In vivo confocal microscopy assessment of meibomian glands microstructure in patients with Graves' orbitopathy

Background To evaluate microstructural changes in the meibomian glands (MGs) in patients with active and inactive Graves' orbitopathy (GO), using in vivo confocal microscopy (IVCM), and to investigate the correlations between clinical and confocal findings. Methods Forty patients (80 eyes) with GO (34 eyes with active GO, 46 eyes with inactive GO), and 31 age- and sex-matched control participants (62 eyes) were enrolled consecutively. A researcher recorded the clinical activity score (CAS) for each patient. A complete ophthalmic examination was then performed, including external eye, ocular surface and MGs. IVCM of the MGs was performed to determine the MG acinar density (MAD), MG longest and shortest diameters (MALD and MASD), MG orifice area (MOA), MG acinar irregularity (MAI), meibum secretion reflectivity (MSR), acinar wall inhomogeneity (AWI), acinar periglandular interstices inhomogeneity (API), and severity of MG fibrosis (MF). Results All confocal microscopy assessments of MGs significantly differed among groups (all P = 0.000). Compared to controls, GO groups showed lower MOA (1985.82 +/- 1325.30 mu m(2) in active GO and 2021.59 +/- 1367.45 mu m(2) in inactive GO vs. 3896.63 +/- 891.90 mu m(2) in controls, all P = 0.000) and MAD (87.21 +/- 32.69 /mm(2) in active GO and 80.72 +/- 35.54 /mm(2) in inactive GO vs. 114.69 +/- 34.90 /mm(2) in controls, P = 0.001 and 0.000, respectively); greater MALD (118.11 +/- 30.23 mu m in active GO and 120.58 +/- 27.64 mu m in inactive GO vs. 58.68 +/- 20.28 mu m in controls, all P = 0.000) and MASD (44.77 +/- 19.16 mu m in active GO and 46.02 +/- 20.70 mu m in inactive GO vs. 27.80 +/- 9.90 mu m in controls, all P = 0.000); and higher degrees of MAI, MSR, and MF (all P<0.05). Eyes with active GO had higher degrees of MAI (P = 0.015), AWI (P = 0.000), and API (P = 0.000), while eyes with inactive GO had higher degrees of MSR (P = 0.000) and MF (P = 0.017). In GO groups, AWI and API were positively correlated with CAS (r = 0.640, P = 0.000; r = 0.683, P = 0.000, respectively), and MF was negatively correlated with CAS (r = - 0.228, P = 0.042). Conclusions IVCM effectively revealed microstructural changes of MGs in eyes with GO and provided strong in vivo evidence for the roles of obstruction and inflammation in the ocular surface disease process. Furthermore, it revealed discernible patterns of MG abnormalities in eyes with active GO and inactive GO, which are not easily distinguishable by typical clinical examinations.