rapidly and is accompanied by conjunctival injection and corneal edema due to hypoxia and secondary corneal decompensation. The pupil is midsize and fixed. In subacute cases, the angle reopens spontaneously and symptoms and signs resolve. Between attacks the examination is usually normal although careful inspection will often reveal the narrow angle that predisposes to acute closure. The diagnosis is established by gonioscopy or ultrasound biomicroscopy. Although assessment of intraocular pressure by digital examination is generally considered to be unreliable, this technique may be useful in cases with markedly elevated pressures when biomicroscopy is not immediately available.

When the onset of pain is explosive and accompanied by a vasovagal reaction and vomiting, as was the case above, the clinical scenario mimics acute intracranial pathology. The presence of a dilated pupil further adds to the impression of a cerebral aneurysm. It is important that neurologists keep

the possibility of acute angle closure glaucoma in the differential diagnosis of painful isolated mydriasis and seek urgent ophthalmic referral in selected patients before proceeding with neurologic investigations.

Diagnosis: Acute angle closure glaucoma

Tip: Acute angle closure glaucoma causes acute headache and an unreactive pupil. A history of blurred vision with halos in the eye with mydriasis suggests the diagnosis.

Invisible retinal disease

In most cases, retinal disease can be detected by a thorough dilated fundus examination. Occasionally, however, such abnormalities are absent either due to the nature of the disease process, the timing of the examination or the expertise of the examiner. In