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Quan V Hoang, Jonathan Tang, Julie Goldman, Jane Y Pan, Stanley Chang; Gaze-Induced Axial Length Changes in Highly Myopic Eyes as Gauged by Magnetic Resonance Imaging. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3596.
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To determine if axial length changes occur in highly myopic eyes undergoing the stress and strain of normal eye movement.
A prospective imaging study was performed on highly myopic patients (> 26 mm of axial length) with a clinical diagnosis of staphyloma. 3-D MRI scans were acquired while subjects gazed in 5 directions (primary, nasal 15°, temporal 15°, superior 10°, inferior 10°). Volume renderings were manually reoriented so that the plane of the limbus (the cornea-sclera interface) was normal to the plane of the screen. Four axial length measurements were taken at 90-degree rotations around the central axis and averaged for each eye in every gaze. Eye axial lengths at each eccentric gaze were compared to the axial length in primary gaze using a fixed effects regression allowing for person-specific and eye-specific effects (n = 40).
Axial lengths were unchanged in temporal gaze when compared to primary gaze (p = 0.89). Axial lengths shortened in nasal gaze (-0.07 mm, p = 0.04, 95% CI -0.148 to 0.008) and in superior gaze (-0.08 mm, p = 0.03, 95% CI -0.163 to 0.003). Axial lengths increased by +0.12 mm when changing from primary to inferior gaze (p = 0.001, 95% CI [0.043 to 0.196]). Linear regressions for individual patients demonstrated that the F-test of the axial length measured in the four gazes were jointly different from the axial length measured in primary gaze. This difference was significant at the p < 0.05 level in 33 out of 40 eyes (82.5%).
Eye lengthening appears to occur only in inferior gaze, which is of interest given past clinical studies suggesting an association between excessive near work and myopia development and progression.
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