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A. P. Wells, A. Poostchi, T. Wong, K. Chan, N. Sachdev, D. F. Garway-Heath; Ocular Dimensions, Corneal Viscoelasticity, and Optic Nerve Surface Compliance. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1248.
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© ARVO (1962-2015); The Authors (2016-present)
To describe relationships between anterior segment properties and optic nerve deformability.
Prospective experimental study of 100 subjects: 38 with glaucoma, 62 without. Data collected included central corneal thickness (CCT), axial length, spherical equivalent, Goldmann intraocular pressure (IOP), Pascal IOP and ocular pulse amplitude, and Ocular Response Analyzer (ORA) measurements of corneal hysteresis (CH). Elevation of IOP was induced in the right eye of all subjects with a modified LASIK suction ring, to an average of 64 mmHg for less than 30 seconds. Heidelberg Retinal Tomography (HRT-II) was used to image the optic nerve heads before and during IOP elevation.
Both CH and CCT were lower in the glaucoma group (8.8mmHg and 532µm) than in the non-glaucoma group (9.6mmHg, p=0.012 and 551µm, p=0.011 respectively). There were no statistically significant differences in spherical equivalent, cylinder, axial length, optic disc size, or ocular pulse amplitude between the glaucoma and non-glaucoma groups. There was no difference between the amount of IOP elevation between the two groups (p=0.41), and the average difference in mean cup depth between baseline and during IOP elevation was 33µm (29.8µm in glaucoma and 36.1µm in non-glaucoma, p=0.5). Multivariate analysis, controlling for age and gender, showed that CH was correlated with mean cup depth increase (p=0.032). This relationship persisted (p=0.032) after controlling for glaucoma status, in addition to age and gender. Other factors including CCT (p=0.3), axial length (p=0.9), ocular pulse amplitude (p=0.22), and spherical equivalent (p=0.38) were not significant in this model.
Corneal hysteresis, but not central corneal thickness or other anterior segment parameters, was associated with increased deformation of the optic nerve surface during transient elevations of intraocular pressure.
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