Oblique cannula insertion may lower postoperative hypotony risk

Small-gauge vitrectomy surgery has increased in popularity among vitreoretinal surgeons over the past six years. The institution of this new technology has brought new challenges. Wound leakage, hypotony and postoperative endophthalmitis have been reported at higher rates than with standard, 20-gauge vitrectomy surgery with sutured scleral wound closure. Several scleral entry techniques have been reported to decrease these problems. The authors of the current article describe their experience using oblique entry of the 25-gauge trocar/cannula system to potentially reduce postoperative hypotony.

They conducted a prospective, consecutive interventional series of 55 eyes that underwent 25-gauge pars plana vitrectomy with oblique cannula insertion. IOP measurements were taken preoperatively and one day and one week postoperatively and compared with data from a historical case series of 40 consecutive eyes that had undergone 25-gauge surgery with direct trocar/cannula insertion.

There was only one case (1.8 percent) of hypotony, which the authors defined as IOP of 5 mmHg or less, in the oblique insertion group one day after surgery compared with four hypotony cases (10 percent) in the direct insertion group. Preoperative and postoperative IOP were similar in the oblique insertion group, whereas postoperative IOP was significantly lower in the direct insertion group compared to preoperative IOP measurements. All hypotony cases spontaneously resolved within one week.

The concept of sutureless wound construction for vitrectomy continues to evolve. This article supports the idea that a shelved incision may reduce unwanted hypotony, which may be increasing endophthalmitis risk. Vitreoretinal surgeons should consider making this relatively simple modification to their small-gauge surgery technique if they have not already done so.

Financial Disclosures
Dr. Jumper receives grant support from Alcon Laboratories, Inc., Bausch & Lomb Surgical, Eyetech (OSI), Genentech, Inc., Novartis Pharmaceuticals Corp., Allergan, Inc., and Ista Pharmaceuticals. Dr. Jumper is also a consultant to and receives lecture fees from Genentech.