The eye naturally produces fluid all the time. This fluid drains out of the eye near the front of the eye, in the angle between the iris and cornea (the iridocorneal angle). Some people’s eyes have too little room at the front of the eye to allow adequate drainage – they are at risk of the pressure suddenly rising (acute angle closure glaucoma). This event can cause permanent loss of vision, so patients with narrow or occludable angles are normally advised to have preventive treatment, either in the form of laser iridotomy (to place an alternative drainage hole in the iris) or cataract surgery (to widen the iridocorneal angle). The choice of treatment depends on a number of factors and is best discussed between surgeon and patient on an individual basis.