Download Branch Retinal Vein Occlusion

Branch Retinal Vein Occlusion
Author: Lihteh Wu, MD, Consulting Surgeon, Department of Ophthalmology,
Vitreo-Retinal Section, Instituto De Cirugia Ocular, Costa Rica
Coauthor(s): Diego Mena, Associate Surgeon, Instituto de Cirugia Ocular
Lihteh Wu, MD, is a member of the following medical societies: American Academy of
Ophthalmology, and Association for Research in Vision and Ophthalmology
Editor(s): Vytautas A Pakainis, MD, Chief of Ophthalmology, Dorn Veterans
Administration Medical Center, Professor of Ophthalmology, Ophthalmology, University
of South Carolina School of Medicine; Francisco Talavera, PharmD, PhD, Senior
Pharmacy Editor, eMedicine; Steve Charles, MD, Director of Charles Retina Institute;
Clinical Professor, Department of Ophthalmology, University of Tennessee College of
Medicine; Lance L Brown, OD, MD, Ophthalmologist, Regional Eye Center, Affiliated
With Freeman Hospital and St John's Hospital, Joplin, Missouri; and Hampton Roy, Sr,
MD, Associate Clinical Professor, Department of Ophthalmology, University of Arkansas
for Medical Sciences
INTRODUCTION
Background: Much confusion exists in the literature because central and
branch retinal vein occlusions (BRVOs) often are grouped and studied
together. The natural history and complication rate for each entity differ. The
treatments and their results vary from one condition to the other. This article
deals exclusively with BRVO. Hemiretinal vein occlusions are probably
variants of central retinal vein occlusions, and as such, they are not included in
this discussion.
Pathophysiology: Hypertensive, atherosclerotic, inflammatory, or
thrombophilic conditions may lead to retinal endothelial vascular damage. In
eyes with an anatomic predisposition, intravascular thrombus formation may
occur. Eyes with arteriovenous crossings appear to be at risk for BRVO. In
these eyes, the artery is anterior to the vein in most cases. The artery and the
vein share a common adventitial sheath.
Arterial compression of the vein is believed to be the main cause of BRVO.
Compression of the vein may lead to turbulent flow in the vein. The turbulent
flow in combination with the preexisting endothelial vascular damage from the
different conditions creates a local environment favorable to intravascular
thrombus formation. Up to two thirds of BRVOs occur in the supertemporal
quadrant. This rate may be related to the increased number of arteriovenous
crossings in this quadrant with respect to the rest. In addition, nasal BRVO
often are asymptomatic; therefore, patients with this type of BRVO do not seek
ophthalmic evaluation.
Frequency:

In the US: Retinal vein occlusions (branch and central) are the second
most common retinal vascular diseases after diabetic retinopathy.

Internationally: In a population-based study from Australia, the Blue
Mountains Eye Study, the prevalence of BRVO in the population older
than 48 years was 1.1%.
Race: No racial predilection for the disease is apparent.
Sex: No predilection for either sex is apparent.
Age: The patients who are affected are usually in their fifth or sixth decade of
life.
CLINICAL
History:

The Eye Disease Case-Control Study reported the following findings:
o
Systemic hypertension is a risk factor for BRVO.
o
Diabetes mellitus and open-angle glaucoma are not risk factors
for BRVO.
o
Moderate alcohol consumption reduces the risk of BRVO.

Patients often complain of a sudden painless decrease of vision in the
affected eye.

Some may complain of a scotoma.
Physical:

In 1877, Leber first described the condition ophthalmoscopically. During
the acute phase, intraretinal hemorrhages (usually flame shaped),
retinal edema, and cotton-wool spots are seen in the distribution of a
retinal vessel. The horizontal raphe is respected.

During the chronic stage, hemorrhages may be absent. Macular edema
may be the only sign present. Telangiectatic vessels that extend across
the horizontal raphe usually can be demonstrated angiographically.

In certain eyes with large areas of nonperfusion, retinal
neovascularization may be seen.
o
Vitreous hemorrhage with tractional retinal detachments may
ensue.
o
Further traction may create retinal breaks, creating combined
rhegmatogenous and tractional retinal detachments.
o
Neovascular glaucoma and neovascularization at the disc are
rare events with BRVO.
Causes:

Most cases of BRVO are due to idiopathic factors. Usually, patients
have an anatomic predisposing factor, such as an arteriovenous
crossing where the artery compresses the vein. This compression leads
to clot formation and subsequent BRVO.

Inflammatory conditions that affect the retinal veins may cause local
damage that predisposes the individual to intravascular clot formation
with subsequent BRVO. Some of the inflammatory conditions reported
in the literature are the following:

o
Sarcoidosis
o
Lyme disease
o
Serpiginous choroiditis
Thrombophilic conditions, such as the following, may also be involved:
o
Protein S deficiency
o
Protein C deficiency
o
Resistance to activated protein C (factor V Leiden)
o
Antithrombin III deficiency
o
Antiphospholipid antibody syndrome
o
Lupus erythematosus
o
Gammopathies
DIFFERENTIALS
Hypertension
Macular Edema, Diabetic
Retinopathy, Diabetic, Background
Retinopathy, Diabetic, Proliferative
WORKUP
Lab Studies:

The authors of the Branch Vein Occlusion Study (BVOS) has
recommended against extensive testing in patients with typical BRVO.

Certain laboratory studies may be useful in atypical cases, ie, those in
young patients, bilateral cases, or those in patients with a personal or
family history for thromboembolism. Determinations of following may be
helpful:
o
Prothrombin time (PT) and activated partial thromboplastin time
(aPTT)
o
Protein C, protein S, factor V Leiden, and antithrombin III
o
Homocysteine
o
Antinuclear antibody (ANA), lupus anticoagulant, and
anticardiolipin
o
Serum protein electrophoresis (SPEP) results
Imaging Studies:

Fluorescein angiography
o
A fluorescein angiogram is obtained as soon as the hemorrhages
have cleared if the patient's vision is still depressed. The test is
usually done 3 months after the event.
o
The purpose is to determine the cause of visual loss (eg, macular
edema or macular ischemia). If the visual loss is secondary to
macular edema, laser photocoagulation in a grid pattern may be
of benefit. Conversely, if macular ischemia is responsible for the
loss of vision, laser photocoagulation should not be offered to the
patient.

Optical coherence tomography: Given its ability to measure retinal
thickness in a quantitative fashion, optical coherence tomography (OCT)
is a useful adjunct in the follow-up of patients with macular edema
secondary to BRVO.
Histologic Findings: Histopathologic studies confirm the importance of
arteriovenous crossings in the pathogenesis of this condition. Inner retinal
ischemic atrophic areas have been described distal to the occlusion site.
Variable degrees of arteriolar sclerosis have been reported. An intravascular
fresh or recanalized thrombus is often found at the site of venous occlusion.
TREATMENT
Medical Care: Medical treatment is not effective in this condition. In the past,
anticoagulants, fibrinolytic agents, clofibrate capsules (Atromid-S), and
carbogen inhalation have been used but without success.
More recently, intravitreal injection of triamcinolone has gained popularity
among vitreoretinal specialists. Because of its potent antipermeability and
anti-inflammatory properties, intravitreal triamcinolone has recently been used
to treat macular edema of different etiologies. A few cases of macular edema
secondary to BRVO treated with an intravitreal triamcinolone injection have
been reported. The exact dose remains unclear. Doses from 4 to 25 mg have
been reported to be effective. Complications resulting from this treatment
include cataract formation, elevation of intraocular pressure, infectious
endophthalmitis, noninfectious endophthalmitis, and retinal detachment.
Further study is warranted to define what role, if any, intravitreal triamcinolone
has in the management of macular edema secondary to BRVO.
Surgical Care: BRVO have a relatively benign course. Nevertheless, certain
complications that lead to visual loss may occur. These complications include
macular edema and the sequelae from retinal neovascularization (eg, vitreous
hemorrhage, tractional retinal detachment, neovascular glaucoma). Several
surgical and laser techniques are available to deal with these situations.

Macular grid laser photocoagulation
o
Macular grid laser photocoagulation was effective in the
treatment of macular edema in a large prospective BVOS trial.
o
o
o
The current recommendation is to wait 3 months to see if the
patient's vision spontaneously improves.
If no improvement occurs and if the hemorrhages have mostly
cleared from the macular area, a fluorescein angiogram is
obtained. If the angiogram shows leakage in the macular area
that is responsible for the decrease in vision, treatment with a
macular grid laser is recommended. After 3 years of follow-up
care, 63% of laser treated eyes improve by 2 or more lines of
vision compared with 36% of control eyes.
If the fluorescein angiogram reveals macular nonperfusion, laser
therapy is not warranted, and observation is recommended.
Finkelstein reported that eyes with macular nonperfusion have a
good visual prognosis. The median visual acuity in his series was
20/30.

Scatter photocoagulation
o The BVOS also demonstrated that scatter photocoagulation
reduces the prevalence of neovascularization from 40% to 20%.
o However, if all eyes with nonperfusion were treated, 60% of
patients who would never develop neovascularization would be
treated.
o If only the eyes that develop neovascularization were treated, the
events of vitreous hemorrhage would decrease from 60% to
30%.
o Therefore, the recommendation is to wait until
neovascularization actually develops before scatter
photocoagulation is considered.

Laser-induced chorioretinal anastomosis

o
Bypass of the normal retinal venous drainage channels is
attempted by creating a communication between the obstructed
vessel and the choroid.
o
Problems with this technique are the lack of reliability in creating
an anastomosis (most groups report a 30-50% success rate) and
its complications. Complications from the procedure include
tractional retinal detachment and vitreous hemorrhage.
Vitrectomy and arteriovenous decompression
o Virtually all cases of BRVO occur at arteriovenous crossings.
o Because arterial compression is believed to be the major cause
of this condition, some have recommended lifting the artery from
the underlying vein to relieve the compression.
Several small, uncontrolled series have shown good results in
improving macular edema and macular perfusion. However,
others have reported a lack of efficacy of this procedure.
Planning of a multicenter controlled trial is currently underway.
Several surgeons have reported resolution of macular edema
secondary to BRVO after vitrectomy with or without peeling of the
internal limiting membrane.
o


Pars plana vitrectomy techniques with or without scleral buckling may
be necessary in eyes with tractional and rhegmatogenous retinal
detachments.

Retinal vein cannulation is an experimental technique that some have
advocated. If one can safely cannulate the obstructed vessel, one can
deliver clot-busting medications, such as tissue plasminogen activator,
and thus improve flow in the vessel.
Consultations:

Consult a vitreoretinal specialist if complications arise.

In atypical cases where a thrombophilic condition is suspected,
consultation with a hematologic specialist is recommended.
MEDICATION
The goals of pharmacotherapy are to reduce morbidity and to prevent
complications.
Drug Category: Intravitreal corticosteroids -- Have potent
anti-inflammatory and antipermeability properties.
Drug Name
Triamcinolone (Kenalog-40) -- Through its
antipermeability properties secondary to its anti-VEGF effects, strengthens
blood retinal barrier and prevents its disruption.
Adult Dose
4 mg is most common dose because it is easy
to aliquot and inject 0.1 cc from commercially available 40 mg/mL vial; apart
from convenience of dosing, no studies support this dose over any other dose
Pediatric Dose
Not established
Contraindications
Documented hypersensitivity; fungal, viral,
and bacterial skin infections
Interactions
None reported
Pregnancy
C - Safety for use during pregnancy has not
been established.
Precautions
Complications include progression of nuclear
sclerosis, increased intraocular pressure, retinal detachments, sterile
endophthalmitis, and infective endophthalmitis; after 4-6 wk of topical
corticosteroid use, 5% of eyes develop elevated intraocular pressure >16 mm
Hg, and 30% develop intraocular pressure elevation of 6-15 mm Hg; unclear
how long it takes for intraocular pressure to rise following initial intravitreal
injection; unknown what effect initial dose, frequency of reinjection, or
cumulative corticosteroid dose has on intraocular pressure; all reported
studies show that 4-mg dose and 25-mg dose appear to have similar effect on
intraocular pressure; most treated eyes respond to topical antiglaucoma
medication but few may require filtering procedures; cataract formation
appears to be associated with rise in intraocular pressure (most cataracts
develop slowly; posterior subcapsular cataracts appear to be more common);
to avoid endophthalmitis, use one vial per eye and sterile technique
(endophthalmitis occurs in approximately 0.1% of injections)
FOLLOW-UP
Further Outpatient Care:

After the condition is diagnosed, a patient must receive follow-up care to
monitor the development of possible complications.

If visual acuity remains depressed, a good-quality fluorescein
angiogram can be obtained when most of the hemorrhages have
cleared, usually by 3 months.

The angiogram guides further therapy.
Complications:

Macular edema

Retinal neovascularization

o
Vitreous hemorrhage
o
Tractional retinal detachment
o
Rubeosis iridis
Epiretinal membrane
Prognosis:

An analysis of several series indicates that 53% of eyes obtain 20/40 or
better visual acuity, 25% have a visual acuity between 20/50 and
20/100, and 22% have a visual acuity of 20/200 or worse.

The more distal the occlusion is from the optic disc, the better the visual
prognosis.
Patient Education:

Instruct patients with BRVO to seek attention if further visual loss occurs
during follow-up.
MISCELLANEOUS
Medical/Legal Pitfalls:

Early recognition may reduce sequelae.