Purpose. Ocular surface sensitivity plays a role in dry eye and ocular comfort through its probable influence on the neural feedback loop that regulates tear secretion, but little is known specifically about the role of lid or lid margin sensitivity in ocular surface health. The aim of this study was to characterize the eyelid margin and explore the relationships between lid margin sensitivity and staining, meibomian gland dysfunction, tear osmolarity, and ocular symptoms. A secondary aim was to look for differences and associations between lower- and upper-lid characteristics.
Methods. Pilot study involving 27 healthy subjects (7 men, 20 women; mean age: 31 ± 14 years). Measurements included ocular symptoms (Ocular Surface Disease Index, Dry Eye Questionnaire), tear osmolarity, lid margin staining (fluorescein and lissamine green), meibomian gland dysfunction, and mechanical sensitivity of lower and upper lids.
Results. Lower-lid margins were more sensitive (45.0 ± 13.2 vs. 40.0 ± 14.7 mm; p = 0.02) and displayed more staining (1.5 ± 1.0 vs. 0.2 ± 0.6, p < 0.001), but less evidence of meibomian gland dysfunction (2.0 ± 2.8 vs. 7.3 ± 6.2, p < 0.001), than upper-lid margins. Lid margin staining was more frequent in lower than upper lids (78% vs. 15% of subjects). Tear osmolarity correlated with upper-lid staining (r = 0.41, p = 0.04) and lower-lid sensitivity (r = 0.46, p = 0.02). Lid sensitivity was also inversely correlated with meibomian gland dysfunction at the lower lid (r = −0.51, p = 0.01). Surprisingly, there were no associations between symptoms and lid staining.
Conclusions. Our study highlighted clear clinical differences between the lower and upper lids and demonstrated, for the first time, significant relationships between tear osmolarity and lid characteristics, including lid sensitivity.