Dorzolamide influences the autoregulation of major retinal vessels caused by artificial intraocular pressure elevation in patients with POAG: A clinical study

Purpose: The study investigated whether dorzolamide influences the autoregulatory behavior of major retinal arterioles in glaucoma patients via a moderate perfusion pressure reduction. Methods: The study included one eye each of 12 untreated patients with a primary open- angle glaucoma ( POAG) ( age 60.8 +/- 8.3, IOP 22.3 +/- 6.5 mmHg). Changes in the diameter of a retinal artery segment before ( 120 s), during ( 100 s), and after ( 380 s) artificial IOP elevation to 38 mmHg for 100 s were recorded continuously by means of a Retinal Vessel Analyzer. The measurement was repeated after 4- week treatment with dorzolamide eye drops t.i.d. Results: Ocular perfusion pressure (mmHg) was reduced by the intraocular pressure ( IOP) elevation from 58 ( +/- 10) to 41 ( +/- 11) in the pretreatment examination and from 60 ( +/- 8) to 40 ( +/- 8) posttreatment ( differences between the examinations n.s.). Before IOP elevation, the arterial diameter was found to be + 1.7 +/- 3.5% greater in the posttreated eyes than in the pretreated eyes ( p < 0.02). During IOP elevation, the arterial diameter decreased by - 1.8% +/- 3.8 in the pretreated eyes, whereas dilatation by + 1.4% +/- 2.5 was observed in the posttreated eyes ( p = 0.02). At the end of the observation period following IOP elevation, the vessel diameter in the pretreated eyes had increased by + 1.8% +/- 4.2, whereas in the posttreated eyes it had decreased by- 1.7% +/- 3.0. On average, dorzolamide reduced IOP by- 5.6 mmHg ( p = 0.001). Conclusions: The arterial diameter dilatation during IOP elevation in dorzolamide- treated eyes could be an accelerated counter- regulation on the induced elevated IOP and could constitute an additional therapeutic effect.