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Nimesh Bhikhu Patel, Kwame Antwi-Boasiako, Ronald S Harwerth; Relationship between Optical Coherence Tomography and Visual Field Structural Measures in Experimental Glaucoma in Non-Human Primates.. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):642. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Optical coherence tomography (OCT) derived structural measures of the optic nerve head (ONH), peripapillary retinal nerve fiber layer (RNFL), and macula ganglion cell complex (GCC) thickness are used clinically for the diagnosis and assessment of progression of optic neuropathies. The minimum rim width (MRW), RNFL thickness, and GCC thickness are often used as surrogates for ganglion cell content. The present study was undertaken to investigate the relationship between these structural measures and their relationship with ganglion cell estimates based on standard automated perimetry (SAP), in the non-human primate experimental glaucoma model.
Unilateral Argon laser application to the trabecular meshwork was used to elevate the intraocular pressures in eight monkeys that were followed longitudinally. Six of these animals were behavior trained to perform 24-2 SAP. Sensitivity measures were then converted to ganglion cell estimates (VF-GCE). For structural measures, radial and raster OCT scans centered on the ONH and raster scans centered the macula were used. From scaled scans, the MRW at the Bruch’s membrane opening (BMO), RNFL thickness at 550 µm from the BMO, and macula GCC thickness within the central 3 mm centered on the foveal pit, were measured.
For structural measures, the relationships between global RNFL (R2=0.76) and macula GCC thickness (R2=0.66) were best described using a non-linear, one-phase association fit (difference in AIC>62.54). In contrast, RNFL and GCC thickness were linearly related (slope=0.42, R2=0.82, p<0.01). Similarly, both RNFL (R2=0.48, p<0.01) and GCC thickness (R2=0.71, p<0.01) were linearly related to VF-GCE for the six animals followed with SAP. However, the relationship between VF-GCE and MRW was best described using a non-linear fit (R2=0.63, difference in AIC=74.75).
In experimental glaucoma, OCT derived measures of the RNFL and macula GCC thickness are likely better surrogates for the ganglion cell content in the eye based on the relationship with visual field derived ganglion cell estimates. Although MRW contains the same neural tissue, it is also likely influenced by the biomechanical stresses on the ONH.
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