Patients with this congenital, nonprogressive condition often have nystagmus as infants which may improve later. Eccentric fixation secondary to a small central scotoma is often present. Visual acuity is 20/200 or worse. Hyperopia is common. Photophobia is extreme and vision under daylight conditions improves in dim light. Patients are unable to distinguish any colors. However, there is considerable variability in symptoms and some individuals retain some color perception and have better visual acuity (sometimes 20/80) than others suggesting some residual cone function. The term ‘incomplete achromatopsia’ is sometimes applied to such cases but the molecular basis for this variation is unknown. Optical coherence tomography reveals the central retina to be thinner than in normal controls. The fundus appearance is normal, however.
ERG responses indicate an absence of cone function with no photopic responses.