Fildena contains sildenafil citrate, a PDE5 inhibitor used for erectile dysfunction (ED). One of its rare side effects is temporary changes in vision, such as seeing blue tints, blurred vision, or increased light sensitivity. Here’s why it happens: Mechanism Behind Vision Changes PDE Enzyme Inhibition Sildenafil primarily inhibits phosphodiesterase type 5 (PDE5) in the ***** to increase blood flow. It can also partially inhibit PDE6, an enzyme found in the retina of the eye. PDE6 is involved in phototransduction, the process by which the eye converts light into visual signals. Temporary Effect When PDE6 is partially inhibited, retinal signaling is altered, causing: Blue or green tints Blurred or less sharp vision Increased light sensitivity These effects are usually temporary and disappear within a few hours as the drug is metabolized. Factors That Increase Risk Higher doses of sildenafil (e.g., Fildena 100–200 mg) Pre-existing eye conditions (retinal disorders, glaucoma) Use of other PDE inhibitors or certain medications