conedystrophies

Cone dystrophies are a group of inherited retinal disorders in which the cone photoreceptors are primarily affected, leading to impaired central vision, color vision defects, and light sensitivity. The condition exists on a spectrum; when rods are involved early or later, it is referred to as cone-rod dystrophy. The onset can be in childhood or adulthood, and the rate of progression varies among individuals.

Clinical features typically include decreased central visual acuity, reduced or altered color vision, and photophobia. Central or paracentral scotomas may appear as the disease advances. Fundoscopic findings can range from macular lipofuscin-like changes to geographic atrophy or bull’s-eye maculopathy. Peripheral vision is often relatively preserved early in the disease. Electrophysiological testing usually shows diminished or absent cone responses with relatively preserved rod function in pure cone dystrophy, while cone-rod dystrophy demonstrates a progressive decline in both cone and rod function.

Diagnosis relies on a combination of clinical examination, multimodal imaging, and genetic testing. Optical coherence tomography often reveals disruption of the ellipsoid zone and thinning of the outer retina. Fundus autofluorescence can show central hypoautofluorescence or a bull’s-eye pattern. Electroretinography helps distinguish cone-dominant disease from mixed cone-rod involvement. Genetic testing identifies pathogenic variants and informs inheritance patterns.

Inheritance is heterogeneous, including autosomal dominant, autosomal recessive, and X-linked forms. Variants have been found in several genes, such as ABCA4, PRPH2, GUCA1A, and CACNA1F, among others, reflecting genetic and phenotypic diversity.

There is no cure; management focuses on visual rehabilitation, assistive devices, and environmental light protection. Regular monitoring for disease progression and associated complications is recommended, with prognosis varying by genotype and individual course.