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Abstract #15139 Published in IGR 8-4
The rate of functional recovery from acute IOP elevation
He Z; Bui BV; Vingrys AJInvestigative Ophthalmology and Visual Science 2006; 47: 4872-4880
PURPOSE: To evaluate the recovery of retinal function after acute IOP elevation. METHODS: The electroretinogram (ERG) was measured before, during, and after IOP increased to 50 and 70 mmHg at different durations in anesthetized, dark-adapted rats (n = 5-7). Signals were collected for dim and bright flashes (-4.95 and 1.0 log cd ·s/m2 ) and analyzed in terms of the photoreceptoral (P3), postreceptoral (P2), and inner retinal (negative scotopic threshold response [nSTR]) responses. Parameters (treatment/baseline, %) were compared across time by using repeated-measures ANOVA and t-tests. The rate of recovery was quantified with a logistic function and compared by bootstrap. RESULTS: IOP spikes induce greater loss (P < 0.01) and slower recovery (P < 0.001) in the nSTR compared with the P2 and P3 responses. IOP spikes having common integral (pressure x duration, 2100 mmHg x minutes) for insult gave significantly greater P2 and nSTR dysfunction at the higher pressure (70 vs. 50 mmHg, nSTR reduced to -2.5% ± 0.5% vs. 20.3% ± 6.5%, P < 0.05). The higher pressure also produced significantly slower nSTR recovery (50% recovery time [t0.5 ] 70 vs. 50 mmHg: 33.1 vs. 21.7 minutes; P < 0.05). At a given IOP (70 mmHg), t0.5 showed a linear relationship with duration (15 vs. 30 vs. 60 minutes' exposure: t0.5 16.7 vs. 33.1 vs. 63.2 minutes; P < 0.05) and integral. CONCLUSIONS: Ganglion cell function recovers slower than the outer retina after IOP insult, with peak IOP being the principle determinant of functional loss and recovery. For a fixed pressure, functional recovery is linearly related to exposure.
Dr. Z. He, Department of Optometry and Vision Sciences, University of Melbourne, Parkville 3010, Victoria, Australia
Classification:
5 Experimental glaucoma; animal models
6.7 Electro-ophthalmodiagnosis (Part of: 6 Clinical examination methods)
6.1 Intraocular pressure measurement; factors affecting IOP (Part of: 6 Clinical examination methods)
2.13 Retina and retinal nerve fibre layer (Part of: 2 Anatomical structures in glaucoma)