Recent Noteworthy Studies to Stimulate Discussion and Debate
■ Largest comparative vitrectomy study published. The controversy over 20-gauge vs smaller-gauge vitrectomy is far from over. Sure to fuel the debate further is an article published online in August 2011 by Graefe's Archive of Cli nical and Experimental Ophthalmology, in which a team of French surgeons reports on 553 epiretinal membrane cases operated on with 20-, 23- and 25-gauge vitrectomy.
In this retrospective study, 347, 115 and 91 patients were submitted to 20-, 23- and 25-gauge vitrectomy, and surgery duration, visual acuity improvement, intraocular pressure variation and complications were compared. The patient groups were statistically comparable in terms of demo graphic data, preoperative VA, and other preop variables.
While the smaller gauges proved effective in providing shorter operative times and while visual acuity was better eight days after surgery with those gauges as well, at six weeks, there were no significant differences in VA among the three gauges. The greatest differences were found vis-à-vis IOP, with 20-g producing significant IOP elevation on postop day 1, and 23-g reducing IOP on day 1 (but not significantly). Twenty-five gauge vitrectomy produced no significant changes in IOP. There were no cases of endophthalmitis in the three groups.
In short, the three vitrectomy gauges studied produced similar results with the exception of operative time, for which the smaller gauges produced greater time savings. The authors thus indicate that surgeon choice should remain the deciding factor.
■ Ryan's Hope. The Surgeon's Corner column in the August 2011 issue of Archives of Ophthalmology, written by Edwin H. Ryan, Jr., MD, of VitreoRetinal Surgery in Edina, MN, offers an alternative to sutureless closure in 23-gauge vitrectomy. Dr. Ryan suggests using 6-0 plain gut sutures fashioned as a tape and offers a retrospective review of 116 cases treated with 23-g vitrectomy.
While 23-g vitrectomy is theoretically sutureless, wounds can still leak, leading to such postop complications as hypotony. Air tamponade is frequently used to treat leaking wounds, as are sub- or transconjunctival polyglactin 910 sutures. Dr. Ryan suggests plain gut tape based, among other reasons, on com fort and low cost.
After describing the technique, Dr. Ryan reports on his 116 cases. Of the first 30 patients, only three received gut sutures, but by the time the last 30 patients were operated on, 18 had been given the gut sutures. Thus, 43 patients of the 116 total received at least one gut suture, with 73 sclerotomies closed. Of the 73 sclerotomies, suture reaction was seen in three tape sites, and there were no cases of endophthalmitis or retinal detachment.
Subscribers to Archives can view a video of this suturing procedure online at www.archophthmol.com.
■ Fifty-year retinoblastoma data. One of the largest retrospective histopathological studies on retinoblastoma yet published appears in the August 2011 issue of the British Journal of Ophthalmology. The study, on 1,234 eyes enucleated for retinoblastoma between 1957 and 2006, was conducted in Beijing.
Among the more important findings was that the prevalence of extraocular tumor extension significantly decreased during the study period. Further, when comparing the first years of the study to the last period, from 2002 to 2006, the frequencies of tumor invasion into the retro-lamina cribrosa tissue and the choroid decreased by 21.5% and 18.6% respectively. The children diagnosed with unilateral disease were significantly older than those with bilateral disease.
It is important to note the limitations of this study despite its size. In addition to the study's retrospective design and the hospital-based nature of the study predisposing to referral bias, the rate of enucleation for retinoblastoma in China up to 2000 was significantly greater than in other industrialized nations. Nevertheless, the Chinese team was able to report significant improvements in the treatment of retinoblastoma over this 50-year period, with implications both for present advances in retinoblastoma treatment worldwide, as well as future treatment specific to China.
■ AMD genetics. Based on findings that AMD is linked to variants in the CFH, ARMS2 and HTRA1 genes, a team of retinal physicians at the University of Pennsylvania's Scheie Eye Institute reviewed 150 cases of wet AMD treated with anti-VEGF agents to review genotypes and determine whether response to anti-VEGF therapy (or lack thereof) was correlated with genetic variables. Their findings were published online in August by Retina.
Fifty-seven patients characterized as negative responders to anti-VEGF and 93 positive responders were analyzed for several single-nucleotide polymorphisms (SNPs) of the three aforementioned genes. However, although the frequency of at-risk alleles was higher in the positive responders (not statistically significant), there were no associations between the studied genotypes and numbers of injections or absolute changes in VA.
The conclusion of the study is that, while it is clear that SNPs in these three genes have been definitely linked to AMD, this linkage does not seem to extend to susceptibility to anti-VEGF treatment. However, the authors do concede that a larger and better-powered study might yield opposite results. RP