Ten normal, healthy, nonsmoking volunteers participated in a double-masked, placebo-controlled one-day trial of 2,000 mg of oral pentoxifylline to determine the short-term effects of orally administered pentoxifylline on retinal circulation and rheologic properties of whole blood. Retinal capillary blood velocity and leukocyte density, whole blood viscosity, and whole blood filterability were measured before and after therapy by the blue-field entoptic phenomenon computer simulation, rotational viscometry, and micropore filtration techniques, respectively. Treatment with pentoxifylline for one day resulted in a significant improvement in retinal capillary blood flow velocity (P = .02) and in viscosity (P < .01), but not filterability, of whole blood. These results suggest that pentoxifylline may be useful in the treatment of early diabetic retinopathy.

Objective: The purpose of this study was to determine whether oral pentoxifylline would improve retinal microvascular hemodynamics and blood theology in patients with diabetes. Design: Patients were enrolled in a double-masked, placebo-controlled trial of pentoxifylline at 2000 mg/d. Retinal capillary blood velocity and leukocyte density, filterability, viscosity, and fibrinogen content were measured by the blue-field entoptic phenomenon simulation, filtration, rotational viscosimetry, and heat precipitation techniques, respectively, before, during, and after drug therapy. Results: Treatment with pentoxifylline resulted in a 23.2%, 26.8%, and 37.8% increase in capillary blood flow velocity at 1, 2, and 3 months oi therapy, respectively, with a return to pretreatment baseline levels 1 month after cessation of therapy. There were no apparent effects on the remaining variables during treatment. Conclusion: Pentoxifylline increases retinal capillary blood flow velocity in patients with diabetes.

A mydriatic used for outpatient indirect ophthalmoscopy should produce prompt, maximal, transient mydrasis after a single instillation. Cycloplegia or systemic side effects should be minimal. A solution of tropicamide with phenylephrine hydrochloride seems to achieve this most effectively. In a general retina clinic population, the percentage of pupils dilated, the degree of dilation, and the resistence of the dilation to intense illumination were used to evaluate various concentrations of the drugs. Eight-tenths percent tropicamide with 5% phenylephrine adequately dilated 98.8% of the eyes, among which 25% had dark irides and 9% were receiving miotic therapy. Reduction of the concentration of either component produced less adequate mydriasis; an increase of the tropicamide concentration resulted in a saturated solution with drug precipitate forming on storage and a less adequate dilation. With the optimal combination, 1 drop adequately dilates the general population; 2 drops appear on more effective than 1.