The nature of "spots" on soft lenses

Of 278 consecutive therapeutic soft lens wearers, 19 (6.8%) developed discrete lens opacities on the anterior (air) surface of the lens. The incidence rose to 16.6% in patients fitted for dry eye syndromes, to 19% in bullous keratopathy and to 20% in exposure keratitis and trichiasis, if worn for longer than 2 weeks. These opacities were not associated with medications. Scanning electron microscopy demonstrated cracks on the anterior lens surface associated with these opacities. Transmission electron microscopy demonstrated the opacities to be amorphous material with extensions of the contact lens polymer into the substance of these opacities. Lipid, as demonstrated by histochemical methods, was found in these opacities. It is likely that the combination of dryness, stress on the lens surface, and lipid deposition act to alter the structure of the plastic and cause these opacities.