EyeWorld Asia-Pacific December 2012 Issue

23 EWAP CATARACT/IOL December 2012 Is cataract surgery an effective glaucoma operation? by Tony Realini, MD Could cataract surgery be an overlooked safe alternative to trabeculectomy? I n the search for a safer alternative to trabeculectomy for IOP reduction in glaucoma, are we overlooking an effective candidate—cataract surgery? “Several studies have evaluated the effect of cataract surgery on IOP in patients with suspected or established glaucoma,” said Anne L. Coleman, MD, University of California-Los Angeles, Calif., USA. These data are mixed, with some studies showing significant and enduring IOP reduction and others showing little long-term benefit to IOP control. “In general,” said Steven Mansberger, MD , Devers Eye Institute, Portland, Ore., USA, “prior Views from Asia-Pacific Abhay VASAVADA, MD Iladevi Cataract & IOL Research Centre Raghudeep Eye Clinic, Gurukul Road, Memnagar, Ahmedabad – 380 052, India Tel. no. +91-79-27492303, 27490909 Fax no. +91-79-27411200 icirc@abhayvasavada.com T his is a very good article summarizing the information related to the effect of cataract surgery on lowering of IOP in patients with glaucoma. Several studies have shown reduction in IOP following cataract surgery. Post hoc analysis of the important study OHTS showed IOP reduction of 20% from baseline at 36 months. However, not all studies are in agreement. Some studies have shown no significant difference in the mean IOP and number of IOP lowering medications. In our clinical experience, we do find a reduction of IOP ranging from 2-6 mmHg postoperatively. There is also a reduction in the number of drugs used, but the duration of this improvement is very variable. Reduction in IOP lasts from 3 to 6 months. Moreover, Goldmann applanation tonometry, which has been the gold standard for IOP pressure determination, depends on thickness and rigidity of the cornea combined with curvature, biomechanical properties or edema. It is therefore possible that a postoperative change in corneal biomechanics contributes to the decline in IOP. We therefore advocate keeping a very close watch on IOP along with other parameters of glaucoma progression, repeating nerve fiber layer analysis and visual fields frequently. However, our experience in early primary angle close glaucoma or suspect patients is very encouraging. Removal of the lens does significantly deepen the anterior chamber and opens the angles, thereby reducing the IOP and delaying the need for laser peripheral iridectomy. Therefore, we recommend that a patient who has angle closure or impending angle closure will be benefitted by cataract surgery. But in patients with OHT and POAG, our approach is a little conservative. We do recognize that some short-term benefit can be achieved by operating cataract in these eyes but at the same time we do not recommend injudicious removal of lens as a treatment for glaucoma. The decision to operate cataract depends on the stage of cataract and the patient’s visual requirement. The decision to operate cataract should be titrated individually, taking into consideration risk/benefit of surgery in the surgeon’s hands and experience. Editors’ note: Dr. Vasavada declared no financial interests related to his comments. studies have suggested that there is about a 1.5 mmHg reduction in IOP after cataract surgery.” One study is the exception. “In the iStent Trabecular Micro- Bypass [Glaukos, Laguna Hills, Calif., USA] study, the control group underwent cataract surgery alone without implantation of the device, and the mean IOP reduction in control eyes was 8.5 mmHg,” said Thomas Samuelson, MD , Minneapolis, Minn., USA. He attributed this dramatic change to the study design, which required a high baseline IOP to qualify for enrollment. Earlier studies have shown that a higher pre-op IOP generally results in greater IOP reduction following cataract removal. Even so, the strict eligibility criteria may have predisposed study eyes to exhibit “regression to the mean” following Pannet PANGPUTHIPONG, MD Director, Mettapracharak Hospital and Eye Institute Tambon Raiking, Ampur Sampran, Nakornpathom Province, Thailand 73210 Tel. no. +6681-9118134 Fax no. +6634-321243 pannetp@hotmail.com C ataract surgery plays different roles in controlling glaucoma. Acute angle closure glaucoma (PACG) patients benefit most from cataract surgery with and without goniosynechialysis (GSL). Intraocular pressure (IOP) returns to normal without anti- glaucoma medication in many cases. In chronic angle closure glaucoma (CACG) with some degree of cataract, cataract surgery may prevent progression of peripheral anterior synechia (PAS) resulting in more effective immediate and long-term post-op IOP control. In primary open angle glaucoma (POAG) with some degree of cataract with marginal IOP control, cataract surgery may be considered as adjunct treatment to help reduce IOP before glaucoma surgery is needed. In normal-tension glaucoma (NTG), the benefit from cataract surgery’s IOP lowering effect needs further investigation. Editors’ note: Dr. Pangputhipong has no financial interests related to his comments. continued on page 24