THE LATEST PUBLISHED RESEARCH

Bevacizumab vs. PDT for Neovascular AMD
After prospectively randomizing 62 patients with neovascular age-related macular degeneration to treatment with either intravitreal bevacizumab (Avastin) or verteporfin (Visudyne) photodynamic therapy, a group of researchers concluded bevacizumab was more effective for six months but additional randomized trials are needed to determine whether its superiority is sustained with longer follow-up.

In the study, patients received standard PDT (n=30) or 2.5-mg injections of bevacizumab (n=32). Mean central retinal thickness was significantly better at three (p=.04) and six months (p=.002) in the bevacizumab group. At three months, mean best-corrected visual acuity and greatest linear dimension were not significantly different between the two groups. However, at six months, mean BCVA (p<.001) and GLD (p=.02) were significantly better in the bevacizumab group).

Source: Bashshur ZF, Schakal A, Hamam RN, et al. Intravitreal bevacizumab vs verteporfin photodynamic therapy for neovascular age-related macular degeneration. Arch Ophthalmol 2007;125:1357-1361.

Persistent Vitreomacular Adhesion May Be Risk Factor for Wet AMD
According to the results of a prospective, observational case series, persistent attachment of the posterior vitreous cortex to the macula may be a risk factor for the development of neovascular AMD. In the study, B-scan ultrasonography and optical coherence tomography were performed in 163 eyes of 82 subjects (50 eyes with neovascular AMD, 57 with non-neovascular AMD and 56 controls). Ultrasonography showed that 34 percent of the neovascular eyes had posterior vitreous detachment compared with 71.9 percent of the non-neovascular eyes (p=.00002) and 60.7 percent of the controls (p=.017). OCT detected persistent central vitreoretinal adhesion surrounded by a detached posterior vitreous cortex in 36 percent of the neovascular eyes, which was significantly higher than in non-neovascular eyes (7 percent, p<.0001) and in controls (10 percent, p=.002).

The authors of the study paper wrote that persistent vitreomacular adhesion may increase risk for neovascular AMD via vitreoretinal traction inducing chronic low-grade inflammation by maintaining macular exposure to cytokines or free radicals in the vitreous gel, or by interfering in transvitreous oxygenation and nutrition of the macula. They also wrote that inducing PVD may provide a prophylactic benefit against neovascular AMD.

Source: Krebsab I, Brannathc W, Glittenbergb C, et al. Posterior vitreomacular adhesion: a potential risk factor for exudative age-related macular degeneration? Am J Ophthalmol 2007;144:741-746.

Bevacizumab for Macular Edema Secondary to CRVO
Two studies published in the October issue of Retina indicated that bevacizumab can be an effective treatment for macular edema associated with central retinal vein occlusion. The authors of one of the study papers pointed out that the treatment benefits are apparent early but not sustained without repeat injections.

One study, by Priglinger et al., was a prospective, noncomparative, consecutive, interventional case series with six months of follow-up. Among the 46 patients who received repeated intravitreal injections of bevacizumab (1.25 mg), mean visual acuity improved from 20/250 at baseline to 20/80 (p<0.001), mean visual acuity gain was 13.9 +/-14.4 letters, and mean central retinal thickness decreased from 535 +/-148 µm at baseline to 323 +/-116 µm. Ischemic CRVO was associated with significantly lower visual acuity than nonischemic CRVO (p<0.001), but visual acuity gain was similar in both groups.

The second study, by Hsu et al., was a retrospective consecutive case series of 30 eyes of 29 patients. Mean follow-up was 18.1 weeks. At the one-month follow-up mean visual acuity improved from the baseline of 20/394 to 20/237 (n=26, p=0.04). At the two-month follow-up mean visual acuity improved to 20/187 (n= 21, p=0.008). At the three- and four-month follow-up, visual acuity improved from 20/228 to 20/157 (n=15, p=0.05) and from 20/313 to 20/213 (n=11, p=0.03), respectively. No significant changes in visual acuity occurred after four months, and the authors of the study paper reported that the duration of the treatment’s effect appeared to be limited to two months for most patients.

Sources: Priglinger SG, Wolf AH, Kreutzer TC, et al. Intravitreal bevacizumab injections for treatment of central retinal vein occlusion: six-month results of a prospective trial. Retina 2007;27(8):1004-1012. Hsu J, Kaiser RS, Sivalingam A, et al. Intravitreal bevacizumab (Avastin) in central retinal vein occlusion. Retina 2007;27:1013-1019.

IVTA Complications More Frequent in Patients with Uveitis
In a retrospective observational case series, patients with macular edema due to uveitis were more likely to experience intraocular pressure elevation and posterior subcapsular cataract (PSC) progression than patients with macular edema from other causes when treated with intravitreally injected triamcinolone acetonide.

The review included 222 eyes of 173 patients (45 eyes of 31 patients with macular edema due to uveitis and 177 eyes of 142 patients with macular edema secondary to other etiologies). They received intravitreal triamcinolone at the Cole Eye Institute in Cleveland between 2001 and 2005. The uveitis patients were significantly younger, more likely to be female and more likely to have had previous sub-Tenon’s capsule steroid injection and/or glaucoma therapy than the nonuveitis patients. The presence of uveitis was the strongest risk factor for an adverse IOP event (odds ratio 2.5; 95 percent CI, 1.0-6.1; p=0.05). The odds of having a documented increase in PSC after triamcinolone injection were 5.6 times greater in uveitis eyes (95 percent CI, 1.6-19.6; p=0.007).

Source: Galor A, Margolis R, Brasil OMF, et al. Adverse events after intravitreal triamcinolone in patients with and without uveitis. Ophthalmology 2007;114:1912-1918.

OCT Superior for Detecting Vitreomacular Interface Abnormalities after Laser Treatment of Eyes with Persistent DME
A prospective observational case series involving 50 eyes showed that OCT was 1.94 times more sensitive than traditional techniques combined in detecting vitreomacular interface abnormalities following focal laser treatment in patients with persistent diabetic macular edema (p=.00003). The authors of the study paper reported that such abnormalities were prevalent and may impact treatment decisions.

An epiretinal membrane associated with persistent diabetic macular edema following focal laser treatment. (Image courtesy of Nicola G. Ghazi, MD)

The eyes in the study had at least one focal laser treatment. Two were excluded because of incomplete data. Among the remaining 48 eyes, 25 (52.1 percent) demonstrated definite vitreomacular interface abnormalities, including anomalous vitreal adhesions, epiretinal membrane or both, and six eyes (12.5 percent) had questionable abnormalities. The number of focal laser sessions and diffuse leakage on fluorescein angiography were not associated with increased prevalence of abnormalities (p=.13 and p=.47, respectively).

Source: Ghazi NG, Ciralsky JB, Shah SM, et al. Optical coherence tomography findings in persistent diabetic macular edema: the vitreomacular interface. Am J Ophthalmol 2007;144:747-754.

Researchers Identify Cell that Causes Retinoblastoma
Investigators at St. Jude Children’s Research Hospital have identified the cell that causes retinoblastoma, disproving a longstanding principle of nerve growth and development. The finding suggests for the first time that it may be possible for scientists to induce fully developed neurons to multiply and coax the injured brain to repair itself.

The study appeared in the October 19 issue of Cell. The discovery occurred after the investigators developed different populations of mice whose retinas lacked one or more members of the Rb family of genes that include Rb p107 and p130. These genes are critical to the ability of an immature cell to stop dividing and begin to differentiate. In the study, when the mouse retina had reduced Rb family function, fully differentiated horizontal neurons could multiply while retaining all of the differentiated features of normal horizontal neurons. The researchers showed that as the horizontal interneurons multiplied their numbers up to 50-fold, they maintained their normal position in the retina and their normal connections to other cells. When they allowed the horizontal interneuron cell division to proceed unchecked, highly differentiated tumors resembling normal horizontal neurons formed. Unexpectedly, these tumors were aggressive and spread rapidly.

The investigators concluded that the Rb family’s only task is to prevent mature horizontal interneurons from multiplying as they did when they were immature cells. The findings surprisingly showed that retinoblastoma can arise from fully matured nerves in the retina called horizontal interneurons--disproving the scientific principle that such nerves cannot multiply the way young, immature cells can.

Source: Ajioka I, Martins RAP, Bayazitov IT. Differentiated horizontal interneurons clonally expand to form metastatic retinoblastoma in mice. Cell 2007;131(2):378-90.

More Complications Follow 25-Ga. Procedures in Case Series
In a retrospective case series, 25-ga. vitreoretinal procedures were associated with a greater incidence of some postoperative complications compared with 20-ga. procedures. The charts of consecutive patients who underwent primary 25-ga. (129 eyes) and 20-ga. (129 eyes) surgeries were reviewed. The procedures were performed by four surgeons at a single center between September 2002 and November 2005. Mean follow-up was 9.1 +/-4.9 months in 25-ga. eyes and 14.3 +/-8.4 months in 20-ga. eyes.

Intraoperative complications were mainly rhegmatogenous in nature and occurred at statistically similar rates in both groups; however, postoperative hypotony and serous choroidal effusions occurred in 7.9 percent of 25-ga. eyes compared with 1.6 percent of 20-ga. eyes (p=0.02). Endophthalmitis was noted only in 25-ga. eyes in two cases (1.6 percent). Other postoperative complications included retinal tears and detachments (5.4 percent in 25-ga. vs. 4.7 percent in 20-ga. eyes), persistent vitreous hemorrhage (5.4 percent in each group), and new vitreous hemorrhage (3.9 percent in 25-ga. eyes vs. 0.8 percent in 20-ga. eyes). Cataract progression occurred at similar rates in both groups (46 percent).

Source: Shaikh S, Ho S, Richmond PP, et al. Untoward outcomes in 25-gauge versus 20-gauge vitreoretinal surgery. Retina 2007;27:1048-1053.