> **mnemonic:** *Rule of 5s*: pilocarpine 2% Q5 min, timolol 0.5% Q0.5 hours, acetazolamide 500mg IV . Then Laser (5 letters) peripheral iridotomy - acute or chronic - increased intraocular pressure (usually >26mmHg for any glaucoma) - **normal** is 10-20, average ~15 mmHg - results from a problem with flow of the aqueus humor through the trabecular meshwork and canal of schlemm - leads to damage of the optic nerve # Overview Acute glaucoma occurs when the lens plasters up against the back of the iris, **blocking aqueous flow through the pupil**. This resistance produces a **pressure gradient** across the iris that forces the iris and lens to move anteriorly. When the iris moves forward, the irido-corneal angle closes, blocking the trabecular meshwork. Without an exit pathway, aqueous fluid builds up, eye pressure increases rapidly, and the retina is damaged from stretching and decreased blood supply. **pupil dilation** (from iris thickening) correlates with higher risk for acute glaucoma and precipitate blockade of aqueous humour flow. meds that dilate pupils (eg antihistamines) increase the risk.   pts present with red and painful eye, nausea/vom. exam shows slugish, midly dilated pupil and preasures 60 mmHg or higher. pts see halos around lights.   Tx: **timolol** (topical beta blocker) diamox (carbonic anhydrse inhibitor), **mannitol**, **pilocarpine** (to induce miosis  Surg: A high intensity laser can burn a hole through the iris and create a communication between the posterior and anterior chambers, relieving the pressure gradient across the iris, and allowing it to move back into a normal position. This opens up the trabecular meshwork and allows aqueous fluid to flow freely out of the eye. This procedure is typically performed on both eyes because these patients are predisposed to having attacks in the other eye as well. # Chronic glaucoma - open angle - age > 40, more common in african american, may have family history - raised pressures - Tx ophthal referral, topical/systemic meds # Acute angle closure glaucoma - painful eye, loss of vision, headache, nausea, vomiting, visual halos surrounding lights - eye appears injected with fixed semi-dilated pupil and steamy cornea - “Mid-dilated, poorly reactive or un-reactive pupil” - shallow anterior chamber (Van Herick technique) - IOP 40-70 (usually >30) - severe unilateral pain - blurred vision - *haloes* around lights - aching eye or brow pain - headache - red eye - nausea - vomiting ![[Pasted image 20240328193218.png]] **Risk factors** - asian - topical or systemic medications that dilate pupil - OTC decongestants - motion sickness medications - anticholinergic agents - sulfonamides - topiramate - phenothiazines - advanced age - FMx - shallow anterior chamber - female > M by 3x **Precipitants** - drugs with anticholinergic actions - [[atropine]] - nebulised ipatropium - beta agonists - mydriatics - emotional upset - ==dim light may precipitate it== (eg walks into a theatre or a dark room) **Assessment** - [[pupil exam|Pupil]] often irregular / ==oval== or mid-dilated - hazy cornea - raised intraoccular pressure (>35 usually, but >26 concerning) - globe is stony hard to palpation - ↑ optic disc cupping - Van Herick limbal chamber depth (LCD) can help estimate the depth of the angle as a percentage of the peripheral corneal thickness (PCT). use a very narrow slit of light on the slit lamp, projected at the limbus at an angle of 60 deg. ![[Pasted image 20240411220742.png]] ![[Pasted image 20240411220925.png]] ## Treatment for acute glaucoma - urgent ophthal referral - IV carbonic anhydrase inhibitor: *acetazolamide* 500mg IV stat then 250mg po TDS or *mannitol* 1g/kg - acetazolamide contraindicated if decreased renal function or patients with allergy to sulphonamides - ensure pt supine while giving it - Helps remove excess aqueous humor - opiate for pain/anti-emetics - *pilocarpine* 2% every 5 min for 1 hour for miotic (constricting) effect → assists with aqueous outflow - *timolol* 0.5% 1 drop q30-60 min acutely (avoid if contraindication) → prevent pupil dilation - d/w ophthal re: prednisolone acetate 1% 1 drop - **laser peripheral iridotomy** (see [guideline](x-devonthink-item://78370A80-29C7-4A96-9945-4B0300C3437E)) ASAP via ophthal referral **Mnemonic:** “Rule of 5s: pilocarpine Q5 min, timolol 0.5% q0.5 hours, acetazolamide 500mg IV. Then Laser (5 letters) peripheral iridotomy”