confirming the essential function of both the alpha- and beta-subunits of the cGMP-gated cation channel in cone photoreceptor function. Small remaining cone responses in a few of the younger patients and mid-peripheral pigmentary degenerations in the oldest patient examined indicate that there could be some degree of progression in retinal dysfunction in at least some patients with RM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Color Vision Defects / diagnosis
  • Color Vision Defects / genetics*
  • Cyclic GMP / metabolism
  • Cyclic Nucleotide-Gated Cation Channels
  • Electroretinography
  • Female
  • Fluorescein Angiography
  • Genotype
  • Humans
  • Ion Channels / genetics*
  • Male
  • Middle Aged
  • Mutation
  • Pedigree
  • Phenotype
  • Photoreceptor Cells*
  • Photoreceptor Cells, Vertebrate / pathology
  • Sweden / epidemiology


  • CNGB3 protein, human
  • Cyclic Nucleotide-Gated Cation Channels
  • Ion Channels
  • Cyclic GMP