Prostaglandin analogue drops for the treatment of soft tissue expansion and exophthalmos in patients with inactive thyroid eye disease

Objective: Thyroid eye disease (TED) is characterized by an inflammatory response leading to soft tissue expansion within the bony orbit, which may cause exophthalmos. Studies of glaucoma patients reported periorbital fat atrophy after treatment with prostaglandin analogue drops. We hypothesize that owing to this side effect, prostaglandin analogue drops may benefit patients with TED-induced exophthalmos. Design: Interventional prospective pilot study. Participants: Five adults with inactive TED and exophthalmos treated with a single daily drop of bimatoprost to both eyes for 6 months. Methods: The effect of treatment was evaluated by clinical examinations, Hertel exophthalmometry, marginal reflex distance (MRD), and comparison of digital photographs from before and after treatment by 3 masked oculoplastic surgeons. Patients’ subjective satisfaction was recorded as well. Results: Hertel exophthalmometry showed an improvement in exophthalmos after treatment in 3 patients and no change in 2. Both MRD1 and MRD2 increased (for MRD2 p = 0.007). Two observers correctly identified the photograph taken after treatment in 4 patients, and the third observer correctly identified 2 patients and was indecisive about the others. Four patients reported an improvement in their appearance, although additional eyelid retraction was observed. Adverse effects were minimal. Conclusion: Topical prostaglandin analogue treatment of TED-associated exophthalmos appears safe. Although this pilot study was statistically underpowered to show positive results, our findings suggest a treatment-related reduction in periorbital fat volume in most cases and a subjective improvement in appearance. These findings have potential implications for the treatment of exophthalmos in the clinical setting, but more research is required.