Matrix metalloproteinases and their tissue inhibitors after selective laser trabeculoplasty in pseudoexfoliative secondary glaucoma

BACKGROUND The aim of this study was to assess changes in metalloproteinases (MMP-2) and tissue inhibitor of metalloproteinases (TIMP-2) following selective laser trabeculoplasty (SLT) in patients with pseudoexfoliative glaucoma (PEXG). METHODS We enrolled 15 patients with PEXG and cataracts (PEXG-C group) and good intraocular pressure (IOP) controlled with beta-blockers and dorzolamide eye drops who were treated by cataract phacoemulsification and 15 patients with pseudoexfoliative glaucoma (PEXG-SLT group). The PEXG-SLT patients underwent a trabeculectomy for uncontrolled IOP in the eye that showed increased IOP despite the maximum drug treatment with beta-blockers and dorzolamide eye drops and after ineffective selective laser trabeculoplasty (SLT). The control group consisted of 15 subjects with cataracts. Aqueous humor was aspirated during surgery from patients with PEXG-C, PEXG-SLT and from matched control patients with cataracts during cataract surgery or trabeculectomy. The concentrations of MMP-2 and TIMP-2 in the aqueous humor were assessed with commercially available ELISA kits. RESULTS In PEXG-SLT group in the first 10 days after SLT treatment a significant reduction in IOP was observed: 25.8 +/- 1.9 vs 18.1.0 +/- 1.4 mm/Hg (p < 0.001), but after a mean time of 31.5 +/- 7.6 days IOP increased and returned to pretreatment levels: 25.4 +/- 1.6 mm/Hg (p < 0.591). Therefore a trabeculectomy was considered necessary.The MMP-2 in PEXG-C was 57.77 +/- 9.25 microg/ml and in PEXG-SLT was 58.52 +/- 9.66 microg/ml (p < 0.066). TIMP-2 was 105.19 +/- 28.53 microg/ml in PEXG-C and 105.96 +/- 27.65 microg/ml in PEXG-SLT (p < 0.202). The MMP-2/TIMP-2 ratio in the normal subjects was 1.11 +/- 0.44. This ratio increase to 1.88 +/- 0.65 in PEXG-C (p < 0.001) and to 1.87 +/- 0.64 in PEXG-SLT (p < 0.001). There was no statistically significant difference between the PEXG-C and PEXG-SLT ratios (p < 0.671). CONCLUSION This case series suggest that IOP elevation after SLT can be a serious adverse event in some PEXG patients. The IOP increase in these cases would be correlated to the failure to decrease the TIMP-2/MMP-2 ratio. TRIAL REGISTRATION Current Controlled Trials ISRCTN79745214.