January 5, 2011
An Affordable, Accessible Test for Genetic Eye Diseases? (and) New Scorecard Helps Predict Vision, Life Quality after Cataract Surgery
Research highlights, January's Ophthalmology journal
SAN FRANCISCO, CA—This month's Ophthalmology reports on new tools designed to advance diagnosis and care in two important areas: inherited retinal diseases and cataract surgery. Ophthalmology is the journal of the American Academy of Ophthalmology.
Multiple Retinal Diseases, Multiple Patients, Screened Simultaneously
Scientists in top genetics centers in the Netherlands have taken the first step toward large scale, inexpensive genetic testing for eye diseases. Their new retinal DNA re-sequencing chip and patient pooling strategy enables detection of multiple retinal disease gene sequences in multiple patients, at the same time. The chip is fully validated for DNA diagnostic purposes, and an upgraded version will be available in early 2011 at the Netherlands Institute for Neuroscience, Amsterdam.
In the Western world about one in 350 children and young adults suffer from inherited diseases that can result in blindness. Gene therapy may soon be available for retinitis pigmentosa and several other disorders, but successful treatment will depend on accurate diagnosis of DNA defects. This makes the demand for quick, inexpensive DNA tests more urgent. Precise genetic information is also important to other treatment decisions and genetic counseling with prospective parents.
Screening multiple genes simultaneously is key, since 150 genes related to 30 retinal diseases have been identified, and on average, at least five genes must be considered for each type of disease. The new chip can screen up to 90 retinal disease genes in as many as 20 patients at the same time and return results more quickly than current tests. But because the chip could not detect deletions of genetic material and since 24 percent of mutations are known to be small deletions or insertions, the researchers say the best use of their chip would be to prescreen patients so that subsequent, formal DNA testing would be more efficient.
"In initial and replicated tests, we achieved high detection rates (99 percent), high reproducibility of results (100 percent) and no false-positives," said lead researcher Arthur A.B. Bergen, PhD. "Unlike current methods, our chip can detect both known and new genetic sequence changes associated with retinal disorders, an advance that will further our understanding of disease mechanisms as well as improving diagnosis and treatment," he said.
New Scoring Tool Helps Predict Cataract Surgery Success
Who is most likely to benefit from cataract removal? How much improvement in vision and quality of life can people expect after surgery? Cataract removal is the most common surgery in the United States and many other countries, but surprisingly, until now there has been no standard assessment tool to help doctors and health planners answer these questions. A Spanish research group recently developed such a tool and validated it in a large, diverse study population.
"This easy-to-use scoring tool can help physicians determine whether a patient is highly or moderately likely to benefit from surgery and provides a cut-off score below which patients are unlikely to benefit; it can also help doctors set realistic expectations for vision gains and life improvement with their patients," said Silvia Vidal, MD, who led the study by the Investigacion en Resultados de Salud Y Servicios Sanitarios (IRYSS) Cataract Group. "Cataract patients' assessment of their visual function and quality of life is an important element of this tool," she added.
In terms of early improvement after surgery, the scoring tool demonstrated a positive predictive value of 74 percent for visual acuity and of 85 percent for visual function/quality of life. (Early improvement was defined as within one to two months post-surgery.) Considering this degree of accuracy, the tool is best used as a guide for people considering cataract surgery, rather than as criteria to exclude some patients from treatment.
Patient variables associated with vision improvement were: lower visual acuity before surgery, age less than 75 years, and uncomplicated cataract (defined as no other eye diseases, such as uncontrolled glaucoma, retinopathy, or other blood vessel/blood flow problems that affect the central vision). The study group comprised 5,512 patients on waiting lists for cataract surgery at 17 public health centers in 2004 and 2005. Data from 60 percent of the group were used to develop the scoring tool, and data from 40 percent were used to validate the accuracy of the tool's predictions.
Data components used in the development of the scoring tool were: visual acuity, age, and ocular co-morbidity (variables were assigned for eye diseases and conditions that could complicate surgery and/or affect visual outcomes). Also incorporated were patients' responses to the Visual Function-14 questionnaire (VF-14), in which patients self-evaluate their vision and whether/how it limits their daily activities. V-14s were used to categorize patients' status as "no impairment," "difficulties with light intensity/ glare," "difficulties not impacting autonomy," or "difficulties impacting autonomy," with each category assigned a variable. Variables representing the level of complexity of cataract surgery were assigned based on surgical records. Data used to validate the scoring tool included patients' responses to a second VF-14, completed about a month post-surgery; the researchers used these results to assess changes in visual acuity and function.
Eds: Full texts of the studies are available from the Academy's media relations department.
About the American Academy of Ophthalmology
AAO is the world's largest association of eye physicians and surgeons — Eye M.D.s — with more than 29,000 members worldwide. Eye health care is provided by the three "O's" — opticians, optometrists and ophthalmologists. It is the ophthalmologist, or Eye M.D., who can treat it all — eye diseases and injuries — and perform eye surgery. Find an Eye M.D. in your area.
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