Congenital achromatopsia is a stationary retinal disorder with
autosomal recessive inheritance. It is characterized by significant
attenuation of cone-photoreceptor function. Symptoms include
photophobia, nystagmus, and poor visual acuity from birth. Unlike in
cone or cone–rod dystrophies, the retinal fundus usually appears
normal. Here we describe two siblings with congenital achromatopsia,
who exhibit different ophthalmic phenotypes. History was taken, and
ophthalmic examinations were performed in a 7-year-old girl and her
5-year-old brother, who were referred to our department because of poor
visual acuity. Two of their grandparents were brother and sister,
suggesting an autosomal recessive transmission in inheritance. They
have been followed for more than 13 years since the initial evaluation.
Symptoms, visual acuity, and kinetic visual field were very similar to
each other, consistent with findings of typical congenital
achromatopsia. However, color-vision tests suggested that the brother
had residual color discrimination, but the sister did not. The siblings
had different full-field electroretinographic and spectral-sensitivity
findings: residual cone functions were detected in only the brother, in
agreement with his residual color vision. They also had different
findings of retinal fundi and ocular refractions: the sister had
bilaterally atrophic-appearing macular lesions and myopic errors. In
contrast, the brother remains hyperopia and has exhibited no specific
retinal findings until age 18 years. The causes why both complete and
incomplete achromats occur in the siblings are uncertain but might be
caused by modifying effects of sex-related genes or by environmental
factors influencing certain gene regulations in cone photoreceptors.