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Show Journal of Neuro- Ophthalmology 14( 2): 87- 90, 1994. 1994 Raven Press, Ltd., New York Can the Arterial Supply of the Retina in Man Be Exclusively Cilioretinal? Luiza H. L. Barroso, M. D., William F. Hoyt, M. D., Michael Narahara Exclusive cilioretinal supply has been anatomically proven in a monkey's eye. This paper presents and discusses fundus photographs of six optic discs from normal human eyes, in which the configuration of the retinal arteries emerging from the optic disc suggests that they might all be cilioretinal. Key Words: Multiple cilioretinal arteries- Anomalous retinal arteries- Retinal circulation. Nettleship ( 1), in 1905, recognized that cilioretinal arteries are frequent features of the retinal circulation in lower mammals and that in some species they supply the whole retina. In the monkey, whose retinal blood supply closely resembles man's, Hayreh ( 2) proved anatomically in one exceptional specimen that the retinal blood supply could be entirely cilioretinal. The second eye of his monkey had what appeared ophthalmoscopically to be a total cilioretinal vascular supply, but on serial sections the retinal arteries proved to be both central and cilioretinal. In 1895, Lawford ( 3) published a drawing of an optic disc from a normally functioning eye in which all retinal vessels, arteries and veins, appeared to arise at or near the disc margin ( Fig. 1). The central portion of the disc was vacant. His drawing may be the first recording in the medical literature of an all cilioretinal fundus in man. Collier ( 4), in 1957, from his study of 250 eyes with From the Neuro- ophthalmology Unit, Departments of Ophthalmology, Neurological Surgery and Neurology, School of Medicine, University of California, San Francisco, California, U. S. A. Address correspondence and reprint requests to Dr. William F. Hoyt, 533 Parnassus Avenue, Room U- 521, U. C. S. F., San Francisco, CA 94143- 0350, U. S. A. FIG. 1. Lawford's drawing of an optic disc in which all retinal vessels, arteries and veins, leave and enter the disc near its margin, leaving the central portion of the disc empty. 87 L. H. L. BARROSO ET AL. FIG. 2. All arteries emerging from this disc appear to be cilioretinal ( arrows). The retinal vein enters the disc at 11 o'clock near the margin. This represents a rare venous anomaly called an edge vein ( of Kraupa). From Barroso et al. ( 5), with permission. cilioretinal arteries, claimed he had seen one example of an ocular fundus with a retinal blood supply that was exclusively cilioretinal, but he provided no illustration of the appearance of the retinal arteries. Here we present and discuss fundus photographs of six optic discs from normal human eyes, in which the configuration of the retinal arteries emerging from the optic disc suggests that they might all be cilioretinal. from the Kodachrome slide collection of one of us ( W. F. H.). The photographs were obtained over a period spanning 35 years. They represent optic discs from normally functioning eyes, exhibiting peculiar appearances of mainstem retinal vessels. In all six photos the retinal arteries emerged at or near the disc edge. In 4 of 6 cases ( Figs. 2- 4) the retinal veins entered the disc near its margin leaving its central portion vacant. Fluorescein angiograms were not obtained in any of these eyes. CASE MATERIAL The six optic disc photographs that comprise the material for this report ( Figs. 2- 6) were selected DISCUSSION The ciliary origin of retinal arterioles can be established in some, but not all, cases from their ap- FIG. 3. In this disc all major vessels enter or leave midway between the disc margin and its center. It is not clear in this example whether the arteries are cilioretinal or simply branches of a main arterial trunk that lies out of sight deep within the nerve head. J Neuro- Ophtlmlmol, Vol. U, No. 2, 1994 FIG. 4. All vessels enter and leave near the disc margin in these two discs distinguished by the blurred white glial tissue in their center. These disc anomalies resemble morning glory disc colobomas, but their disc diameters are not enlarged and they were present in normally functioning eyes. FIG. 5. All the arteries leaving this disc appear to be cilioretinal ( arrows). One vein at 12 o'clock enters near the disc edge, while another plunges into the central disc tissue. 90 L. H. L. BARROSO ET AL. FIG. 6. This disc has a central retinal vein, but the arteries appear to be cilioretinal ( arrows). pearance in photographs of the optic disc. When a retinal arteriole arises at the disc margin with a visible hook configuration, its origin is surely from the ciliary arterial system. When a retinal arteriole arises inside the disc margin without a hook, it may be a retinociliary arteriole or it may be a branch of a deeply buried central retinal artery ( 6). Which of these possibilities exists can sometimes be settled by timing the arrival of fluorescein in the arteriole during early phases of a fluorescein angiogram. If the arteriole fills a second or two after the dye appears in the choroid, the vessel is probably a branch of a central retinal artery. If, however, the arteriole fills at the same time that the dye appears in the choroid, the vessel might derive from either arterial system ( 6). It is hoped that modern Doppler ultrasonographic methods ( 7,8) will contribute to the differentiation of central retinal and ciliary origins of arterioles arising near the disc margin. Any or all of the photographs that we have presented here could depict total cilioretinal arterial supply with all arterioles exiting from the disc near its margin. Lawford's illustration ( Fig. 1) and our Figs. 2 and 5 are the best examples. Optic discs with such arteriolar configurations are rare indeed. Recognizing them with their variations is a necessary first step toward clinical confirmation in humans of the occurrence of exclusive congenital cilioretinal supply. REFERENCES 1. Nettleship E. Notes on the blood vessels of the optic disc in some of the lower animals. Trans Ophthalmol Soc UK 1905; 25: 338- 59. 2. Hayreh SS. The cilioretinal arteries. Br J Ophthalmol 1963; 47: 71- 89. 3. Lawford JB. Unusual arrangement of retinal vessels. Trans Ophthalmol Soc UK 1895; 15: 195. 4. Collier M. Frequence des vaisseaux cilioretiniens, leur rapport avec les ametropies, leur association avec d'autres anomalies du fond de l'oeil. Bull Soc Ophthalmol Fr 1957; 9: 598- 601. 5. Barroso L, Hoyt WF, Narahara M. Disc edge veins of Kraupa: rare exit anomalies of the retinal vein. Br / Ophthalmol 1992; 76: 442- 3. 6. Brown GC, Tasman WS. Vascular anomalies. In: Congenital anomalies of the optic disc. New York: Grune & Stratton; 1983: 80- 6. 7. Lieb WE, Cohen SM, Merton DA, Shields JA, Mitchell DG, Goldberg BB. Color Doppler imaging of the eye and orbit: technique and normal vascular anatomy. Arch Ophthalmol 1991; 109: 527- 31. 8. Augustyniak E, Swietliczko I. Comparative evaluation of blood flow velocity and pulsation curve in the posterior ciliary arteries supplying the choroid and the anterior part of the optic nerve. Klin Oczna 1991; 93: 191- 3. / Neuw- Ophthalmol. Vol. 14, No. 2. 1994 |
