INFLUENCE OF DYNAMIC CONTACT OF HARD CONTACT-LENS MATERIALS ON CORNEAL EPITHELIAL-CELLS EXAMINED BY ROSE-BENGAL STAINING

Purpose. To establish a method for evaluation of less irritating conta ct lens materials by dynamic contact with cornea, we examined epitheli al and endothelial cell injury to the porcine cornea caused by rotator y rubbing with four kinds of hard contact lenses (HCL). Methods. The H CLs used were (1) polymethylmethacrylate (PMMA) HCL, (2) gas-permeable HCL composed of a graft co-polymer of dextran derivative and methylme thacrylate (MMA) (Suncon Mild II(TM), 12 Dk), (3) gas-permeable HCL co mposed of a graft co-polymer of dextran derivative, a monomer containi ng silicone, a monomer containing fluorine and MMA (New Dr HCL-136, 32 Dk), and (4) gas-permeable HCL composed of a monomer containing silic one, a monomer containing fluorine and MMA (RGPL-A, 216 Dk). Using a s pecially designed apparatus, we produced a standardized injury to the epithelium or endothelium of porcine corneas by holding the HCL agains t the corneal surface while rotating the lens rapidly. Results. After rotatory rubbing of the HCL on the epithelium, the degree of rose beng al staining of the epithelial cells, indicating degeneration of the ce lls and mucin detachment, were significantly different among these HCL s (New Dr HCL-136 < Suncon Mild II(TM), PMMA < RGPL-A), and the cell i njury rates of the endothelium were also significantly different among them (Suncon Mild II(TM) < New Dr HCL-136, PMMA < RGPL-A). The water- wettability of HCLs was not directly correlated with cell injury rates on epithelial and endothelial cells. Conclusions. Both the New Dr HCL -136 and Suncon Mild II(TM), which have a common composition of graft co-polymer of dextran derivative, are less irritating to the epitheliu m and to the endothelium. Also very few patient complaints regarding S uncon Mild II(TM) wearing in individuals with dry eyes have been repor ted.