Ocular mydriatics are diagnostic agents that generally facilitate a preferable ophthalmoscopic examination. However, the optometrist should be aware of certain iatrogenic side effects including the precipitation of an acute angle-closure. The purpose of this paper is to summarize the mechanism of mydriatic angle-closure glaucoma. In addition, a shallow anterior chamber is a fundamental ocular variable which should be evaluated before inducing mydriasis and/or cycloplegia. The technical procedures for the oblique illumination shadow test and the van Herick slit lamp test are presented, both of which provide an accurate estimation of the anterior chamber angle. The risk of precipitating an attack after reasonable circumspection by such evaluations approaches zero. However, should an attack occur, the procedures to rapidly lower the intraocular pressure and open the chamber angle are discussed.