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Cascade genetic testing identifies those at-risk for POAG early
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Myocilin cascade genetic testing for primary open-angle glaucoma allows identification of at-risk individuals at an early stage or even before signs of glaucoma are present, according to researchers in Ophthalmology.
The retrospective clinical and molecular study utilized 73 Myocilin mutation carriers identified through the Australian and New Zealand Registry of Advanced Glaucoma and clinical cases referred by a general practitioner or optometrist. They consisted of 43 clinical cases and 30 genetic cases. There were 39 female and 34 male patients.
At first examination, 83% of genetic cases were unaffected, and 17% were glaucoma suspect; in clinical cases, 44% were glaucoma suspect, 28% had glaucoma and 28% had advanced glaucoma.
Researchers determined that genetic cases were significantly younger at presentation than clinical cases. Mean highest IOP, cup-to-disc ratio and mean deviation on visual field testing were all significantly worse in clinical cases compared with genetic cases.
The mean age at presentation was significantly lower among genetic cases compared with clinical cases.
In genetic cases, the researchers found 19 were unaffected and five were glaucoma suspects at presentation, whereas 12 clinical cases were glaucoma suspects, eight had nonadvanced glaucoma and eight had advanced glaucoma.
All individuals achieved a normal range of IOP using IOP-lowering therapy. The mean highest IOP before treatment was 31.8 mm Hg versus 16.8 mm Hg after initiating treatment, researchers wrote.
Patients identified via cascade genetic testing presented 7 years younger than those identified through ophthalmic referral, according to researchers.
Most carriers identified through genetic testing were asymptomatic at presentation, whereas half of the patients from clinical referral had early signs of glaucoma, and the other half already had glaucoma, including 28% with advanced disease.
“These findings highlight the usefulness of cascade genetic testing irrespective of the age of the family members,” the researchers wrote. –by Abigail Sutton
Disclosure: Souzeau reported no relevant financial disclosures. Please see the full study for all remaining authors’ financial disclosures.
Perspective
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Scott Anthony, OD, FAAO
One could say that the human genome’s purpose is to procreate a functional living system, not a perfect living system. Not surprisingly, small genetic variations inherent within the human genome have the potential to contribute to disease formation, especially as we age.
By and large, glaucoma is a disease of aging and genetics. As clinicians, we readily factor age into our glaucoma screening, diagnostic and management strategy. However, utilizing genetics in the clinical setting is not currently feasible
Cutting-edge research is pushing toward bringing genetic analysis into the glaucoma arena, and this study is a window into the future possibilities in glaucoma management.
How far are patients willing to go to know what is wrong with them or could be wrong with them in the future? Can clinicians enhance their diagnostic and treatment strategies using glaucoma genetics, or will we inappropriately label some patients glaucoma suspects who would never have developed the disease?
Scientists and clinicians must be judicious as they move forward with this extraordinary insight into the fabric of our being (MacArthur et al.)
Reference:
MacArthur D, et al. Nature. 2014;508:469-476. doi:10.1038/nature13127.
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