Abstract
Purpose:
Warm compresses have long been used as a treatment for MGD. Part of the inefficiency of heating the meibomian glands in this way is that the heat must conduct through the lid and lid vasculature before it reaches the internal glands. It is therefore beneficial to develop a means of effectively heating the meibomian glands from the inside of the lid where the inefficiencies of conduction and heat loss through the eyelid can be eliminated. Electrically conductive plastics have long been used for thermal heat sinks and electrical shielding. This report will demonstrate the utility and benefits of using conductive plastic to fabricate a cost effective heater for use in heating the meibomian glands from the inside of the eyelid. In particular, the thermal performance of a plastic heater shaped like a small scleral lens is evaluated against other potential heater technologies which could be used for heating the meibomian glands.
Methods:
The plastic heaters were fabricated using an injection molding process which over-molded the electrically conductive plastic onto electrodes in the shape of a scleral lens. Additional heaters were fabricated using flexible circuit technology and thick film technology. The heaters were placed in a wind tunnel which simulated the heat extraction by the eyelid. The average temperature of each heater was set by adjusting the voltage of a DC power supply to the heater. Once the heater reached equilibrium an IR thermography camera was used to characterize the resulting heat uniformity, which is of particular importance.
Results:
The electrically conductive plastic showed the best heat uniformity having less than a 3 deg. C difference in heater uniformity across the surface of the heater as compared to a 4.7 deg. C difference for the flexible circuit technology and a 9.8 deg. C difference for the thick film technology.
Conclusions:
Electrically conductive plastics provide an inexpensive method of producing small, low wattage heaters with complex geometries and excellent heat uniformity. These heaters are capable of being molded into any shape, including the semi-circular shape required to fabricate a heated scleral lens for direct heat application to the meibomian glands on the inside of the eyelid.
Keywords: 583 lipids •
526 eyelid •
486 cornea: tears/tear film/dry eye