Acid Red 94 lactone, a synthetic fluorescein derivative, is a deep red dye primarily composed of 4,5,6,7-tetrachloro-2,4,5,7-tetraiodo fluorescein. It is widely used as an ophthalmic diagnostic agent to detect dry or damaged cells on the ocular surface. Acid Red 94 lactone exhibits antitumor activity and can inhibit Friend Leukemia Virus (FLV) infection through photodynamic action. Acid Red 94 lactone can inhibit Abeta aggregation through light irradiation. Acid Red 94 lactone holds potential for use in cancer, viral infections, and neurodegenerative disease research[1][2][3][4][5][6].