Table 1

Summary of the cone dysfunction syndromes

Cone dysfunction syndromeAlternative namesMode of inheritanceVisual acuityRefractive errorNystagmusColour visionFundiMutated gene(s) or chromosome locus
LCR  =  locus control region; deletion in this region abolishes transcription of all L and M genes in the opsin pigment gene array and therefore inactivates both L and M cones.
*In the second class of mutations the LCR is preserved but changes within the L and M gene array lead to loss of functional pigment production. The most common genotype in this class consists of a single inactivated L/M hybrid gene. The most frequent inactivating mutation described results in a cysteine to arginine substitution, (Cys203Arg), a mutation known to disrupt the folding of cone opsin molecules.
Complete achromatopsiaRod monochromatismAutosomal recessive6/36–6/60Often hypermetropiaPresentAbsentUsually normal CNGA3
Typical achromatopsia CNGB3
Chromosome 14
Incomplete achromatopsiaAtypical achromatopsiaAutosomal recessive6/24–6/60Often hypermetropiaPresentResidualUsually normal CNGA3
Oligocone trichromacyOligocone syndromeAutosomal recessive6/12–6/24Equal incidence of myopia and hypermetropiaUsually absentNormalNormal
Cone monochromatismUncertain6/6AbsentAbsent or markedly reducedNormal
Blue cone monochromatismX linked atypical achromatopsiaX linked6/24–6/60Often myopiaPresentResidual tritan discriminationUsually normal(i) Deletion of the LCR
X linked incomplete achromatopsia(ii) Single inactivated L/M hybrid gene*
Bornholm eye diseaseX linked6/9–6/18Moderate to high myopia with astigmatismAbsentDeuteranopiaMyopicXq28