Relationship of Optic Disc Topography to Optic Nerve Fiber Number in Glaucoma | Glaucoma | JAMA Ophthalmology | JAMA Network
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Laboratory Sciences
April 1998

Relationship of Optic Disc Topography to Optic Nerve Fiber Number in Glaucoma

Author Affiliations

From the Glaucoma Center (Drs Yücel, Gupta, de Souza Lima, Zangwill, and Weinreb) and the Department of Pathology (Drs Kalichman and Mizisin), University of California, San Diego; the Department of Ophthalmology, University of Toronto, Ontario (Dr Gupta); and the Department of Biological Sciences, Allergan Inc, Irvine, Calif (Dr Hare). Dr Yücel is now with the Department of Ophthalmology, University of Toronto. The authors have no proprietary interest in the Heidelberg Retina Tomograph.

Arch Ophthalmol. 1998;116(4):493-497. doi:10.1001/archopht.116.4.493
Abstract

Objective  To assess the relationship between in vivo measurements of optic disc topography and histomorphometric measurements of optic nerve fiber number in glaucoma.

Methods  Both eyes of 10 monkeys (Macaca fascicularis) with laser-induced glaucoma in the right eye were studied. Optic disc topography was measured in vivo with a confocal scanning laser ophthalmoscope. Histomorphometry was performed on optic nerve cross sections using bright-field microscopy with camera lucida. Nerve fiber density was estimated by unbiased random sampling. Nerve fiber number was estimated for each sector by multiplying nerve fiber density with neuroglial area. Nerve fiber count was compared with each of 13 global optic disc topographic parameters.

Results  For neuroretinal measurements in the glaucomatous eyes, rim area, retinal nerve fiber layer (RNFL) cross-sectional area, rim volume, and RNFL thickness correlated significantly with optic nerve fiber number. Differences in nerve fiber count between control and glaucomatous optic nerves showed the strongest correlation with differences in mean height contour; this was followed by RNFL cross-sectional area, RNFL thickness, rim volume, and differences in rim area. For cup measurements in the glaucomatous eyes, cup volume below reference, cup area, mean cup depth, the ratio of cup area to disc area, and cup shape correlated significantly with nerve fiber number. Differences in nerve fiber number between control and glaucomatous optic nerves showed the strongest correlation with differences in cup shape; this was followed by mean cup depth, cup volume below reference, the ratio of cup area to disc area, cup area, and differences in cup volume below surface. No association was found between optic nerve fiber number and optic disc area in glaucomatous eyes.

Conclusions  In experimental glaucoma, most optic disc topography measures correlated significantly with optic nerve fiber number. The results of this histomorphometric study support the use of confocal scanning laser ophthalmoscopy to evaluate optic nerve damage in glaucoma.

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