This first clinical trial of dexamethasone eye drops for topical treatment of diabetic macular edema (DME) shows that eye drops may someday play a role in treating retinal diseases.
In an effort to find a noninvasive drug-delivery platform that avoids the adverse events associated with intravitreal injections and slow-release drug capsules, researchers have developed an eye drop based on cyclodextrin microparticles that dissolve in the tear fluid to form water-soluble drug/cyclodextrin complex microparticles. Previous studies in rabbits and humans suggested that cyclodextrin microparticle dexamethasone eye drops may reach the human retina and thus be therapeutically effective for retinal disease such as DME.
To investigate further, the authors of this pilot study treated 19 DME patients with 1.5% topical dexamethasone eye drops with cyclodextrin microparticles. After four weeks of treatment, patients showed significantly reduced retinal thickness and improved visual acuity.
Central macular thickness decreased more than 10 percent in 63 percent of eyes, and visual acuity (logMAR) improved more than 0.1 in 74 percent of eyes. At weeks zero, four, and eight, logMAR visual acuity was 0.52, 0.37 and 0.45, respectively, central macular thickness was 512 µm, 399 µm, and 488 µm.
No cataract formation was noted, and IOP rose only modestly during the study. One patient experienced an increase as high as 8 mm Hg. The pressure regressed after cessation of treatment, and no patient needed treatment for increased IOP. The authors note that the eye drops do not provide a sustained treatment effect - the effect stops once the treatment stops, which is expected with eye drops. It may be an advantage, in that the side effects, such as IOP increase, also stop.
Though this was a small, short-term study, the authors conclude that dexamethasone-cyclodextrin microparticle eye drops challenge the "old dogma that drugs in eye drops cannot reach the retina and are therefore useless in treatment of retinal disease is wrong. Eye drops can play a role in drug delivery to the retina and treatment of retinal disease, including DME."
While more study is required, the authors believe that dexamethasone-cyclodextrin microparticle eye drops may have a role as monotherapy and also in combination with intravitreal injections, implants, and laser treatment.