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Although initially introduced for the purpose of facilitating the procedure of 'canaloplasty', the illuminated microcatheter (iTrack 250A, iScience Interventional, Menlo Park, CA) has become an increasingly popular tool for achieving complete cannulation of Schlemm canal during trabeculotomy surgery. While no randomized, prospective study has compared 360-degree trabeculotomy against one goniosurgery for control of congenital glaucoma, a retrospective study suggested that 360-degree suture trabeculotomy, had a higher success than goniotomy.1 Girkin and colleagues present results of a small retrospective clinical series in which they compare the oneyear success of trabeculotomy using the iTrack illuminated flexible microcatheter versus traditional single goniotomy in children with congenital glaucoma. The authors reviewed their cases of surgery (by either goniotomy or circumferential trabeculotomy) for congenital glaucoma over a four-year period, with minimum 12-month follow-up, and noted demographic data, surgical technical success and complications, and one-year intraocular pressure (IOP) results. Reported were results from 24 eyes (20 children), 13 after goniotomy vs. 11 after trabeculotomy. At 12 months post-surgery, both 'unqualified success' (IOP < 21mmHg and > 30% reduction from baseline without medication) and 'qualified success' (same ± medications) was higher in the trabeculotomy than the goniotomy group (83.3 vs. 46.2%, and 91.6% vs. 53.3%, respectively). In the 11 eyes having trabeculotomy, complete 360-degree Schlemm's canal cannulation was achieved in six eyes, while three had 270- and three had 180-degree trabeculotomy. No complications were reported in either surgical group, and prior angle surgery had occurred in six eyes of the total series. Some cases were not primary congenital glaucoma (four eyes total).
iTrack-facilitated trabeculotomy appears to have low complications rates and excellent short-term success in primary infantile glaucoma
Limitations include the non-randomized, retrospective nature of the study, the relatively small numbers and short follow-up time, inclusion of both eyes of each child, inclusion of eyes with prior angle surgery, and inclusion of varied glaucoma types. The eyes were not entered over the same time period, and no details were provided to compare severity of the glaucoma at entry (other than starting IOP). The success reported using goniotomy is quite low compared to the literature, as noted by the authors. In addition, we lack confidence intervals on the Kaplan Meier success curves. It is not clear whether eyes with prior angle surgery had patent clefts at entry, how the iTrack-assisted trabeculotomy clefts differed from the original clefts, and whether longer follow-up might yield different results. Since only half of the eyes receiving trabeculotomy actually had full cannulation of Schlemm's canal, it is not clear how these procedures compare against more traditional trabeculotomy procedures, which also have high success rates reported in many larger, earlier series.2 Limitations notwithstanding, this study confirms several earlier published reports that iTrack-facilitated trabeculotomy appears to have low complications rates and excellent short-term success in primary infantile glaucoma.3 Longer term study of larger series will help determine whether the iTrack actually improves surgical success of trabeculotomy for primary infantile glaucoma.