Central retinal vein occlusion CRVO

this is a simplified overview on Central retinal vein occlusion CRVO

1. Central retinal vein occlusion (CRVO) Md. Suzon Islam

2. Anatomy and function of retina .. The eye is made up of three layers The retina is the innermost light-sensitive layer of tissue that lines the back of the eye on the inside. It is located near the optic nerve. ..The neural retina consists of several layers of neurons interconnected by synapses, and is supported by an outer layer of pigmented epithelial cells. ..The primary light-sensing cells in the retina are the photoreceptor cells, which are of two types: rods and cones. Rods function mainly in dim light and provide black-and-white vision. Cones function in well-lit conditions and are responsible for the perception of color. ..The retina processes the information gathered by the photoreceptor cells and sends this information to the brain via the optic nerve. .. Due to the retina's vital role in vision, damage to it can cause permanent blindness

3. Retinal blood supply .. Blood supply of eye consists of central retinal artery , central retinal vein and their branches ..The human retina is supplied by two sources: the central retinal artery (CRA) and the choroidal blood vessels, both of which originate from the ophthalmic artery. ..The  Central retinal artery and its accompanying vein pierce the optic nerve, and enter the bulb of the eye through the porus opticus . ..The artery immediately bifurcates into an Superior and inferior branch. ..Each of these again divides into a medial or nasal and a lateral or temporal branch, which at first run between the hyaloid membrane and the nervous layer; but they soon enter the latter, and pass forward, dividing dichotomously. ..From these branches a minute capillary plexus is given off, which does not extend beyond the inner nuclear layer. ..The macula receives two small branches (superior and inferior macular arteries) from the temporal branches and small twigs directly from the central artery; these do not, however, reach as far as the fovea centralis, which has no blood vessels.

4. Branches of Central Retinal Artery .. Superior temporal ..superior nasal ..inferior temporal ..inferior nasal

5. What is CRVO? .. Retinal vein occlusion (RVO) was first described in 1855 by Liebreich and in 1878 by Michel, who indicated that RVO was a complication of systemic vascular status that can be observed on the fundus of the eye. Disease was named as Apoplexia retinae. ..Central retinal vein occlusion, also known as CRVO. ..It is a condition in which the main vein (central retinal vein) that drains blood from the retina closes off partially or completely. ..When the vein is blocked, blood and fluid spills out into the retina. The macula can swell from this fluid, affecting your central vision. Eventually, without blood circulation, nerve cells in the eye can die and you can lose more vision.

6. Types of CRVO CRVO comes in 2 types: Ischemic and Non-ischemic CRVO Non-ischemic CRVO —a milder type characterized by leaky retinal vessels with macular edema. Ischemic CRVO —a more severe type with closed-off small retinal blood vessels. Ischemic CRVOs are less common, accounting for one-third of CRVOs, and the other two-thirds are non-ischemic CRVOs

7. Pathophysiology Various local and systemic factors play a role in the pathological closure of the central retinal vein. The central retinal artery and vein share a common adventitial sheath as they exit the optic nerve head and pass through a narrow opening in the lamina cribrosa. Because of this narrow entry in the lamina cribrosa, the vessels are in a tight compartment with limited space for displacement. This anatomical position predisposes to thrombus formation and occlusion in the central retinal vein. Occlusion of the central retinal vein leads to the backup of the blood in the retinal venous system and increased resistance to venous blood flow. This increased resistance causes stagnation of the blood and ischemic damage to the retina. Ischemic damage to the retina stimulates increased production of vascular endothelial growth factor (VEGF) in the vitreous cavity. Increased levels of VEGF stimulate neovascularization of the posterior and anterior segment. Also, it has been shown that VEGF causes capillary leakage leading to macular edema which is the leading cause of visual loss in both ischemic CRVO and nonischemic CRVO.

8. Epidemiology A study reported a 4-year incidence of retinal vein occlusion of 2.14 cases per 1000 of general population older than 40 years and 5.36 cases per 1000 of general population older than 64 years. Sex: CRVO occurs slightly more frequently in males than in females. Age: More than 90% of CRVO occurs in patients older than 50 years, but it has been reported in all age groups

9. Symptoms ..Unilateral blurry or distorted vision .. Transient visual obscurations ..Often have pain, redness, irritation and other problems Ischemic CRVO : ..Rapid onset ..Severe visual loss Non-ischemic CRVO: ..Sudden, unilateral blurred vision ..Mild to moderate loss of acuity

10. Causes and risk factors Age : Age is the most important factor, since over 90% of cases occur in patients over the age of 55 years. Hypertension : A high blood pressure is present in up to 73% Hyperlipidaemia Diabetes mellitus Oral contraceptive pill Raised intraocular pressure Smoking Systemic lupus erythematosus Sarcoidosis Tuberculosis

11. Diagnostic testing evaluation Symptoms: blurry or distorted vision Discomfort Redness Watering Signs: Pupil : Pupillary reactions may be normal and may present with relative afferent pupillary reflex Conjunctiva : Advanced stages may show congestion Cornea : Advanced stages may show diffuse corneal edema Iris : The iris may be normal. Advanced stages may show neovascularization Fundus examination : Retinal hemorrhages may present in all 4 quadrants. Hemorrhages can be superficial, dot and blot, and/or deep. In some patients, hemorrhages may be seen in the peripheral fundus only. Hemorrhages can be mild to severe, covering the whole fundus and giving a "blood and thunder appearance.“ Dilated tortuous veins : Veins may be dilated and tortuous Optic disc edema : The optic disc may be swollen during the early-stage disease History: various systemic and local factors (risk factors) predisposing the central retinal vein occlusion (CRVO) is indicated.

12. Fundal examination Scattered hemorrage Optic disc edema Dilated tortuous veins

13. Laboratory investigation ƟLaboratory investigations include  : Imaging Studies Complete blood cell (CBC) count Glucose tolerance test Lipid profile Serum protein electrophoresis Chemistry profile Thyroid function tests ECG Urea, electrolytes and creatinine Hematologic tests Other test may be done according to suspicion Chest X-ray (sarcoidosis, tuberculosis) C-reactive protein Thrombophilia screen (thrombin time, prothrombin time and activated partial thromboplastin time) Autoantibodies (rheumatoid factor, anti-nuclear antibody, anti-DNA antibody) Serum angiotensin-converting enzyme (ACE) Fasting plasma homocysteine level Treponemal serology Carotid duplex imaging

14. Imaging Studies: Fluorescein Angiography: Fluorescein angiography is the most useful test for the evaluation of retinal capillary nonperfusion, posterior segment neovascularization, and macular edema. Fluorescein angiography is one of the tests used in the classification of CRVO. Optical Coherence Tomography: Optical coherence tomography (OCT)   scanning is a noninvasive, noncontact, transpupillary imaging technology that can image retinal structures in vivo. Spectral-domain OCT is used to detect intraretinal and subretinal fluid and to measure the thickness of individual retinal layers. OCT provides information regarding the health of photoreceptors and ganglion cell layers. OCT is used exclusively to monitor macular edema over time and the response with various treatment modalities. Fundus Autofluorescence: Fundus autofluorescence can detect, in patients with recent-onset CRVO, a perivenular hypoautofluorescence with a fern-like appearance. Color Doppler imaging: Color Doppler imaging is a noninvasive quantitative method of assessing the retrobulbar circulation. Detection of low venous velocities has been used to predict the onset of iris neovascularization. Optical coherence tomography angiography: OCT angiography (OCTA) generates high-resolution noninvasive angiograms (no dye injection required) that qualitatively illustrate most clinically relevant findings in retinal venous occlusion.

15. Differential diagnosis Ocular ischemic syndrome Proliferative diabetic retinopathy Hyperviscosity retinopathy Branch retinal vein occlusion

16. Treatment The main goal of treatment is to keep your vision stable. This is usually done by sealing off any leaking blood vessels in the retina. This helps prevent further swelling of the macula. Macular edema is one of the prominent treatable causes of decreased visual acuity in patients with CRVO. Treatment includesto hault and prevent some conditions such as thrombosis macular edema neovascularisation

17. Medical treatment: Aspirin Anti-inflammatory agents Isovolemic hemodilution Plasmapheresis Systemic anticoagulation with warfarin, heparin, and alteplase Fibrinolytic agents Systemic corticosteroids Local anticoagulation with intravitreal injection of alteplase Injection VEGF Intravitreal injection of ranibizumab Intravitreal injection of aflibercept Intravitreal injection of triamcinolone Intravitreal injection of bevacizumab Dexamethasone intravitreal implant Surgical treatment: Laser photocoagulation Chorioretinal venous anastomosis Radial optic neurotomy Vitrectomy

18. complication Ocular neovascularization Macular edema Cellophane maculopathy phthisis bulbi macular degeneration optic atrophy complications due to treatment with intravitreal injections include endophthalmitis, vitreous hemorrhage, and retinal detachment

19. Prognosis For nonischemic CRVO, complete recovery with good visual recovery occurs only in about 10% of cases. Fifty percent of patients will have 20/200 or worse vision. About one third of patients convert to ischemic CRVO. For ischemic CRVO, more than 90% of patients will have 20/200 or worse vision. About 60% of patients develop ocular neovascularization with associated complications. About 10% of patients can develop CRVO or other type of vein occlusions within either the same eye or the contralateral eye within 2 years. It has been reported that the fellow eye may develop retinal vein occlusion in about 7% of cases within 2 years. In another report, the 4-year risk of developing second venous occlusion is 2.5% in the same eye and 11.9% in the fellow eye. Neovascular glaucoma may result in a painful blind eye. The long-term prognosis of CRVO has significantly improved with new anti-VEGF agents and steroids, maintaining good visual acuity for a long duration in most patients, except those with severe ischemic maculopathy. Development of neovascular complications has also decreased with continued monitoring and anti–VEGF treatment.