This drug has lesser affinity for isoenzyme PDE6, an enzyme found in the retina. This lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels.
Nonarteritic anterior ischemic optic neuropathy developed in one eye within minutes to hours after ingestion of sildenafil. Four of the five patients had no vascular risk factors for ischemic optic neuropathy.
-Abnormal Vision: Mild to moderate and transient, predominantly color tinge to vision, but also increased sensitivity to light, or blurred vision.
-Visual color distortions: Chloropsia, chromatopsia, cyanopsia, erythropsia and xanthopsia
-Lacrimation disorders: Dry eye, lacrimal disorder and lacrimation increased [ Ref ]
In addition to the mentioned side effects several others have been reported. In both males and females acne are frequently reported, as well as hypertrophy of sebaceous glands, increased tallow excretion, hair loss, and alopecia. There is some evidence that anabolic steroid abuse may affect the immune system, leading to a decreased effectiveness of the defense system. Steroid use decreases the glucose tolerance, while there is an increase in insulin resistance. These changes mimic Type II diabetes. These changes seem to be reversible after abstention from the drugs.