Optimal conditions required for the creation of an iatrogenic chorioretinal venous anastomosis in the dog using argon green laser photocoagulation

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

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.

Two-Year Efficacy of Ranibizumab Plus Laser-Induced Chorioretinal Anastomosis vs Ranibizumab Monotherapy for Central Retinal Vein Occlusion: A Randomized Clinical Trial

Importance

Adding a laser-induced chorioretinal anastomosis (L-CRA) to current treatments for central retinal vein occlusion (CRVO) may improve outcomes and lessen therapy burdens.

Objective

To determine the 2-year efficacy of intravitreal ranibizumab with an L-CRA vs ranibizumab alone for patients with macular edema caused by CRVO.

Design, Setting, and Participants

In this randomized clinical trial conducted at a single university clinic from March 2012 to June 2015, 58 participants with macular edema caused by CRVO were randomized 1:1 to either an L-CRA or sham procedure at baseline. All participants received monthly intravitreal injections of ranibizumab, 0.5 mg. Data were analyzed from April 2017 to September 2017.

Interventions

Random assignment to L-CRA plus monthly injections of intravitreal ranibizumab, 0.5 mg, (combination group; n = 29) or to a sham L-CRA procedure plus monthly injections of intravitreal ranibizumab, 0.5 mg, (ranibizumab alone group; n = 29) for 6 months. From month 7 to month 24, participants were evaluated monthly and received an injection of ranibizumab if a loss of 5 or more letters of best-corrected visual acuity (BCVA) on ETDRS chart from previous highest score occurred or if there was evidence of residual macular edema on optical coherence tomography.

Main Outcomes and Measures

Mean number of injections from month 7 to month 24, change in BCVA, and change in central subfield thickness (CST).

Results

Of the 58 included participants, 38 (66%) were men, and the mean (SD) age was 68.6 (11.8) years; participants had a mean (SD) BCVA of 57.09 (11.87) ETDRS letters (Snellen equivalent, 20/73) and a mean (SD) CST of 738.36 (175.54) μm. A successful L-CRA was created in 24 of 29 participants (83%) in the combination group. The mean number of injections from month 7 to month 24 was 3.2 (95% CI, 2.5-3.8) in the combination group and 7.1 (95% CI, 6.0-8.0) in the ranibizumab alone group. The ratio of the number of injections in the combination group compared with the ranibizumab alone group was 0.46 (95% CI, 0.36-0.61; P < .001). Mixed-effects regression modeling showed a difference in mean BCVA at 2 years between the combination and ranibizumab alone groups (combination, 70.3 letters [Snellen equivalent, 20/40]; ranibizumab alone, 61.6 letters [Snellen equivalent, 20/60]; difference, 8.8 letters; 95% CI, 0.2-17.3; P = .05). There was also a difference in CST at 2 years between the combination and ranibizumab alone groups (mean CST: combination, 303.6 μm; ranibizumab alone, 394.5 μm; difference, 90.9 μm; 95% CI, 24.3-157.5; P = .01). Four participants (14%) in the combination group required a vitrectomy for early macular traction or vitreous hemorrhage.

Conclusions and Relevance

For macular edema caused by CRVO, an L-CRA significantly reduced the number of ranibizumab injections required.

Trial Registration

anzctr.org.au Identifier: ACTRN12612000004864.

Evidence-Based Treatment of Diabetic Retinopathy

Diabetic retinopathy (DR) is the most frequent microvascular complication from diabetes and requires annual screening and at least annual follow-up. A systemic approach to optimize blood glucose and blood pressure may halt progression to severe stages of DR and obviate the need for ocular treatment. Although there is evidence of benefit from fenofibrate or intravitreous antiVEGF treatment for eyes with nonproliferative DR (NPDR), these therapies are not standard care for NPDR at this time. Some patients with severe NPDR, especially those with type 2 diabetes, benefit from early panretinal photocoagulation (PRP). Once DR progresses to proliferative DR (PDR), treatment is often necessary to prevent visual loss. PRP remains mainstay treatment for PDR with high-risk characteristics. However, intravitreous antiVEGF injections appear to be a safe and effective treatment alternative for PDR through at least two years. Vitreoretinal surgery is indicated for PDR cases with non-clearing vitreous hemorrhage and/or tractional retinal detachment.

Laser-induced chorioretinal venous anastomosis using combined lasers with different wavelengths

AIM

To evaluate the effectiveness of combined lasers with different wavelengths in creating chorioretinal venous anastomosis (CRVA) in nonischaemic central retinal vein occlusion (CRVO).

METHODS

In this retrospective, noncomparative, consecutive case series, records of all patients with a diagnosis of nonischaemic CRVO who underwent combined laser treatment to induce CRVA and who were followed-up for 6 months or longer were reviewed.

RESULTS

Records of 85 patients (85 eyes) were analysed. These patients were divided into two groups. In group 1 (24 cases, 24 eyes), combined lasers with two different wavelengths (argon blue-green laser combined with Nd-YAG laser were used. In group 2 (61 cases, 61 eyes), combined lasers with three different wavelengths (argon blue-green laser combined with krypton red laser and Nd-YAG laser) were used. Functional anastomosis formed in 13 out of 24 eyes (54%) in group 1 and 47 out of 61 eyes (77%) in group 2. In patients with successful anastomosis, visual acuity improved for two or more lines in 49 out of 60 eyes (82%), with the remaining eyes undergoing no change. There were no serious complications.

CONCLUSION

The use of three laser wavelengths results in the creation of laser anastomosis and the success rate may be higher than when using two wavelengths alone.

Laser-induced chorioretinal venous anastomosis for nonischemic central retinal vein occlusion: evaluation of the complications and their risk factors

PURPOSE

To evaluate the complications of laser-induced chorioretinal venous anastomosis in nonischemic central retinal vein occlusion (CRVO) and to identify the associated risks.

METHODS

A retrospective consecutive series of 91 eyes (91 patients) with nonischemic CRVO with a mean +/- SD duration of 15.0 +/- 15.2 weeks (range, 3 to 72 weeks )and corrected visual acuity reduced to 20/100 or less because of perfused macular edema were reviewed. All eyes had one or more anastomotic attempts using argon laser (combined with Nd-YAG laser in 46 eyes) and a minimum of 12 months of follow-up.

RESULTS

Successful chorioretinal venous anastomoses were created in 49 eyes (54%). Eighteen eyes (20%) had neovascular complications. These consisted of intravitreal, intraretinal, and subretinal neovascular membranes and were significantly associated with retinal ischemia (P < .001). There was avascular fibrous tissue proliferation at the anastomotic site in eight eyes (9%), and it was not associated with retinal ischemia (P = .727). No eye developed further capillary nonperfusion once an anastomosis became functional. A chorioretinal venous anastomosis was associated with improved vision (P < .001); 84% of eyes had an average +/- SD improvement of 4.3 +/- 3.8 lines (range, 2 to 20 lines), with the remaining 16% having no improvement or reduced vision.

CONCLUSION

The major vision-threatening complication of laser-induced chorioretinal venous anastomosis for nonischemic CRVO is neovascular membranes occurring at the anastomotic site; these are associated with retinal ischemia. Prompt laser photocoagulation to areas of retinal ischemia that develop after the anastomotic attempt has been made may reduce the risk and severity of this complication.

Laser chorioretinal venous anastomosis for nonischemic central retinal vein occlusion

OBJECTIVE

This study aimed to test the efficacy and safety of laser chorioretinal anastomosis for central retinal vein occlusion (CRVO).

DESIGN

The study design was a consecutive case series.

PARTICIPANTS

Eight eyes of eight patients were treated.

INTERVENTION

The argon laser was used in the method of McAllister and Constable to attempt to form an anastomosis. The patients were observed for 1 to 19 months (median, 11 months).

MAIN OUTCOME MEASURES

Visual acuity, anastomosis success, and complications were measured.

RESULTS

Twenty attempts to create anastomoses were made with 2 successful anastomoses but not of a therapeutic type. Three patients developed rubeosis, retinal neovascularization at the laser site, and vitreous hemorrhage. Traction retinal detachment occurred twice and neovascular glaucoma occurred once. Secondary panretinal photocoagulation, pars plana vitrectomy, and glaucoma seton were required in three patients, one patient, and one patient, respectively. Visual acuity improved in two patients independent of failed attempts at anastomosis creation and did not improve or worsened in six patients, including the two patients with the successfully created anastomoses.

CONCLUSION

Laser chorioretinal anastomosis for nonischemic CRVO has greater risks and less success than the initial report suggested. Further refinement of the technique is needed before it is adopted extensively. Even when successful, macular pigment epithelial scarring can limit vision, implying a relatively short time window for its effective application in the face of severe macular edema. Successful laser chorioretinal anastomosis does not preclude development of anterior segment neovascularization.