Getting to the root of eye disease

Getting to the root of eye disease

For many people, going blind is their worst nightmare, but for the millions of people each year who are told that their sight is failing, this is an unfortunate reality.

While many means of vision correction exist, from contact lenses to glasses to laser eye surgery, there are some conditions which can not be fully treated, and this will remain the case until new developments in the field of science open the door for therapies.

Thankfully, there are hundreds of scientists around the world currently working on new cures for some of the worst conditions, including glaucoma and retinitis pigmentosa.

In a recent report published Online First by Archives of Ophthalmology, one of the JAMA/Archives journals, experts claim that frequent visual field testing may be associated with earlier detection of the glaucoma"s progression.

The research was carried out by Dr Kouros Nouri-Mahdavi and colleagues from the Jules Stein Eye Institute, University of California, Los Angeles, who examined data compiled in the Advanced Glaucoma Intervention Study (AGIS).

It involved studying the eyes of 381 patients aged 35 to 80 years with primary open-angle glaucoma no longer controlled by maximally tolerated medical treatment and included all visual field tests performed within the first year of follow-up as well as the last available visual field tests.

The specialists also assembled a low-frequency data set by deleting, for one group, every other visual field test from the second year of follow-up onward; and a high-frequency data set for which none of the visual field tests were deleted, and compared the two data sets in terms of the proportion of progressing eyes and the time to progression.

Each patient was then followed for an average of nine years, with the researchers determined that the high-frequency data set was more likely to detect progression.

Improvement was also detected in some eyes, while, when data was curtailed to account for partially unknown values at five years, the results did not change significantly.

The authors concluded: "In summary, we found that a twice-yearly schedule of visual field testing resulted in earlier detection of glaucoma progression compared with a yearly schedule, especially with global trend analyses.

"Validation of these findings in other patient populations would be desirable. Our results have significant healthcare policy implications with regard to determining the frequency of visual field testing in patients with glaucoma."

Meanwhile, a separate study carried out by University of Iowa (UI) researchers has found a new genetic cause of the blinding eye disease retinitis pigmentosa (RP) and, simultaneously, discovered an entirely new version of the message that codes for the affected protein.

The study was was published in the online edition of the Proceedings of the National Academy of Sciences (PNAS) Early Edition and suggests that the mutation may be a significant cause of RP in people of Jewish descent.

According to experts working on the study, the findings also "lay the groundwork" for developing prevention and treatment for this form of RP, using a combination of genetic testing, gene therapy and cell replacement approaches.

By using the latest DNA sequencing techniques to analyse the protein-coding regions of a single RP patient"s genome, the specialists found a mutation in a gene called MAK (male germ cell associated kinase).

This gene had not previously been associated with eye disease in humans, but examination of the tissue from donated eyes showed that MAK protein was located in the parts of the retina that are affected by the disease.

Dr Budd Tucker, UI assistant professor of ophthalmology and visual science and lead study author, commented: "What we found was a new retina-specific exon; no other tissue that we tested had this version of the protein-coding transcript.

"This is important because the gene mutation identified prevents the production of the retina-specific MAK protein."

Dr Tucker added that new technology has "greatly enhanced" experts" ability to find and validate disease-causing mutations, which is critical in progressing to actually treating diseases such as RP.

It is innovations such as these which people with blinding conditions such as RP and glaucoma will be relying on in the years ahead to provide some relief from their condition, and perhaps even cure it. 

by Martin Burns

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