Chorioretinal venous anastomosis

Chorioretinal venous anastomosis ^{[39, 40, 41, 42, 43]} is performed by creating an anastomosis to bypass the site of venous occlusion in the optic disc. In this procedure, retinal veins are punctured, either using laser or by surgery, through the retinal pigment epithelium and the Bruch membrane into the choroid, thereby developing anastomotic channels into the choroid.

 

Chorioretinal venous anastomosis reduces macular edema and may improve vision in nonischemic CRVO. The success rate is low, and the complication rate can be quite high, including vitreous hemorrhages and choroidal neovascularization at the anastomosis site.

 

The exact indication and timing of the procedure has not been clearly studied.

Radial optic neurotomy

Radial optic neurotomy (RON) ^{[44, 45, 46, 47, 48, 49]} is a new surgical technique in which a microvitreoretinal blade is used during pars plana vitrectomy to relax the scleral ring around the optic nerve. The central retinal artery and vein passes through the narrow openings of the cribriform plate in the optic disc.

 

Promoters of this technique suggest that CRVO may be due to the compression of the central retinal vein at this location creating a compartment syndrome. If this procedure is successful, it decompresses the closed compartment and leads to an improvement in venous outflow and a reduction of macular edema.

 

In one recent study, RON resulted in clinically relevant improvements on a long-term basis. Patients with nonischemic CRVO may respond more favorably than patients with ischemic CRVO.

 

In another study, significant improvements were observed in the b-to-a ratio of the standard combined ERG after surgery in eyes with CRVO.

 

The benefits from surgery have not been clearly documented. One study, looking into the biomechanical effect of RON, found negligible change in the space around the central retinal vein; RON is unlikely to be a procedure that could mechanically ameliorate the clinical sequelae of a central vein occlusion. The improvement of retinal function is most likely due to improved oxygenation of the retina caused by vitrectomy and not by RON.

 

In addition to the regular complications of vitrectomy, RON can result in significant hemorrhage and neovascularization at the incision site.

 

No consensus currently exists among various researchers regarding the exact criteria for the use of RON.

Vitrectomy

A vitrectomy ^[50] is a technique in which the vitreous is surgically removed along with removal of the posterior hyaloid.

 

Some studies have shown that a vitrectomy may be beneficial for macular edema due to CRVO. One theory is that a vitrectomy may relieve traction on the macula and, thus, reduce macular edema. According to another hypothesis, removing the vitreous will also remove cytokines and VEGF associated with a venous occlusive event; thus, the stimulus for macular edema will be reduced.

 

At the present time, no convincing evidence indicates that a vitrectomy is the best approach.

 

Consultations

A general ophthalmologist should consult a retinal specialist for management of CRVO complications. Other consults include an internist for proper evaluation and management of any systemic medical problems. If patients develop neovascular glaucoma, a glaucoma specialist should be consulted.

Diet

Diet should be tailored to systemic medical problems.

 

Activity

No restrictions usually exist. If patients develop vitreous hemorrhage, they are advised to avoid strenuous activities, sleep with few pillows, and avoid bending and lifting heavy weights.

 

 

Medication

Medication Summary

 

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

 

Vascular Endothelial Growth Factor (VEGF) Inhibitors

Class Summary

These agents bind to VEGF-A receptors to arrest macular edema and improve visual acuity associated with CVRO.

Ranibizumab (Lucentis)

VEGF antibody. Indicated for macular edema following retinal vein occlusion.

Aflibercept intravitreal (Eylea)

Binds and prevents activation of vascular endothelial growth factors (VEGF-A) and placental growth factor (PIGF). Activation of VEGF-A and PIGF can result in neovascularization and vascular permeability. It is indicated for treatment of macular edema following retinal vein occlusion (branched or central retinal vein occlusion).

Bevacizumab (Avastin)

Bevacizumab (Avastin, Genentech, Inc.) is a recombinant, humanized monoclonal antibody that binds all isoforms of VEGF-A. It is used as an off-label medication in various ocular conditions associated with up-regulation of VEGF and increased vascular permeability and neovascularization.

Corticosteroids

Class Summary

These agents have anti-inflammatory properties and cause profound and varied metabolic effects. Corticosteroids modify the body's immune response to diverse stimuli.

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