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B. Fortune, H. Yang, N. G. Strouthidis, G. A. Cull, J. L. Grimm, J. C. Downs, C. F. Burgoyne; The Effect of Acute Intraocular Pressure Elevation on Peripapillary Retinal Thickness, Retinal Nerve Fiber Layer Thickness and Retardance. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5824.
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© ARVO (1962-2015); The Authors (2016-present)
To determine whether acutely elevated intraocular pressure (IOP) alters peripapillary retinal thickness, retinal nerve fiber layer (RNFL) thickness or retardance.
Nine adult non-human primates (NHPs) were included in this study. All procedures were performed under isoflurane anesthesia. IOP was controlled manometrically. Retinal and RNFL thickness were measured by spectral domain optical coherence tomography (sd-OCT, Spectralis, Heidelberg Engineering, GmbH) 30 min after IOP was set to 10 mmHg and 60 min after IOP was set to 45 mmHg. A 15º radial B-scan pattern was used with either 40 or 48 sections. B-scan image segmentation was performed manually using custom software. RNFL retardance was measured by scanning laser polarimetery (SLP, GDxVCC, Carl Zeiss Meditec, Inc) in 10 min intervals for 30 min while IOP was 10 mmHg, then for 60 min while IOP was 45 mmHg, then for another 30 min after IOP was returned to 10 mmHg.
After 60 minutes of acute IOP elevation from 10 to 45 mmHg, the most readily apparent changes revealed by sd-OCT were in the architecture of the optic nerve head (ONH) as previously reported (Burgoyne et al, ARVO 2008). In contrast, there were only minimal changes outside of the ONH. RNFL thickness measured 1120 µm from the ONH center (to match the SLP location) decreased from 118.1 ± 9.3 µm at an IOP of 10 mmHg to 116.5 ± 8.4 µm one hour after IOP was increased to 45 mmHg, or by 1.4% ± 1.8% (p<0.0001, ANOVA). There was a significant interaction between IOP and eccentricity (p=0.0006). Within 800 µm of the ONH center, the RNFL was 4.9% ± 3.4% thinner after 60 min of IOP elevation (p<0.001), but there was no significant change for larger eccentricities. The same pattern was observed for retinal thickness, with 1.1% ± 0.8% thinning overall one hour after IOP was elevated to 45 mmHg (p<0.0001), and a significant effect of eccentricity (p<0.0001). The retina was 4.8% ± 1.2% thinner within 800 µm (p<0.001), but unchanged beyond that eccentricity. Retardance increased by a maximum of 2.2% ± 1.1% 60 min after IOP was increased to 45 mmHg (p = 0.0031).
Acute IOP elevation from 10 to 45 mmHg for 60 minutes in normal NHP eyes had minimal effects on retinal thickness, RNFL thickness or retardance.
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