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L. C. McCann, A. Tomlinson, E. I. Pearce; Tear and Meibomian Gland Function in Blepharitis. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1542.
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To investigate the differences in tear physiology and meibomian gland (MG) function amongst normals and patients with blepharitis. The potential of tests in the diagnosis of blepharitis was evaluated.
Two groups of subjects, 15 with ophthalmologically defined blepharitis (11F/5M; mean age 60.9±12.5; range 41-79) and 15 age and sex matched controls (11F/5M; mean age 60.7±12.6; range 40-78), were included in the study. Tests including evaporimetry, interferometry, MG expression and meibography were performed on all patients.
Tear evaporation rate was significantly higher (p<0.001) in blepharitics (46.3±22.9g/m2/h) than in normals (18.0±10.7g/m2/h). Using the grading scale of Thai, the lipid pattern was found to be significantly less stable (p=0.001) in the blepharitic group (2.1±0.8 v 3.1±0.6). MG drop out was assessed and found to be significantly higher (p=0.001) in blepharitics in both the upper (UL) (1.0±0.8 v 0.1±0.3) and lower (LL) (2.1±0.8 v 0.6±0.7) eyelids. The drop out score was equal, or greater, for the LL than UL, in all cases. Using Mathers system, a significant difference (p=0.000) in MG expression was found between blepharitics and normals. Meibum was thicker and more opaque in blepharitics in both the UL (2.2±0.7 v 1.0±0.2) and LL (2.6±0.7 v 1.3±0.4). For all tests sensitivity (SS) and specificity (SP) ranged from 33-86% and 66-100% respectively. Evaporation was the most useful lab based test with SS of 73%; SP of 86%. Interferometry was less so with SS of 67%; SP of 73%. MG expression of the UL was more useful than the LL with SS (86% v 53%) and SP (73% and 66%) respectively. MG drop out of the LL was found to be the most useful clinical test, with SS of 86%; SP of 86%. The information for MG drop out of the UL was less useful with a SS of 33%; SP of 100%.
Significant differences were observed in tear physiology and meibomian gland function in patients with blepharitis. These were consistent with tear film instability and increased fluid loss from the eye, which could account for signs and symptoms of dry eye in these patients. MG drop out of the LL was found to be the most effective measure in differentiating between these two conditions.
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