Achromatopsia 3 is a congenital, nonprogressive form of blindness. It is sometimes referred to as a rod monochromacy or stationary cone dystrophy. Symptoms are usually present at birth or shortly thereafter. Patients have pendular nystagmus, progressive lens opacities, severe photophobia, 'day' blindness, and, of course, color blindness. High myopia is a feature in some populations. Vision in daylight is often 20/200 or less but vision in dim light is somewhat better. The central scotoma often leads to eccentric fixation.
The ERG shows a complete absence of cone function. Optical coherence tomography has demonstrated a reduction in macular volume and thickness of the central retina, most marked in the foveolar region, presumably due in some way to the absence or dysfunction of cone photoreceptors. Few histologic studies of adequately preserved retina have been reported but those available suggest dysmorphism of cones in the central macula. The clinical appearance of the retina is usually normal.
