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Melissa D. Bailey, Katherine A. Weibel, Loraine T. Sinnott; The Relationship Between Refractive Error And Globe Width Is Dependent Upon Axial Length. Invest. Ophthalmol. Vis. Sci. 2012;53(14):138.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a measurement of globe width from anterior segment optical coherence tomography (AS-OCT) images that is simple and feasible and can be used as a measurement of globe shape for studies of eye growth and refractive error.
The subjects were 219 children (mean ± SD age = 8.7 ± 1.5 years). Measurements included cycloplegic, spherical equivalent refractive error (RE, Grand Seiko autorefractor), axial length (AL, IOLMaster), and the anterior scleral chord (ASC). The ASC is a measurement of the horizontal width of the globe (inner sclera boundaries) just posterior to the iris, and it was obtained from dewarped AS-OCT images of the anterior segment. Globe Shape was calculated as ASC / AL. Univariate correlation coefficients were calculated for the relationships among RE, AL, Globe Shape, and ASC. For multivariate analyses, AL and ASC data were binned by rounding to the nearest whole number. Multilevel regression analyses were used to determine the relationship between RE and AL and ASC.
For univariate analyses, significant correlations were found for RE and AL (r = –0.57, p ≤ 0.001), RE and Globe Shape (r = 0.59, p ≤ 0.001), AL and ASC (r = 0.56, p ≤ 0.001). RE and ASC, however, were not correlated (r = –0.05, p > 0.05). In the best multivariate model, RE was significantly associated with all ocular variables: AL (β = –1.18, p < 0.001), AL2 (β = 0.19, p = 0.001), and ASC (β = 0.78, p <0.01), after controlling for age (β = –0.01, p = 0.9) and gender (β = –0.63, p < 0.001), and there was a significant interaction between AL and ASC (β = –0.35, p = 0.03).
It is both simple and feasible to measure the horizontal width of the globe just posterior to the iris (ASC) in a commercially-available AS-OCT instrument. As one would expect, much of a child’s refractive error is explained by his or her axial length, but the models suggest that ASC provided additional information about refractive error and that its relationship with refractive error depends on axial length. In shorter eyes, a wider ASC was associated with a more hyperopic refractive error, but this trend diminished in eyes that were longer.
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