Zinn-Haller arterial ring observed by ICG angiography in high myopia.

AIMS To delineate the entire Zinn-Haller arterial ring angiographically in vivo. METHODS 382 highly myopic eyes (210 patients) with refractive errors greater than -8.25 D were examined using indocyanine green (ICG) videoangiography. A control group of 80 eyes (40 patients) had refractive errors within plano +/- 3D. RESULTS The Zinn-Haller ring was visible in 206 of 382 highly myopic eyes (53.9%) by ICG angiography. Although only a part of the Zinn-Haller ring was visible in 162 of 206 eyes, in the remaining 44 eyes it was observed almost completely around the optic nerve head. No anastomotic channels between lateral and medial short posterior ciliary arteries were filled by ICG angiography. In 22 of the 44 eyes (50.0%) the Zinn-Haller ring was supplied by branches of the lateral and medial short posterior ciliary arteries; in seven eyes, it was supplied only by the lateral short posterior ciliary artery; and in seven eyes, it was supplied only by the medial short posterior ciliary artery. In none of the control subjects was the Zinn-Haller ring visible by ICG angiography. CONCLUSIONS The Zinn-Haller ring observed by ICG angiography was not a complete collateral circle between lateral and medial posterior ciliary arteries. Also, the patterns in supply vessels to the Zinn-Haller ring varied. ICG angiography made possible the detailed observation of the Zinn-Haller ring in human eyes in vivo.