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Central Retinal Vein Occlusion

Occlusion of Central Retinal Vein

Central retinal vein occlusion involves the obstruction of blood flow in the central retinal vein caused by a thrombus.  


Presentation

Visual distortion or loss is the primary symptom of CRVO and can arise abruptly or gradually over a period of days or weeks. Pain is not usually present, unless complications such as glaucoma arise.

Angiomatosis
  • The association between Wyburn-Mason syndrome and cutaneous reactive angiomatosis is also a novel finding.[ncbi.nlm.nih.gov]
Retinal Hemorrhage
  • None of the examined eyes had flame-shaped retinal hemorrhages in the periphery. All hemorrhages were rounded-dot or blot and were variable in size.[ncbi.nlm.nih.gov]
  • Five days later, there were improvements in disc swelling and retinal hemorrhage.[ncbi.nlm.nih.gov]
  • He received sustained-release intravitreal dexamethasone, which led to the resolution of retinal hemorrhage, optic disc swelling, and cotton-wool spots. Three months after the injection, retinal hemorrhages were not detectable.[ncbi.nlm.nih.gov]
  • One month later, optic disc edema and retinal hemorrhage gradually diminished and eventually disappeared; however, visual acuity did not recover.[ncbi.nlm.nih.gov]
  • Dilated examination revealed significant optic nerve head edema and diffuse retinal hemorrhages in all 4 quadrants consistent with a central retinal vein occlusion. The patient underwent an urgent 3-wall orbital decompression on the right.[ncbi.nlm.nih.gov]
Rubeosis Iridis
  • Ischemic CRVO’s can also lead to development of abnormal growth of blood vessels in the front of the eye on the iris (Rubeosis Iridis) and over the trabecular meshwork (drain for fluid to exit the eye).[retinacenternj.com]
  • Neovascularization (abnormal new vessel formation) of the retina or iris (rubeosis iridis) occurs in about 16% of patients with central retinal vein occlusion and can result in secondary (neovascular) glaucoma, which can occur weeks to months after occlusion[msdmanuals.com]
  • See fluorescein angiography ; rubeosis iridis ; central retinal vein. Fig. R12 Major inferior branch retinal vein occlusion. Note the extensive dot-blot and flame-shaped haemorrhages affecting the sector of the retina drained by the obstructed vein.[medical-dictionary.thefreedictionary.com]
  • Kaye SB, Harding SP (1988) Early electroretinography in unilateral central retinal vein occlusion as a predictor of rubeosis iridis. Arch Ophthalmol 106:353–356 PubMed Google Scholar 21.[link.springer.com]
  • This may lead to profound vascular leakage, rubeosis iridis and raised intraocular pressure. The prognosis is extremely poor due to macular ischemia.[eyewiki.aao.org]
Flame-shaped Hemorrhage
  • Fundus examination of the RE revealed whitening of the retina along the distribution of cilioretinal artery, sparing fovea, flame-shaped hemorrhages, and roth spots with minimally dilated and tortuous retinal veins.[ncbi.nlm.nih.gov]
  • Blockage of flow in vein that drains inner retina Common causes: systemic hypertension, diabetes, arteriosclerosis, hypercoagulable states Patient reports acute or subacute monocular vision loss, sometimes with flickering ("scintillations") Flame-shaped[kellogg.umich.edu]
  • Fundoscopy shows tortuosity and dilatation of all branches of the central retinal vein, dot/blot and flame-shaped hemorrhages, throughout all four quadrants and most numerous in the periphery, and optic disc and macular edema.[eyewiki.aao.org]
Corneal Edema
  • Visual acuity was hand motion in the right eye and 20/40 in the left eye with corneal edema.[ncbi.nlm.nih.gov]
Roth's Spots
  • Fundus examination of the RE revealed whitening of the retina along the distribution of cilioretinal artery, sparing fovea, flame-shaped hemorrhages, and roth spots with minimally dilated and tortuous retinal veins.[ncbi.nlm.nih.gov]

Workup

CRVO is not diagnosed directly with blood tests. These tests are carried out in order to detect a possible underlying condition, which could have led to the development of a central retinal vein occlusion in older individuals. In the younger population, blood tests are individualized and may include:

  • Complete Blood Count
  • Thrombophilia Screening - Proteins C and S, lupus anticoagulant, activated protein C, antithrombin III etc.
  • Lipid profile
  • Glucose tolerance
  • protein electrophoresis

Imaging techniques are also a very helpful tool towards the detection of CRVO. A fundoscopic examination will illustrate retinal hemorrhaging of various degrees, profound edema and distended veins. A Color Doppler test has been also performed in the context of research [10], as it is able to reveal low blood flow, a piece of information that constitutes an indication for a future neovascularization process.

Optical coherence tomography scanning (OCT) is also a non-invasive procedure which can provide retinal measurements with great accuracy and identify macular edema [11] [12]. It is an important diagnostic tool because a profound hemorrhage prevents an angiography from detecting macular edema and without OCT, a crucial complication would be left undiagnosed.

Treatment

Intraocular injections of anti-VEGF medications or a dexamethasone implant are used to treat patients with CRVO and fovea-affecting macular edema. Anti-VEGF drugs hinder the production of the vascular endothelial growth factor that causes neovascularization and include ranibizumab, bevacizumab etc. Another sub-category of patients who benefit from the same treatment are those with CRVO and an acuity of >20/400 prior to the development of the occlusion. The latter group can also be treated with an intraocular injection of triamcinolone and an improvement of vision is to be expected in up to half of the patients.

Another possible treatment plan involves focal laser photocoagulation which is used to treat individuals with an occlusion of the branches of the retinal vein, even though this procedure is not effective to treat macular edema. The complication of neovascularization is treated with panretinal laser photocoagulation, in order to decrease vitreous hemorrhage and prevent neovascular glaucoma.

Prognosis

Prognosis is variable: it depends on the severity of the symptoms, the CRVO type and the clinical presentation at the time of diagnosis. Generally, non-ischemic CRVO that does not relapse into the ischemic type can regress spontaneously and vision is restored either to normal or almost normal in more than half of the patients, given that macular edema does not develop.

The majority of the patients will experience some visual loss. the best prognostic factor is good visual acuity (up to 20/40) at the time of diagnosis. Such a ratio is not likely to exhibit degradation. Acuity of 20/200 or worse, however, tends to stay poor, even after proper treatment and blood flow restoration.

As a general rule, a visual acuity that amounts to 20/60 or higher is expected to stay as it is, a 20/100-20/200 does have a margin of improvement but may fail to do so and an acuity <20/200 is not likely to increase.

Prognosis is unfavorable for patients with ischemic CRVO. Macular edema is a poor prognostic factor alongside neovascular glaucoma. A natural mechanism that can protect the individual from the development of neovascularization and glaucoma is the formation of opticociliary shunts.

Etiology

CRVO is more common amongst people of older age (>50 years old) and rather uncommon amongst adolescents or young adults. Hypertension, diabetes, glaucoma and high blood viscosity can all provide the substrate for clot formation and CRVO. In some other cases, CRVO is an idiopathic condition.

Epidemiology

Both the occlusion of the central retinal vein (CRVO) and of its branches are extremely common amongst the vascular disorders that affect the eye. CRVO's incidence has been estimated in a USA study to amount to 0,5% [6], whereas in Israel it appears to be 0.2% for people younger than 40 years old and 0.5% for people older than 64 years old. Australian epidemiologic studies have calculated the incidence of CRVO as amounting to a significant 4.6% in the age group of people that have surpassed the 80th year of their lives [7].

CRVO is more frequently observed in men, although the difference between men and women is not particularly significant. Mortality rates are not a useful calculation, as the condition itself does not lead to death. As far as the morbidity is concerned, however, it greatly depends on the type of the disease:

  • Non-ischemic CRVO may regress spontaneously, followed by complete vision restoration. More than half of the patients, however, will eventually display poor visual acuity (20/200) and the possibility of a relapse into ischemic CRVO is present, even after a year following the original event.
  • Ischemic CRVO is expected to lead to a 20/200 vision in over 90% of the patients and to neovascularization to more than 60% of the patients.

A second CRVO incident within the 2-year period after the initial event has been observed in 7% of the patients and affects the previously unaffected eye.

Sex distribution
Age distribution

Pathophysiology

There appears not be no general consent regarding the pathophysiological mechanisms that lead to CRVO, which is thus considered to be a multifactorial disorder [8] [9].

Regarding the anatomy of the region, both the retinal vein and artery are in close proximity as they cross the restricted opening of the lamina cribrosa. the confined space may cause problems with blood flow and in the vascular walls, which will eventually lead to a thrombus formation. Additionally, an incidence of arterial sclerosis will exert extra pressure on the walls of the retinal vein as well, as the two are closely connected. Blood flow may be distorted, followed by significant alterations in the endothelium; both factors may also lead to the formation of a clot.

Another suggested mechanism include other types of external pressure exerted on the retinal vein walls, eg. due to density changed in the lamina cribrosa itself, or an optic nerve inflammation, given that the optic nerve is also at close proximity with the arterial and venous vessels. Coagulation disorders can naturally also play a part in the formation of thrombi, as can a hyperdynamic circulation pattern.

A significant complication of CRVO is neovascularization, which can lead to glaucoma and blindness in the affected eye. It has been attributed to the occlusion, which causes a retrograde venous flow to the retinal system and hypoperfusion. Hypoperfusion is believed to lead to the increased production of vascular endothelial growth factor (VEGF) in the vitreous cavity, which, in turn, causes neovascular activity both posteriorly and anteriorly. Another important complication involves macular edema, which is also thought to be a result of fluid loss from the vessels, caused by VEGF.

Prevention

CRVO is caused by various underlying conditions. An appropriate treatment plan for these conditions and a responsible patient adherence to it can help prevent the development of CRVO. Regular visit to an ophthalmologist by patients with risk factors, such as diabetes and glaucoma, can also prove very beneficial.

Summary

Central retinal vein occlusion (CRVO) is a vascular disease affecting the central retinal vein. The clinical presentation of individuals affected by CRVO tends to fluctuate, with symptoms exhibiting great variability and different degrees of severity.

A general categorization divides CRVO into two distinct types, based on the effect it has on retinal perfusion: the ischemic type and non-ischemic type. Distinguishing the type of CRVO may be a challenge to the physician initially, as the symptomatology accompanying the condition alters with time. Non-ischemic CRVO causes no significant vision distortion and upon clinical examination, minor hemorrhaging of the retina is observed, alongside some cotton-wool spots and an adequate blood flow to the region. Vision is not expected to be impaired once non-ischemic CRVO regresses on its own, but there is a possibility that it will relapse into the ischemic type.

Ischemic CRVO, on the other hand, is a result of a complete occlusion of the vein. It is the severer counterpart type and upon clinical examination, substantial hemorrhage and cotton-wool spots are detected, as well as diminished blood flow of the retina. Symptoms may be accompanied by pain in the eye and vision is severely distorted or lost.

Generally, CRVO poses a considerable threat to vision, and every type of classification that has been proposed takes into consideration the region where inadequate blood flow is observed and the subsequent neovascularization [1] [2] [3] [4] [5]. An obstruction of the smaller branches of the retinal vein can also occur.

Diagnosis of CRVO is achieved through fundoscopy, optical coherence tomography and blood tests; the latter are performed with an aim to detecting the underlying disease. Treatment consists of intraocular injections of medications and focal laser photocoagulation, if the occlusion affects a branch of the central retinal vein. Neovascularization is treated with panretinal laser photocoagulation.

Patient Information

CRVO stands for central retinal vein obstruction. Each eye has two major vessels, which are responsible for the blood flow: the central retinal artery and vein. CRVO is a blockage of the blood flow in the central retinal vein, which stops the blood from exiting the retina and reaching the heart in order to be re-oxygenized. Blood remains in the region of the macula- an anatomical structure which mediated central vision- and causes problems with vision.

CRVO is a very common disorder of the eye. It can be caused by many underlying conditions, most commonly diabetes, glaucoma, arterial hardening (atherosclerosis) and coagulation disorders. In some cases the exact cause is not known.

There are two types of CRVO: the ischemic and non-ischemic type. The non-ischemic type is a mild form of the disease which does not result in complete vision loss and may go away on its own. The ischemic type is expected to cause significant vision distortion or even loss and causes much more damage to the eye structures. The primary symptom in CRVO is vision distortion without pain. If pain is present, this means that the complication of CRVO known as neovascular glaucoma has developed.

CRVO is treated with eye injections of various medications or laser photocoagulation, if only a smaller artery is affected and not the central one. If glaucoma secondary to CRVO arises, a laser therapy (panretinal photocoagulation) is performed. The underlying disease, if there is any, should be appropriately managed in order to avoid a CRVO recurrence, as well as a better outcome.

References

Article

  1. Central Vein Occlusion Study Group. Natural history and clinical management of central retinal vein occlusion. Ophthalmol. 1997 Apr; 115(4):486-91. 
  2. Hayreh SS. Classification of central retinal vein occlusion. Ophthalmology. 1983 May; 90(5):458-74.
  3. Hayreh SS. Retinal vein occlusion. Indian J Ophthalmol. 1994 Sep; 42(3):109-32. 
  4. Hayreh SS, Zimmerman MB, Podhajsky P. Incidence of various types of retinal vein occlusion and their recurrence and demographic characteristics. Am J Ophthalmol. 1994 Apr 15; 117(4):429-41. 
  5. Williamson TH. Central retinal vein occlusion: what's the story?Br J Ophthalmol. 1997 Aug; 81(8):698-704.
  6. Klein R, Moss SE, Meuer SM, et al. The 15-year cumulative incidence of retinal vein occlusion: the Beaver Dam Eye Study. Arch Ophthalmol. 2008 Apr; 126(4):513-8. 
  7. Mitchell P, Smith W, Chang A. Prevalence and associations of retinal vein occlusion in Australia. The Blue Mountains Eye Study. Arch Ophthalmol. 1996 Oct; 114(10):1243-7.
  8. David R, Zangwill L, Badarna M, et al. Epidemiology of retinal vein occlusion and its association with glaucoma and increased intraocular pressure. Ophthalmologica. 1988; 197(2):69-74. 
  9. Ota M, Tsujikawa A, Kita M, et al. Integrity of foveal photoreceptor layer in central retinal vein occlusion.Retina. 2008 Nov-Dec; 28(10):1502-8.
  10. Baxter GM, Williamson TH. Color Doppler flow imaging in central retinal vein occlusion: a new diagnostic technique?. Radiology. 1993 Jun; 187(3):847-50. 
  11. Moschos MM, Moschos M. Intraocular bevacizumab for macular edema due to CRVO. A multifocal-ERG and OCT study. Doc Ophthalmol. 2008 Mar; 116(2):147-52. 
  12. Gupta B, Grewal J, Adewoyin T, et al. Diurnal variation of macular oedema in CRVO: prospective study. Graefes Arch Clin Exp Ophthalmol. 2009 May;247(5):593-6.

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Last updated: 2019-07-11 20:12