CRVOBRVOHemispheric VOHemicentral VOPapillophlebitisMacular BRVO

Ischemic CRVO Non ischemic CRVO Distinction between two varieties is

important becoz it assists the clinician in the following-

1.Prediction of the risk of subsequent neovascularisation.

2.identification of patients who have poorer visual prognosis

3.Determination of the likelihood of spontaneous visual improvement.

4.Decision as to appropriate follow up intervals.

Patients with an ischemic pattern are usually aware of a sudden, painless decrease in visual acuity. Vision ranges from 20/200(6/60) to hand movements. The onset, however, is generally not as rapid or the visual loss as extensive as in central retinal artery occlusion.

Patients with ischemic occlusion have an average age of 68.5 years.

It represents 20-25% of all CRVOs. A prominent afferent pupillary defect is common. Cotton wool spots are usually present and are

numerous. Characterized by extensive retinal haemorrhages

most notably centerd in posterior pole.

Ophthalmoscopic featuresOphthalmoscopic features

The retina is edematous, particularly in the posterior pole. Cotton-wool patches (soft exudates) are often present. The disc margin is blurred or obscured, and the precapillary arterioles appear engorged. Splinter hemorrhages and edema are present on the disc surface and extend into the surrounding retina. The physiologic cup is filled, and the venous pulse is absent. The arterioles, often overlooked because of the other more striking pathologic features, are frequently narrowed. Sometimes in central retinal vein occlusion of acute onset, the fundus picture is less dramatic, and all of the findings previously discussed may be present, but to a lesser degree.Visiondepends on extent of macular involvement.

Nonischemic central retinal vein occlusion is a much milder and more variable disease in appearance, symptoms, and course compared with ischemic central retinal vein occlusion.

Patients with nonischemic CRVO are on an average 5 years younger (average age, 63 years) than those with ischemic vein occlusion.

It represents 75-80% of all CRVOs. Pupillary testing rarely reveals an afferent

defect,which if present is only slight. Cotton wool spots if present are few in number

and located posteriorly. Ophthalmoscopy reveals a variable number of

dot and flame retinal haemorrhages.

WITH MINIMAL INTRARETINAL HEMORRHAGE AND DILATEDBUT NOT TORTUOUS RETINAL VEINS

CYSTOID MACULAR EDEMA IS PRESENT ON THE OCT AS BLACK, HYPOREFL ECTIVE INTRARETINAL SPACES.

VENOUS DILATATION,TORTUOSITY AND EXTENSIVE FLAME SHAPED HGE

FA SHOWS STAINING OF BLD VESSELS BUT GOOD CAPILLARY PERFUSION

The actual mechanisms producing the clinical picture of central retinal vein occlusion may be roughly divided into those conditions that produce a physical blockage at ,or posterior to lamina cribrosa, and those conditions in which hemodynamic factors result in an obstruction to the flow of blood. These mechanisms probably coexist in many patients with central VO.

"Blood and thunder" appearance of a central retinal vein occlusion.

Histopathologic evaluation of eyes removed because of a central retinal vein occlusion demonstrates an occlusion at or just behind the level of the lamina cribrosa.

At this location, there are certain anatomic factors that predispose the central retinal vein to occlusion. First, the lumina of the central retinal artery and central retinal vein are narrower than they are in the orbital optic nerve, and the vessels are bound by a common adventitial sheath.

Green studied 29 eyes that were enucleated 6 hours to 10 years after occlusion. As a result of this study, they hypothesized that the flow of blood through the central retinal vein becomes increasingly turbulent as the vein progressively narrows at the lamina cribrosa, where it also may be further impinged upon by arteriosclerosis of the adjacent central retinal artery. This turbulence damages the endothelium in the retrolaminar vein, which exposes collagen and initiates platelet aggregation and thrombosis.

Their studies show the evolution of this thrombus. Thrombus adheres where the endothelium has been severely damaged.

Recently, color Doppler ultrasound imaging has been used to examine the blood flow in the orbit, including the optic nerve head, and has been used to examine patients with central retinal vein occlusion.

As might be expected, the venous velocity in the eye of a patient with central retinal vein occlusion is markedly reduced compared either with the unaffected eye or to control eyes.

In addition, vascular resistance is slightly higher in the ophthalmic artery and short posterior ciliary arteries of both the involved and the clinically healthy fellow eye of patients with central retinal vein occlusion compared with control eyes.

Open angle glaucoma is a relatively common finding in patients who have CRVO.Patients with a history of glaucoma are five times more likely to have CRVO than those who do not ,presumably becoz of structural alterations of lamina cribrosa induced by elevated IOP.

Acute angle closure glaucoma may precipitate CRVO.

All patients with central retinal vein occlusion should have a comprehensive ophthalmic evaluation, including an appropriate evaluation for glaucoma. In addition, they should be referred to their primary care physician for an evaluation of cardiovascular risk factors, including hypertension and diabetes

GENERAL PRINCIPLESGENERAL PRINCIPLES

Maximise Recovery and VisionMaximise Recovery and Vision

Prevent re-occlusionPrevent re-occlusion

Detect associated systemic diseaseDetect associated systemic disease

Detect / Prevent GlaucomaDetect / Prevent Glaucoma

Protect other eyeProtect other eye

CBC, PV, ESRUrea ,electrolytes,creatinineLFT, Protein ElectrophoreseisRandom Glucose, LipidThyroid function tests.

VASlit lamp examinationGonioscopy –to look for angle

neovascularisationFFAOCTCDI (Carotid duplex imaging )

  Clotting screen Protein C,S defficiency Elevated factor V Actviated protein C resistance Factor V Leiden a major risk factor in

females (Five percent of European population)

Dysfibrogenaemia (1/3000) Prothrombin Antiphopholipid antibodies

(A) COLOR PHOTOGRAPH OF CRVO

(B) FA OF CRVO SHOWING EXTENSIVE CAPILLARY NON PERFUSION

The intravenous fluorescein angiogram pattern of an ischemic CRVO is usually characterized by a delayed filling time of the venous tree of the retina, capillary

Also characterized by venous dilation, and extensive leaking of fluorescein into the retina, particularly in the macular area and in the area adjacent to the larger venous trunks.

And capillary nonperfusion may not be noted at the time of initial occlusion, but usually manifest shortly thereafter.

Late-phase photographs show patchy extravascular areas of fluorescence and staining of the retinal veins.

Microaneurysms may not

be noted at the time of initial occlusion, but are usually manifest shortly thereafter.

Fluorescence in the macula indicates capillary leakage and edema; this not only may account for much of the initial visual loss in the acute phase, but may eventually result in permanent structural changes.

The amount of nonperfusion or ischemia is determined by inspecting the fluorescein angiography negative under magnification. The photographer inspects not only the central 30° or 45°, but as much of the peripheral retina as possible.

Another method has been to classify eyes with less than 10 disc diameters of perfusion on fluorescein angiography as perfused or nonischemic, and eyes with 10 or more areas of nonperfusion as nonperfused or ischemic.

Fluorescence in the macula indicates capillary leakage and edema; this not only may account for much of the initial visual loss in the acute phase, but may eventually result in permanent structural changes.

The prognosis for ischemic central retinal vein occlusion is generally poor because of decreased visual acuity and neovascularization.

Visual loss occurs because of macular edema, capillary nonperfusion, overlying hemorrhage (either retinal or vitreal), or a combination of all of these.

Retinal edema usually gradually subsides except in the macula, where it may persist for many months or years.

Macular holes or cysts may form.

The most serious complication of central retinal vein occlusion is neovascularization.

Neovascularization elsewhere (NVE) occurs less frequently than neovascularization of the iris (NVI), and usually only in ischemic occlusions.

The low incidence of retinal surface neovascularization in ischemic central retinal vein occlusion is thought to be due to the destruction of endothelial cells, which provide the source for endothelial proliferation and neovascularization.

Neovascularization of the iris and frequently neovascular glaucoma occurs in approximately 8%6to 25% of all central retinal vein occlusions and generally only in those eyes that exhibit an ischemic pattern of occlusion.

Magargal and co-workers have shown that the incidence of neovascularization increases dramatically above approximately 50% capillary nonperfusion. The incidence of anterior segment neovascularization in nonischemic central retinal vein occlusion is approximately 1%, compared with approximately 35% to 45% for ischemic central retinal vein occlusion.

Neovascularization of the iris or angle is significantly correlated with the extent of capillary nonperfusion on the fluorescein angiogram.

Rubeosis developed in 80% to 86% of the eyes with severe nonperfusion of three to four quadrants of the posterior pole or the periphery, but in only 3% to 9% of those with less capillary nonperfusion.

Neovascularization of the iris may develop as early as 2 weeks after central retinal vein occlusion or as late as 2½ years.

Neovascularization of the iris will develop in almost all patients within the first year, but usually in the first 3 months.

Symptomatically, patients complain of tearing, irritation, pain, and further blurring of vision as the intraocular pressure in the affected eye begins to rise.

The pain may become excruciating. The cornea is hazy and the pupil dilated, and a network of fine vessels is seen over the surface of the iris (rubeosis iridis) on slit-lamp examination

By the time gonioscopy reveals extension of this neovascular membrane into the trabecular network and throughout the angle, the intraocular pressure is usually markedly elevated.

The angle is initially open, but later in the disease, peripheral anterior synechiae develop and the angle may become irreversibly closed, resulting in neovascular glaucoma.

Large, extremely irritating bullae may form on the surface of the cornea and then break down. Dense cataracts eventually form, obscuring the fundus.

The terms hemicentral retinal vein occlusion and hemispheric retinal vein occlusion refer to eyes in which approximately half of the venous outflow from the retina, either the superior or the inferior, has been occluded. In approximately 20% of eyes, the branch retinal veins draining the superior and inferior halves of the retina enter the lamina cribrosa separately before joining to form a single central retinal vein.

Hemicentral retinal vein occlusion is an occlusion of one of these dual trunks of the central retinal vein within the nerve.

Hemispheric retinal vein occlusion is an occlusion involving the venous drainage from approximately half of the retina, either the superior or the inferior retina

In some eyes, the nasal retina is not drained by a separate vein, but by a branch of either the superior or the inferior temporal vein. It is the occlusion of one of these veins draining both the nasal retina and the superior or inferior retina near the optic disc that accounts for the majority of hemispheric retinal vein occlusions.

The treatment and classification are similar to that of branch retinal vein occlusion.

EXTENSIVE HGE INFERIORLY

FA SHOWING HYPOFLUORESCENCE DUE TO CAPILLARY NON PERFUSION& MILD PERI VASCULAR HYPERFLUORESCENCE

Hayreh and associates conducted a prospective but nonrandomized study of panretinal photocoagulation in ischemic central retinal vein occlusion. They found no statistically significant difference between the treated and untreated groups in the incidence of angle neovascularization, neovascular glaucoma, retinal or optic nerve neovascularization, vitreous hemorrhage, or visual acuity. The only significant finding was that fewer patients in the treated group had neovascularization of the iris compared with nontreated controls, but only if the panretinal photocoagulation was applied within the first 3 months after the onset of central retinal vein occlusion and panretinal photocoagulation resulted in a significant loss of the peripheral field.

Once neovascularization in the anterior segment is detected, panretinal photocoagulation should be instituted promptly. This will often result in regression of the iris vessels and prevent complete angle closure; this is also true in patients with some increase in intraocular pressure but in whom the angle is not occluded for 360°.

The Central Retinal Vein Occlusion Study Group performed a randomized, prospective clinical trial on the effect of macular grid photocoagulation compared with no treatment on eyes with 20/50 or worse visual acuity due to macular edema with no capillary nonperfusion on fluorescein angiography.

Although grid photocoagulation lessens macular edema both angiographically and clinically, there was no difference in visual acuity between the treated and untreated patients. For treated patients, there was a trend toward decreased visual acuity in patients older than 60 years and visual improvement in patients younger than this; this effect was not seen in untreated patients.

Although this study suggests a possible benefit to visual acuity in younger patients with macular edema who are treated compared with untreated controls, the number of patients in this subgroup is too small for a statistically valid comparison of treated versus untreated eyes.

Once developed, neovascular glaucoma responds poorly to any type of treatment. Cycloplegics, topical pressure-lowering agents, carbonic anhydrase inhibitors, and corticosteroids, though failing to lower the intraocular pressure significantly, may make the patient more comfortable.

Panretinal photocoagulation often cannot be applied in cases of advanced neovascular glaucoma in which the angle has been substantially occluded and the cornea may be too cloudy to allow treatment.

Trans-scleral cyclocryotherapy or trans-scleral laser cyclodestruction, sometimes combined with 360° of trans-scleral panretinal cryoablation,has also been used to preserve the globe.

In some cases where visibility is poor and the angle is closed, we have had some success in the last few years combining pars plana vitrectomy and endophotocoagulation with a drainage implant

Panretinal photocoagulation has been recommended for the treatment of neovascularisation secondary to CRVO's. There is currently debate regarding the timing of this therapy. Whether delayed intervention (after the development of iris new vessels) offers as good an outcome as early laser treatment(at the time of neovascularisation of the retina alone) needs still to be shown.

Grid therapy for macular oedema in CRVO has not been shown to improve visual acuity.

NO PROVED EFFECTIVE TREATMENT

PRP if intraocular neovascularisation is present

Lower IOP if elevatedTreat underlying medical conditionsMacular edema generally does not

respond to grid laser..

Defn-Obstruction of a branch of a retinal vein.

Associated features Macular edema Macular subretinal fluid Retinal neovascularisation Vitreous haemorrhage Dilated,tortuous retinal vein Capillary non perfusion Cotton wool spots Optico cilliary shunt vessels Sheathing of vessel Microaneurysms

A.Major at discB. major away from discC. minor macularD.E periferal not involving F macula

SHOWS FLAME & BLOT HGE WITH COTTON WOOL SPOTS AND VENOUS TORTUOSITY

FA SHOWS BLOCKAGE BY BLOOD AND AREAS OF CAPILLARY NON PERFUSION

COLOR PHOTO SHOWING VENOUS SHEATING,COLLATERALS,EXUDATES AND RESIDUAL HGES

FA SHOWS CAPILLARY NON PERFUSION AND TORTUOUS COLLATERALS EXTENDING ACROSS HORIZONTAL RAPHE B/W SUP. & INF. ARCADES

(B) THE VASCULAR CHANGES DO NOT INVOLVE THEFOVEA ON FA.

(A) THE OCCLUDED VEIN IS SCLEROTIC

(A) INTRARETINAL HEMORRHAGE

(B) LATE LEAKAGE ON FA

Enlargement of the foveal avascular zone, causing decreased vision to 20/100. Note that there is no leakage in the macula as seen .

Grid laser was not performed.

Both fluorescein angiography1and histopathologic examination confirm that most occlusions occur at an arteriovenous crossing.

Histologically, where the vein and artery cross, they share a common adventitial sheath, and the venous lumen may be diminished by as much as a third at this crossing.

The clinical picture of branch retinal vein occlusion is retinal hemorrhages that are segmental in distribution.

The apex of the obstructed tributary vein almost always

lies at an arteriovenous crossing. Usually some degree of pathologic arteriovenous nicking is present.

The occlusion is commonly located one or two disc diameters away from the optic disc. However, the occlusion may lie at a point near the disc edge or, less frequently, may involve one of the smaller, more peripheral tertiary or macular branches.

GENERAL PRINCIPALS Maximise Recovery and Vision Prevent re-occlusion Detect any associated systemic disease Detect / Prevent Glaucoma Protect other eye

Neovascularization of the iris and neovascular glaucoma are uncommon and occur in only approximately 1% of affected eyes.

More commonly, neovascularization of the disc occurs in approximately 10% of eyes, and neovascularization elsewhere occurs in approximately 20% of eyes. Generally, retinal neovascularization occurs within the retinal area served by the occluded vessel, but it has been reported to occur outside in presumably normal retina.

Vitreous hemorrhage due to neovascularization occurs in approximately half of the eyes with neovascularization.Butner and McPherson239 found that 11.3% of spontaneous vitreous hemorrhages were due to a branch retinal vein occlusion, an incidence second only to proliferative diabetic retinopathy as a cause of vitreous hemorrhage.

Oyakawa and co-workers found that in 38.3% of eyes undergoing a vitrectomy for a nondiabetic vitreous hemorrhage, the hemorrhaging was due to a branch retinal vein occlusion.

RED-FREE PHOTOGRAPH FA SHOWING NEOVASCULARISATION

CAPILLARY NON PERFUSION

Hypertensive retinopathyDiabetic retinopathyOcular ischemic syndrome Juxtafoveal telengiectasiaCombined BRAO and BRVORadiation retinopathy

Branch vein obstruction is often associated with pre-existing vascular disease. Evaluation for systemic abnormalities, in particular hypertension, should be performed.

Exclusion of diabetes, hyperlipidaemia, hyperviscosity/coagulation states, antiphospholipid syndrome, or any other predisposing condition should be performed.

Regular review is required until the haemorrhages clear so that the most suitable treatment option can be achieved.

Approximately one third to one half of patients with BRVO have recovery of visual acuity to 20/40, or better, without therapy.

Avoid oral contraceptives Aspirin Treat hypercholesterolemia and

hypertension Lower IOP Anticoagulants if required

For macular edema ,VA of 6/12 or worse -Wait for clearance of retinal hge to

allow adequate FFA. -Determine if decreased VA is caused

by macular edema(versus macular nonperfusion)

If macular edema xplains visual loss and no spontaneous improvement has occurred by 3 mnths,grid macular photocoagulation is recommended.

If capillary non perfusion explains decreased VA , laser treatment is not advised.

Good quality FFA is obtained after retinal hge has cleared sufficiently.

If more than 5 Disc diameters of non perfusion are present,the patient should be followed at 4 mnths interval to seek the development of neovascularisation.

If neovascularisation develops PRP to the involved retinal sector should be applied using argon laser to achieve “medium”white burns , 200-500 um in diameter –one burn width apart to cover the entire involved segment.

In patients with neovascularisation treated with laser ,only 29% developed vitreous haemorrhage,versus 61% of those untreated.

The data showed no advantage with treatment before neovascularisation occurred,even if extensive capillary non perfusion existed.

If laser is applied to all non perfused BRVOs a large % of patients will be treated unnecessarily.

Can photocoagulation improve visual acuity in eyes with macular edema reducing vision to 20/40 or worse?

Eyes with branch vein occlusion occurring 3 to 18 months earlier with 20/40 vision or worse because of macular edema (but not hemorrhage in the fovea or foveal capillary nonperfusion) were treated with the argon laser in a "grid" pattern in the area of capillary leakage.

The treatment did not extend closer than the edge of foveal avascular zone and did not extend outside the peripheral arcade. At the 3-year follow-up, there was a statistically significant improvement in the visual acuity of treated eyes compared with untreated eyes.

An occlusion limited to a small venous tributary draining a section of the macula and located between the superior and inferior temporal arcades is considered a subgroup of branch retinal vein occlusion.Most patients with macular branch vein occlusion complain of blurring or distortion of vision. Superior macular vein occlusions are more common than inferior macular vein occlusions, and some degree of macular edema is present in approximately 85% of these eyes.

Although small areas of capillary nonperfusion are present in approximately 20% of eyes, neovascularization is not seen. This type of macular vein occlusion can be remarkably subtle at times. Joffe and associates pointed out that clues such as small collateral channels and microaneurysms often suggest the diagnosis. Treatment of macular edema in macular vein occlusion by photocoagulation is identical to the treatment of other branch retinal vein occlusion.

In 1961, Lyle and Wybar described six young, healthy patients with a unilateral, relatively benign condition characterized by mild blurring of vision, essentially normal visual acuity, dilated and tortuous retinal vessels, a varying amount of retinal hemorrhage, and optic disc edema

All six patients improved spontaneously, but were left with sheathing of retinal vessels and the formation of vessels on the optic disc. Lyle and Wybar called this condition "retinal vasculitis" and believed it to be due to a central retinal vein occlusion secondary to an inflammatory vasculitis of the venous system.

Lonn and Hoyt agreed with this etiology, but felt that "papillophlebitis" was a more appropriate descriptive term. Hart and co-workers, however, pointed out that an inflammatory etiology for this disease is tenuous, and no well-documented cases have been studied histopathologically.

Characteristic features Also called optic disc vasculitis. These eyes tend to have optic disc

edema out of proportion to the retinal findings,cotton wool spots that ring the optic disc and occasionally cilioretinal artery obstructions or even partial CRAOs.

Although spontaneous improvement is common,the course is not always benign.

Up to 30% of these patients may develop the ischemic type of occlusion.

THE END