DYNAMICS OF EXTERNAL OCULAR BLOOD-FLOW STUDIED BY SCANNING ANGIOGRAPHIC MICROSCOPY

The scanning angiographic microscope (SAM) provides a solution to the considerable technical difficulties associated with conventional episc leral fluorescein angiography. Standardised anterior segment fluoresce in videoangiograms were performed using the SAM in each episcleral qua drant of the right eye in 6 normal subjects; frame-by-frame analysis p roved important. Centripetal flow was seen in all 37 scleral perforati ng arteries investigated. Other features were the marked individual va riability, much larger vertical anterior ciliary arteries, the high fr equency of arteriovenous anastomoses, the complex pow patterns, the ab sence of a 'watershed' zone between anterior ciliary and posterior epi scleral circulations, a characteristic and discontinuous distribution of 'leaky' episcleral veins, and the primacy of venous drainage into t he plexus of muscular veins. Reports of retrograde blood how in the an terior ciliary arteries in most fluorescein angiographic studies are p robably incorrect, the result of unappreciated methodological problems . The SAM is an important advance on previous anterior segment fluores cein angiography techniques.