Effect of Repeated Low-Level Red-Light Therapy on Visual Field Damage in Primary Open-angle Glaucoma: A Randomized Cross-over Clinical Trial

Glaucoma is one of the main causes of visual impairment worldwide. Elevated intraocular pressure (IOP) is an important risk factor for glaucoma and the majority of anti-glaucoma therapies focus on the control of IOP. However, IOP-lowering treatments cannot directly attenuate optic neurodegeneration and rescue vulnerable retinal ganglion cells (RGCs). The glaucomatous symptoms could continue to deteriorate in some patients after optimal IOP control, which highlighted the need for alternative therapies targeting neuroprotection. Chronic ischemia is another potential factor in the pathogenesis of glaucoma. Clinical trials suggested that calcium channel blockers such as nilvadipine could increase ocular blood flow and postpone visual field deterioration in normal-tension glaucoma. Furthermore, it was found that Ginkgo biloba extract, another vasoactive drug, could reverse existing visual field damages, which indicated that improved ocular circulation would salvage dysfunctional RGCs and its efficacy could be observed in a relatively short time frame. The repeated low-level red-light (RLRL) therapy has regulatory effects on blood supply, which provides an innovative and non-invasive approach for the treatment of glaucoma. Considering the possible ischemic mechanism of POAG, it is expected that RLRL therapy could improve ocular circulation and reverse compromised visual functions. Using a randomized clinical trial with cross-over design, the purpose of this study is to investigate the effect of RLRL therapy on existing visual field damages in POAG patients. This study is a 24-week, prospective, randomized, cross-over clinical trial, enrolling POAG patients with well-controlled IOP as participants. Study participants will be randomly allocated to two groups, with one group receiving RLRL therapy from the 1st to the 12th week and the other receiving RLRL therapy from the 13th to the 24th week. Use of IOP-lowering medications is allowed throughout the 24 weeks. An interim analysis to ensure the safety of RLRL therapy is scheduled after the 12th week. Linear mixed models will be used to determine changes in visual field and assess other secondary outcomes.