[Angiography by scanning laser ophthalmoscope with fluorescein compounds of different physicochemical properties]

We performed angiography in photocoagulated eyes using four fluorescent dyes that have different molecular weight, lipid solubility, and electric charge. These findings were compared with those of sodium fluorescein (Naf) and indocyanine green (ICG). Angiograms were obtained with Naf, ICG and two fluorescein isothiocyanate dextrans at different molecular weight (FITC-D4: MW 4,400, FITC-D40: MW 38,900). We also used two other dyes: carboxyfluorescein (Caf: less lipid soluble) and calcein (Calc: a highly negatively charged molecule). Two and four days after laser photocoagulation of retina, dye leakage was still evident at the photocoagulated sites with Naf, Caf, Calc and FITC-D4. Angiograms taken after Caf and Calc injection showed more intense and rapid dye leakage than with Naf. Contrary to this, little dye leakage was observed with ICG and FITC-D40. These findings indicated that the critical molecular weight for permeation lay between 4,400 and 38,900 once the breakdown of blood retinal barrier occurred. In addition, difference in molecular weight is a major factor determining dye permeability at the photocoagulated retinal lesions, among other possibilities such as lipid solubility and electric charge.