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Primary open angle (OAG) glaucoma is a leading cause of vision impairment and blindness in the United States and worldwide. 1 The incidence of glaucoma increases with age, and it is higher among African-Americans than most other racial and ethnic groups. 1 - 3 As a broad category, thyroid condition may potentially have an effect on the development of glaucoma. Several case reports and case series have found an association with hypothyroidism, 4 - 8 and a recent population-based study found that glaucoma was more common among thyroxine users and those with a history of thyroid surgery. 9 However, that study comprised Australians largely of European ancestry, thus limiting the generalizability of the results. Other studies, however, have failed to find any significant association between hypothyroidism and glaucoma. 10 - 13 Thus, there is a lack of consistent epidemiological evidence on associations between hypothyroidism and glaucoma. Additionally, though considerably less common, significant relationships have been demonstrated between thyroid-associated orbitopathy (Graves orbitopathy/ophthalmology) with open-angle glaucoma, ocular hypertension (OHT), and dysthyroid optic neuropathy (DON). 14 - 17
Glaucoma is characterised by progressive optic nerve damage, resulting in the death of retinal ganglion cells, which ultimately impedes the transmission of visual impulses from the eye to the brain. 2 Although elevated intraocular pressure (IOP) is a primary risk factor, glaucomatous injury may occur at normal IOP. 3 There are a number of purported mechanisms by which thyroid disorders and their treatment are believed to affect the development of glaucomatous damage. In Graves disease, IOP may be raised as a result of contraction of the extraocular muscles against intraorbital adhesions or orbital congestion due to increased tissue volumes. 17 18 In the case of hypothyroidism, excessive mucopolysaccharide accumulation within the trabecular meshwork acts like a surfactant, sticking together adjacent endothelial membranes. 9 The purpose of this study is to determine, in a large American population-based cohort of participants, if thyroid problems are associated with glaucoma.
MATERIALS AND METHODS
Data source
The data used for this study are drawn from the 2002 National Health Interview Survey (NHIS), which serves as the principal source of health information of the civilian, non-institutionalised, household population of the United States, and it represents a key data-collection programme of the National Center for Health...