The Evaluation of Anterior Segment Ischemia in Pigmented Rabbits Using Indocyanine Green (ICG) Iris Angiography

ABSTRACT

To evaluate the usefulness of indocyanine green (ICG) iris angiography in darkly pigmented iris and to investigate whether the anterior segment ischemia can be produced by tenotomies of two or more rectus muscles in rabbits, twenty one eyes of 21 pigmented rabbits wer divided into four groups according to the surgical procedures. Group I (2 eyes) underwent only conjunctival peritomy as a control. Group II (6 eyes), Group III (9 eyes), Group IV (4 eyes) underwent tenotomies of two, three and four rectus muscles, respectively. All these eyes underwent ICG iris angiography at pre-op, post-op 10 housrs, 3 days, 7 days and 14 days. In eight eyes of Group I and Group II, fluorescein iris angiography was taken simultaneously. The quality of fluorescein iris angiography was much lower in the pigmented iris and the interpretation was more difficult compared to ICG iris angiography. The peritomy (Group I) or tenotomies of two rectus muscles (Group II) produced no circulatory defect of the iris even after 10 hours postoperatively. After tenotomies of three rectus muscles (Group III) there were transient mild filling defects in superior or inferior sector of iris in 7 of 9 eyes. These defects lasted for 1 to 3 days. Tenotomies of four rectus muscles (Group IV) produced transient filling defects which lasted for 1 to 7 days. ICG iris angiography was suitable for the evaluation of anterior segment circulation in darkly pigmented iris, thus, it can be applied to the coriental brown iris. And in contrast to the previous concept that the rabbits iris arteries derive solely from the long posterior ciliary arteries, circulatory disturbance of iris, even though transient, could be produced by severance of rectus muscles.