The vascular response to contact lens wear.

The ocular limbal blood vessels were studied in daily wearers of soft contact lenses and hard contact lenses, and in eyes of subjects who had never worn a contact lens. The degree of filling of vessels and the number of vessels crossing the limbus were measured photographically at the inferior limbus. The extent to which vessel filling in contact lens wearers could be considered as capillary injection, as apposed to new vessel growth, was estimated by comparing the degree of injection in lens wearers to that found in nonwearers given a vasodilating stimulus. It was found that soft lens wearers showed greater limbal injection than hard lens wearers. The limbal vasculature of hard lens wearers was indistinguishable from that of nonwearers. The vascular response to soft lens wear was similar in magnitude to that produced by vasodilating agents in noncontact lens wearers, and was therefore considered to be due to the filling of preexisting capilliaries rather than new vessel growth. The chronic level of vessel dilation in soft lens wearers is cause for concern, as sustained dilation of the limbal vessels may be a precursor to new vessel growth.