Factors associated with macular thickness in the COMET myopic cohort.

Myopia is a risk factor for glaucoma, retinal detachments, and degenerative changes in the central retina, conditions which can lead to significant vision loss.1, 2 Because the prevalence of myopia is increasing, the economic and visual burden of these related diseases may also increase.3 It is therefore important to understand why the myopic eye seems to be more susceptible to disease. Some previous studies have utilized more traditional examination methods, such as binocular indirect ophthalmoscopy.4–6 However, retinal structures can now be visualized in vivo using optical coherence tomography (OCT). 7 The resolution of commercially available OCT systems is approximately 5 to 10 microns, allowing visualization of distinct layers within the retina.8 This technology allows more sensitive and standardized measures of the retina in the living eye, which should enhance our understanding of the pathophysiology of myopia and its relationship to the development of other ocular diseases. Previous OCT studies have suggested that macular thickness is associated with age, gender, ethnicity, axial length, and refractive error.9–21 These studies have used different instruments and algorithms and include populations that differ by age, gender, ethnicity, country of origin, and refractive status. Despite these differences, most 10,11,15–18 but not all 9,14 studies report that females have thinner maculas than males. In addition, persons of African descent have thinner central foveas and some quadrants of the outer foveal regions compared to other ethnic groups, with some variation among studies.9–15 Some OCT studies, mainly performed in Asia, have explored the potential relationship between macular thickness and axial length and/or amount of myopia.15–21 In these studies, increased axial length has been associated with thicker central foveas17–20 and some thinner quadrants in the para- and peri-foveal regions, 16–20 with one study finding no association.15 Results for refractive error are more mixed; some studies find that myopia is associated with a thicker central fovea and some thinner para- and peri-foveal quadrants, 18–21 while others find no association.15–17 No prior studies have included large numbers of myopic young adults of different ethnic backgrounds. Data from the Correction of Myopia Evaluation Trial (COMET) allow the investigation of macular thickness and related factors in a large, multi-ethnic group who were aged 6–11 years with low to moderate myopia when they enrolled in COMET in 1997 and aged 17–22 years at the time of OCT measurements, 11 years later. The purpose of this study is to determine whether macular thickness is related to ethnicity, gender, axial length and amount of myopia in a large cohort of myopic young adults, in which over one-quarter have high myopia (worse than –6.0 D). These data should enhance our understanding of factors associated with macular thickness in individuals with myopia, which has increased in prevalence in recent years to 40% of the population aged 12–54 years living in the United States.3