New Delhi: Scientists thought they understood the EFEMP1 gene which causes blindness, but they have found that a different mutation of the same gene leads to a new type of vision loss.
The findings were published in JAMA Ophthalmology on 10 September by an international team of researchers in the UK, Switzerland, Germany, and the US.
“The different disease expression in this family was thought to be similar to a condition caused by C1QTNF5 gene variants. However, none of the variants associated with that disease were found. Our collaborators then discovered a new variant in the EFEMP1 gene that normally causes a different disease where the macula, which is tied to central vision, is affected first,” Artur V Cideciyan, researcher and co-director of the Center for Hereditary Retinal Degenerations in Philadelphia, said in a statement.
The newly discovered condition has not been officially named but researchers are calling it “EFEMP1-associated late-onset retinal degeneration (L-ORD)”. The p.Arg140Trp variant of the gene causes abnormally thick material to build up between the eye’s cells.
The EFEMP1 gene is already associated with a different retinal disease which affects the central retina. However, the new variant affects the peripheral retina and night vision. It can appear in people who seem to have normal eyesight for most of their life but suddenly begin to have trouble seeing in low-light conditions. The disease can be caught if doctors observe the way a person’s eyes transition from lighted areas to low-light conditions.
“We can detect a major abnormality in the way rod photoreceptors recover in darkness with retinas that still look structurally intact. This gives us a functional marker of disease at a stage when photoreceptor cells have not yet been lost,” Cideciyan added.
For now the study’s authors are unsure how widespread the gene is if many people might have L-ORD. They suggest that the disease is likely to be rare and only larger studies can establish that.