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Original Investigation
September 27, 2018

Myocilin Gene Gln368Ter Variant Penetrance and Association With Glaucoma in Population-Based and Registry-Based Studies

Author Affiliations
  • 1Statistical Genetics, QIMR Berghofer Medical Research Institute, Brisbane, Australia
  • 2School of Medicine, University of Queensland, St Lucia, Brisbane, Australia
  • 3Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, Australia
  • 4Menzies Institute for Medical Research, University of Tasmania, Hobart, Australia
  • 5Eye Department, Greenlane Clinical Centre, Auckland District Health Board, Auckland, New Zealand
  • 6Discipline of Ophthalmology, Sydney Eye Hospital, University of Sydney, Sydney, Australia
  • 7Centre for Vision Research, Westmead Institute for Medical Research, University of Sydney, Sydney, Australia
  • 8Ophthalmology and Vision Science, Faculty of Medicine and Human Sciences, Macquarie University, Australia
  • 9Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, University of Melbourne, Melbourne, Australia
  • 10Ophthalmology, University of Melbourne, Department of Surgery, Melbourne, Australia
  • 11Department of Ophthalmology, Royal Children’s Hospital, Melbourne, Australia
  • 12South Australian Institute of Ophthalmology, Royal Adelaide Hospital, University of Adelaide, Adelaide, Australia
  • 13Centre for Ophthalmology and Visual Sciences, Lions Eye Institute, University of Western Australia, Perth, Australia
JAMA Ophthalmol. Published online September 27, 2018. doi:10.1001/jamaophthalmol.2018.4477
Key Points

Question  How does the penetrance and association of myocilin (MYOC) gene p.Gln368Ter variant with glaucoma and ocular hypertension differ across studies ascertained in different ways?

Findings  This cross-sectional study found that 48% of p.Gln368Ter carriers older than 65 years had glaucoma or ocular hypertension, with an odds ratio for primary open-angle glaucoma of 6.76 (95% CI, 4.05-11.29) compared with noncarriers. In registry-based studies, penetrance was very high, with the odds ratio being markedly increased in individuals with advanced glaucoma (12.16 [95% CI, 6.34-24.97]) compared with individuals with nonadvanced glaucoma (odds ratio, 3.97 [95% CI, 1.55-9.75]).

Meaning  Our results suggest the penetrance in population-based studies is higher than previously shown and support the need for early screening of p.Gln368Ter carriers.

Abstract

Importance  The p.Gln368Ter (rs74315329) risk allele in the myocilin gene (MYOC) was initially reported to have high penetrance in glaucoma registry-based studies, but much lower estimates were recently obtained from population-based studies. We investigated this disparity using data from Australia and the United Kingdom.

Objectives  To examine the penetrance and effect size of the MYOC p.Gln368Ter variant with glaucoma and ocular hypertension (OHT).

Design, Setting, and Participants  This cross-sectional study within the UK Biobank (UKBB) included participants of white British ancestry. Glaucoma cases were defined by International Classification of Diseases, Ninth Revision (ICD-9) and Tenth Revision (ICD-10) diagnoses and self-reported questionnaires. Carriers of the MYOC p.Gln368Ter variant were identified using genotype imputation from arrays. In contrast, 2 Australian registry-based studies, the Australian and New Zealand Registry of Advanced Glaucoma and the Glaucoma Inheritance Study in Tasmania, ascertained glaucoma cases referred by eye care clinicians, with historic control participants recruited from other Australian studies. Samples were either directly sequenced or had genotypes determined by imputation (for the Australian registry and historic control participants). Recruitment to the UKBB occurred between 2006 and 2010, and data analysis occurred from September 2017 to July 2018.

Main Outcomes and Measures  The penetrance and odds ratio (OR) were estimated for the MYOC p.Gln368Ter variants in participants with glaucoma and OHT.

Results  A total of 411 337 UKBB participants of white British ancestry (mean [SD] age, 56.6 [8.0] years) were included, plus 3071 Australian registry and 6750 historic control participants. In the UKBB, the minor allele frequency of the MYOC p.Gln368Ter variant was 1 in 786 individuals (0.13%). The odds ratio of p.Gln368Ter in patients with primary open-angle glaucoma (POAG) was 6.76 (95% CI, 4.05-11.29); glaucoma (POAG, self-reported glaucoma, and unspecified glaucoma), 4.40 (95% CI, 3.38-5.71); OHT, 3.56 (95% CI, 2.53-4.92); and OHT and glaucoma combined, 4.18 (95% CI, 3.05-5.67). The penetrance of the MYOC p.Gln368Ter variant was 7.6% in patients with glaucoma, 24.3% in patients with OHT, and 30.8% in patients with OHT and glaucoma combined. In the Australian registry studies, the odds of MYOC p.Gln368Ter variant were 12.16 (95% CI, 6.34-24.97) in patients with advanced glaucoma and 3.97 (95% CI, 1.55-9.75) in those with nonadvanced glaucoma; the penetrance of glaucoma was 56.1%, and penetrance in those considered to have glaucoma or be glaucoma suspects was 69.5%.

Conclusions and Relevance  The MYOC p.Gln368Ter variant confers a very high-risk effect size for advanced glaucoma; the risk is lower in nonadvanced glaucoma and OHT. In the general population sample, approximately 50% of MYOC p.Gln368Ter carriers 65 years and older had glaucoma or OHT, with higher prevalence in the Australian registry studies.

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