Relationship between intraocular pressure-lowering effects and alterations in scleral birefringence following micropulse cyclophotocoagulation

Abstract

To examine the changes in scleral birefringence, a marker of collagen-related fibrotic responses, following micropulse cyclophotocoagulation (MP-CPC) using polarization-sensitive optical coherence tomography, we conducted a prospective observational study involving 18 eyes of 16 glaucoma patients who underwent MP-CPC. The procedure employed a Cyclo G6 glaucoma laser system (IRIDEX, Mountain View, CA, USA) with laser power set at 2,500 mW and an 80-second duration per hemisphere. Over 6 months, we evaluated clinical outcomes and scleral birefringence, correlating them with intraocular pressure (IOP) reduction. Post-MP-CPC, IOP significantly decreased, while birefringence notably increased at 1 and 3 months compared to pre-treatment levels (pretreatment: 1.00 ± 0.08, 1 week: 1.20 ± 0.11, 1 month: 1.27 ± 0.06, 3 months: 1.42 ± 0.07, and 6 months: 1.26 ± 0.15). This elevation suggests collagen remodeling in the sclera post-laser therapy. Notably, a positive correlation was observed between IOP reduction rate and birefringence increase at 3 and 6 months post-procedure. Our findings indicate a substantial rise in scleral birefringence following MP-CPC, positively associated with IOP reduction. These results shed light on a potential mechanism for IOP reduction and underscore the clinical significance of birefringence assessment in MP-CPC.