Abstract
Introduction: :
Aim: To determine the effect of eyewear on periocular humidity (PH) in normal subjects under a range of ambient conditions. Any improvement in PH observed could then be used to alleviate the symptoms of dry eye.
Methods: :
Fifteen subjects participated in the study (11 men and 4 women) with a mean age of 33 years. Experiments took place in a Controlled Environment Chamber (CEC). The CEC allows precise control of relative humidity and temperature. Four different types of eyewear were worn successively by the subject during a session Normal spectacles (Normal) Micro Environment Glasses (MEGS) Norville Wrap Around Spectacles (Wrap) Swimming goggles (Swim). A miniature temperature/humidity sensor was attached to each pair of spectacles so that the periocular conditions could be observed. A second probe was used to measure the environment outside the periocular area. The difference between the two probes indicated the change in periocular humidity caused by the frame. Each frame was tested for 5 minutes and the data was recorded on a computer. The order of testing of the spectacles and the environmental conditions were randomised using a Latin square, each subject attended for 3 visits on separate days. The back vertex distance (BVD) for each frame was measured and blink rate was also observed.
Results: :
At the 5% RH condition the median change in periocular humidity with each frame was found to be; -0.83% (Normal), +1.78% (MEGS), +11.43%(Wrap) and +75.53% (Swim). The change in periocular humidity at 40%RH was -2.31% (Normal), +0.54% (MEGS), +3.24% (Wrap) and +48.33(Swim). The change in periocular humidity at 80%RH was -4.08 (Normal), -3.30 (MEGS), -1.71 (Wrap) and +19.07 (Swim). At low humidity the swim goggles produced significantly higher levels of periocular humidity compared to the Normal, MEGS and Wrap frames (p=<0.005). Though the MEGS and Wrap did produce a significant improvement over the Normal frames (p = <0.005).
Conclusions: :
Using eyewear for this purpose is a simple and non-invasive method to increase the humidity surrounding the eyes. This in turn would decrease tear evaporation rate from the ocular surface and reduce symptoms associated with environmentally induced dry eye. The swim goggles showed the greatest improvement. If these prove cosmetically unacceptable then both the MEGS and Wrap significantly outperform the Normal frame.
Keywords: cornea: tears/tear film/dry eye