Recent noteworthy studies to stimulate discussion and debate.
■ AMD conversion prophylaxis still elusive. While anti-VEGF drugs continue to blunt the progression of exudative AMD, the search continues for prophylaxis to prevent dry AMD from progressing to the wet form. In the November/December 2009 issue of Ophthalmic Surgery, Lasers & Imaging, the Prophylactic Treatment of Age-related Macular Degeneration study group reports on a laser treatment designed to do just that.
Overall, 639 patients were subjected to the single placement of an annular grid of 48 applications of a 810-nm laser, with the fellow eyes serving as a control group. All the patients studied had bilateral dry AMD, with at least five drusen ≥63 μm in diameter. Two years after treatment, mean visual acuity in study eyes had increased by 1.5 letters, with an even larger improvement (4.0 letters) at the two-year mark among patients whose baseline visual acuity was between 20/32 and 20/63. However, this improvement had evaporated by the three-year follow-up.
Not only was laser treatment not effective in preventing conversion to wet AMD, the study authors report that eyes treated actually experienced a slightly greater rate of choroidal neovascularization than eyes that acted as controls. While the results in this study were not as alarming as some earlier reports that indicated that laser treatment might actually aid in the development of CNV, the authors confirm that laser appears to provide no benefit in patients with dry AMD with regard to conversion to wet AMD.
■ Myopic CNV and anti-VEGF. Four studies published in the March 2010 issue of Retina report on the use of anti-VEGF drugs in myopic CNV. The articles — from retinal physicians in France, Portugal, Italy and Japan — all found a statistically significant relationship between intravitreal injections of ranibizumab and some improvement in CNV.
Though only the Japanese study was of sufficient size to draw larger conclusions (128 patients), there were a few results among the four studies of interest. For instance, the French study found three-line improvements in visual acuity in nearly half of all the patients they studied. In the Italian study, all 11 patients studied experience complete resolution of subretinal fluid. And although almost one-quarter of patients in the Portuguese study had three-line improvements in visual acuity, patients who had previously been treated using photodynamic therapy developed no improvements in visual acuity.
While only the Portuguese study looked at bevacizumab in addition to ranibizumab, and while the Retina study found no statistically significant difference between the two therapies, follow-up data published online by Graefe's Archive for Clinical and Experimental Ophthalmology found no significant visual acuity gain among patients treated with bevacizumab at two-year follow-up.
■ Intravitreal injections in the 2000s. Seeking to determine how the introduction of anti-VEGF agents has affected rates of intravitreal injections, physicians from Ontario have conducted a population-based retrospective study, looking at over eight years of data.
It turns out 2005 was a banner year for intravitreal injections, according to the results published in the March 2010 issue of Archives of Ophthalmology. Because of the approvals of pegaptanib sodium and the advent of off-label bevacizumab for AMD, injection rates went up eightfold during that year in Ontario.
Even the regulatory approval of ranibizumab two years later did not have as great an impact on the number of injections as the two events in 2005. This fact leads the study authors to conclude that the off-label use of bevacizumab has had a greater impact that the development and approval of ranibizumab. However, the authors are also quick to note that, while off-label use of bevacizumab is prevalent and very cost-effective, efficacy and safety data from clinical trials, notably the CATT study, are still pending.
■ Glaucoma drug for XLRS. A new trial of the antiglaucoma drug dorzolamide has provided more evidence that the ophthalmic solution may be beneficial in patients with juvenile X-linked retinoschisis (XLRS).
Writing in the February 2010 issue of Archives of Ophthalmology, scientists at the University of Illinois at Chicago report that 59% of eyes treated in their small trial showed a reduction in cystoid macular edema in patients with XLRS.
These results add to the growing body of data suggesting that dorzolamide may be a beneficial adjunct to treating CME in these patients. Significantly, the study authors found that some patients in the study took up to five months to répond to treatment with dorzolamide. This is particularly important, since previous studies have indicated that, although CME consequent to XLRS may resolve on its own, these patients may still develop atrophic lesions of the macula further down the road.
Furthermore, although 25% of patients in the study whose eyes did not improve after five months, three of these five patients experienced improvement in CME in follow-up treatment with dorzomalide. RP