Preliminary Findings of a Dedicated Ocular Myasthenia Gravis Rating Scale: The OMGRate

There is a pressing need for a robust rating scale for ocular myasthenia gravis (OMG). Rating scales for myasthenia gravis (MG) research have a predominant focus on generalised disease. We present results of the first dedicated rating scale for OMG: the ocular myasthenia gravis rating scale (OMGRate). The OMGRate was developed through an international collaboration between neuromuscular and neuro-ophthalmology experts in OMG. It comprises two components: a physician- examination (OMGRate-e) and a patient questionnaire (OMGRate-q).. The OMGRate was prospectively validated in patients attending a neuro-ophthalmology clinic from April 2017 to October 2018. External validity and reliability of OMGRate were evaluated using validated MG rating scales: the Myasthenia Gravis Composite (MGC), the Myasthenia Gravis Quality of Life (MG-QOL), and the ocular component from the Myasthenia Gravis Impairment Index questionnaire (MGII). Two hundred and eleven assessments were completed in 104 patients (67 males, mean age 55 y, range 18–86 y). There was very good external validity of the OMGRate: good correlation between OMGRate-e and MGC (r = 0.64, 95% confidence intervals [CI] 0.54–0.74, p < .0001); excellent correlation between OMGRate-q and MGII (r = 0.85, 95% CI 0.78–0.91, p < .0001) and good correlation between OMGRate and MG-QOL (r = 0.68, 95% CI 0.60–0.77, p < .0001). A higher correlation of OMGRate and MG-QOL compared with MGC and MG-QOL (r = 0.47, 95% CI 0.34–0.59, p < .0001) suggests that OMGRate is better able to capture significant QOL information in patients with OMG. It had excellent reliability with an intraclass correlation coefficient of 0.83 (95% CI 0.67–0.92). Feedback from examiners and patients indicated that the OMGRate was easy to use. In conclusion, OMGRate is an easy-to-use, valid and reliable rating scale for monitoring the severity of OMG.