Interobserver and Intra-Observer Reliability of Eyelid Tests for Ocular Myasthenia Gravis

Lid fatigability test (LFT), Cogan lid twitch (CLT), and forced eyelids closure test (FECT) are simple clinical screening tests for ocular myasthenia gravis (OMG). However, these tests are subjectively interpreted. We thus evaluated the interobserver and intra-observer reliability of each test.

The 3 eyelid tests were performed in ptotic patients associated with various conditions, including OMG and others. Video clips of all tests were recorded using smartphone with built-in camera in the following order; LFT, CLT, and FECT. All video clips were distributed to 3 neuro-ophthalmologists and 3 general ophthalmologists, who were trained to evaluate the tests using a single standard instruction. After 3 months, all video clips were re-organized for the second evaluation. Interobserver and intra-observer reliability were calculated using Cohens' Kappa coefficient and Fleiss Kappa statistic.

The 3 eyelid tests were performed and recorded in 35 patients, which included the diagnosis of OMG, levator muscle dehiscence, partial oculomotor nerve palsy, and Horner syndrome. CLT received moderate-to-substantial interobserver reliability in neuro-ophthalmologist group (Fleiss Kappa 0.77 [95% CI 0.60-0.94] and 0.66 [95% CI 0.46-0.85] in first and second evaluation respectively), but the results varied in general ophthalmologist group (Fleiss Kappa 0.58 [95% CI 0.37-0.79] and 0.54 [95% CI 0.33-0.76] in first and second evaluation respectively). FECT and LFT received lower interobserver reliability in both groups. CLT also received moderate-to-almost perfect intra-observer reliability in neuro-ophthalmologist group (Cohen Kappa 0.55, 0.58, and 0.92), whereas FECT and LFT received lower intra-observer reliability. The intra-observer reliability varied among general ophthalmologists for all 3 eyelid tests.

CLT is the most reliable test among the 3 eyelid tests. However, all tests should be interpreted with caution by general ophthalmologists.