The Glaucoma Inheritance Study in Tasmania (GIST) is a population survey of Australia's island state, Tasmania (population 450,000). Its aim is to find families with autosomal dominant, adult-onset, primary open angle glaucoma (POAG) suitable for genetic linkage analysis. POAG is relatively common, affecting around 3% of the Australian population. By finding the large families with POAG and identifying all the descendants in a captive population, it is possible that there may be overlap of different glaucoma pedigrees. Three of the first thirteen families in the study were composed of overlapping pedigrees. In one GIST family, GTas3, there has been intermarriage with other pedigrees with glaucoma on five occasions. The possibility of multiple genotypes was also reinforced by the inability to determine a single glaucoma phenotype in this family. When finding large families of POAG for linkage analysis, researchers must be aware of the risk of affected individuals inheriting their gene from the alternate parent. Thus, the alternate parents or their families must be examined, especially if the phenotype is atypical for the rest of the family.
Objective: To outline the difficulties in making management decisions associated with normal tension glaucoma. To suggest treatment strategies according to the clinical presentation of the disease. Method: Literature review and findings based on clinical experience.
Conclusions:The treatment of normal tension glaucoma involves many difficult decisions including whether to intervene and, if so, when and how to treat. Providing the patient with information is essential to gain co-operation and confidence. At present, the treatment objectives are to prevent further visual field loss by reduction of intraocular pressure by 30 per cent or more. This may be achieved by using medical or surgical regimens. Recently, there has been emphasis on the use of neuroprotective drugs that may act independently of the effect of intraocular pressure lowering. The balance between protecting vision and iatrogenic damage is not always easy.
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