Editorial

Glaucoma: time to talk to the family

In the last couple of decades, a few large population-based eyestudies have changed our understanding of glaucoma prevalence,incidence and risk. We are indeed fortunate that three of thesestudies are based in Australia. In this edition of the journal Greenet al. ask ‘How significant is a family history of glaucoma?’. Usingcases from the Glaucoma Inheritance Study in Tasmania (GIST) andcontrols from the Twin Eye Study in Tasmania (TEST), the authorsconclude that approximately 60% of open-angle glaucoma in thatstate is familial.1

The predominance of familial glaucoma has significant implica-tions for detection and treatment of this important disease. Theother two major Australian eye studies, the Blue Mountains EyeStudy (BMES) and the Melbourne Visual Impairment Project(MVIP) have both reported that 50–60% of older Australians withglaucoma and significant vision loss have never been diagnosed.2,3

Can knowledge of the familial nature of glaucoma help us do better?When clinicians take a family history, they are primarily think-

ing of they way in which the presence and natural history of adisease in relatives may affect the prognosis of the patient in frontof them. The problem is that we are not really establishing a familyhistory as much as establishing recall of a family history. Is thisimportant? The role of such bias in self-reported family history ofglaucoma was examined in the BMES.4 It found that significantrecall bias existed with glaucoma family history being reportedalmost twice as often in women as in men. There was also importantconfounding of glaucoma family history by ocular hypertension(OH). More subjects with OH reported a family history of glau-coma than subjects who actually had glaucoma. While this mightpartly be explained by progression from OH to glaucoma, it islikely that in some subjects with OH, a reported family history ofglaucoma was in fact a family history of OH.

The BMES and MVIP found a large difference in reported familyhistory among those with glaucoma, depending on their diagnosisstatus. In both studies, twice as many subjects with previouslydiagnosed glaucoma reported a family history compared with thosepreviously undiagnosed.2 Could this finding mean that those withfamilial glaucoma have all already been diagnosed? This does notseem to be the case when we compare the 15.7% familial glaucomaidentified in first-degree relatives from family history in the BMES4

to the 39% identified in first-degree relatives from examination inthe GIST.1 Furthermore, a previous report from the GIST suggeststhat even in large pedigree families, over a quarter of previouslydiagnosed cases were unaware of their own very strong familyhistory of the disease.5 There is another explanation for this higherrate of glaucoma family history among previously diagnosed cases.Once diagnosed, some patients may urge their family members beexamined or find out that they have been already diagnosed. Alter-natively, knowing that someone in their family had glaucoma, theysaw an ophthalmologist and were diagnosed themselves. Either

explanation, when taken together with the selection bias showinghigher family history rates among patients with glaucoma attendingclinic-based studies,1 is evidence that family history knowledgedoes affect behaviour – in a positive way.

For the patient in front of us, while knowing that a reportedfamily history of glaucoma confers a threefold increased risk ofprevalent disease3,4 is helpful, ultimately it is the examination andinvestigation findings that lead to the diagnosis. So in addition tothinking about the patient when we take a family history, let usthink about the undiagnosed members of that patient’s family. Theinformation we provide to our patients about the familial nature ofglaucoma – and the importance of having relatives examined – canhave far reaching effects. Simply talking about glaucoma at familygatherings has a cascade effect, enriching family history knowledgeamong relatives. If every relative carries that knowledge to anotherit should quickly reach the 60% of all those with open-angle glau-coma in whom the disease in familial, whether or not they have yetbeen diagnosed. The increased awareness of glaucoma that wouldresult may result in a higher rate of diagnosis in sporadic glaucomacases as well.

So the single most effective measure to reduce glaucoma blind-ness may just be for every person who has glaucoma to tell all theirfamily members and for every person who does not, to ask theirfamily members. This approach has one additional advantage. Itcosts nothing but a few minutes of our time.

Paul R Healey PhD FRANZCOWestmead Hospital, Sydney, New South Wales, Australia

REFERENCES

1. Green CM, Kearns LS, Wu J et al. How significant is a familyhistory of glaucoma? Experience from the Glaucoma InheritanceStudy in Tasmania (GIST). Clin Experiment Ophthalmol 2007; 35:793–9.

2. Mitchell P, Smith W, Attebo K, Healey PR. Prevalence of open-angle glaucoma in Australia. The Blue Mountains Eye Study.Ophthalmology 1996; 103: 1661–9.

3. Weih LM, Nanjan M, McCarty CA, Taylor HR. Prevalence andpredictors of open-angle glaucoma: results from the visualimpairment project. Ophthalmology 2001; 108: 1966–72.

4. Mitchell P, Rochtchina E, Lee AJ, Wang JJ. Bias in self-reportedfamily history and relationship to glaucoma: the Blue MountainsEye Study. Ophthalmic Epidemiol 2002; 9: 333–45.

5. McNaught AI, Allen JG, Healey DL et al. Accuracy and implica-tions of a reported family history of glaucoma: experience fromthe Glaucoma Inheritance Study in Tasmania. Arch Ophthalmol2000; 118: 900–4.

Clinical and Experimental Ophthalmology 2007; 35: 790doi: 10.1111/j.1442-9071.2007.01626.x

© 2007 The AuthorJournal compilation © 2007 Royal Australian and New Zealand College of Ophthalmologists