It is the visual component of Usher Syndrome

(from Wikipedia)

Retinitis pigmentosa (RP) is a genetic disorder of the eyes that causes loss of vision. Symptoms include trouble seeing at night and decreased peripheral vision(side vision). Onset of symptoms is generally gradual.^[2] As peripheral vision worsens, people may experience “tunnel vision“. Complete blindness is uncommon.

Retinitis pigmentosa is generally inherited from a person’s parents.^[1] Mutations in one of more than 50 genes is involved. The underlying mechanism involves the progressive loss of rod photoreceptor cellsin the back of the eye. This is generally followed by loss of cone photoreceptor cells. Diagnosis is by an examination of the retina finding dark pigment deposits. Other supportive testing may include an electroretinogram, visual field testing, or genetic testing

There is currently no cure for retinitis pigmentosa. Efforts to manage the problem may include the use of low vision aids, portable lighting, or a guide dog.^]Vitamin A palmitate supplements may be useful to slow worsening.^[1] A visual prosthesis may be an option in certain people with severe disease.^[1] It is estimated to affect 1 in 4,000 people. Onset is often in childhood but some are not affected until adulthood.