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P E T E R G . S WA N N B S c ( H o n s ) , M A p p S c , F C O p t o m , FA A O Unusual retinal vessels and vessel formations As optometrists, we constantly scrutinise the retinal vasculature and so we are well aware of its normal characteristics. Retinal arterioles and veins steadily ramify to nourish and drain each quadrant of the fundus. They branch as curving rather than acute bifurcations and arterioles usually cross veins. There is an arteriolar-to-vein size relationship of 2:3 and a spontaneous venous pulse is present at most optic discs. Retinal vessels rarely ‘invade’ the macula. These are all routine observations. Occasionally, however, we see vessels or vessel formations that are unusual and may impact significantly on the patient’s vision. This paper will seek to clarify some of these situations. REMNANTS OF THE HYALOID SYSTEM The hyaloid artery and its ramifications are derived from the ophthalmic branch of the internal carotid artery, and form during the internal eye’s most active period of growth and differentiation. It enters the developing globe via the inferior foetal fissure around the fourth week of gestation, and forms a group of vessels which nourish the primary vitreous, and a second group which become the posterior vascular tunic of the lens. The system normally atrophies late in the foetal period but may persist as a Mittendorf dot, Bergmeister’s papilla, a vessel at the disc, Vogt’s arcuate line or, very occasionally, the whole vessel being preserved from disc to lens. Potential associations include persistence of the primary vitreous, coloboma and optic nerve head hypoplasia. The patient shown in Figure 1 presented for a cosmetic contact lens assessment as she had a uveal coloboma in one eye. A Mittendorf dot with a small vascular tag was present on the posterior lens surface. The patient in Figure 2 has a triangular, white area of thin tissue protruding from the optic disc. This is a typical Bergmeister’s papilla and is quite innocuous. Figure 3 depicts a white hyaloid vessel remnant at the optic disc. The disc itself may be slightly colobomatous. CILIORETINAL ARTERIOLES These vessels are a variant of the normal vascular tree and are present in 30-40% of eyes. They are derived from the posterior ciliary arteries and usually arise from the temporal optic disc in a hook-like manner, often traversing the papillomacular area. They are said to be more common in cases of optic disc pit, situs inversus, pre-papillary loops and optic disc drusen. In occlusion of the central retinal artery, the presence of a 24 cilioretinal arteriole may enable some degree of central vision to be retained. Occasionally, cilioretinal arterioles may themselves become occluded. The patient in Figure 4 has a well developed cilioretinal arteriole coursing above the left macula. Figure 5 shows the fundus of a patient who presented to the optometrist with a sudden, painless loss of vision in the left eye. She had a central retinal arterial occlusion with some preservation of central vision due to the cilioretinal vessel. CONGENITAL TORTUOSITY This condition more commonly involves retinal arterioles than veins. It is usually non-progressive with all other findings being normal, although there is a progressive form which is inherited as an autosomal dominant trait and may be associated with retinal haemorrhages. Congenital tortuosity should be differentiated from that secondary to other problems, such as epiretinal membrane, vein occlusion and diabetes. Figures 6 and 7 show the fundi of a patient with congenital tortuosity of the retinal veins. All other findings were normal and she was placed on regular review. SITUS INVERSUS Here, the retinal vessels emerge from the optic disc in an anomalous direction. It is typically seen in tilted disc syndrome and also in myopic eyes. A dragged disc and vessels can have a similar appearance and occurs in retinopathy of prematurity. The patient in Figure 8 has a classic tilted disc. The vessels emerge or exit from an inferio-nasal direction. The inferio-nasal fundus is ectatic and depigmented. There was reduced sensitivity in the superio- NOVEMBER 19 • 1999 OPTOMETRY TODAY temporal visual field that, most importantly, did not respect the vertical midline. CONGENITAL RETINAL MACROVESSEL This is an uncommon situation where a retinal vessel, usually the inferio-temporal retinal vein, is enlarged and drains an area superior to the macula. Vision may be slightly reduced by the large vessel crossing the macula. There has been a suggestion that macular cysts are more common in these patients. This patient in Figure 9 presented for a routine eye examination. The macrovessel, a branch of the inferio-temporal vein, crosses the macular area. Vision was 6/5 in each eye. PRE-PAPILLARY LOOPS Ninety-five percent of these vessels are arterioles, and usually originate from and return to an arteriole on or near the disc. The loops may be small and simple or large and corkscrewed. Many are surrounded by the white remnants of Bergmeister’s papilla. Most cases are unilateral with associated cilioretinal arterioles. They fill before or with other retinal arteries on fluorescein angiography and do not leak. Vitreous haemorrhage and occlusion of the loop have been reported. The patient in Figure 10 has a typical pre-papillary arteriolar loop. It projects forward into the vitreous for a short distance from the left optic disc. ARTERIO-VENOUS MALFORMATIONS In this condition, arterioles and veins communicate without an intervening capillary bed. It may be isolated to a small arteriole and venule or be widespread involving the entire vascular tree. Intracranial and facial vascular malformations may be associated and constitute the Wyburn-Mason syndrome. Similar vascular anomalies can involve the orbit, conjunctiva, sclera and iris, and neovascular glaucoma can be a complication. The condition should be differentiated from the phakomatosis von Hippel-Lindau’s disease. These patients should be referred for neurological assessment. U N U S U A L Figure 1 Typical uveal coloboma with a Mittendorf dot and small hyaloid remnant attached R E T I N A L V E S S E L S A N D V E S S E L Figure 2 A small triangular area of white tissue protrudes from the optic disc representing Bergmeister’s papilla F O R M AT I O N S Figure 3 A white hyaloid vessel courses from the inferior part of the optic disc Figure 5 The patient suffered a central retinal artery occlusion in the left eye; some vision was preserved due to a patent cilioretinal artery Figure 4 A large cilioretinal artery traverses the retina above the left macula Figures 6 and 7 (right and left) Congenital tortuosity of the retinal veins in the right and left eyes; there is a small choroidal naevus in the superio-temporal fundus of the left eye Figure 8 A tilted disc with situs inversus and depigmentation of the inferio-nasal fundus Figure 9 Congenital retinal macrovessel in the inferior fundus of the patient’s left eye Figure 10 A pre-papillary arteriolar loop projects from the left optic disc (reprinted with permission from Practical Optometry 1992; 3 (1): 49-50) NOVEMBER 19 • 1999 OPTOMETRY TODAY 25 U N U S U A L The patient shown in Figures 11 and 12 came to our clinic for a routine examination. The enlarged, tortuous retinal vein and arteriole were noted running to and from the left optic disc in the nasal fundus. When the pupil was dilated, it was clear that they were directly joined in the nasal periphery. A CT scan was normal. COLLATERAL VESSELS These vessels are preformed capillaries connecting retinal, and retino-choroidal circulations. They indicate a preceding vascular disorder which may point to a significant ocular and/or systemic disease. Unlike new vessels, they do not leak on fluorescein angiography. Potential causes include retinal vein thrombosis and glaucoma. If the patient, especially a middle-aged female, has a chronic, progressive vision loss, together with a pale, swollen optic disc and a disc collateral, then optic nerve sheath meningioma is a likely cause. It is important to observe these vessels through a dilated pupil with the fundus lens and slit-lamp. Red-free illumination is often helpful. The patient in Figure 13 had an inferio-temporal branch vein occlusion in the right eye several years ago. A small collateral vessel is present on the temporal aspect of the right optic disc. Figure 14 is of a patient who had a superio-temporal branch vein occlusion. There are small collaterals on the disc and another collateral vessel near the site of the occlusion. R E T I N A L V E S S E L S A N D V E S S E L NEW VESSELS New vessels proliferate following ischaemia in conditions such as diabetic retinopathy and central retinal vein thrombosis. They may form on the optic disc, elsewhere in the fundus and in the anterior segment. They have a delicate feathery appearance and leak fluorescein. Bleeding from new vessels may seriously threaten vision in these patients and referral needs to be most expedient. The patient shown in Figure 15 came in for a routine eye examination. There was a history of vein thrombosis in the eye. Ophthalmoscopy revealed a large frond of new vessels stretching into the vitreous. This patient was referred to the ophthalmologist without delay, and laser photocoagulation was undertaken. ABOUT THE AUTHOR Peter Swann is Associate Professor in the School of Optometry at the University of Technology in Brisbane, Australia. F O R M AT I O N S BIBLIOGRAPHY Paton, D., Hyman, B.N. and Justice, J. (1979) ‘Introduction to ophthalmoscopy’. Upjohn, Michigan. Kritzinger, E.E. and Beaumont, H.M. (1987) ‘A colour atlas of optic disc abnormalities’. Wolfe Medical Publications, London. Wood, J. and Swann, P. (1996) “Cilioretinal artery occlusion”. Br. J. Optom. Disp. 4: 137-138. Sears, J., Gilman, J. and Sternberg, P. (1998) “Inherited retinal arteriolar tortuosity with retinal haemorrhages”. Arch. Ophthalmol. 116: 1185-1188. Swann, P.G. and Da Rin, J. (1992) “A congenital retinal macrovessel”. Practical Optometry 3: 49-50. Figures 11 and 12 The left fundus of a patient with an arteriovenous malformation Figure 13 A small collateral vessel is present on the right optic disc following an inferior branch vein occlusion 26 Figure 14 Another patient who had a branch vein occlusion; collaterals are present on the optic disc together with another collateral vessel superior to the macula, near the site of the occlusion NOVEMBER 19 • 1999 OPTOMETRY TODAY Figure 15 A patient with a history of vein occlusion, who presented for routine eye examination; a large frond of new vessels stretches forward into the vitreous