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Kevin M. Ivers, Nripun Sredar, Nimesh B. Patel, Lakshmi Rajagopalan, Hope M. Queener, Ronald S. Harwerth, Jason Porter; High-resolution Longitudinal Examination Of The Lamina Cribrosa And Optic Nerve Head In Living Non-human Primates With Experimental Glaucoma. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3697.
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© ARVO (1962-2015); The Authors (2016-present)
The lamina cribrosa has been suggested to be the location of initial insult to axons in glaucoma. We present initial data from a long-term study to characterize early in vivo changes to the anterior lamina cribrosa and optic nerve head (ONH) in a monkey model of experimental glaucoma.
En face adaptive optics scanning laser ophthalmoscope (AOSLO) images of the anterior lamina cribrosa were acquired in vivo in left and right eyes of 5 rhesus monkeys before and following laser treatments to induce unilateral experimental glaucoma. Laminar pore area, nearest neighbor distance (NND), and elongation (ratio of major to minor axis lengths of an ellipse best-fit to a given pore) were calculated and compared to baseline. Spectral domain optical coherence tomography (SDOCT) [Spectralis HRA+OCT] cross-sectional radial scans (20° field, 48 B-scans) of the ONH were acquired using Enhanced Depth Imaging at each time point. The termination of the retinal pigment epithelium (RPE)/Bruch’s membrane (BM) interface and the anterior lamina cribrosa were manually marked in SDOCT B-scans to determine the area of the neural canal opening [NCO] (area of an ellipse fit to the RPE/BM marked points) and the anterior lamina cribrosa surface (ALCS) height (mean distance from the marked ALCS points to a plane best fit to the NCO). AOSLO and SDOCT images were scaled based on biometric data measured using the IOLMaster. Intraocular pressure (IOP) was measured at each time point (Tono-Pen XL tonometer).
The mean change in IOP from baseline at the most recent time point following laser treatment was +2.8 mmHg (range: -5 to +9 mmHg) across all monkeys. NCO area did not vary by more than 7% (0.08 mm2) of the mean value in all lasered eyes. No eyes showed a significant change in ALCS height from baseline. There were no significant changes (from baseline) in laminar pore parameters in the monkey with the largest increase in IOP [paired t-test, P>.05]. Mean pore areas, NNDs, and elongations in the baseline vs. most recent time point were 812.2 ± 504.3 μm2 vs. 796.6 ± 488.8 μm2, 40.0 ± 9.7 µm vs. 40.4 ± 10.3 µm, and 1.62 ± 0.34 vs. 1.63 ± 0.39, respectively, while mean ALCS heights were 160.5 ± 25.0 µm vs. 159.1 ± 35.1 µm.
The lack of change in laminar pore geometry and ALCS height is consistent with the minimal change in IOP measured thus far in all lasered eyes. Lamina cribrosa pore and ONH geometries will continue to be tracked over the time-course of IOP elevation in these monkeys to detect early changes during the progression of experimental glaucoma.
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