Which of the following is a potential adverse effect of sildenafil?

Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor commonly used to treat erectile dysfunction and pulmonary arterial hypertension. One notable adverse effect associated with sildenafil is cyanopsia, which is characterized by the perception of a bluish tint to vision. This phenomenon occurs because sildenafil can affect the photoreceptors in the retina and influence color vision due to its action on the retinal PDE enzyme.

Understanding how sildenafil interacts with the visual system helps clarify why cyanopsia is a recognized side effect. Furthermore, the adverse effect is particularly relevant as it can impact the patient's quality of life and their perception of safety when driving or operating machinery.

Other options are less relevant as potential adverse effects of sildenafil. Constipation and urinary retention are not commonly reported with sildenafil use and do not relate to its pharmacological action. Prostate-specific antigen elevation is typically associated with prostate conditions rather than sildenafil use specifically. Thus, the connection of cyanopsia with the mechanism of action of sildenafil makes it the correct choice as a potential adverse effect.