Changes in intraocular pressure during and after the dark-room test.

The dark-room test has an established place in the investigation of glaucoma, its purpose being to decide whether there is a threat of angle closure. The conduct of the test is simple and is usually as follows. The intraocular pressures are measured and the patient is put in complete darkness for I hour, after which the intraocular pressures are measured again. The commonest indications for carrying out a dark-room test are a history suggestive of intermittent closed-angle glaucoma or the gonioscopic finding of narrowness of the angle or of peripheral anterior synechiae. The mechanism of the dark-room test is usually assumed to be that the pupil dilates in the dark thereby causing the root of the iris to hinder aqueous outflow from a narrow angle.