A Study of the Vascular Network of the Iris Using Flat Preparation

PURPOSE: This study was performed to examine the vascular network of the human iris using flat preparation. METHODS: The ciliary body-iris structures were separated from human eyeballs, and a portion of the irises were treated with trypsin to remove the pigment granules. These iris tissues were unfolded and placed onto glass slides using flat preparation, and the vascular network of each iris was examined by fluorescein microscopy. The ciliary body-iris structures separated from the remaining eyes were stained with hematoxylin-eosin without trypsin treatment and were examined by light microscopy. RESULTS: The long posterior ciliary artery formed several branches before entering the iris root, and such branches formed the major arterial circle of the iris with diverse diameters in the vicinity of the iris root and the ciliary process. In the pupillary margin, the iris vasculature network formed a cone shape and then formed an arcade by connecting to adjacent vasculatures. In the vicinity of the collarette, the iris vasculature network formed the minor arterial circle of the iris with diverse diameters perpendicular to the arcade of the iris network located in the pupillary margin. In the pupillary margin, the capillaries were somewhat thick and connected to the irregular traveling iris vein. CONCLUSIONS: The above findings explain the human iris vascular network and provide a theoretical basis for the sectoral filling of the iris vasculature seen in fluorescein iris angiography.

Aspectos patológicos da retinopatia diabética / Pathological features of diabetic retinopathy

A retinopatia diabética continua sendo importante causa de cegueira entre adultos americanos e brasileiros. Existem fatores ambientais determinantes para o desenvolvimento da retinopatia diabética apesar de número crescente de evidências sugerirem um componente genético na retinopatia diabética. Os avanços realizados nas últimas décadas com o objetivo de melhorar o entendimento dos mecanismos envolvidos no desenvolvimento e progressão da retinopatia diabética estimularam esta revisão. Este artigo tem como objetivo revisar e atualizar conceitos acerca da fisiopatologia ocular do diabetes mellitus.

Iris neovascularization in Sturge-Weber syndrome.

An unusual case of Sturge-Weber syndrome with raised intraocular pressure is presented. The slit lamp examination and anterior segment fluorescein angiography were consistent with iris neovascularization. Cause and effect relationship of iris neovascularization with glaucoma in this syndrome is discussed.

Effect of a modified rectus tuck on anterior ciliary artery perfusion

Strabismus surgery results in the permanent interruption of anterior ciliary blood flow, predisposing the eye to anterior segment ischemia (ASI). A primate model was used to assess the effectiveness of a new muscle-scleral tuck for preserving anterior ciliary artery circulation. The model consisted of removing 3 rectus muscles from both eyes of 2 rhesus monkeys, then performing a tuck on the inferior rectus (IR) right eye while leaving the left IR as a control. Four weeks later, a modified tuck was performed on the virgin left IR. Fluorescein iris angiograms of both eyes were obtained, and preoperative angiograms at 5-15 sec. showed normal 360 degrees perfusion. Postoperative follow-up angiograms showed segmental superior temporal filling defects and preservation of perfusion in the distribution of the IR. Comparison of fellow eyes tucked vs control IR showed no difference in the filling pattern in both monkeys. Comparison of the same eye before and after tuck also showed essentially the same filling pattern in all 4 eyes with preservation of inferior circulation. Our conclusion is that the modified tuck preserves the anterior ciliary blood flow and may be useful as a muscle-strengthening procedure in patients predisposed to developing ASI.

Clinico-pathologic correlates in Fuch's heterochromic iridiocyclitis--an iris angiographic study.

Iris Angiography in a case of Fuchs' heterochromic iridocyclitis (FHI) is described. The finding of iris angiography and hylainzed iris vessels on histopathology suggested ischemic etiology of FHI. This is the first report on Iris Angiography in a pigmented eye with Fuchs' heterochromic iridocyclitis.

Ultrastructure and blood-iris barrier in experimental rubeosis iridis in rabbit

Iris neovascularization was produced in rabbits by hypotony following repeated aspiration of the vitreous. The hypotony was produced after 0.3 ml of vitreous fluid was aspirated using a 25-gauge needle through the pars plana of 10 rabbits. For the histochemical study, horseradish peroxidase(HRP) was injected through the ear lobe vein. After fixation of the iris tissue, the tissue was treated with diaminobenzidine and examined with both light microscopy and transmission electron microscopy. The newly-formed vessel was abundant, particularly on the upper stroma of the iris. The new vessel formation was evident due to the proliferation of endothelial cells, which may have been derived from preexisting iris vessels. The endothelial cells of the newly-formed vessels revealed prominent villous processes into the vascular lumen, formation of the marginal flap, numerous fenestrations in the endothelial junction, and reaction product onto extravascular space by the cytochemical electron microscopy. These results suggest that hypotony in the rabbit produces the disruption of the blood-iris barrier and the balance between angiogenesis-antiangiogenesis modulation.

The effect of combined application of argon and Nd-YAG lasers on iridectomy in rabbits

Recently iridectomy using an argon or Nd-YAG laser to treat narrow angle glaucoma has become popular, and is now the procedure of choice over the standard surgical technique. However, the shock wave of the Nd-YAG laser causes hemorrhage in almost all cases and the high energy level of the Nd-YAG laser, which is required for iridectomy, causes injury to the lens and cornea. Furthermore, there is a tendency toward closure of the iridectomy site after argon laser application. We performed iridectomies by a combined application of argon and Nd-YAG lasers in pigmented rabbits to improve iris bleeding, iridectomy patency, and lens and corneal damage. The iridectomy patency and the lens and corneal damage were examined with a scanning electron microscope. The rabbits that underwent laser iridectomies with only the Nd-YAG laser were used as a control group. Based on the results, it can be concluded that laser iridectomy by a combined application of argon and Nd-YAG lasers results in a lower rate of bleeding, a higher rate of patency, and less damage to the lens and cornea as compared with iridectomy performed by Nd-YAG laser only.