Exfoliation syndrome: prevalence and inheritance in a subisolate of the Finnish population

To estimate the prevalence of pseudoexfoliation syndrome or exfoliation syndrome (ES) in a cross-sectional study and during a long-term follow-up, and to analyse how ES has been inherited in a large pedigree on an isolated population of Kökar island in southern Finland.

In a population-based study conducted between 1960 and 1962, a comprehensive ophthalmological examination was performed on 595 subjects (85% of the population). From then until 2002, 965 subjects were examined at least once. A pedigree was constructed for all ES-affected subjects according to genealogical studies. The genetic contribution to ES was investigated in this pedigree by segregation analysis and the heritability of the intraocular pressure (IOP) quantitative trait estimated using SOLAR and SAGE software.

In the cross-sectional study, the prevalence of ES was 8.1% for 247 subjects over 50 years of age (males 7%, females 9%) and increased to 18.4% for 70 subjects over 70 years of age (males 13%, females 25%). In addition, two females less than 50 years of age were ES-affected. Between 1960 and 2002, 76 (14.3%) of 530 subjects over 50 years of age had ES [23 males (10%) and 53 females (18%)]. Exfoliation glaucoma (EG) was found more often in males (11 patients, 48%) than in females (13 patients, 25%) whereas primary open-angle glaucoma (POAG) was almost as frequent in males (seven patients, 3%) as in females (five patients, 2%). The relative risk (RR) of glaucoma (ES versus no ES) was 11.9 [95% confidence interval (CI) 6.2-22.9] for all the subjects - 14.6 for males (95% CI 6.3-34.0) and 11.8 for females (95% CI 4.4-31.6). Seventy-five pedigrees of 78 ES-affected patients were linked together into one large pedigree with 110 nuclear families. The segregation ratio of ES was 18% (8% for males, 24% for females) when both parents were unaffected, and 16% (9% for males, 27% for females) when at least one parent was affected. The heritability of IOP was estimated to be 30%.

In this population-based family study, ES is consistent with an autosomal dominant trait with incomplete penetrance, where the penetrance is more reduced in males than in females. However, the presence of ES was a greater risk factor for developing glaucoma in males than in females.