Posterior Routes of Choroidal Venous Flow in High Myopia

Abstract

A few reports in the ophthalmic literature have described choroidal blood outflow through posterior routes. Most of these patients were highly myopic; therefore, a correlation between such posterior routes and high myopia has been suspected. We examined highly myopic eyes using indocyanine green (ICG) videoangiography to investigate the prevalence and clinical significance of posterior routes. We examined 255 highly myopic eyes (146 patients) using ICG videoangiography. All had refractive errors greater than -8.25 D. We also examined a control group consisting of 42 eyes (26 patients) that had refractive errors within ±3D. Of the 255 highly myopic eyes, 61 (23.9%) had choroidal blood outflow through posterior routes. These routes were classified by type of vein according to its penetration site. One was the choriovaginal vein, which drains into the margin of the optic nervehead. The other was the macular vortex vein, which penetrates the sclera near the macula. On the other hand, only one of the 42 eyes (2.4%) in the control group showed choroidal outflow by a posterior route. The prevalence of posterior routes was significantly higher in the highly myopic eyes than in the control eyes (P < 0.05). As posterior routes for choroidal blood outflow were observed in nearly 25% of highly myopic eyes, these vessels would appear to be one of the major routes of posterior choroidal outflow in these eyes.