Leber's Hereditary Optic Neuropathy

Leber's Hereditary Optic Neuropathy is a rare maternaly inheredited eye condition that affects men more than women at a rate of 90% to 10%.

LHON was first discovered by Theodore Leber in the 19th century, but we didn't really start to understand how it was inherited until the late 1980's. Leber's usually affects one eye first and central vision is lost in that eye over a period of a few weeks. A month or two later, the second eye is affected in the same way. After a few weeks the eyesight stops getting worse.

This is the most common pattern of development, but LHON can affect someone very suddenly, or can affect them more gradually over a period of years. Not everyone in a family affected by Leber's will lose their eyesight, and we can't tell yet know who will get symptoms and who won't. We do know that Leber's is inherited through a gene which is passed on only through the egg cell from the mother. Men can't pass on Leber's Hereditary Optic Neuropathy to their children.

Scientists believe that the particdular gene changes linked to Leber's Hereditary Optic Neuropathy lower the amount of energy available to the cells of the optic nerve and retina. These cells are damaged and can even die because of this lack of energy. The damage to the optic nerve and retina is what causes the symptoms of Leber's.

Doreid Berro has written an informative paper about LHON and it's published on the internet with documentation.

Genetics Home Reference also has quite a bit of information about Leber's on their site.

Carver Laboratory has information about Leber's and other hereditary eye conditions. They also have some interesting pictures on their website.

I never knew there were so many different causes of low vision.

Dale L. Edwards

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Blind Mice Regain Sight

Scientists say they've restored the vision of blind mice by introducing light-sensitive cells into their retinas. These are not stem cells, but come from a later stage of cell development when stem cells have already determined what type of cells they will be. In this case we're talking about the rod-and-cone photoreceptors the eye uses to sense light.

"We think this is a major breakthrough because it shows what can be achieved," said study lead researcher Dr. Robert MacLaren, a consultant vitreoretinal surgeon at Moorfields Eye Hospital and a clinician scientist at the University of London, in England.

Scientists have tried to use stem cells before to restore sight, but their efforts failed. Dr. MacLaren believes that timing is crucial to success. He transplanted the photreceptors from newborn mice into the blind mice's retinas (they are looking for a way to use adult stem cells) and the retinas accepted these photoreceptors and made connections to the mice's brains. The mice are receptive to light.

"These cells were transplanted extremely quickly (i.e., 30 minutes out of their normal environment)," MacLaren said. This rapid transfer, plus their positioning in a conducive retinal environment, means that the cells "were able to form quick connections with host cells," he said.

This certainly sounds hopeful. If they can learn how to use adult stem cells they won't need embryonic stem cells.

Dale L. Edwards