By Lucy Piper, Senior medwireNews Reporter
The formation of collateral vessels does not appear to improve visual acuity in patients with branch or central retinal vein occlusion (BRVO, CRVO), and is unaffected by anti-vascular endothelial growth factor (VEGF) therapy, a retrospective analysis suggests.
There has been much debate over the role of collateral vessels in RVO, with some studies suggesting that such vessels may develop as a consequence of RVO and predict stable or improved visual acuity. The current findings call into question this side of the debate, however.
The analysis involved data from two phase III randomised, controlled trials on 789 patients aged an average of 67 years with macular oedema secondary to RVO. Of these, 397 had BRVO and 392 CRVO. The patients received monthly intravitreal injections of ranibizumab 0.3 mg or 0.5 mg or sham 0.5 mg for 6 months followed by 6 months of as-needed treatment with open-label ranibizumab.
Over the course of the year, there was a change in the distribution of collateral vessels on the optic disc and within the retina depending on whether patients had BRVO or CRVO. Among patients with BRVO, vessels declined on the disc, from 32.6% to 19.6% in those receiving sham and from 33.6% to 16.7% in those receiving ranibizumab. But collateral vessels increased within the retina in these patients, from 31.8% to 48.2% and from 26.8% to 47.2%, respectively.
By contrast, patients with CRVO experienced an increase in collateral vessels on the disc, from 50.0% to 57.9% among sham-treated patients and from 56.5% to 59.2% among ranibizumab-treated patients and a decline within the retina, from 21.0% in both groups to 12.1% and 15.1%, respectively.
Whether patients received sham or ranibizumab had no significant effect on the presence of collateral vessels on the disc or within the retina, the researchers note in Retina.
And the gains in best-corrected visual acuity with ranibizumab treatment were similar for BRVO and CRVO patients, irrespective of the prevalence of collateral vessels.
“This result suggests that VEGF inhibition does not regulate the presence of these vessels”, say the researchers led by Rishi Singh (Cleveland Clinic, Ohio, USA).
“A reasonable hypothesis given this information is that the presence of retinochoroidal collateral vessels indicates vasodilation of preexisting vessels over time rather than the formation of new vessels in response to treatment.”
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