Purpose: To determine the effect of wearing a protective eye shield (mask) on limbal strain magnitude and variability in glaucoma eyes when sleeping with 1 side of the face down (FD) against a pillow.
Methods: A prospective, randomized, interventional trial was conducted at the Wilmer Eye Institute with 36 glaucoma patients. A contact lens sensor measured limbal strain (output in equivalent millivolts) during intervals of up to 60 minutes in lateral decubitus, FD, and supine positions. Eighteen subjects wore a mask during 1 of 2 FD intervals, with randomized assignment of the interval. Data from additional trials with no mask were included in some analyses. In addition, some facial-feature dimensions from 3D scanned images of 23 subjects were compared with limbal strain data.
Results: Wearing a mask trends toward a reduced mean change in contact lens sensor output (limbal strain) on moving to a FD positions [+34.1 mVeq, P=0.01 reduced by -22.3 mVeq, P=0.09 (n=36)]. Mask wearing reduced variability in strain while FD [-22.8 mVeq, P=0.04 (n=18)]. In eyes with past progressive visual field loss, the effect of the mask reduced mean strain change when moving to FD [-44.8 mVeq, P=0.02 (n=31)]. Longer corneal apex to nose-tip and to temple lengths were associated with reduced variability while FD [P=0.02 and 0.04, respectively (n=23)]. Treating both lengths as confounding factors increased statistical significance, particularly for analysis of the no-mask change in strain data moving to and from the FD position [P=0.004 to 0.002 and P=0.03 to 0.01 (n=23)].
Conclusion and relevance: Wearing a mask reduced limbal strain and variation in limbal strain during simulated FD sleep, particularly in eyes with past field worsening, as did some facial features.