Which side effect is characterized by 'pigmentation of corneal endothelium'?

The pigmentation of the corneal endothelium is a well-documented side effect associated with the use of Phenothiazines, a class of antipsychotic medications. These drugs are known to cause a variety of ocular side effects, one of which is the deposition of pigment in the corneal endothelium. This can result in the observed change in corneal appearance and may be due to the accumulation of melanin or other pigments as a reaction to the medication.

Phenothiazines primarily block dopamine receptors and are used in the treatment of various psychiatric disorders. Their side effects can include anticholinergic effects, sedation, and the potential for ocular complications like corneal deposits. Understanding this association is crucial for clinicians who prescribe these medications, as it can impact the management of patients with psychiatric conditions who may experience visual changes due to their treatment.

In contrast, the other conditions or side effects listed do not typically result in pigmentation of the corneal endothelium, which further reinforces why Phenothiazines are the correct answer in this context.