Achromatopsia
What is it?
Achromatopsia is a hereditary visual disorder characterized by lack of color vision, decreased vision, light sensitivity, and nystagmus (tremor of the eyes). The cause of this disorder is the absence of functioning cones (photoreceptors) in the retina. There are two types of achromatopsia: complete and incomplete, depending on the presence of some functional cones. The difference between these types is the severity of the symptoms. Patients with complete achromatopsia can perceive black, white, and shades of gray, while the patient with incomplete achromatopsia may perceive some limited colors.
Achromatopsia is an autosomal recessive disorder, meaning that for the disease to develop, both copies or alleles of the gene should be mutated.
Signs & symptoms
Children with achromatopsia have reduced vision, no color vision, sensitivity to light (photophobia), and nystagmus (shaking of the eyes).
The world of children with complete achromatopsia consists of different shades of gray ranging from black to white, rather than seeing the world as black and white. The world of patients with incomplete achromatopsia may perceive some limited colors.
They see better in subdued light, which is why achromatopsia is sometimes called "Day Blindness". Children with incomplete achromatopsia may have better vision and have fewer visual symptoms. Nystagmus and photophobia, marked in infancy, may improve with age. Achromatopsia is a non-progressive disorder, meaning the vision is usually stable over time.
Diagnosis
The diagnosis of achromatopsia will be made by the ophthalmologist. Family history and symptoms like light sensitivity and reduced vision will provide critical clues for diagnosis. Most of the time, the retinal examination will be normal. In the clinic, the doctor will perform a few color vision tests: Ishihara pseudoisochromatic tests, H-R-R tests, Farnsworth panel D15 color test, and the City University tests.
Other tests that are important in making the diagnosis are optical coherence tomography (OCT), fundus autofluorescence, visual fields, as well as electroretinogram (ERG) to measure cone function.
For confirming the diagnosis, a genetic test can be performed to test the mutations in the most common genes.
Treatment
Currently, there is no cure for achromatopsia, so the treatment today is symptomatic for improving the vision somewhat but not restoring normal levels of vision. Glasses can correct refractive conditions such as far-sightedness (hyperopia), near-sightedness (myopia), and astigmatism.
Red-colored or darkly tinted lenses can help to reduce the sensitivity to light and thus enhance visual functioning. NoIR (injection-molded) plastic wrap-around glasses have a top ״shield״ that covers the top of a prescription frame as well as broadside shields which is important since stray light can be disabling.
A newer device, known as the Eyeborg system can help people with no color vision to perceive color through sound waves.
☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.
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