Following anatomical changes predisposes to angle closure glaucoma except: March 2007

Ans. B: Flat cornea Angle closure glaucoma is caused by contact between the iris and trabecular meshwork, which in turn obstructs outflow of the aqueous humor from the eye. Predisposing factors include sho eye, small corneal diameter, a shallow anterior chamber, and a relative anterior positioning of the lens-iris diaphragm. These all lead to a very narrow space at the angle of the anterior chamber. In over half of all cases, prolonged contact between iris and TM causes the formation of synechiae (effectively "scars"). These cause permanent obstruction of aqueous outflow. Diagnosis is made from physical signs and symptoms: very highly raised intraocular pressure,pupils are veically oval and mid-dilated and unresponsive to light, cornea edematous (cloudy), reduced vision, redness, pain. Once any symptoms have been controlled, the first line (and often definitive) treatment is laser iridotomy. This may be performed using either Nd:YAG or argon lasers, or in some cases by conventional incisional surgery. In early to moderately advanced cases, iridotomy is successful in opening the angle in around 75% of cases. In the other 25% laser iridoplasty, medication (pilocarpine) or incisional surgery may be required.