Recent noteworthy studies to stimulate discussion and debate.
■ Endophthalmitis risk in 25-g vitrectomy significant? No significant difference in endophthalmitis rates was found by retinal physicians at the Jules Stein Eye Institute at UCLA who undertook a head-to-head study, published in the July 2009 Ophthalmology, between groups of patients who underwent para plana vitrectomy with 20- vs 25-g instruments. A total of 3372 consecutive vitrectomies were examined and patients were put into two groups based on sclerotomy status. One group consisted of patients with three-suture 20-g sclerotomies, while the other was made up of patients with at least one unsutured 25-g sclerotomy. Both groups underwent a standard anti-infection protocol.
There was a single case of endophthalmitis in the 25-g group, with no cases in the 20-g cohort. Although the statistical difference was not significant (P=0.46) between occurrence in the two groups, air/gas endotamponade and the use of intravitreal triamcinolone acetonide was more common in the 25-g group to a highly statistically significant extent.
This study is significant in that a common complaint of 25-g surgery is that it entails a higher risk of postoperative endophthalmitis. While the difference in rates between gauge groups was not statistically significant, the incidence was so low (one case of infection in 1424 vitrectomies by 25-g) that, the authors state, careful perioperative preventive measures should reduce the risk of endophthalmitis in 25-g victrectomy to that of 20-g.
■ ROLF to the rescue? A team of German ophthalmologists have found that low-dose recombinant tissue plasminogen activator (rt-PA) as an intravenous thrombolytic agent improved visual outcomes in patients with central retinal vein occlusions (CRVOs). One year after treatment with rt-PA, 45% of 41 patients with CRVO had maintained ≥3 lines of improvement vs 21% with hemodilution. Final mean BCVA was 20/60 in the rt-PA group vs 20/400 in the hemodilution group.
The study, dubbed ROLF (Retinal vein Occlusion and Low-dose Fibrinolytic therapy) by the researchers, was published in the July/August issue of Retina. No serious side effects were observed by the authors, who were operating on the hypothesis that the re-establishment of blood flow to the retina would best address CRVO. While hemodilution reduces blood viscosity and does increase blood perfusion, the Retina study clearly indicates that thrombolysis may work as well or better.
■ Optic nerve effects from PRP. The retinal nerve fiber layer's thickness is affected by laser panretinal photocoagulation (PRP), according to a study conducted by retinal physicians in California and Brazil. Responding to frequent reports that the optic nerve in diabetic eyes that have undergone PRP often appears to have sustained damage similar to that caused by glaucoma, the authors of a study in the July 2009 issue of Archives of Ophthalmology compared OCT imaging in over 200 eyes in three groups: patients with diabetes who had PRP, patients with diabetes who did not, and healthy patients.
The findings of the study indicate that the visible changes in the optic nerve in PRP patients are not the result of comorbid glaucoma. Rather, PRP appears to cause thinning of the retinal nerve fiber layer.
■ Avastin on the move. The July/August 2009 issue of Retina is positively loaded with bevacizumab studies, with articles covering branch and hemiretinal vein occlusions, recurrent vitreous hemorrhage, macular edema, and retinal angiomatous proliferation — this last study looking at Avastin in combination with photodynamic therapy. In addition, the issue's leadoff article, on the topic of intravitreal injection of therapeutic agents, includes a section on bevacizumab.
While results in the recurrent vitreous hemorrhage study were unimpressive, there was significant evidence of the efficacy of bevacizumab in the other three studies, indicating a likely continued role of Avastin in treating retinal conditions. These studies' publication comes as the headto- head CATT trial comparing Avastin to Lucentis nears full enrollment.
■ Antihypertensives and diabetic retinopathy. A comparative study in the July 2, 2009, issue of the New England Journal of Medicine contrasting the effects of two antihypertension drugs on the renal system and retina had a promising result for the treatment of diabetic retinopathy.
The drugs tested, enalapril and losartan, both work on the renin-angiotensin system, which regulates fluid balance and blood pressure. While treatment with neither drugs was effective in slowing the progressive of kidney disease, the study concluded that early blockade of the renin-angiotensin system in patients with type 1 diabetes slowed the progression of retinopathy. (Type 2 diabetes patients were not included in the study.) The authors indicate that, because synthesis of angiotensin occurs in parts of the eye affected by diabetic retinopathy, enalapril and/or losartan may play a role in the treatment of diabetic retinopathy, independent of the presence of hypertension. RP