Makindo Medical Notes

Related Subjects: |Episcleritis |Scleritis |Assessing a Red eye |Acute Angle Closure Glaucoma |Allergic and Infective Conjunctivitis |Anterior and Posterior Uveitis |Herpes simplex keratitis (HSK)

About

• Acute Angle Closure Glaucoma (AACG) is an urgent cause of a red eye requiring immediate treatment.
• May be triggered by low lighting conditions or any situation causing pupillary dilation.
• Uncommon in those with prior cataract surgery.
• Firmness of the globe can be assessed by digital palpation.

Digital palpation tonometry involves gently ‘balloting’ the eyeball under closed eyelids using both index fingers to compare the firmness of the affected eye with the unaffected one. If intraocular pressure is elevated, the affected eye will feel very hard, similar to a golf ball.

Aetiology

• Caused by a blockage in the drainage of aqueous humor from the anterior chamber, leading to elevated intraocular pressure (IOP).
• Triggers include any factors that cause pupillary dilation, such as night-time darkness or certain medications (e.g., anticholinergics or sympathomimetics).
• Primarily affects individuals over 60, with increased prevalence at older ages.
• Delay in treatment risks optic nerve damage and permanent vision loss.

Precipitants: Half-dilated Pupil

• Situations such as stress, excitement, or exposure to dim lighting.
• Use of anticholinergic drugs or other medications that dilate the pupil.

Epidemiology

• Affects approximately 1 in 1,000 white individuals, 1 in 100 Asians, and 2-4 in 100 Eskimos.
• More common in females due to a shallower anterior chamber.

Clinical Features

• Painful, red eye with tenderness and firmness upon palpation.
• Pupil appears mid-dilated and fixed; cornea may be hazy or cloudy.
• Systemic symptoms, including nausea and vomiting, can obscure the diagnosis.
• Other indicators: shallow peripheral anterior chamber, reduced visual acuity, injection of circumcorneal redness.

Investigations

• Gonioscopy to examine the anterior chamber angle.
• Slit-lamp examination for structural assessment.
• Automatic static perimetry to evaluate visual fields.
• Tonometry showing elevated intraocular pressure, often >30 mmHg, and can reach 60-70 mmHg.

Management

• Immediate referral to an ophthalmologist is crucial.
• Administer IV Acetazolamide 500 mg to reduce aqueous humor production.
• Consider IV Mannitol 20% (1-2 g/kg) to decrease aqueous humor volume rapidly.
• Apply topical Beta-Blocker (e.g., Timolol 0.5%) to further block aqueous humor production.
• Instill Pilocarpine drops to constrict the pupil and unblock the drainage canal.
• In emergency cases, an anterior chamber paracentesis may be performed.
• Definitive treatment includes laser iridectomy, typically in both eyes, though not necessarily simultaneously.