Corneal thickness in extended wear of soft contact lenses

SUMMARY The continual wearing of a soft contact lens for a period of 20 weeks is shown to produce no significant evidence of corneal swelling, although the use of soft lenses in conjunction with a topically applied solution is shown to produce evidence of transient swelling. The extent of corneal thinning during waking hours is also shown to be reduced among wearers of contact lenses for long periods. Some corneal swelling invariable accompanies the wearing of contact lenses (Mandell and Polse, 1969). Such swelling is usually provoked by a disturbance to the available oxygen supply (Hill and Cuklanz, 1967), though other factors may also influence the cornea (Kempster and Larke, 1978). In the present study the thickness of the cornea of patients wearing contact lenses without removal for a period of 20 weeks was examined. During the study it was intended to distinguish between those effects which were solely attributable to extended contact lens wear, and those effects which were attributable to extended lens wear in conjunction with proprietary solutions, as recommended by at least one manufacturer (Ganju, personal com-munication). For this reason 2 groups of lens-wearing subjects were examined in conjunction with a control group of non-lens wearers. Patients and methods Fifty-seven volunteer Caucasian subjects who came within a previously determined acceptance profile were assembled. One-third (the non-solution users' group) were fitted with a hydrogel lens manufac-tured from a copolymer of vinyl pyrrolidone and methyl methacrylate (Sauflon PW, manufactured by Contact Lens Manufacturing Ltd.). A further third (the solution users ' group) were fitted with similar lenses that were removed and cleaned overnight at 8-week intervals with a proprietary cleaning agent (Monoclens and Monoclens C40, manufactured by Contact Lens Manufacturing Ltd.). In addition the solution users also instilled 1 drop of proprietary buffered saline on waking and before retiring eac