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J. Wheat, L. Carter-Dawson, N. V. Rangaswamy, X. Lao, R. S. Harwerth; Comparison of Confocal Microscopy With Optical Coherence Tomography Measurements of the Retinal Nerve Fiber Layer in Experimental Glaucoma. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4639. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare histological measurements made by confocal microscopy to measurements of the retinal nerve fiber layer (RNFL) obtained with optical coherence tomography (OCT) in macaque monkeys with experimental glaucoma
Five macaque monkeys with unilateral glaucoma induced by argon laser treatment of the trabecular meshwork were allowed to progress until they had significant visual field defects. OCT was used to obtain measurements of the retinal nerve fiber layer using a 3.4 mm diameter circle centered on the optic nerve head, with three scans captured per eye while the animals were under general anesthesia. The monkeys were then sacrificed, the eyes were enucleated and fixed in paraformaldehyde, and the retinal tissue was dissected from the eye in the area surrounding the optic nerve head. The specimens were then stained with DAPI to identify nuclei and phalloidin Alexa Fluro 488 to identify nerve fibers. Image sequences were captured using the Zeiss 510 LSM confocal microscope and Zeiss LSM software in regions corresponding to the superior, inferior, nasal, and temporal poles at approximately 1300 microns from the optic nerve center, which corresponds to the location of the OCT scan in the monkey eye. OCT and confocal image measurements were then compared for agreement using a Bland-Altman analysis.
Both OCT and confocal microscopy measurements showed a decrease in RNFL thickness for glaucomatous eyes when compared to the control eyes for all regions measured. Average measurements taken with the confocal microscope were 83.0, 85.6, 37.5, and 39.1 microns for the inferior, superior, temporal, and nasal poles. Corresponding averages in similar regions obtained from the OCT were 103.8, 95.9, 37.0, and 37.5 microns. The mean difference between measurements for the glaucoma group was -9.5 ± 14.4 microns for eyes with induced glaucoma, and -5.5 ± 19.8 microns for control eyes.
In vivo measurements of the RNFL thickness by OCT appear to agree with in vitro confocal microscopy measurements for both glaucomatous and control eyes in macaque monkeys.
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