Abstract
Purpose:
<br /> Scleral lenses (ScLs) are large diameter rigid lenses that bear only on the sclera of the eyeball. ScLs are used as prosthetic devices for distorted corneas and in the treatment of ocular surface diseases. Accumulation of deposits on the front surface and discomfort, despite satisfactory fit, contribute to discontinuation of ScL wear. Plasma treatment of ScLs after manufacture improves surface wettability and reduces fouling and discomfort. Recent studies indicate that lower friction is correlated to contact lens comfort. Proteoglycan 4 (PRG4) is an effective ocular surface boundary lubricant that is naturally present on the ocular surface. PRG4 has been demonstrated as an effective lubricant for soft contact lenses, but has never been tested for ScLs. Full length recombinant human PRG4 (rhPRG4) has recently become available. The purpose of this study was to determine if rhPRG4 is an effective lubricant for ScLs sliding against a human eyelid.
Methods:
Fresh human eyelids were obtained the University of Calgary body donation program. Plasma (pScL) and non-plasma treated (nScL) fluoro-silicone-acrylate ScLs were supplied by the Boston Foundation for Sight. Lubris LLC provided the rhPRG4, which suspended in phosphate buffered saline (PBS) at 300µg/mL as determined by bicinchoninic acid assay. Eyelids and ScLs were mounted on a BOSE ELF3200 biomechanical tester, forming a ScL-eyelid interface. These surfaces were articulated at an effective sliding velocity of 0.3 mm/s, and under pressures of 11- 15 kPa. pScLs and nScLs were tested in PBS and PRG4 (n=5). Kinetic friction coefficients were calculated from measured torque and compressive load and are presented as mean±SEM.
Results:
rhPRG4 reduced friction compared to PBS for both pScLs and nScLs articulated against human eyelids. Kinetic friction coefficients for pScL in PBS (0.21±0.08) were significantly reduced in rhPRG4 (0.08±0.02, p<0.05). Similarly, values for nScL in PBS (0.21±0.11) were reduced in rhPRG4 as well (0.08±0.03, p<0.01).
Conclusions:
rhPRG4 is an effective friction reducing boundary lubricant of both plasma and non-plasma treated scleral lenses articulated against a human eyelid. This finding represents the development of a novel approach to reduce ocular friction and address the discomfort and fouling that lead to discontinuation of wear of scleral lenses.