ALPI vs Medical Therapy Effects on Optic Nerve Structure & Function

Inclusion Criteria: * Age more than 21 years with ability to give informed consent and cooperate for a slit lamp laser procedure * Subjects at their first presentation of acute primary angle closure attack. * Intraocular pressure levels of 40 mm Hg or higher by applanation tonometry or tonopen * Pupillary block as the main mechanism of angle closure * No previous treatment Exclusion Criteria: * Age less than 21 years * Angle closure due to non-pupil block mechanism (e.g. plateau iris, pseudoplateau, phacomorphic, malignant glaucoma) or other secondary causes (subluxed lens, neovascular, uveitic, traumatic, post-operative) * Angle closure patients whose IOP's are not lowered by 20% or more, and are unresponsive to maximum medical IOP-lowering agents after one hour of initiating treatment and needing other intervention/s to lower IOP(e.g. iridoplasty, surgery). * Corneal opacities or abnormalities obstructing laser application * Use of contact lens * Single-eyed patients