Effects of high intraocular pressure on the glucose metabolism in the retina and optic nerve in old atherosclerotic monkeys.

BACKGROUND

There are reasons to suspect that in patients with high intraocular pressure and glaucoma, there is underperfusion of the intraocular tissues and optic nerve head, leading to tissue hypoxia and neuronal damage. Studies in young, healthy monkeys have demonstrated that there is efficient autoregulation of the blood flow, and essentially normal glucose consumption, even at very high intraocular pressures that reduce the perfusion pressure to levels around 30 mm Hg. It seemed likely that the conditions might be different in old monkeys that had been on atherogenic diet for long periods of time and that such monkeys were a better model for glaucomatous patients.

METHODS

The perfusion pressure in one eye was reduced to 30-35 mmHg in four old rhesus monkeys that had been on atherogenic diet for 12.5 years, and the glucose consumption in the eyes and optic nerves was studied with the 14C-2-deoxyglucose (2DG) method of Sokoloff et al.

RESULTS

There was enhanced uptake of 2DG in the inner as well as outer parts of the retina and in the optic nerve head in all four monkeys studied, indicating compromised supply of oxygen resulting in anaerobic glycolysis.

CONCLUSION

Old monkeys that have been on atherogenic diet seem more susceptible to elevation of the intraocular pressure than young, healthy monkeys, thereby suggesting defective autoregulation in them. Such differences in susceptibility may play a role also in the development of ischemic disorders of the optic nerve head and glaucomatous optic neuropathy.