A patient with acute primary angle-closure crisis (PACG) presents to the emergency department with IOP of 58 mmHg, corneal oedema, mid-dilated fixed pupil, and severe pain. Which drug given FIRST reduces IOP most rapidly in this emergency?

• A Topical pilocarpine 4%
• B Oral acetazolamide 500 mg
• C Topical timolol 0.5%
• D IV mannitol 20% (1-2 g/kg over 45 minutes) ✓

Explanation

IV mannitol 20% causes rapid osmotic dehydration of the vitreous body, the most rapid reduction in IOP, acting within 30-45 minutes and reducing IOP by 30-50%. It is the fastest-acting agent in acute angle-closure crisis. Oral acetazolamide (500 mg IV or oral) also reduces IOP rapidly but less dramatically. Pilocarpine can miose the pupil but is ineffective when the pupil sphincter is ischaemic at very high IOP. Timolol is an adjunct but slower. The combination is used, but mannitol acts fastest.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.