<prompt> A patient presents with ho evening halos and occasional headache for some months. His examination shows normal IOP but shallow AC. He is in which stage of glaucoma?AcuteAbsoluteProdromeConstant instability  <response>: Five clinical stages are discernable in primary angle closure glaucoma PACG: Prodromal stage: Patient sees coloured haloes due to high intraocular pressure IOP with some obscuration of vision Chronic instability stage: The intermittency of the prodromal stage is replaced by the regularity of attacks. Acute ACG stage: Acute attacks glaucoma Chronic ACG stage: The recurrent attacks of angle closure eventually lead to peripheral anterior synechiae that may permanently block the exit pathways Absolute glaucoma: It is the end result of untreated attacks ACG or chronic ACG. It results in a stony hard, painful, blind eye. Ref: Concise Textbook Of Ophthalmology By Sharma, 2006, Page 118. 