Working with an Amish-Mennonite family tree, Johns Hopkins researchers at the Wilmer Eye Institute have discovered what appears to be the first human gene mutation that causes extreme farsightedness. The researchers report that nanophthalmos, Greek for “dwarf eye,” is a rare, potentially blinding disorder caused by an alteration in a gene called MFRP that helps control eye growth and regulates the organ’s shape and focus. The study is described in the July 5 issue of the Proceedings of the National Academy of Sciences."The MFRP protein is only made in a tiny portion of the human eye, and it can alter eye refraction, or focus,” said Olof Sundin, Ph.D., assistant professor of ophthalmology at the Johns Hopkins School of Medicine in the Wilmer Eye Institute. “We hope this protein holds the key to unlocking not only nanophthalmos, but other forms of farsightedness and nearsightedness as well."Hyperopia (farsightedness) and myopia (nearsightedness) -- the ability to see only distant or near objects clearly, respectively -- stems from the complex growth of the human eye. All human eyes have a slight degree of farsightedness at birth. As the child grows and gains more visual experience, the eye adjusts its focus by growing, which changes the distance between the lens and the retina, the light-detecting layer of cells at the back of the eye. Once the retina is the right distance from the lens for proper focus of images on the retina, a largely unknown mechanism that uses visual experience causes the eye to stop growing.Due to natural genetic mutations, some eyes continue to grow beyond this point, causing nearsightedness. Other mutations cause the eye to stop growing too soon, causing farsightedness. In the case of nanophthalmos, a mutation in MFRP completely wipes out the function of the protein coded for by the gene. In people with this condition, the retina is too close to the lens, but the lens and cornea, the eye’s outermost layer, are of normal size and shape.
