Efficacy and Safety of an Innovative Chinese Herbal Formula for the Treatment of Macular Edema: A Double-blind, Randomized, Placebo-Controlled Trial

Macular edema (ME) is characterized by hyperpermeability of retinal vessels and/or decreased efflux of fluid across the retinal pigment epithelium, and the condition can be induced by outer/inner blood-retinal barrier dysfunction (BRB). It is most commonly seen following a number of local and systemic diseases and procedures such as diabetes, intraocular surgery, uveitis, retinal vein occlusion, posterior segment inflammatory disease, and cataract surgery. Pathologically, ME is characterized by a retinal thickening in the macular area due to the breakdown of the BRB. ME patients often suffer from blurred vision, dark spots, and deformation, which can seriously affect their central vision, and in severe case, can lead to blindness.

Nowadays, ME treatment options include intravitreal anti-vascular endothelial growth factor (VEGF) agents, intravitreal long-acting steroid, non-steroidal anti-inflammatory drugs, corticosteroids, carbonic anhydrase inhibitors, and subthreshold macular laser. Although the above treatment options have made great progress, the possible side effects of the potentially toxic pharmaceutical agents should be always alert by clinician. A stepwise therapeutic approach is a challenge for the management of ME arises in the chronic and persistent case. Additionally, surgical management should be considered for unremitting cases of ME. Side effects such as scotomas, corresponding to the laser burns, have been frequently noticed by the patients following photocoagulation.

Currently, there is no cure for ME in conventional medicine. Chinese medicine (CM) is becoming popular for managing ME in China and other East Asian countries. Several research groups worldwide have previously conducted clinical studies to evaluate the effectiveness of Chinese herbal medicines for the treatment of ME in recent decades. This study is of an innovative Chinese herbal formula modified from a famous ancient formula for the treatment of macular edema. The goal of this treatment modality is to reduce the accumulation of intraretinal fluid, thus leading to improved visual acuity. Among different Chinese herbal formulae for ME, Shenling Baizhu San (SBS), which was originally described "Formulas from the Imperial Pharmacy" (Taiping Huiming Hejiju Fang in Chinese), has been reported have good efficacy in the treatment.

This study will use an innovative Chinese herbal formula modified from a famous ancient formula for the treatment of ME. This clinical study will be able to provide robust clinical evidence on the efficacy and safety of mSBS for ME. Subjects will be recruited and assigned to receive orally mSBS or placebo twice a day for 12 weeks, with follow-up for another 4 weeks after stopping the treatment to observe the duration of efficacy.