Silicon oil is a frequently utilized adjunctto surgical repair of complex retinal detachment. Glaucoma can complicate the post-operativecourse of such procedures with incidence that varies between 2.2% and 56%1,2.
Mechanism of intraocular pressure (IOP) elevationcan be from acute angle closure with or without pupillary block; open-angleglaucoma with silicone oil in the anterior chamber; rubeosis irides leading tosecondary angle closure; or primary open-angle glaucoma.Several risk factors fordevelopment of IOP elevation have been studied previously but remained unclear.These include preexisting glaucoma, diabetes, and aphakia3, silicone oilin the anterior chamber; early postop pressure spike; trauma; and postopneovascularization of the iris. Also, an association has beenfound with the quantity of emulsified oil in the AC and the use of heavytamponading agents4Several mechanisms of IOP elevation have beenproposed and are generally classified into early postoperative IOP elevationand late-onset glaucoma. Early IOP elevation may be from preexisting glaucoma, pupillaryblock, inflammation, and/or mechanical impediment to filtration caused by displacedsilicone oil into the AC. Late-onset IOP elevation can be caused byinfiltration of the trabecular meshwork by silicone bubbles, synechially closedangle, iris neovascularization, and/or primary open angle glaucoma4.Treatment strategy of silicone oil relatedglaucoma should be based on the mechanism of IOP elevation.
Topicalantiglaucoma medication coupled with cycloplegics and steroids may effectively lowerIOP in 30-78% of patients2,5. Eyes with silicone oil are at risk ofpupillary block glau. however, spontaneous closure of PI may occur in 11-32% ofcases and need to be reopened2,4,6.Cyclophotoablation may be an alternative ineyes at high risk of re-detachment after silicone oil removal, or in eyes withpoor visual potential. However, no data on success rate were reported inliterature.
Decision for therapeutic early silicon oilremoval is usually made difficult by the significant risk of re-detachment(11-33%)2. Reported rates of IOP normalization after siliconeoil removal varies widely. In one study, SOR resulted in control of IOP in 93.4%of patients, whereas another study reported persistence in all eyes even aftersilicone oil removal7,8. Some researchers attribute the persistent IOPrise after silicone oil removal to inflammation of the trabecular meshwork, andits obstruction by silicone oil droplets4. Other studies compared results of SOR withincisional glaucoma surgery versus either one done alone yielding variableresults2,9,10. Incisionalglaucoma surgery and shunt implants may be considered in patients with unresponsiveglaucoma, especially in eyes where the angle is synechially closed.
However, trabeculectomycan be technically difficult due to subconjunctival fibrosis from prior retinalsurgery, and carry high risk of complications and failure. As an alternative, inferiorlyplaced glaucoma valve implant can be used with success rate of 86% at 6 months and 76% at one year afterimplantation5