Purchase this article with an account.
Z. He, A. J. Vingrys, J. A. Armitage, B. V. Bui; The Effect of Ocular Perfusion Pressure on Inner Retinal Function in Rats. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2752.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To characterize the relationship between ocular perfusion pressure and retinal function at various levels of intraocular pressure (IOP) and mean arterial pressure (MAP).
Dark-adapted adult Long-Evan rats were anaesthetized (60:5 mg/kg ketamine:xylazine) and subjected to step-wise IOP elevations (10-120 mmHg, 5 mmHg steps every 3 minutes) via unilateral vitreous chamber cannulation. The fellow eye remained uncannulated. In Group 1 (n = 7), MAP was unaltered from its normal state (~110 mmHg). In Groups 2 (n = 5) and 3 (n = 4), MAP was elevated and targeted ~150 and ~170 mmHg, respectively, by adjusting the rate of Angiotensin II infusion (0.1 - 2 µg/Kg/min) into the femoral vein. Blood pressure was monitored by sphygmomanometry and by femoral artery cannulation and was stabilized for 5 mins before IOP challenge. Electroretinograms (ERG) to bright and dim stimuli (1.42 and -4.56 log cd•s•m-2) were serially recorded at every IOP step. Signals were analysed in terms of rod bipolar (P2) and ganglion cell function (nSTR). The ERG-IOP relationship was modelled with a cumulative normal function and the IOP50 (IOP for 50% ERG loss) compared using non-parametric bootstrap.
MAP achieved in Groups 1, 2 and 3 was 106 ± 7, 153 ± 3 and 173 ± 4 mmHg, respectively (mean ± SEM). Both the P2 and nSTR amplitude decreased with IOP elevation in all three groups, while amplitude remained stable in control eyes. The IOP50 for P2 amplitude was significantly increased from Groups 1 to 3 (mean [95%CI]: 60 [58 - 62], 101 [88 - 104], 117 [111 - 130] mmHg, respectively; p < 0.05). Likewise, the IOP50 for the nSTR became higher with MAP elevation (Groups 1 to 3: 59 [57 - 62], 106 [97 - 115], 123 [113 - 182] mmHg, respectively; p < 0.05). For both P2 and nSTR, there was a linear relationship (p < 0.05) between IOP50 and MAP when individual rats from all three groups were pooled.
Ganglion cell and bipolar cell dysfunction caused by acute IOP challenges can be ameliorated by blood pressure elevation, which reinforces the importance of ocular perfusion pressure to retinal integrity.
This PDF is available to Subscribers Only