View Full Version : Avastin is more effective than PDT for myopic CNV

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09-02-2012, 04:28 PM

Intravitreal Avastin (bevacizumab, IVB) is more effective for myopic choroidal neovascularization (CNV) than photodynamic therapy (PDT), according to a new study.

Extreme myopia may result in degenerative changes of the retina. These degenerative changes may lead to complications such as retinal detachment or macular degeneration. Degenerative changes affecting the macula include Lacquer crack lesions, atrophy, and CNV. Previous studies have found that myopic CNV appears to respond well to anti-VEGF therapy. The degree of vision improvement appears to be more variable than is seen with AMD, with fewer patients experiencing vision improvement and CNV closure, at least in some studies. The more guarded prognosis for myopic CNV may be due to other complications of pathologic myopia, such as macular atrophy. The treatment of myopic CNV by PDT was found to have a more beneficial effect than placebo therapy at 1 year, but was not significantly better after 2 years.

Methods and Results

In the current study, 44 eyes of 42 consecutive patients with myopic CNV treated with PDT, and 43 eyes of 43 consecutive patients with myopic CNV treated with IVB, were evaluated. For control, 74 eyes of 71 consecutive patients with untreated myopic CNV were evaluated. The comparison of best-corrected visual acuity (BCVA) using analysis of covariance (ANCOVA) during the 12-month follow-up period was performed among the 26 IVB-treated patients without prior treatment, 35 PDT-treated patients without prior treatment, and 71 nontreated controls.

Discussion and Conclusions

The results clearly demonstrated that the VA at 1 year in IVB-treated eyes was significantly better than in the PDT-treated eyes and in the nontreated controls. The question then arises as to the reason for this difference. The rate of angiographic closure of CNV was high in both IVB-treated eyes and PDT-treated eyes (88.5% and 91.7%, respectively). In addition, the number of treatments to obtain the angiographic closure was similar in IVB-treated patients and in PDT-treated patients. In both the IVB-treated and PDT-treated patients, >50% obtained the angiographic closure of the CNV by a single treatment.

The better visual outcome in IVB-treated eyes than PDT-treated eyes was probably attributable to 2 factors. The first factor was the difference in the CNV regression pattern, and the second was the difference in the rate of development of chorioretinal atrophy. The most striking difference between IVB-treated eyes and PDT-treated eyes was that all of the CNVs that had an angiographic closure were accompanied by a shrinkage of CNV in the IVB-treated eyes, whereas the CNV size did not decrease, or even increased, in 65% of the successfully treated PDT eyes. This difference in the pattern of the CNV regression may be the reason why IVB-treated eyes had better visual outcomes than PDT-treated eyes.

The development of a chorioretinal atrophy around the regressed CNV is a major complication of myopic CNV and a major cause of long-term visual decrease in eyes with myopic CNV. The percentage of eyes that developed a chorioretinal atrophy was significantly higher in PDT-treated eyes than in the other 2 groups at 12 months. In contrast, the rate of chorioretinal atrophy was not significantly different between the IVB-treated patients and nontreated controls. Also, the area of chorioretinal atrophy at 12 months in the PDT-treated patients was significantly larger than in the other 2 groups. Because PDT has been reported to damage the collateral choroidal vessels as well as the retinal pigmented epithelium, PDT might possibly increase the risk of a chorioretinal atrophy developing in eyes with a myopic CNV. On the other hand, inhibition of VEGF by bevacizumab might not facilitate the development of a chorioretinal atrophy.

The investigators conclude that IVB is more effective for myopic CNV than PDT. The differences in the regression pattern of CNVs and the rate of chorioretinal atrophy probably explain the better BCVA in the IVB-treated eyes. This is consistent with an earlier study that found IVB improves vision in patients with myopic CNV that previously underwent PDT without success or suffered recurrence.