A Case Series: Methylene-Blue-Related Toxic Anterior Segment Syndrome.

An intracameral injection of methylene blue 1% during cataract surgery induces extreme cytotoxicity, primarily affecting the corneal endothelium and iris epithelium. This case series illustrates the clinical presentation, management, and outcomes of three patients who underwent cataract surgery, with unintended exposure to methylene blue. All patients demonstrated early-onset corneal edema and anterior segment inflammation shortly after surgery. Two patients developed severe, irreversible endothelial decompensation, leading to persistent corneal edema, decreased visual acuity, and eventual need for Descemet's stripping endothelial keratoplasty (DSEK). In contrast, the third patient experienced transient corneal edema, which gradually resolved with medical therapy, resulting in significant, though incomplete, visual recovery. No intraocular pressure spikes or retinal toxicity were noted. In conclusion, methylene blue is highly cytotoxic to intraocular structures, particularly the corneal endothelium and iris epithelium. Accidental administration can cause serious and irreversible visual impairment. Vigilant dye verification protocols, enhanced labeling systems, and multidisciplinary checks are critical in preventing such adverse events. Surgeons must remain cautious and ensure that only approved agents are utilized for anterior capsule staining during cataract surgery.