Abstract
Purpose: :
To compare the efficiency of heat transfer through the upper eyelid to the meibomian glands and resulting unintended corneal heating with two treatments for MGD.
Methods: :
Subjects (n = 13) were recruited for the study. 10 subjects received 10 minutes of warm compress therapy whereby a compress heated to 45 degrees C was placed over the closed eyelid and replaced every 2 minutes with a freshly heated compress. At baseline, prior to heating, and at each 2-minute interval during eyelid heating, the temperature of the upper inner eyelid surface and the cornea were recorded using an infrared pyrometer. The remaining three subjects received a 12-minute treatment with the LipiFlow whereby the inner eyelid surfaces are heated directly with the LipiFlow heater. This heater is under rigorous temperature control (range 40.0-43.0 with a target of 42.5 degrees C). Prior to, during and immediately following treatment the upper inner eyelid surface and the corneal temperatures were recorded using thermocouples and an infrared camera.
Results: :
Inner lid surface temperature: The LipiFlow required only 10 seconds to reach the mean maximum inner lid surface temperature of 41.7 +/- 0.1 degrees C. In contrast, warm compresses required at least 6 minutes to reach the mean maximum inner eyelid surface temperature of 40.0 +/- 0.6 degrees C. Corneal surface temperature: The LipiFlow: the mean maximum corneal temperature after 12 minutes of heating was 38.2 +/- 0.3 degrees C. Warm compresses: the mean maximum corneal temperature after 6 minutes of heating = 40.1 +/- 0.6 degrees C.
Conclusions: :
Warm compresses are able to heat the inner lid surfaces up to 40 degrees C provided that they are replaced with a reheated compress every 2 minutes and maintained for at least 6 minutes. However, they also heat the ocular surface tissue to this temperature. Conversely, LipiFlow technology allows for more direct and remarkably more efficient heating of the inner eyelid surfaces while also shielding the cornea and ocular surface from the heat. This provides optimal therapeutic levels of heat for the treatment of MGD while also, for the first time, shielding the cornea from heat and pressure.
Keywords: cornea: tears/tear film/dry eye • eyelid