Eighty one eyes of 48 patients with raised IOP and shallow anterior chambers underwent Nd:YAG iridotomy to prevent further angle closure glaucoma and to remove any pupil block that might be contributing to the raised IOP. These eyes were followed for 18-34 months to assess the effect on IOP control. Seventy three eyes of 43 patients were asymptomatic. In eyes with no PAS none responded with drop in IOP but in eyes with well established PAS 69% showed a drop in IOP. By comparison eight eyes of five patients had a history of episodes of subacute angle closure glaucoma. All had PAS present pre-operatively. Iridotomy reduced IOP in 87.5% of the eyes in this group and rendered 100% symptom free. Permanent posterior synechiae between lens and iris were an invariable complication in those eyes that required long-term miotic treatment for IOP control following iridotomy. In asymptomatic eyes with chronic pressure elevation and narrow angles laser iridotomy is unlikely significantly to reduce the IOP. We recommend that in such eyes iridotomy should be reserved for those eyes with established closure of the angle by PAS in which IOP control can be achieved without the use of miotics.