Yonago Acta medica 1993;36:1-13

Effects of Intraocular Pressure on the Optic Nerve Head in Albino Rabbits

Shiro Hatta, Yoshika Takahashi and Akihiko Tamai

Department of Ophthalmology, Faculty of Medicine, Tottori University, Yonago 683, Japan

The effects of intraocular pressure (IOP) on the blood flow in the laminar portion of the optic nerve head in adult albino rabbits were investigated employing the hydrogen clearance method. The blood flow volume at the normal IOP level of 15 mmHg was 119.0 ± 25.0 mL/min/100 g (mean ± SD). When the IOP was elevated every 30 min from 5 mmHg to l5, 25, 35, 45, 55 mmHg in a stepwise fashion, the mean blood flow volume at 5 mmHg was almost the same as the volume at l5 mmHg, but a significant linear decrease was observed at 35 mmHg and more. The decreased blood flow returned to the initial level when the elevated IOP was restored to normal. When the IOP was elevated to 55 mmHg, the optic nerve potential (ONP) amplitude decreased and the peak latency was prolonged gradually with time, and finally the ONP was detected within 5 min after returning to the normal level of 15 mmHg. These findings indicate that vascular changes might play an important role in the optic nerve head function.

Key words: electroretinogram; hydrogen clearance method; intraocular pressure; optic nerve head blood flow; optic nerve potential

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