Ocular surface alterations and in vivo confocal microscopic characteristics of corneas in patients with myasthenia gravis

Purpose: To evaluate ocular surface alterations and characteristics of corneal basal epithelium and subbasal nerves in patients with myasthenia gravis. Materials and methods: Myasthenia gravis patients (n = 21) and healthy controls (n = 20) were enrolled. All participants underwent ocular surface testing in the following order: tear break-up time, lissamine green staining, Schirmer 1 test with anesthesia, and Ocular Surface Disease Index questionnaire. The Cochet-Bonnet esthesiometer was used to measure corneal sensitivity. Basal epithelial cells and subbasal nerves were evaluated using in vivo confocal microscopy. Results: Myasthenia gravis patients had higher Ocular Surface Disease Index score (13.9 +/- 15.0 vs 1.4 +/- 2.2, p < 0.001) and lissamine green staining score (0.6 +/- 0.4 vs 0.2 +/- 0.4, p = 0.007). Break-up time score (9.3 +/- 3.0 vs 9.9 +/- 1.9, p = 0.481) and Schirmer 1 test score (16.5 +/- 9.2 vs 19.3 +/- 8.4, p = 0.323) did not differ significantly. Corneal sensation was 0.4g/mm(2) in all eyes. Patients with myasthenia gravis had lower basal epithelial cell density (3775.7 +/- 938.1 vs 4983.1 +/- 608.5, p < 0.001) and total nerve density (1956.1 +/- 373.3 vs 2277.9 +/- 405.0, p = 0.012) and higher subbasal nerve tortuosity (1.9 +/- 0.8 vs 1.6 +/- 0.7, p = 0.007) than controls. A significant increase in Ocular Surface Disease Index scores was found with decreasing basal epithelial cell density (rho = -0.518, p = 0.001). There was a significantly moderate negative correlation between the duration of myasthenia gravis and the number of corneal nerves (rho = -0.497, p = 0.022). Conclusion: Significant alterations of basal epithelial cells and subbasal nerves were demonstrated in myasthenia gravis patients although there was no difference of corneal sensitivity between myasthenia gravis patients and healthy controls. Thus, it should be borne in mind that myasthenia gravis patients deserve further evaluation with regard to ocular surface disease.