Higher prevalence of myocilin mutations in advanced glaucoma in comparison with less advanced disease in an Australasian disease registry.

OBJECTIVES: To determine the proportion of all Myocilin coding mutations responsible for advanced primary open-angle glaucoma (POAG) in early-age-at-onset individuals and to investigate the prevalence of exon 3 Myocilin mutations in advanced POAG at any age at onset in a large Australasian cohort. DESIGN: Cross-sectional study using a national disease registry. PARTICIPANTS: One thousand sixty individuals with advanced POAG (103 with age at onset of 40 years or younger) and 320 with nonadvanced POAG all recruited by the Australian and New Zealand Registry of Advanced Glaucoma. METHODS: Participants were examined and referred by their eye practitioner, and Myocilin genetic testing was performed by direct sequencing. Cascade genetic testing was made available for relatives of participants found to carry a Myocilin mutation. MAIN OUTCOME MEASURES: Advanced glaucoma diagnosis based on strict visual field entry criteria. Prevalence and spectrum of Myocilin mutations in individuals with advanced and nonadvanced POAG. RESULTS: This is the first study to report Myocilin mutations in an advanced POAG cohort. No pathogenic Myocilin mutations were identified in exons 1 and 2 in early-age-at-onset advanced POAG cases. Exon 3 Myocilin mutations were identified in 45 advanced POAG patients (4.2%), which is significantly higher (P = 0.02) compared with nonadvanced POAG patients (1.6%). A novel mutation (Trp373X) and a new variant of uncertain pathogenicity (Ala447Thr) also were reported. The prevalence of Myocilin mutations rose from 16% to 40% in selected advanced POAG subgroups based on different thresholds of maximum recorded intraocular pressure, age at diagnosis, and the presence and strength of positive family history. Twenty-six individuals with Myocilin mutations were identified through cascade genetic testing of first-degree relatives of affected mutation carriers. CONCLUSIONS: The prevalence of Myocilin mutations in glaucoma cases with severe visual field loss is significantly greater than in nonadvanced glaucoma patients. Myocilin screening in phenotypically selected cases can have a much higher yield than in previous unselected series. Identifying individuals who have Myocilin mutations provides an opportunity to screen at-risk clinically unaffected relatives and to reduce glaucoma blindness through early management and intervention. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Australian and New Zealand Registry of Advanced Glaucoma: methodology and recruitment.

BACKGROUND: Glaucoma is a sight-threatening disease affecting 3% of the population over the age of 50. Glaucoma is treatable, and severe vision loss can usually be prevented if diagnosis is made at an early stage. Genetic factors play a major role in the pathogenesis of the condition, and therefore, genetic testing to identify asymptomatic at-risk individuals is a promising strategy to reduce the prevalence of glaucoma blindness. Furthermore, unravelling genetic risk factors for glaucoma would also allow a better understanding of the pathogenesis of the condition and the development of new treatments. DESIGN: The Australian and New Zealand Registry of Advanced Glaucoma is a prospective study that aims to develop a large cohort of glaucoma cases with severe visual field loss to identify novel genetic risk factors for glaucoma blindness. METHODS: Clinical information and blood are collected from participants after referral by eye practitioners. Samples are collected across Australia and New Zealand using postage kits. PARTICIPANTS: Our registry has recruited just over 2000 participants with advanced glaucoma, as well as secondary and developmental glaucomas. RESULTS: A positive family history of glaucoma is present in more than half of the advanced glaucoma cases and the age at diagnosis is significantly younger for participants with affected relatives, which reinforces the involvement of genetic factors in glaucoma. CONCLUSIONS: With the collection of glaucoma cases recruited so far, our registry aims to identify novel glaucoma genetic risk factors to establish risk profiling of the population and protocols for genetic testing.