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Editors Selection IGR 12-4

Family history

Paul Healey

Comment by Paul Healey on:

13983 Disease severity of familial glaucoma compared with sporadic glaucoma, Wu J; Hewitt AW; Green CM et al., Archives of Ophthalmology, 2006; 124: 950-954


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Predictors of disease severity in glaucoma are vital for the efficient prevention of disability. Family history of glaucoma is a risk factor for both its presence and development. This paper, byWu et al. (623)asks the question: "Is familial glaucoma a more severe form of the disease?" The authors compared subjects with and without a family history of glaucoma from the Glaucoma Inheritance Study in Tasmania (GIST). To overcome the major problem of recall bias in family history studies, the GIST has spent the last 15 years identifying every individual in the Australian state of Tasmania with glaucoma, and then tracing and examining their relatives to give us the most accurate ascertainment of familial glaucoma every undertaken. As part of the study, a scoring system using disc, field and IOP criteria was developed. It was these GIST scores that were compared to determine glaucoma severity.

The majority of glaucoma (60%) has a familial basis
The authors reported that GIST scores were higher in the familial glaucoma group despite being younger both at time of examination and first diagnosis. The disease severity differences were not only due to higher IOPs in the familial group as the differences remained when disc and field criteria only were compared. Among subjects over 75 years, a dose response was found between glaucoma severity and subjects with first degree, second degree or no relatives with the disease. The other important finding was that in contrast to studies that ask participants whether they have a family history of glaucoma, the more thorough assessment in GIST revealed that the majority of glaucoma (60%) has a familial basis.

As the authors point out, the study has someweaknesses. Firstly, the GIST scoring system was designed to calculate pedigree probability rather than disease severity. Secondly, a known family history of glaucoma may encourage earlier assessment and diagnosis. However, this would bias towards finding less severe glaucoma in the familial group, thereby strengthening the reported findings.

The clinical and scientific implications of this study are two-fold. Firstly, it suggests that genetic abnormalities may underlie more severe glaucoma. Secondly, if familial and sporadic glaucoma is equally undiagnosed, case detection based on family history may select a population at a greater risk of visual disability.


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