Patients with ocular myasthenia gravis (MG) are typically treated with systemic drugs, but a new study in the British Journal of Ophthalmology suggests dexamethasone peribulbar or extraocular muscle injection may be good partial replacement for oral drug therapy.

The study included 14 Chinese patients with MG who were seen at the researchers’ hospital between 2016 and 2019. Participants were given dexamethasone via peribulbar injection or direct injection into the main paralyzed extraocular muscles once a week, for four to six weeks. Patients assigned to the extraocular muscle injections group received 0.5% dexamethasone (0.2mL) and 2% lidocaine (0.2mL). Patients assigned to the peribulbar injection group received 0.5% dexamethasone (0.5mL)

The severity of diplopia, blepharoptosis, eye position and eye movement were evaluated before and after treatment, and follow up was done at six months or more.

After treatment, 12 patients (85.7%) experienced relief from symptoms. One patient (7.1%) had partial response to treatment, and another patient (7.1%) had no response. Two patients (14.2%) experienced symptom recurrence during the follow-up period.

Specifically, two had intermittent exotropia without obvious limitations in duction, and their symptoms resolved after a single injection. The other nine patients with limited duction presented with a resolution of ptosis, neck weakness and headache symptoms after one-time treatment. Diplopia symptoms disappeared in all patients after four injections. However, the complete recovery of extraocular muscle strength was delayed in some patients.

Three patients received another one-to-two injections due to persistent limitations in ocular duction. After three months of follow-up, ocular duction returned to normal in these patients. Among the patients who ultimately recovered from ptosis, recovery time was one week or less.

Larger controlled studies are needed to further explore these findings, the researchers noted.

Shi M, Ye Y, Zhou J, et al. Local use of dexamethasone in the treatment of ocular myasthenia gravis. BMC Ophthalmology. October 28, 2020. [Epub ahead of print].