vascular occlusion of retina.pptx
- 1. VASCULAR OCCLUSION OF RETINA ROLL NO- 2181
- 2. NORMAL FFA • TO UNDERSTAND THE IMAGING OF THE VARIOUS DISEASES WE FIRST MUST KNOW THE NORMAL FFA OF EYE • NORMAL VASCULATURE FILLING AND PATTERN IS OBSERVED • MACULA APPEARS AS DARK BECAUSE IS RELATIVELY AVASCULAR • An obstruction, complete or partial, permanent or temporary, may affect either the retinal arteries or veins.An obstruction, complete or partial, permanent or temporary, may affect either the retinal arteries or veins.
- 3. NORMAL FFA
- 4. CRAO • Obstruction of a retinal artery is usually due to an embolus; superadded spasm often completes the occlusion • There may be associated arteriosclerosis, hypertension or Buerger disease .or giant cell arteritis • Obstruction by an embolus is often secondary to a plaque of atheroma situated at the bifurcation of the common carotid artery in the neck, or occasionally to a diseased mitral or aortic valve • Hollenhorst plaque= Cholesterol emboli
- 5. • Might involve the whole artery (panretinal) or a peripheral branch when the effects are localized • CRAO is nearly always at the lamina cribrosa, where the vessels normally become slightly narrowed. Such an accident causes sudden and complete retinal ischaemia and this tissue rapidly loses function. The eye becomes suddenly blind, although when the causative factor is minute emboli, premonitory obscurations of vision may occur • Examination of the fundus reveals a very typical picture- Cherry red spot at macula. (Oedema at ganglion cell layer which is absent at foveola)
- 7. • The larger arteries are reduced to threads; the smaller are invisible but the veins are little altered except on the disc where they are contracted. Within a few hours, the retina loses its transparency, becoming opaque and milky-white, especially in the neighbourhood of the disc and macula. At the fovea centralis, where the retina is extremely thin, the red reflex from the choroid is visible and appears as a round cherry-red spot, presenting a strong contrast to the cloudy white background. • Clinical features include- Sudden painless LOV, consective optic atrophy, • When obstruction to the blood flow is not complete, the flow may be partially restored in the course of a few days, in which case gentle pressure upon the globe may break up the column of venous blood into red beads separated by clear interspaces. The beads move in a jerky fashion through the vessels, sometimes in the normal direction of blood flow, sometimes in the opposite direction (the ‘cattle-truck’ appearance). If the veins are easily emptied of blood or arterial
- 8. • The white appearance of the retina takes several weeks to clear up but eventually the membrane regains its transparency and appears normal; it is, however, completely atrophic apart from the outer layers which receive their nourishment from the choroid • The vessels are contracted or reduced to white threads, although some of them refill at a later stage due to the establishment of a feeble collateral circulation through an anastomosis with the ciliary system around the disc. The disc is atrophic. There is no direct pupillary reaction and light perception is lost. (RAPD/ Marcus gunn pupil) • In some cases, a certain degree of central vision persists in spite of apparent complete occlusion of the central artery
- 9. • This is due to the presence of cilioretinal arteries which, when present, always supply the macular region and naturally escape occlusion, or due to a macular branch of the central artery given off proximal to the block. • This is due to the presence of cilioretinal arteries which, when present, always supply the macular region and naturally escape occlusion, or due to a macular branch of the central artery given off proximal to the block.
- 11. • Treatment seldom helps, but attempts should be made to relieve spasm or drive an embolus into a less important branch if the patient is seen early. Massaging the globe is probably the most effective method but paracentesis has been employed for this purpose; to be effective, such measures must be adopted without delay. Inhalation of amyl nitrite produces vasodilatation. Branch occlusion may be relieved in this way. The normal result of an occlusion of the central artery, however, is blindness. • Alternative vasodilators used: sublingual isosorbide dinitrate + corbogen inhalation. • IV mannitol • Paracentesis
- 12. FEATURES OF VENOUS STASIS RETINOPATHY • Unilateral disc oedema with variable retinal vascular changes in young healthy adults. • The individual is usually 20–40 years of age and the initial symptom is a vague, unilateral fogginess of vision • Visual acuity remains good and vitreous haemorrhage is never present. Neuro-ophthalmological examination is negative and fluorescein angiography shows venous stasis with delayed venous drainage • There is generally no permanent visual defect
- 13. • The fundus picture simulates that of central venous thrombosis and probably results from phlebitis affecting the central vein within the optic nerve head. The cause is unknown, although increased levels of circulating IgM have been reported in a large number of patients • Venous thrombosis usually occurs in elderly people with cardiovascular disease or glaucoma. In these cases, the obstruction is usually in the central vein just behind the lamina cribrosa where the vein shares a common sheath with the artery so that the two are affected by the same sclerotic process • At other times in arteriosclerotic patients, the block may be peripheral, usually at a bifurcation or where a sclerosed artery crosses a vein, an event which is particularly prone to occur in
- 14. • In young people, it may be due to an infective periphlebitis in which case a branch of the central vein is affected • Thrombosis may also be due to local causes, such as a chronic glaucoma, orbital cellulitis or facial erysipelas. In all cases, the condition is to be regarded as a danger signal and constitutional investigation and treatment should be assiduously undertaken.
- 16. CRVO • In CRVO, all the veins of the retina become enormously engorged with blood and extremely tortuous, and the retina is covered with haemorrhages. • Sight is much impaired, though not as rapidly as in obstruction of the central retinal artery • In many cases, tortuous new vessels are formed upon the optic disc ; in others, a collateral circulation is effected by similarly tortuous new vessels in the retina • Eventually the affected retina becomes atrophic with fine pigmentary changes.
- 18. • The prognosis is rendered worse by the fact that secondary glaucoma ensues in 2–3 months in a considerable number of cases, due to neovascularization at the angle of the anterior chamber.
- 19. BRVO • In BRVO when a single branch of the central vein is blocked, the oedema and haemorrhages are limited to the area supplied by the vein • In these cases, the visual defect is partial but not exactly sectorial as in the case of occlusion of a branch of the artery • The prognosis for central vision is better, but unfortunately blockage of the superior temporal vein frequently involves the macula • Eyes with intact or complete perifoveal capillary arcades have a better visual prognosis than eyes with incomplete arcades as demonstrated by angiography.Secondary glaucoma rarely
- 21. • No treatment is effective in cases of venous occlusion once the blockage has become complete. • If there is widespread capillary occlusion, panphotocoagulation of the retina (or cryoapplications if the media are hazy) may forestall neovascular glaucoma and rubeosis iridis • Widespread capillary occlusion is associated with cotton-wool spots, delayed arteriovenous transit time, large vessel leakage and retinal oedema • In branch occlusion, destruction of areas of poor perfusion (as seen by closure of retinal capillaries in an angiogram) may relieve persistent oedema and inhibit neovascularization • Photocoagulation should not be done until most of the intraretinal blood is absorbed. Anti-VEGF therapy, as intravitreal injections, is now an established treatment to improve visual recovery and prevent late
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