Contact diode laser transscleral cyclophotocoagulation for refractory glaucoma: comparison of two treatment protocols

Background: Diode laser transscleral cyclophotocoagulation has shown promising results in the treatment of refractory glaucoma. Treatment with a lower energy level per pulse and lower total energy is safer but may be less effective. We performed a study to evaluate the clinical effectiveness and safety of contact transscleral cyclophotocoagulation using two different protocols in the treatment of Chinese patients with refractory glaucoma. Methods: Review of the records of 129 patients with refractory glaucoma who underwent contact transscleral cyclophotocoagulation for the first time performed by two different surgeons. In group 1 (73 eyes) the output was 2.5 W and the exposure time 2 seconds; in group 2 (56 eyes) the corresponding values were 2.0W and 1.5 seconds. We recorded the number of antiglaucoma medications used, Snellen visual acuity, slit-lamp biomicroscopic findings, intraocular pressure (IOP) and findings on ophthalmoscopy with pupil dilation before and I day, I week, I month, 3 months and 6 months after treatment. Results: The mean age of the patients was 56.4 years (standard deviation [SD] 18.3 years) in group 1 and 53.5 (SD 18.0) years in group 2. The most frequent diagnoses were neovascular glaucoma secondary to proliferative diabetic retinopathy or central retinal vein occlusion, and glaucoma associated with penetrating keratoplasty. The mean number of laser pulse applications per patient was 27 (SD 5.1) (range 10-36) in group I and 55 (SD 6.1) (range 40-60) in group 2. One month after treatment, the mean reduction in IOP was 20.2 mm Hg (SD 14.2 mm Hg) in group I and 13.7 mm Hg (SD 15.8 mm Hg) in group 2, a significant difference (P = 0.035). There was no difference between the two groups in the mean reduction in IOP at 6 months (19.1 mm Hg [SD 15.1 mm Hg] vs. 14.2 mm Hg [SD 16.3 mm Hg]). The mean reduction in the number of antiglaucoma medications was 1.2 (SD 1.1) in group I and 0.6 (SD 1.0) in group 2 (p = 0.003). The incidence rates of transient hyphema in the anterior chamber (23.3% vs. 7.1%) and of transient exudate in the anterior chamber (8.2% vs. 0.0%) were significantly higher in group I than in group 2 (p < 0.005). Interpretation: To achieve greater IOP reduction with diode laser transscleral cyclophotocoagulation, an increase in energy per pulse may be more effective than an increase in total applications.