Identifying Pigment Enclosure in Cosmetic Contact Lenses

The presence of surface pigment in cosmetic contact lenses may influence possible ocular health issues and contact lens discomfort. Two in vitro test methods were developed to investigate whether a variety of cosmetic contact lenses are manufactured with a visible clear layer, indicating that the pigment bulk is enclosed within the lens matrix.

Two in vitro test methods using bright field microscopy and optical coherence tomography (OCT) were developed to assess whether a clear layer in a cosmetic contact lens could be identified. The OCT instrument in this study provided a limit of detection (LOD) of 2.4 μm in the identification of a clear layer. The cross-sectioning microscopy method described in this article requires a trained technician to execute; however, the LOD is smaller at 0.4 μm.

Both test methods described were used to assess whether a clear layer could be identified on 19 commercially available cosmetic contact lens products across six manufacturers. Only one of the six manufacturers (5 of 19 products) produced lens images in which a clear layer was identified using either method.

Most of cosmetic contact lenses analyzed in this study contain the bulk of the pigment within 0.4 μm of the surface (beyond the limit of detection of the instruments used in this study) or on the surface itself.