Chorioretinal Anastomosis for Central Retinal Vein Occlusion: A Review of Its Development, Technique, Complications, and Role in Management

Abstract

Treatments for central retinal vein occlusion (CRVO) have improved dramatically with the advent of intravitreal agents aimed at blocking the effects of the dominant hypoxia-induced upreglulated cytokine, which is vascular endothelial growth factor (VEGF). This cytokine breaks down the capillary endothelial barriers and is a major component of the macular edema in this condition. These treatments although impressive only address some of the sequelae of CRVO and have no effect on the underlying cause which is an obstruction to venous outflow leading to retinal blood flow stagnation and an elevation of the retinal central venous pressure (CVP). The creation of a laser-induced chorioretinal anastomosis (L-CRA) between the obstructed high pressure retinal venous circulation and the unobstructed low pressure choroidal venous circulation is a means addressing the causal pathology. The L-CRA will help lower the elevated CVP, which has been up until now an unaddressed component of the macular edema in this condition.This article reviews the preclinical and clinical development of the L-CRA and the results of the studies into its effect on the natural history of CRVO. It now can be used in combination with existing anti-VEGF treatments with the intravitreal agents addressing the component of the CRVO-induced macular edema due to the cytokine dysregulation, and the L-CRA addressing the component due to the elevated CVP and retinal venous stagnation. Improvements in laser technology have led to higher success rates in L-CRA creation and potential complications are now minimized and better controlled. The combination of L-CRA with intravitreal anti-VEGF agents offers the potential of a permanent cure with a significant reduction in the burden of therapy and improved visual outcomes in this condition.

FIGURE 1

CRVO at presentation (BCVA 6/24) and at 18 months (BCVA 6/6) after being treated with a combination of L-CRA and ranibizumab. A, L-CRA attempt showing laser burns on the retinal veins above and below the disc. Minute amounts of hemorrhage were seen from the vein. B, At 18 months showing L-CRAs above and below the disc (small arrows). The inferior one is draining only a localized segment with the vein between the L-CRA and the disc closed (large arrow). C, Fluorescein and (ICG) at 18 months with the L-CRAs seen (arrows). The ICG shows the large choroidal veins the anastomosis is draining into. D, OCT at presentation. E, OCT at 18 months. The patient has not required anti-VEGF for 10 months. BCVA indicates best-corrected visual acuity; CRVO, central retinal vein occlusion; ICG, indocyanine green angiogram; L-CRA, laser-induced chorioretinal anastomosis; OCT, optical coherence tomography; VEGF, vascular endothelial growth factor.

FIGURE 1 (Continued)

CRVO at presentation (BCVA 6/24) and at 18 months (BCVA 6/6) after being treated with a combination of L-CRA and ranibizumab. A, L-CRA attempt showing laser burns on the retinal veins above and below the disc. Minute amounts of hemorrhage were seen from the vein. B, At 18 months showing L-CRAs above and below the disc (small arrows). The inferior one is draining only a localized segment with the vein between the L-CRA and the disc closed (large arrow). C, Fluorescein and (ICG) at 18 months with the L-CRAs seen (arrows). The ICG shows the large choroidal veins the anastomosis is draining into. D, OCT at presentation. E, OCT at 18 months. The patient has not required anti-VEGF for 10 months. BCVA indicates best-corrected visual acuity; CRVO, central retinal vein occlusion; ICG, indocyanine green angiogram; L-CRA, laser-induced chorioretinal anastomosis; OCT, optical coherence tomography; VEGF, vascular endothelial growth factor.

FIGURE 2

CRVO. A, At L-CRA attempt. Two anastomosis sites are seen, above (large arrow) and below (small arrow) the disc. The superior ≥1 hemorrhage from the vein than typically seen with the inferior one more typical of the small amount of blood indicating that the side wall of the vein has been breached. B, 12 months. The superior site has a larger more functional L-CRA with no complications seen from either site. CRVO, central retinal vein occlusion; L-CRA, laser-induced chorioretinal anastomosis

FIGURE 3

CRVO at 12 months post L-CRA. A, Color photo showing 2 L-CRAs (arrows) with the large draining choroidal vessel seen at the inferior site. B, ICG angiogram showing the draining choroidal vessels (arrows). CRVO, central retinal vein occlusion; ICG, indocyanine green angiogram; L-CRA, laser-induced chorioretinal anastomosis.

FIGURE 4

A, CRVO at presentation. B, At 8 months showing avascular fibrous tissue extending from the inferior L-CRA site (arrow) and along the inferior vascular arcade. This was causing some tractional effects on the macula. C, 3 months post vitrectomy. The tractional effects have been resolved and the L-CRA site (arrow) and inferior vascular arcade are now well seen. CRVO, central retinal vein occlusion; L-CRA, laser-induced chorioretinal anastomosis