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Is the risk of endophthalmitis too high in sutureless transconjunctival vitrectomy?
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Yes, even now there is not enough evidence to prove the opposite.
 Bill Aylward |
In 2005 I reported the first case of endophthalmitis following 25-gauge vitrectomy. Since then, several authors with large series have suggested that the risk is up to 11 or 12 times higher than that of 20-gauge.
Even with this increased rate, endophthalmitis remains a rare complication, but to me it is still too high a price to pay for the fairly minimum advantages of 25-gauge.
A lot of the advantages of 25-gauge that are usually promoted are more for the surgeon than for the patient. The only advantage so far proven for the patient is increased comfort, but the absolute degree of discomfort with 20-gauge is very small. The difference may be statistically significant, but it is not clinically significant.
There are at least three theoretical reasons for the increased rate of endophthalmitis in 25-gauge vitrectomy: You are leaving the wound open, the flow of fluid is much less and more vitreous is left in the eye. The other side of the debate will say the studies that sounded the alarm on endophthalmitis are fairly old, that now techniques have changed and endophthalmitis risk is less. If problems remain, they will say they can be fixed. They might be right, but it is the onus of the proponent to prove that now the technique is safe.
There is an interesting contrast between surgical techniques and drugs. Before you introduce a new drug you need massive trials. But complete changes in surgery, such as in vitrectomy, are often introduced without proving safety.
It looks as if 23-gauge may not have the same increased risk. However, it is still too soon to provide convincing evidence of this. If it is proven to be as safe as 20-gauge, then it will be reasonable to adopt it, but I believe that 25-gauge will eventually fade out.
Twenty-gauge vitrectomy is a well-established, very safe technique that has been around essentially unchanged for almost 40 years. Personally, I don’t believe I should change this approach before the safety of the new approaches is proven.
- Bill Aylward, MD, is a consultant vitreoretinal surgeon and medical director at Moorfields Eye Hospital in London.
Not if a thorough vitreous removal is performed.
 Akiko Tominaga |
Microincisional vitrectomy procedures might indeed carry a higher risk of endophthalmitis. However, for a long time we have unjustly placed the blame for this only on sutureless incisions, assuming that contamination was mostly due to bacteria entering the globe through imperfectly sealed wounds after surgery. We have also assumed that better wound management, through oblique incisions and conjunctival displacement, might be the answer. In this respect, a truly self-sealing incision such as in 27-gauge microincision vitrectomy surgery should theoretically lower the risk of endophthalmitis to near zero.
In a study we did with Dr. Oshima in Osaka, we tested vitreous samples for bacteria at the beginning and end of 25-gauge and 20-gauge procedures and found that almost 15% to 20% of the samples were positive for bacteria just after introduction of the trocar/cannula in the globe. The same was not found with the 20-gauge system, even though prophylaxis with antibiotics and povidone iodine had been applied in both groups. This suggests when we do transconjunctival surgery, we may inoculate the bacteria directly from the conjunctiva into the eye with our instruments, no matter how small the gauge is, if you do a transconjunctival procedure, you introduce bacteria into the eye. The 20-gauge blade has no direct contact with the conjunctiva, and this may explain the much lower (2.4%) contamination rate.
However, in our study we also found that if you do an extensive vitreous removal and compare the samples at the end of surgery, there is no significant difference between 20-gauge and 25-gauge. Bacteria are removed away from the vitreous cavity during vitrectomy. If you do a small amount of vitrectomy, you may have a higher chance to leave the bacteria inside the eye. So, we should reconsider the issue of how to prevent postoperative endophthalmitis in transconjunctival vitrectomy. What makes the procedure potentially less at risk for bacterial contamination is not only the incision design and gauge size for self-sealing wounds, but also the amount of vitreous you remove during surgery.
- Akiko Tominaga, MD, is in the Department of Ophthalmology, Osaka University Graduate School of Medicine, Japan.