Increase in aqueous humor production following D1 receptors activation by means of ibopamine.

BACKGROUND

Topically administered 2% ibopamine (a dopaminergic agonist) induces a transitory ocular hypertension in 92% of patients with primary open-angle glaucoma and in 52% of patients with normal tension glaucoma. In normal eyes, ibopamine has no effect on IOP.

PURPOSE

The aim of the present study was to verify, by means of fluorophotometric techniques, which hydrodynamic changes could be induced in normal and glaucomatous eyes, stimulating the D1 receptor with 2% ibopamine administered topically. In addiction, we wanted to evaluate if ibopamine could modify IOP before and after an experimentally induced outflow system impairment in rabbits.

METHODS

In study 1 we performed a measurement of aqueous humor flow in 6 healthy volunteers and in 6 glaucomatous patients, before and after 2% ibopamine administration. In study 2 the alteration of outflow pathways was induced by means of Laminaria Digitata in 10 rabbits.

RESULTS

After 2% ibopamine administration we found a significant increase in aqueous humor production, both in glaucomatous (P = 0.035) and normal eyes (P = 0.004). In rabbits, we found no significant change in IOP at basal conditions. After experimentally induced outflow system impairment by laminaria, we observed a marked increase in IOP (+ 13.5 mmHg SD 7.2; P < = 0.001) following ibopamine administration.

CONCLUSIONS

These experimental data have a diagnostic value in glaucoma, since they show how an intraocular hypertensive response due to ibopamine in normotensive eyes is a sign of initial outflow impairment. Moreover, the possibility to increase the aqueous humor production sets new trends in the treatment of post surgical ocular hypotony.