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Quan V Hoang, K Bailey Freund, Lawrence A. Yannuzzi, Jerome Sherman, Stanley Chang; Effect of Primary Gaze Axial Length on Gaze-Induced Eye Shape Changes in High Myopia Patients. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):2961.
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To determine if gaze-induced axial length elongation in highly myopic eyes is related to baseline axial length (in primary gaze).
A prospective imaging study was performed on 58 eyes of 31 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, temporal, superior and inferior). 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. Analysis was then performed stratifying by baseline eye length into those with axial length of at most 30 mm and those with axial length > 30 mm.
In examining eye axial lengths in the different gazes, we found that the mean change in axial length was near-zero and not statistically significant when comparing the primary gaze to the nasal gaze (p = 0.40) or temporal gaze (p = 0.58). Axial length shortened in superior gaze (-0.08 mm, p = 0.134) and increased in inferior gaze (+0.123 mm, p = 0.015, 95% CI [0.024,0.221]). Linear regressions demonstrated that the F-test of the eccentric gaze axial lengths were jointly different from primary gaze (p < 0.0001). Eyes with baseline axial length > 30mm elongated more versus shorter eyes (p = 0.082).
A reversible, instantaneous axial length elongation appears to occur only in downgaze, which is of interest given past clinical studies suggesting an association between excessive near work and myopia development and progression. The extent of axial length elongation may be related to longer baseline axial length.
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