Purpose: Staining of anterior lens capsules with dye to facilitate completion of continuous curvilinear capsulorrhexis is now being used more frequently in phacoemulsification of white and mature cataracts with poor red reflexes. This study examined the histological characteristics of anterior lens capsules stained with trypan blue. The layer(s) of the lens capsule that stained with dye and the extent of accumulation of dye in these layers of the lens capsule were determined. To the best of our knowledge this has not been described before.
Methods: A series of 10 stained lens capsules were analysed histologically. The dye used in this study consisted of a standard sterile, noninflammatory, nonpyrogenic, 2 ml solution containing 0.6 mg/ml of trypan blue. Following capsulorrhexis, samples were sent to the laboratory for histological analysis. Frozen sections (8 microm) were prepared and examined with the light microscope. All 10 capsules were cut by frozen section to preserve trypan blue staining (which would be leached by processing) and then subjected to immunohistochemistry for collagen IV. Immunohistochemical analysis using markers for type IV collagen were done on formalin-fixed specimens for morphological comparison with the frozen sections. A counterstain highlighted the epithelium.
Results: Continuous curvilinear capsulorrhexis was successfully and easily completed in all cases without any complications. Frozen section analysis using light microscopy demonstrated accumulation of trypan blue dye in the basement membrane of the lens capsule. Staining was concentrated in the portion of the membrane adjacent to the lens epithelium. The lens epithelium could not be clearly identified on the frozen sections. Consequently, immunohistochemical analysis with markers for type IV collagen was performed. A counterstain highlighted the epithelium. This confirmed that the layer staining with trypan blue was the basement membrane, a consistent feature on all the specimens.
Conclusion: Trypan blue selectively stains the basement membrane of the anterior lens capsule. There is a concentration of dye in the basement membrane adjacent to the lens epithelial cell layer. The lens cortex does not appear clinically to stain with trypan blue. This enables surgeons to distinguish the lens capsule from the cortex and provides sufficient contrast for successful completion of continuous curvilinear capsulorrhexis during cataract surgery.