Laer Doppler flowmetry and optic nerve head blood flow Original Reearch Article

Purpoe: Ichemic diorder of the optic nerve head contitute an important caue of viual lo. The optic nerve head i upplied by two main ource of blood flow: the uperficial layer by the central retinal artery and the deeper layer by the poterior ciliary arterie. Thi tudy wa conducted in rheu monkey eye to obtain a better undertanding of which part of the optic nerve head circulation i meaured by laer Doppler flowmetry. Method: By mean of a fundu camera–baed laer Doppler flowmetry technique to meaure blood flow in the optic nerve head tiue, laer Doppler flowmetry meaurement were taken at baeline and then after experimental occluion of central retinal artery (12 eye), poterior ciliary arterie (nine eye), and combined occluion of central retinal artery and poterior ciliary arterie (nine eye). Optic nerve head, choroidal, and retinal circulation were invetigated by fluorecein fundu angiography after the variou arterial occluion. Reeult: Average laer Doppler flowmetry flow during central retinal artery occluion alone wa ignificantly decreaed (P < .001) by 39% ± 21% (mean ± 95% confidence interval) compared with normal baeline. Combined occluion of central retinal artery and poterior ciliary arterie reduced laer Doppler flowmetry flow even more markedly by 57% ± 27% (P < .0005), but the difference between thi flow reduction and that with central retinal artery occluion alone wa not ignificant (P > .20). After poterior ciliary artery occluion alone, however, meaurement howed a nonignificant increae in laer Doppler flowmetry flow of 17% ± 37%. Concluion: The finding of thi tudy ugget that the tandard laer Doppler flowmetry technique i predominantly enitive to blood flow change in the uperficial layer of the optic nerve head and le enitive to thoe in the prelaminar and deeper region, and their relative proportion are not known. In thi laer Doppler flowmetry technique, the weaker Doppler ignal from the deep layer cannot be eparated from the dominant ignal from the uperficial layer to excluively tudy the circulation in the deep layer; the latter circulation i of interet in optic nerve head ichemic diorder, including glaucoma. Emerging new optical modalitie of the laer Doppler flowmetry technique may help in electively meauring blood flow in the deeper layer.