Classification of complete and incomplete autosomal recessive achromatopsia

We studied color vision in 32 patients with autosomal recessive achromatopsia. Color matching revealed complete achromatopsia (rod monochromacy) in ten patients (Group I) and incomplete achromatopsia in the remaining twenty-two patients. Amongst the incomplete achromats, were three groups distinguishable by their color matching. Patients in Group II were dichromats; their color matches were mediated by rods and MWS (middle-wavelength sensitive) cones. Patients in Groups III and IV were trichromats. Color matches of patients in Group III were mediated by rods, LWS (long-wavelength sensitive) cones and MWS cones. Group III patients showed no evidence of SWS (short-wavelength sensitive) cones. Color matches of patients in Group IV were mediated by rods, LWS cones and SWS cones; color matching did not reveal MWS cones.