Intraocular Pressure (IOP) Lowering Effect of Selective Laser Trabeculoplasty Versus Prostaglandin Analogues in Angle Closure Glaucoma

STUDY OBJECTIVES AND PURPOSE The aim of this study is to determine whether selective laser trabeculoplasty (SLT) is an effective treatment for lowering intraocular pressure (IOP) in patients with primary angle closure glaucoma (PACG), compared to prostaglandin analogues, the current first choice IOP-lowering medical therapy. STUDY DESIGN The study design for this project is a prospective randomized controlled trial. It will not be possible to blind either the subject or observer to the intervention due to the use of laser in the intervention group and medical therapy in the control group. Subjects will then be followed-up for 6 months STUDY POPULATION The study population will be patients with primary angle closure glaucoma attending the Singapore National Eye Centre, who fulfil the inclusion criteria and are willing to take part in the study. WASH OUT REGIMEN: for patients already on medication Eligible patients who are already on one or two-glaucoma medications are required to complete a washout period before being randomized. Washout periods will vary according to the previous medication used and are as follows: Prostaglandin analogues 4 weeks Beta blockers 3 weeks Adrenergic agonist 2 weeks Cholinergic agonist 5 days Carbonic Anhydrase Inhibitors 5 days Pre-study washout period check Patients who are on prostaglandin analogues or beta blockers prior to the study will be required to undergo a washout period of 3 and 4 weeks respectively prior to the study. For this group of patients, there will be a safety check during the second week. Patients whose IOP\>30 mm hg during this washout check will be stopped from further washout and be withdrawn from the study. Treatment of subjects PLANNED INTERVENTION Selective laser trabeculoplasty procedure The laser procedure will be performed on all patients as follows * A drop of Brimonidine will be instilled into the eye to be treated 15 minutes prior to the procedure. * Topical anaesthesia will be administered and the Latina SLT lens and coupling fluid will be used for the procedure. * The slit-lamp attached to the laser will be focused on the full height of the trabecular meshwork. * The laser power will be set to 0.6mJ and increased in 0.1mJ steps until small champagne -like bubbles appear from the treated area of the trabecular meshwork. The laser spot size would be 400µm. * Approximately 60-120 non-overlapping shots will be placed onto at least 180 degrees of the trabecular meshwork that is visible and without PAS. More non-overlapping shots can be placed if sufficient extent of the trabeculum is visible. Post - laser the patient will be given a one week course of topical Prednisolone forte four times a day for the treated eye. Intraocular pressure will be checked 30-60 minutes after the procedure. IOP spikes of ≥ 5mmHg or to a level of ≥ 28mmHg will be treated with Diamox if not contraindicated. Intraocular pressure will be checked one week post SLT. If the IOP ≥28mmHg, tablet diamox will be given for 3 days. Retreatment of SLT If IOP remains elevated, one further treatment of SLT will be given to the patient. This treatment will be administered either at the four week or three month follow up visit. If there is a \<20% reduction of IOP from baseline either at the week 4 or month 3 follow-up visit, then SLT will be repeated using the same laser parameters as described above. The patient will be seen again one week after the repeated laser treatment. IIf the IOP is \<21mmHg or there is \>20% reduction of IOP from baseline at at the week 4 or month 3 follow-up visit, then no further treatment will be given to the patient. IOP will be checked one week after repeat SLT. If the IOP is still high (\>24 mmHg), treatment modification will be provided (see Treatment Modification below). Control group Those patients randomized to the control group will be commenced on topical treatment to lower the IOP. The agent for lowering IOP will be a prostaglandin analogue, Travoprost, which will be applied once a day at night. A stepwise addition of Timolol 0.5%, dorzolamide or brimonidine will be implemented until IOP is controlled (see below Treatment Modification).