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Adult Refsum disease (ARD) is a rare inherited disease where a fat called phytanic acid builds up in the body, leading to different symptoms. The most common first sign of ARD is night blindness, caused by retinitis pigmentosa. Other symptoms include deafness, loss of smell, peripheral neuropathy (numbness in the hands and feet), and cardiac abnormalities. ARD is a unique cause of RP, as progression of vision or hearing loss is suspected to be slowed by maintaining a specific restrictive diet that prevents the build up of phytanic acid.

Learn more about ARD.


Axenfeld-Rieger Syndrome (ARS) is a rare autosomal dominant genetic disease that affects eye development. The most common eye symptom is a small or absent iris and about half of individuals with ARS will develop glaucoma. ARS can have other symptoms that affect other parts of the body, including changes in the facial bones or teeth. Medical or surgical intervention is used to manage the glaucoma, which can present anytime but usually occurs in adolescence.

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Best disease (vitelliform macular dystrophy) is an inherited disease that causes macular degeneration. Best disease is usually diagnosed young and shows up as small cysts under the macula, the central area of the retina that is responsible for detail and central vision. Vision may not be affected at early stages when cysts first develop. Peripheral vision generally remains normal. Eventually these cysts rupture and cause fluid to leak throughout the macula. Symptoms of Best disease are loss of central vision, loss of color perception and fine detail. Vision loss is not always the same between eyes and sometimes one eye retains significantly more vision than the other.

Learn more about Best Disease.

Charles Bonnet Syndrome

Charles Bonnet Syndrome (CBS) causes a person with vision loss to see things that aren’t there (visual hallucinations). It is caused by the brain adjusting to significant vision loss. CBS is very common, especially for individuals with age-related vision loss such as age-related macular degeneration or glaucoma. The experience of having visual hallucinations can be compared to phantom limb syndrome in someone who has lost a limb.

The visual hallucinations can be described as simple patterns or more complicated images (people or landscapes), and can last for seconds, minutes, or hours. The hallucinations can change how surroundings look and can make it difficult to function. The hallucinations may be surprising, but they are usually not scary. Many people do not talk about their experience because they may feel embarrassed or afraid that it is a sign of dementia. Visual hallucinations from CBS go away for many people, but there is no cure or specific treatment. If you are experiencing CBS talk to your doctor to learn more about the condition and tips that may reduce symptoms.

Learn more about CBS.


Cone-rod dystrophy (CRD) describes a group of inherited diseases that affect the retina. Unlike the more well-known group of rod-cone dystrophies (RCD) which includes retinitis pigmentosa, CRD affects central vision first. CRD is characterized by gradual deterioration of the cones, which are responsible for central and detail vision. Symptoms of CRD include decreased visual acuity and photophobia (sensitivity to light) that start in childhood.

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Optic nerve hypoplasia (ONH) is a condition that is present from birth and is characterized by a smaller than normal optic nerve. This inherited condition is difficult to diagnose and is often diagnosed through symptoms. The most common symptoms of ONH are uncontrolled rapid eye movements and vision loss. ONH is a stable condition and does not get worse over time.

Learn more about ONH.

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