A dye molecule having the structure (I): where R1 is an SO3− group bound to a hydrogen H atom or to another atom or to an ammonium NH4 group or to a lysine salt or to an arginine salt or to a different monovalent cation, and R2 is an SO3− group, in particular for making dye preparations for use in methods for the treatment of the bodies of humans or animals, for example for dyeing the internal limiting membrane ILM and/or epiretinal membranes EPRM in a surgical method which involves subsequent removal respectively of the ILM and/or of the EPRM； as well as a dye preparation having a density higher than 1.01 g/cm3 and comprising at least one dye and at least one agent for increasing its density which is a polymer with the empirical formula (C12H22O11.C3H5ClO)n, and structure (II).
