Since the
IgG to
IgA ratio in the tear film increases dramatically during
inflammation, the ratio of
immunoglobulins deposited on the
soft contact lens surface should provide some indication of biocompatibility of the
hydrogel. To study this premise, 60
soft contact lenses of low and high water content and ionic and non-ionic compositions were recovered after their useful lifespan from asymptomatic lens wearers and those experiencing active
giant papillary conjunctivitis (GPC).
Lenses were exhaustively extracted with saline to remove loosely bound
immunoglobulins, dissected, and qualitatively assayed by means of chromogenic horse radish
peroxidase-linked antibody probes for tightly bound
IgG and
IgA. The intensity of reaction was scored visually in a random, masked fashion by two independent observers using a standardized scale. The results reveal a consistent, although not statistically significant, increase in
IgG to
IgA deposition on the pathological lens population as compared to normals. This change may be reflective of an immune specific lens response and/or the enhanced titer of tear
IgG resulting from the inflammatory process present with GPC. Deposition correlated more strikingly with two other linked parameters:
hydrogel structure and mode of use. A marked increase in
immunoglobulin deposition and enhanced
IgG to
IgA ratio (P less than 0.001) was common to high water content
lenses (especially of non-ionic composition) used on an extended wear basis, when contrasted with low water content
lenses used on a daily wear basis. It is thus hypothesized that use of high water content
lenses on an extended wear basis leads to a greater degree of inflammatory and/or immune stress.