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Michael Samsom, Amanda Chan, Lyndon Jones, Tannin Schmidt; PRG4 as a Natural Boundary Lubricant for Commercial Silicone Hydrogel Contact Lenses. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5468.
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The mucin-like glycoprotein proteoglycan 4 (PRG4) is expressed and present at the epithelium of the ocular surface. Studies indicate PRG4 reduces friction at ocular biointerfaces, and that PRG4 reduces friction in vivo during blinking by acting as a natural boundary lubricant. Friction may influence, and contribute to, contact lens (CL) discomfort. As such, supplementation with naturally occurring lubricants during CL wear could combat heightened friction and potential CL discomfort. Therefore, the objective of this study was to determine whether PRG4 is an effective in vitro boundary lubricant at a human cornea - CL biointerface.
Fresh human corneas were obtained from the Alberta Lions Eye Bank. Commercially available silicone hydrogel CL were studied: Acuvue TrueEye® (TE); Acuvue Oasys® (OAS); Acuvue2® (AC2); AirOptix® (AO). Tissues and lenses were mounted on a BOSE ELF3200 biomechanical testing machine with custom sample holders, forming a cornea-CL biointerface. These surfaces were articulated against each other at effective sliding velocities ranging from 0.3-30 mm/s under loads of 8-25 kPa. Saline Test: Sequential testing of the 4 lenses in saline was used to compare each lens materials friction against the cornea (order: AC2, AO, TE, OAS; n=4). PRG4 Test: TE and OAS were tested in saline, then soaked in 300 ug/mL PRG4 for 1h and tested. (Order: TE, TE-PRG4, OAS, OAS-PRG4, n=3; OAS, OAS-PRG4, TE, TE-PRG4, n=4).
Saline Test: Kinetic friction coefficients were relatively invariant with sliding velocity. Kinetic friction coefficients (averaged over all speeds) in saline appeared similar for the different CL tested: TE (0.13±0.03, mean±SEM), AC2 (0.16±0.05), OAS (0.18±0.04) and AO (0.23±0.09). PRG4 Tests: PRG4 functioned as an effective friction-reducing boundary lubricant for both TE and OAS lenses. Kinetic friction values were significantly lower in PRG4 for both lenses (TE-PRG4 0.12±0.02); OAS-PRG4 (0.10±0.02), compared their respective Saline controls (TE 0.16±0.03, p<0.05; 0.13±0.03, p<0.01).
These data support the hypothesis that PRG4 acts as an effective ocular boundary lubricant for commercially available CL. TE exhibited similar inherent friction to OAS. Both were effectively lubricated by PRG4. Due the possible association between ocular friction and discomfort, these data support the possible use of PRG4 as a therapeutic treatment for symptomatic CL wearers.
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