Anterior optic nerve blood flow in experimental optic atrophy

This study attempts to establish whether neurogenic optic atrophy induces changes in anterior optic nerve circulation and to determine how noninvasive techniques of measuring blood flow in vivo compare to microsphere distribution. Five cats underwent unilateral optic nerve transection in the orbital apex and a sham procedure in the contralateral eye. Two to three months later, no abnormalities were detected by fluorescein angiography. Laser Doppler measurements demonstrated a 53% decrease in red blood cell speed through the capillaries of the atrophic optic nerve heads in vivo. Optic disk reflectance measurements of anterior optic nerve blood volume in vivo demonstrated a 51% decrease in the estimated blood volume of the capillaries in atrophic optic nerve heads. Flow was calculated on the basis of these noninvasive measurements and demonstrated an average decrease of 74% in optic atrophy. Histologic studies of microsphere distribution demonstrated an average decrease of 80% in flow to the anterior optic nerve in optic atrophy. These results suggest that anterior optic nerve blood flow is significantly reduced in primary neurogenic optic atrophy. This study also demonstrates that the noninvasive measurements of blood flow are substantiated by histologic evaluation of microsphere distribution.