Measurement of superficial optic nerve head capillary blood velocities by scanning laser fluorescein angiography.

Scanning laser ophthalmoscopy is capable of producing video fluorescein angiograms with high spatial and temporal resolution. Digital image analysis of these angiograms has been used to produce measures of capillary flow velocities in perimacular capillaries. We have recently utilized the same technique to measure flow velocities in the superficial capillary layers of the optic nerve head. We performed video fluorescein angiograms using the Ro-denstock (Germany) scanning laser ophthalmoscope. The passage of hyperflu-orescent particles through optic nerve head capillaries was imaged in five healthy subjects (two men and three women). The flow velocity for each of eight to 10 capillaries in each subject was measured three to five times. The mean capillary blood flow velocity for all subjects was 2.71 mm/s. These results are similar to those obtained in perifoveal capillaries. We have demonstrated that scanning laser fluorescein angiography can be adapted for measuring superficial optic disk capillary flow velocities. The possibility remains for the imaging of capillaries in deeper portions of the optic nerve head by using the confocol abilities of the scanning laser ophthalmoscope. Future use of this technique may aid our understanding of the pathophysiology of optic neuropathy.