Pilocarpine lowers intraocular pressure in primary open-angle glaucoma primarily through which action?

• A Increase in uveoscleral outflow through relaxation of ciliary body tone
• B Reduction of aqueous humour secretion by the non-pigmented ciliary epithelium
• C Relaxation of the iris sphincter with deepening of the peripheral anterior chamber
• D Contraction of the longitudinal fibres of the ciliary muscle, pulling the scleral spur and opening the trabecular meshwork ✓

Explanation

Miotics act by contracting the longitudinal fibres of the ciliary muscle, which pulls the scleral spur backward and stretches the trabecular lamellae, lowering outflow resistance. Aqueous suppression is the action of beta-blockers, alpha-2 agonists and carbonic anhydrase inhibitors. Uveoscleral enhancement is the domain of prostaglandin analogues. The iris sphincter contraction narrows, not deepens, the chamber, which explains why miotics can worsen a true pupillary block.

Reference: Khurana AK, Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.