How significant is a family history of primary open angle glaucoma? : experience from the Glaucoma Inheritance Study in Tasmania

AIM: To determine the prevalence of a familial glaucoma amongst glaucoma sufferers in Tasmania. METHODS: With the cooperation of ophthalmologists, optometrists and pharmacists in Tasmania, patients diagnosed with glaucoma and their family members were identified and invited to participate in the study. All patients gave informed consent and a detailed questionnaire was administered. Family history of POAG was noted and pedigrees constructed with the help of a research genealogist. Each participant underwent a detailed examination, including visual acuity, TOP, gonioscopy, disc assessment and visual field testing. A score (termed the GIST score) was given to each patient which denotes the probability of the diagnosis of POAG being present. Subjects were classified as normal, suspect or POAG. Age-matched, unaffected participants in the Twins Eye Study in Tasmania were used as a control group. RESULTS: A total of 1702 POAG patients were identified. 1014 patients belonged to families in which other members were affected (familial glaucoma). 688 patients did not have a known family history of POAG (sporadic glaucoma). The size of the family groups varied from 2 to 29 affected individuals. The patients in the familial group had higher GIST scores than those in the sporadic group. Only 24% of the participants in the control group had a family history of glaucoma. CONCLUSIONS: 59.6% of POAG in Tasmania is familial. This percentage is higher than most previous reports of familial glaucoma and emphasises the importance of genetics in POAG. Patients with familial glaucoma had higher GIST scores, which may reflect an earlier onset and/or higher severity of glaucoma in the familial group. This has important implications for glaucoma screening and for further research in glaucoma genetics.