Studies of the ocular compatibility of hydrogels. White spot deposits — incidence of occurrence, location and gross morphology

Abstract

Light and scanning electron microscopical techniques have been employed to determine the morphology, geographical location and incidence of occurrence of discrete elevated deposits on a variety of commercial lenses of differing bulk and surface chemistries and also wear protocols. Spoilt lenses were derived from controlled lens wear trials and additional clinical sources. This type of elevated deposit displays a complex morphology and is composed of three distinctive yet interactive sub-layers. It is apparent that alterations in lens surface properties, wear protocol, and application of the device are not significant in determining deposit morphology. The rate of deposit formation is however, a function of the lens chemistry, wear protocol and the individual patient. These findings promote the belief that some common biological interface conversion event, or events, occur which reduce the biocompatibility of these materials with their ocular environment.