Message: HI Fred! I am new to this---trying to find information about a condition called "Lemurs" not sure I am even spelling it right, but that's what it sounds like. It's apparently a genetic condition, passed through the mother, only to male children, that causes significant vision impairment, the onset of which usually occurs around age 20-30. Know where I can get more info? Thanks so much. location: North Carolina
Leber's Congenital Amaurosis (LCA) is a rare, hereditary disorder that leads to retinal dysfunction and visual impairment at an early age, often from birth. Of all the retinal degenerations, LCA has the earliest age of onset and can be the most severe.
LCA bears the name of Dr. Theodore Leber who first described the condition. The term amaurosis refers to any condition of blindness or marked loss of vision, especially loss of vision in which there is little or no change in the appearance of the eye itself. LCA is sometimes confused with another condition termed Leber's Hereditary Optic Neuropathy (LHON) that also leads to visual impairment. However, LCA is a separate and distinct disease.
The clinical signs of a disease are collectively called the phenotype. Besides vision loss, other signs of LCA are nystagmus (roving eye), sluggish or nonexistent pupillary response and, in some cases, eye rubbing (oculo-digital reflex). In a smaller number of cases, there can be lens opacity (cataract), cornea abnormality (keratoconus), aversion to light (photophobia), hearing impairment and possibly developmental delays. Retinal blood vessels can become thin and narrow and there can be pigmentary changes that an Ophthalmologist can see within the eye.
A key feature of LCA is an abnormally low electrical response of the retina. This can be measured by the Ophthalmologist using a method called Electroretinography. In this procedure, the retina is stimulated by light and the electrical response pattern is recorded on an electroretinogram (ERG) and compared with ERG responses from normal subjects.
Some LCA types are progressive in that they become more severe with age and some are stationary in that there is little change noted with time.
The Foundation for Retinal Research: http://www.tfrr.org
The AFB site also gives an online reference for more information on this condition: www.icomm.ca/geneinfo/lebersam.htm. I hope this helps, and thanks for the question.
Click this link to visit the American Foundation for the Blind's Glossary of Eye Conditions page: http://www.afb.org/Section.asp?DocumentID=2139