VITREOUS LASER-ABSORPTION FOLLOWING FLUORESCEIN ANGIOGRAPHY IN DIABETIC-PATIENTS

Background: Sodium fluorescein staining of the vitreous following fluo rescein angiography may interact with laser photocoagulation. Methods: We evaluated the laser absorption by fluorescein in the vitreous when photocoagulation is performed following fluorescein angiography in 15 eyes of nine diabetic patients. Axial fluorescein concentration in th e vitreous was measured by a scanning vitreal fluorophotometer. The am ount of light absorbed by the fluorescein within the vitreous was calc ulated according to the Lambert-Beer law. Results: The mean fluorescei n concentration ranged from 2.93 ng cm(-3) to 105.16 ng cm(-3) at 1 h after injection of fluorescein and from 8.03 to 188.56 ng cm(-3) after 4 h. Maximum laser absorption at 488 nm ranged from 6.79% (after 1 h) to 14.53% (after 4 h); at 514.5 nm it ranged from 0.96% to 2.14%; at 532 nm it ranged from 0.03% to 0.07%. At lambda>550 nm, laser absorpti on was found to be negligible. Conclusions: In order to optimize the e ffect of photocoagulation. especially during long photocoagulation ses sions, argon blue laser (488 nm) should be avoided following fluoresce in angiography. Argon green laser (514.5 nm) should be used within 1 h after fluorescein injection. Frequency-doubled Nd:YAG laser (532 nm), krypton laser (647 nm) or semiconductor diode laser (810 nm) may be u sed at any time.