October 2009

 

CATARACT/ IOL

 

Evaluating incision leakage


by Matt Young EyeWorld Contributing Editor

   

OCT images support the importance of incision construction and wound architecture Source: I. Howard Fine, M.D.

Research into cataract incision leakage has often focused on the post-op period, when compromised wound integrity can lead to infection. A new study takes a different approach: analyzing incision leakage during phacoemulsification itself, noting that excessive leakage could pose a risk to anterior chamber stability during the procedure. “The anterior chamber can be viewed for all practical purposes as a closed system that is influenced by atmospheric and posterior vitreous pressure,” according to lead study author Sidath E. Liyanage, M.R.C.Ophth., Department of Ophthalmology, Royal Free Hospital, London. “Any incisional fluid loss can adversely affect anterior chamber stability, with potentially severe complications such as posterior capsule rupture and vitreous loss.”

Technically, irrigation fluid should enter the anterior chamber and leave through aspiration, Dr. Liyanage noted. Fluid loss through the incision affects this balance, and the aforementioned complications could follow. In practice, Dr. Liyanage found a very different fluid flow occurring. Large amounts of fluid were lost through a coaxial incision site.

With certain procedural adjustments, however, surgeons may be able to minimize fluid loss through their incisions during cataract surgery and ensure an optimally stable ocular environment.

Cutting down on leakage

Dr. Liyanage analyzed 105 consecutive patients undergoing cataract surgery with a coaxial technique. Mean incision leakage was 127 +/–60 mL. The mean percentage of incision leakage was surprisingly 67% +/–11%, a figure obtained through simple calculation. “Incisional leakage was defined by the difference between the total volume of irrigation fluid used and the volume aspirated by the phacoemulsification machine,” Dr. Liyanage noted. This method was based on certain assumptions but was an appropriate mathematical equation to use, Dr. Liyanage explained. “Based on the fluidics principle that the anterior chamber is a closed system during phacoemulsification, we propose that most fluid loss was due to leakage through the incisions,” Dr. Liyanage reported. “A small amount will be lost when irrigation is running when the phaco tip is outside the eye, but the volume lost via this route is generally minimal.”

Dr. Liyanage considered this loss to be “surprisingly significant” and advised attempts to reduce the amount of incisional leakage. Another study conclusion provided one way to do this. “We found that the loss of fluid was reduced significantly by using the technique of endocapsular prechopping of the nucleus followed by removing the chopper from the eye during segment removal,” Dr. Liyanage reported. “The mean fluid loss through incisions was 75% in operations performed with the chopper in situ throughout the phacoemulsification stage and 59% when the chopper was removed after all segments were chopped.”

Dr. Liyanage explained that incisional leakage could only occur at two coaxial sites: through the main incision or through the side port. “With standard incision widths, the standard main section is self-sealing or otherwise occupied by a soft-sleeved phaco needle, which prevents significant loss,” Dr. Liyanage reported. “Most of this fluid loss occurs via the side ports when an instrument is in situ, and it often goes unnoticed.”

Removing the chopper from the side port incision apparently reduces fluid loss—by 16% in this study, Dr. Liyanage noted. There are trade offs involved in removing the chopper during nucleus removal. “Removing the second instrument from the eye has the potential pitfalls of reduced intraoperative control of the globe (especially with topical anesthesia), nuclear segments, and cortical fragments,” Dr. Liyanage noted. He nonetheless advocated taking steps to reduce incisional leakage during surgery, some of which may involve other considerations as well. “Measures must be taken to minimize incisional fluid loss, which is inversely proportional to anterior chamber stability,” Dr. Liyanage reported. “These measures include proper wound construction and correctly matching the size of instrumentation to the wounds.”

Francis S. Mah, M.D., co-medical director, Charles T. Campbell Ophthalmic Microbiology Laboratory, University of Pittsburgh School of Medicine, Pittsburgh, agrees that a chopper introduced through a side port incision has the ability to cause instability. “If your phaco handpiece is in the main incision and something is in the side port, then there is the possibility that saline or BSS could be coming out of your side port,” Dr. Mah said. He noted there are other factors that cause the wound to become destabilized as well—such as the construction of the side port incision itself. “A larger side port incision may lead to more egress of fluid and therefore less stability,” Dr. Mah said. More egress is also likely with thicker-diameter choppers, he said.

“Most surgeons do not keep an instrument in the paracentesis while sculpting,” Dr. Mah said. “That keeps the anterior chamber solid.” Smaller incisions have also led to better anterior chamber stability, Dr. Mah said. He mentioned that his side port incision is 1.0 mm and his main incision is 2.2 mm.

Editors’ note: Dr. Liyanage has no financial interests related to his comments. Dr. Mah has no financial interests related to his comments.

Contact information

Liyanage: sidath@doctors.net.uk
Mah: 412-647-2211, mahfs@upmc.edu

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