Laser treatment in glaucoma : efficacy and safety

Abstract: Glaucoma is a progressive optic neuropathy and the major cause of irreversible blindness worldwide. Although the pathogenesis of glaucoma is not completely understood, the most important risk factor for development and progression of the disease is an elevated intraocular pressure (IOP). Current glaucoma treatment aims to reduce the IOP in the affected eye. This can be achieved by topical drops, laser therapy or surgery. Laser treatment is used at different stages of the glaucoma disease. Some types of laser procedures are used as first-line treatments or as complement to topical medications or surgery, while other types are used in advanced glaucoma as a last option when other therapies have failed. Although laser therapy has long been used to reduce the IOP in glaucoma, knowledge gaps remain. The aim of this thesis was to evaluate the efficacy and safety, in both a short- and long-term perspective, of two of the most frequently used laser procedures in glaucoma: laser trabeculoplasty (LTP) and transscleral cyclophotocoagulation (TCP).In the first study, a retrospective analysis, the long-term efficacy and safety of TCP was evaluated in 300 eyes of 300 glaucoma patients in northern Sweden. We found an overall substantial IOP reduction of more than 10 mmHg that was maintained at least 2 years in various types of glaucoma. Following TCP, the patients could reduce their treatment with an average of one substance of topical glaucoma medication in the treated eye. No case of phthisis bulbi, the most feared complication of TCP, was reported. However, a general decline in visual acuity (VA) was noted during the two-year follow up period, and the cause of this finding was difficult to assess due to the retrospective nature of the study.The short-term effect of TCP on IOP was further investigated in a prospective study of 58 eyes of 58 glaucoma patients. IOP was measured at baseline before TCP and at five additional time-points up to 24 hours after the treatment. The VA was measured before TCP and at the 24 h examination. The results showed a transient IOP spike with a peak at six hours after TCP in approximately 40% of the eyes. Spikes were more common in eyes with pseudoexfoliation glaucoma.The last two studies of the thesis focused on the short- and long-term efficacy of LTP. One-hundred fifty-two eyes of 122 newly diagnosed glaucoma patients that had been randomized to the multi-treated arm in the Glaucoma Intensive Treatment Study (GITS) were included. All studied eyes were treated with three different IOP-lowering substances and after one week, LTP was performed. We demonstrated that there was an additional IOP-lowering effect of LTP but that this effect was strongly associated with the level of IOP before the laser, where a higher IOP pre-LTP yielded a greater IOP reduction. Eyes with pre-laser IOP ³15 mmHg showed a significant IOP reduction that was maintained during four years of follow-up. However, in eyes with pre-LTP IOP <15 mmHg, the effect of laser treatment was limited.In summary, this thesis investigated the efficacy and safety of TCP both retrospectively in a longer perspective and prospectively during the first 24 hours after treatment. An overall high efficacy without serious complications was shown, but a possible decline in VA must be considered in the long run. Furthermore, the risk of IOP spikes after TCP implies that additional IOP-lowering treatment should be considered during the first 24 hours, especially in eyes with pseudoexfoliation glaucoma or severe glaucoma damage. Finally, LTP may provide a valuable long-lasting IOP-lowering effect despite medical multi-treatment in eyes with a pre-LTP IOP ³15 mmHg.