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Da Zhao, Christine Tram Oanh Nguyen, Zheng He, Algis J Vingrys, Bang V Bui; Effects of intracranial and intraocular pressure modification on the optic nerve of young and old rats.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3571.
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© ARVO (1962-2015); The Authors (2016-present)
To consider if the optic nerve in older rat eyes shows an age related change in response to acute simultaneous intracranial pressure (ICP) and intraocular pressure (IOP) modification.
Young (8 m.o., n=5/group) and old (19 m.o., n=6-8/group) anesthetised (60:5mg/kg ketamine:xylazine) Long-Evans rats underwent acute pressure modification. ICP was manometrically set to low (-5mmHg), normal (5mmHg) or high (25mmHg) levels via a double-lumen cannula placed into the lateral ventricle (-1.5mm from bregma, ±2mm from midline). At each ICP level, IOP was elevated from 10 to 90 mmHg in 10mmHg steps (3 minutes each) via an intra-vitreal cannula in the ipsilateral eye. The posterior pole was imaged using spectral domain-optical coherence tomography (Bioptigen) and analysed for peripapillary retinal surface deformation (100um from the optic nerve centre), retinal nerve fiber layer (RNFL) and total retina thickness, the width of Bruch’s membrane opening (BMO width) and minimum rim thickness (MRT). Thickness is expressed as a percentage of baseline (IOP 10mmHg), and deformation is expressed as a difference from baseline (mean±SEM). Data were compared at each ICP level using a two-way ANOVA (IOP effect between ages).
There was significantly more surface deformation in young compared with old rats, particularly at ICP 5 mmHg (p<0.01). The RNFL was more compressed by IOP in older eyes with low ICP compared with younger eyes (old: 80%±5% vs. young: 113%±5%, p<0.01), but not at normal (p=0.99) and high ICP (p=0.18). Total retinal thickness and BMO width showed no age-related effect at any ICP level (all p > 0.05). MRT at BMO was compressed significantly less in older eyes when ICP was -5 (old: 84%±2% vs. young: 77%±5%, p=0.04) and 5 mmHg (old: 86%±3% vs. young: 76±5%, p=0.01), however no difference was observed at 25 mmHg (p=0.08).
Compared with young rats, the peripapillary retina in aged rats shows less surface deformation and rim compression with IOP elevation at all ICP levels. However, with low ICP, IOP-induced RNFL compression was exacerbated by older age. This data suggests the optic nerve in old rats is less compliant to pressure changes, which may produce greater peripapillary RNFL compression.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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