January 2008

 

CATARACT/ IOL

 

Incision construction, architecture fight infection


by Rich Daly EyeWorld Contributing Editor

 

 

Among many factors surgeons cite to prevent clear corneal cataract surgery infection, wound construction and architecture are ‘primary’

OCT images support importance of incision construction and wound architecture in preventing infection

Source: I. Howard Fine, M.D.

Cataract surgeons should focus on wound construction and architecture when working to avoid infections among their patients. A special focus on that area of surgery is credited by two senior surgeons as the main reason they have avoided infections for many years.

More surgeons have focused on infection avoidance as some data have indicated an increasing rate of endophthalmitis as clear corneal incisions have become widespread.

I. Howard Fine, M.D., clinical professor, Casey Eye Institute, Oregon Health & Science University, Portland, said many factors can affect infection rates but one area rises to the top.

“The overall picture of clear corneal incisions and infections is one that has to recognize that there are multiple factors for reducing endophthalmitis and that incision construction and architecture are the primary factors in preventing post-op endophthalmitis,” Dr. Fine said.

His conclusion about the importance of incisions came, in part, from the findings of a study he co-authored in a 2007 issue of the Journal of Cataract and Refractive Surgery, which examined the profile of clear corneal cataract incisions in the living eye using optical coherence tomography (OCT). The research concluded that proper clear corneal incision construction resulted in a markedly more stable and safer incision architecture.

Dr. Fine’s research found that the incision is not the straight, flat plane, as has often been drawn. Instead, he and his co-investigators found cataracts wounds are very much an arcuate incision, like tongue and groove paneling.

“We also found that it is much longer than the cord length of the incision. So these incisions are hyper-square, if you think about how wide they are and how long the incision itself is,” he said.

Another finding that supported the use of clear corneal incisions was that the stromal hydration, which helps seal them by forcing the floor of the incision against the roof of the incision and allowing endothelial pumping to go through the incision to the upper reaches of the cornea, lasts longer than previously thought. The OCT study data indicated that the swelling from stromal hydration of the incision lasts for longer than 24 hours.

Wound construction pearls offered

Knowing the benefits of good clear corneal incisions leads to the question of how surgeons can consistently achieve them. Dr. Fine suggests aiming the blade in the plane of the cornea—not perpendicular to the cornea—and going uphill until the cord length is 2 mm, and then entering Descemet’s membrane. That approach provides the best arcuate construction, which is like tongue and groove paneling.

A trapezoidal blade is also suggested to allow enlargement with the same blade through reinsertion and further advancement, although a correct incision will provide “ideal architecture,” regardless of the knife.

Surgeons should avoid stretching an incision by trying to implant a lens through a too small incision. A slightly larger incision is always better than an IOL insertion tearing it, which violates the incision architecture.

Dr. Fine also suggested stabilizing eyes with a fixation ring instead of putting a forceps into the sideport incisons. In addition, he also places viscoelastic material into the anterior chamber through the sideport incision before making the main incision.

“Because an eye that is firm doesn’t distort unpredictably, as a soft eye does, and therefore allows for a more reproducible incision construction and architecture,” he said.

These incision steps, Dr. Fine said, have contributed to an absence of endophthalmitis for more than 11 years and 10,000 cases in his practice.

Likewise, John D. Hunkeler, M.D., clinical professor and former chair, Department of Ophthalmology, University of Kansas School of Medicine, Kansas City, reported the same lack of endophthalmitis in 10,000 cases over 10 years. His cataract incision and paracentesis uses stainless steel blades (BD Medical-Ophthalmic Systems, Franklin Lakes, N.J.) and a cut, blunted Weck cell on the contralateral side for counter-pressure. His primary incision is made with a 2.8-mm bevel-up blade, which provides an almost square cut “for the best wound integrity.”

Infection rates appear to rise

Not all surgeons have been as fortunate as Drs. Fine and Hunkeler. For many years after Dr. Fine introduced clear corneal incisions in 1992, the incidence of infection appeared unchanged. However, within the last 10 years there appears to be an increased incidence of endophthalmitis, although the research remains “inordinately contradictory.”

Some research has found that the use of fourth-generation fluoroquinolone ophthalmic drops provided solid benefits. An April study in the journal Ophthalmology by Moshirfar, et al. of 20,000 cataract patients found the overall rate of endophthalmitis after uncomplicated cataract surgery among such patients was within the range of previously reported rates of endophthalmitis in the literature.

Another study of 16,603 patients in the June issue of the Journal of Cataract & Refractive Surgery, sponsored by the European Society of Cataract and Refractive Surgeons, found the use of topical antibiotics and clear corneal incisions produced higher endophthalmitis rates than peri-operative Levaquin (levofloxacin, OrthoMcNeil, Raritan, N.J.; in Europe, marketed as Tavanic by Sanofi Aventis, Paris) eyedrops and intracameral Ceftin (cefuroxime, GlaxoSmithKline, United Kingdom).

Although several studies have supported the anti-infective benefits of cefuroxime, the unavailability of a pre-packaged single-use appropriate dose in the U.S. requires surgeons here to mix their own at the time of surgery. “That’s fraught with a considerable amount of difficulty and danger of further infection,” Dr. Hunkeler said about self-mixing. However, because U.S. surgeons use topical anesthesia or short-acting local anesthesia and do not have to leave the eye patched they can begin post-op antibiotic drops on the day of surgery.

Further endophthalmitis prophylaxis offered

Antibiotic prophylaxis in wound construction, Dr. Fine said, should extend to sideport incisions for bimanual phacoemulsification. His OCT research indicated that their quality was not as good as their major incisions, so they altered them to take the same care used with the main incisions.

Dr. Fine noted that the transition to clear corneal incisions also has involved a transition to temporal surgery, which requires right-handed surgeons performing coaxial surgery on left eyes to place the sideport incision for their second instrument in the inferior conjunctival cul-de-sac. This situation could raise the question whether sideport incisions are carefully constructed in left eyes.

Another factor in endophthalmitis prophylaxis is use of an effective pre-op antibiotic regime. Pre-loading patients three days pre-op with a fourth-generation fluoroquinolone was also cited by Dr. Hunkeler as a factor in his ongoing clinical success against infection. His preloading, which also includes a nonsteroidal anti-inflammatory drug, also helps him determine which patients will be compliant with his post-op antibiotic regimen.

His antibiotic regimen also includes three doses pre-op on the day of surgery and a dose immediately post-op. His cataract patients also receive antibiotics for one week post-op. Careful preparation of the surgical field should turn the lashes away from the field, cover the meibomian gland orifices with the drape, and apply Betadine (povidone–iodine, Purdue Pharma, Stamford, Conn.) drops to kill transient microbes on the surface.

According to Dr. Fine, a good surgical technique is important to avoid stressing the incision. Phacoemulsification power modulations should avoid heating the incision, and surgeons should not grab the roof of the incision with a toothed forceps or abrate the corneal epithelium, which acts as a fluid barrier during endothelial pumping and allows creation of the seal.

Dr. Hunkeler also urged surgeons to check the lid and conjunctiva pre-operatively for infection and delay surgery until those problems are resolved. Post-op, he examines patients under the slit lamp 10 minutes after surgery to look for unresolved problems, such as wound leaks.

Dr Fine agreed that more surgeons should test for leakage. His practice always applies fluorescein sodium (2%) dye at the end of the procedure, which allows Dr. Fine to document the lack of leakage.

Editors’ note: Dr. Fine has financial interests with Advanced Medical Optics (AMO, Santa Ana, Calif.), Bausch & Lomb (Rochester, N.Y.), and Alcon (Fort Worth, Texas), among others. Dr. Hunkeler has financial interests with AMO, Allergan (Irvine, Calif.), and Bausch & Lomb, among others.

Contact Information

Fine: 541-687-2110, hfine@finemd.com

Hunkeler: 816-931-4733, jhunkeler@hunkeler.com

       
Incision construction, architecture fight infection Incision construction, architecture fight infection
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