Impotence Medications

In this current study we investigated the effect of sildenafil on retinal vessel diameter in patients with AMD. Sildenafil citrate produced statistically significant dilatation of major retinal veins at 90, 180 and 300 min in this group of patients. The effect of sildenafil on the retinal vessel diameters of AMD patients has not been studied before. Our previous study on the effects of sildenafil on the choroidal circulation of AMD patients did not show any statistically significant differences in the choroidal blood flow parameters after administration of sildenafil or placebo at any of the time points (Metelitsina et al., 2005). The differences between the findings obtained in these two studies may be due to the fact that the retinal and choroidal circulations are two different vascular beds that may have different concentration of target receptors. The significance of this retinal vasodilatation following sildenafil treatment in AMD and normal patients is not known at this time. This issue should be further clarified in the future when the effect of sildenafil on retinal blood flow is elucidated.

We also attempted to measure the effect of sildenafil citrate on retinal arteries. We were able to measure only 11 arteries of 11 patients. One of the major problems was that the light reflex present in the center of the arterioles introduced errors in the diameter measurements and this prevented us from getting an accurate estimation of arterial diameters in many instances. All previous studies of the effect of sildenafil on the retinal vasculature were performed in normal volunteers. Polak et al. (2003) showed a significant 4.7% increase in the retinal venous diameter at 80 min after 100 mg of sildenafil citrate. The findings from this study and the timing of the changes observed are very similar to our current data. Maximum serum levels of sildenafil are reached in 30e60 min (Marmor and Kessler, 1999) and it is interesting that we found statistically significant venous dilatation starting at 90 min and the veins remained dilatated even at 300 min.

Data of Pache et al. (2002) in a study without a control group also showed a 5.8% increase in venous and arterial diameter after administration of 50 mg of sildenafil. The peak of the changes, however, was observed at 30 min and by 120 min both arterial and venous diameters had returned to baseline values. In contrast to this study, Polak et al. (2003) did not observe any statistically significant effect on the retinal arterial diameters, and no effect of sildenafil was found on a flicker-induced vasodilatation in retinal arteries or veins.

Our previous study in normal male volunteers (Grunwald et al., 2002) did not reveal any statistically significant effect in retinal venous and arterial diameters after administration of sildenafil. This study, however, used an older method that had only an 80% power to detect 6.5% difference between the two groups. The lower sensitivity of this older method may explain the discrepancy with the other above-mentioned studies.

In conclusion, our results show a statistically significant vasodilatation of major retinal veins at 90, 180 and 300 min after administration of a 100 mg of sildenafil citrate in AMD patients. This effect is similar to what has been previously reported in normal subjects. Whether increased retinal venous diameters are associated with increased retinal blood flow in AMD patients and whether this effect may be of any therapeutic value are questions that need further investigation.