Acute angle closure is a diagnosis made on the history as much as the eye. A painful red eye with blurred vision, a hazy cornea, a mid-dilated unreactive pupil and a rock-hard globe is unmistakable when you have seen it. The trap is the one that arrives on a medical ward or in a general clinic, where the eye is called conjunctivitis or the headache and vomiting are worked up as a neurological problem, and the precipitant is sitting in the drug chart.
The drugs that do it are ordinary. Anticholinergics: nebulised ipratropium, oxybutynin and tolterodine for bladder symptoms, hyoscine, tricyclic antidepressants, promethazine and other sedating antihistamines. Sympathomimetics: phenylephrine and pseudoephedrine in cold preparations, and nebulised salbutamol. Topiramate causes a distinct bilateral secondary angle closure through ciliary body swelling and myopic shift, which does not respond to a peripheral iridotomy and needs the drug stopped. Serotonergic and adrenergic antidepressants have all been implicated. Nebulised ipratropium and salbutamol together, delivered by an ill-fitting mask to an elderly patient, is the classic hospital cause.
The practical moves are to ask what is new in the drug chart, to feel both globes, and to check the other eye — an occludable angle is usually bilateral, and the fellow eye is the one you can still protect. Ask about the eye going blurred and the halos around lights in the evening, because intermittent subacute closure usually precedes the acute attack and is dismissed as tiredness.
In a patient with an unexplained unilateral red eye and any of these drugs newly started, the intraocular pressure is not an optional part of the examination.
- Read the drug chart before calling a painful red eye conjunctivitis; look for anticholinergics and sympathomimetics
- Measure intraocular pressure in both eyes and feel both globes — occludable angles are usually bilateral
- Ask about evening blurring and haloes around lights, which precede the acute attack
- Recognise topiramate-induced angle closure as a different mechanism: stop the drug, iridotomy will not fix it
- Consider nebulised ipratropium with a poorly fitting mask in an older inpatient with a sudden red eye
Why it matters
The commonest way acute angle closure is missed is that the eye is examined and the prescription is not.
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