Shape of the posterior vitreous chamber in human emmetropia and myopia


PURPOSE - To compare posterior vitreous chamber shape in myopia to that in emmetropia. METHODS - Both eyes of 55 adult subjects were studied, 27 with emmetropia (MSE =-0.55; <+0.75D; mean +0.09 ±0.36D) and 28 with myopia (MSE -5.87 ±2.31D). Cycloplegic refraction was measured with a Shin Nippon autorefractor and anterior chamber depth and axial length with a Zeiss IOLMaster. Posterior vitreous chamber shapes were determined from T2-weighted MRI (3-Tesla) using procedures previously reported by our laboratory. 3-D surface model coordinates were assigned to nasal, temporal, superior and inferior quadrants and plotted in 2-D to illustrate the composite shape of respective quadrants posterior to the second nodal point. Spherical analogues of chamber shape were constructed to compare relative sphericity between refractive groups and quadrants. RESULTS - Differences in shape occurred in the region posterior to points of maximum globe width and were thus in general accord with an equatorial model of myopic expansion. Shape in emmetropia is categorised distinctly as that of an oblate ellipse and in myopia as an oblate ellipse of significantly less degree such that it approximates to a sphere. There was concordance between shape and retinotopic projection of respective quadrants into right, left, superior and inferior visual fields. CONCLUSIONS - The transition in shape from oblate ellipse to sphere with axial elongation supports the hypothesis that myopia may be a consequence of equatorial restriction associated with biomechanical anomalies of the ciliary apparatus. The synchronisation of quadrant shapes with retinotopic projection suggests that binocular growth is coordinated by processes that operate beyond the optic chiasm.

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Divisions: College of Health & Life Sciences > School of Optometry > Optometry
College of Health & Life Sciences > School of Optometry > Optometry & Vision Science Research Group (OVSRG)
College of Health & Life Sciences
College of Health & Life Sciences > School of Optometry > Vision, Hearing and Language
Additional Information: Copyright 2013 The Association for Research in Vision and Ophthalmology, Inc. Creative Commons Attribution Non-Commercial No Derivatives License
Publication ISSN: 1552-5783
Last Modified: 19 Jun 2024 07:10
Date Deposited: 16 Oct 2013 13:24
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Related URLs: http://www.scop ... tnerID=8YFLogxK (Scopus URL)
http://iovs.arv ... ticleid=2127384 (Publisher URL)
PURE Output Type: Article
Published Date: 2013-10-15
Published Online Date: 2013-10-15
Authors: Gilmartin, Bernard
Nagra, Manbir
Logan, Nicola S. (ORCID Profile 0000-0002-0538-9516)

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