The increasing trend towards microincision surgery is evident across several branches of ophthalmology, vitrectomy surgery included. As with most evolutionary routes, the transition to minimally invasive vitrectomy surgery (MIVS) has not been a smooth one, with new techniques and instruments enjoying their fair share of bad press in recent years.

Notwithstanding this, the popularity of MIVS is on the up; as instrument design has become more refined, so too has the surgical technique. Today, the popularity of 25 G vitrectomy surgery is at its highest level yet and is still rising. For example, a survey conducted by the American Society of Retina Specialists found that 70% of US surgeons used 25 G technology in 2007.¹ In contrast, just three years earlier, 70% of surgeons had claimed never to have tried the technique.² This surge in interest has, however, also been accompanied by a rise in postoperative complications, such as hypotony, choroidal detachment and an increased risk of endophthalmitis.

Endophthalmitis risk too high to ignore

"We published a study in December 2007, which showed the risk of endophthalmitis is 12.4 times greater with sutureless 25 G surgery when compared with sutured 20 G surgery,³ " said Dr Richard Kaiser from the Retina Service of Wills Eye Institute, Philadelphia, US. Dr Kaiser's findings were based on a review of the records of 8601 surgeries (20 G cases = 5498; 25 G cases = 3103) performed at a single institute between 1 January 2004 and 1 September 2006.

Having read similar reports elsewhere, Dr Kaiser set up the Micro-Surgical Safety Task Force, the aim of the team being to develop a set of recommendations to attempt to reduce the seemingly higher rate of endophthalmitis associated with 25 G vitrectomy. "The task force did not intend to come up with the solution to eliminating all risks associated with 25 G surgery but, between the members, there are a lot of years of experience," remarked Dr Kaiser. The team is comprised of 12 experienced retina surgeons, including George Williams, Antonio Capone, Robert Avery, Harry Flynn, and Ingrid Scott.

According to Dr Kaiser, the answer does not lie in the instrumentation; rather, it lies in the surgical technique.

"Before we put together a list of recommendations, we met several times, for hours at a time. We analyzed the technique in great detail to see if we could identify steps that could be improved or altered in order to reduce the risk of endophthalmitis," said Dr Kaiser.

The recommendations

The team developed recommendations. The following are some of the highlights:

• Lidocaine gel should be removed completely so that 10% povidone iodine (Betadine) can then be applied directly to the ocular surface.
• For the entry wound, a cotton tip should be used to displace the conjunctiva, thus facilitating displacement without causing microholes.
• An angled incision is recommended instead of a straight incision for improved wound closure and for maintaining the initial postoperative IOP.
• At the end of surgery, vitreous incarceration of the wound must be minimized. Several techniques were suggested to assist with this, such as using a light pipe to push the vitreous gel back into the eyes through the trocar, and then sliding the trocar up the shaft of the light pipe. This technique mechanically places the vitreous back in the eye and avoids creating a vacuum which would ordinarily pull vitreous into the wound. This technique tries to ensure that vitreous remains out of the wound. The team also recommended spending some time at this point to examine and massage the wound with a cotton tip or muscle hook to stimulate vitreous retraction back into the eye.
• An air-fluid exchange is recommended at the end of surgery; this helps to maintain a more normal postoperative IOP and it tamponades the wound better.
• If there is any doubt that the wound integrity is breached, the team recommends adding a single suture; it is quick to perform and well tolerated by the patient.