EVALUATION OF OPTIC NERVE HEAD FUNCTIONS AND TOPOGRAPHY AFTER AN EPISODE OF OPTIC NEURITIS

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Date
2011
Authors
CHUA, CHUI YIN
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Publisher
Pusat Pengajian Sains Perubatan Universiti Sains Malaysia
Abstract
Introduction The retinal nerve fiber layer (RNFL) is the only part of central nervous system where unmyelinated axons can be visualized. Role of Heidelberg Retinal Tomography III (HRT III) in the measurement of RNFL thickness and other optic nerve head topography in non glaucomatous optic neuropathies is still inconclusive. Objectives To compare optic nerve functions and parameters between optic neuritis and healthy control eyes, and to correlate the mean optic nerve functions and parameters in optic neuritis. Methodology 28 subjects with history of single episode of optic neuritis and 28 age and sex-matched controls underwent a complete ocular examination including visual acuity, contrast sensitivity, colour vision and optic nerve head measurement with HRT III. The mean optic nerve functions and parameters were compared between the groups using T test. The relationship between optic nerve functions and parameters in optic neuritis were evaluated using multiple linear regression. Pearson’s correlation was used to determine the correlation between the optic nerve functions and parameters. Results xxi There was significant reduction in global optic nerve functions in the optic neuritis group (p < 0.05). In the optic neuritis group, the mean optic nerve head parameters showed significant RNFL thinning (p < 0.001) and neuroretinal rim volume reduction (p =0.0065). There was also significant increase in the cup shape (p = 0.0005), cup-disc area ratio (p = 0.0093) and optic cup area (p = 0.0300). Significant and good correlations were evident between the mean RNFL thickness and all optic nerve functions, with particularly strongest correlation with contrast sensitivity at high spatial frequency (r = 0.7351, p < 0.001). There was also significant but fair correlation between the cup shape and contrast sensitivity (r= -0.4463, p = 0.016). Conclusions There was significant global reduction of mean optic nerve functions in the optic neuritis group. In this group, the mean optic nerve parameters were also significantly affected, in particularly RNFL thickness, neuroretinal rim volume, cup shape and cup disc area ratio. The correlation between the mean RNFL thickness and optic nerve functions was significant and good, in particular the contrast sensitivity.
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Keywords
Ophthalmology
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