Which of the following is a primary therapeutic use of cholinergic agents?

Cholinergic agents are primarily used in the management of glaucoma because they work by increasing the outflow of aqueous humor from the eye. This mechanism helps to lower intraocular pressure, which is crucial in treating glaucoma and preventing damage to the optic nerve. Medications such as pilocarpine are examples of cholinergic agents that are effective in this context.

The other options do not align with the primary therapeutic uses of cholinergic agents. For instance, hypertension typically requires agents that either decrease heart rate or cause vasodilation, which is not the primary effect of cholinergic agents. Insomnia treatment often involves the use of sedatives or sleep aids rather than cholinergic medications, which can actually have stimulating effects. Lastly, the management of kidney stones focuses on pain relief and the potential to facilitate stone passage, typically requiring different types of medications rather than cholinergic agents.