Wound architecture, size dictate cataract surgery outcomes

Visual, refractive and anatomic outcomes in cataract surgery rely heavily on wound size and architecture. Whether a wound is created with a knife or femtosecond laser, its location, configuration and dimensions affect healing and the potential for complications.

Some surgeons prefer posterior limbal or scleral tunnel incisions, while others favor clear corneal incisions. Some choose to close incisions with glue or sealant rather than sutures. Regardless of location and technique, surgeons strive to minimize surgically induced astigmatism, endophthalmitis and hypotony.

The key to success in cataract surgery, as in any type of surgery, is smaller incisions, according to John A. Hovanesian, MD, FACS, OSN Cataract Surgery Section Editor.

“In cataract incisions, there are a variety of studies that show that less astigmatism results when we have smaller incisions,” Hovanesian said. “Additionally, incisions that are more uniform in shape and size and tend to create a valve-like architecture internally are more likely to self-seal. So, whether using a femtosecond laser, which may offer some repeatability or reproducibility, or a handmade incision, those are really the overarching goals.”

OSN APAO Edition Board Member Amar Agarwal, MS, FRCS, FRCOphth, echoed Hovanesian’s statement.

“The bottom line for any surgery is this: Size of the incision is important. If you are doing a smaller incision, it’s obviously better than a large incision,” Agarwal said. “Whatever incision you do, please be careful. The architecture should be good. You should make a good tunnel so that you don’t have a premature entry into the wound.”

Incision architecture is more important than size in terms of minimizing surgically induced astigmatism, according to Paul H. Ernest, MD.

“Size matters if the geometry is the same, but geometry trumps size,” Ernest said.

Cataract incisions have an impact on refraction, not just anatomy, according to Uday Devgan, MD, FACS, FRCS, OSN Healio.com/Ophthalmology Section Editor.

“In cataract surgery, incisions are very important. They not only give us access to the inside of the eye so we can accomplish our surgery, but they actually have a refractive effect,” Devgan said. “They have an effect on the corneal astigmatism. The larger the incision, the more effect it’s going to have on the astigmatism. This is why there has been a move in the last few years to smaller incisions. A smaller incision seals better and is less likely to need a stitch or other help closing. A small incision is also more astigmatically neutral.”

Surgeon preference, comfort and outcomes are the key factors in choosing wound design, according to Michael A. Saidel, MD.

“In any discussion, it needs to be recognized that the surgeon who is making the wound may prefer to make this wound because of their level of comfort, their experience and their lack of complications,” Saidel said.

“Complications in cataract surgery, thankfully, are very rare. And because they are rare, it’s difficult to make a statistically significant claim regarding wound architecture and risk of complications.”

However, a self-sealing wound is preferable, regardless of architecture, Saidel said.

“As long as the surgeon can create a self-sealing wound, those architectures are clearly superior,” he said.

Blade vs. femtosecond laser

Many experts believe that handmade blade incisions are not as precise as femtosecond laser incisions. According to Hovanesian, femtosecond laser incisions are more reproducible but do not seal better than manual incisions.

A femtosecond laser is not practical for making posterior wounds, Ernest said.

“I use the femtosecond laser a lot. I probably perform around 700 procedures a year,” Ernest said. “I do not use the laser to make my cataract incision, mainly because the laser doesn’t recognize the limbal area and, therefore, it has to be on the corneal area. Now, to the laser’s credit, it will make the architecture precisely the same every time.”

Ernest prefers using a crescent blade to make a linear incision in the posterior limbal area.

“I do it there because there is no sub-Tenon’s space. If you go more posteriorly, you get into the sub-Tenon’s space and risk ballooning of the conjunctiva,” Ernest said.

Ernest uses a crescent blade to dissect the cornea and complete the square configuration. He then uses a 2.2-mm keratome blade to cut through Descemet’s membrane into the anterior chamber, completing the square incision.

“I’ve been doing it this way now for as long as 2.2-mm cartridges have been available,” Ernest said.

Wound architecture and size

Devgan outlined several factors that influence the astigmatic effect of the incision. First, incision width plays a major role.

“That’s why we move toward smaller and smaller incisions. Most surgeons today are using an incision of between 2 mm and 2.8 mm. It is possible to use a slightly smaller incision, but in general, that’s about the range,” Devgan said.

A second important factor is proximity of the incision to the visual axis.

“The more peripheral the incision, the less astigmatic effect it has. That’s one of the reasons why there’s a shift toward using a temporal incision,” Devgan said. “Incisions toward the temple, on the sides, basically end up being the farthest from the visual axis. In fact, if you get two identical incisions made exactly the same, one made temporally and one made superiorly, the temporal incision will only cause half as much astigmatism change because it’s farther from the visual axis.”

Another benefit of a temporal incision is the ability to neutralize part of the against-the-rule astigmatism that is prevalent in many cataract patients. In addition, over time, the cornea has a tendency to shift toward greater degrees of against-the-rule astigmatism in which the axis at 180° becomes steeper, he said.

Incision tunnel length plays a role, with longer tunnels inducing less astigmatism.

“But you can have it too long, and if it’s too long, it actually will make your surgery more difficult because you’re operating through kind of an oarlock,” Devgan said.

An incision with a greater surface area will heal better in the long term, and a three-plane incision may offer more flexibility than one- or two-plane incisions, Devgan said.

“Some people actually make a three-plane incision called a Langerman hinge,” he said. “If you make a deeper groove and then you make the incision a little bit shallower than that, the Langerman hinge allows you to have a little bit more flex and give.”

A two- or three-plane incision can prevent infection and minimize surgically induced astigmatism, Hovanesian said.

“We do know that three-plane incisions, where there’s an initial groove followed by a tunnel and then a third entry point, are a little better sealing than two-plane incisions. And yet both seem to provide very satisfactory results in terms of low rates of infection and creation of astigmatism,” he said.

Agarwal said a two- or three-plane incision is preferable to a straight incision.

“I would like people to go for a three-plane incision or even a two-plane incision rather than a straight entry into the anterior chamber because, with these types of incisions, the wound architecture will go very well,” he said.

Saidel said he prefers a 2.2- to 2.4-mm triplanar square incision.

“Because it’s a three-dimensional wound, what appears to be square on direct examination may actually be longer because of the three dimensions,” he said.

Ernest said a square incision in the posterior limbus best minimizes surgically induced astigmatism.

“Keeping it square is going to give you the lowest amount of [surgically induced astigmatism] rather than having it be rectangular,” he said. “Keeping it in the posterior limbus is going to give you the best healing due to fibroblasts. It’s also going to give you less flattening of the cornea incision site, so you’re not creating astigmatism through your incision. And you’re now going to be able to take on low amounts of corneal astigmatism using low-power toric lenses and femtosecond treatment for astigmatism.”

Square wounds are also less prone to leakage under pressure than rectangular wounds, Ernest said.

“If you make the wound square, where the width and the tunnel length are exactly the same, it will not leak at any intraocular pressure, no matter how much external force you apply,” Ernest said.

Posterior limbal incisions seal within 7 days, while clear corneal incisions take at least 30 days to seal, Ernest said, citing results of a study he and colleagues conducted.

“The corneal cells, called keratocytes, had to undergo a metaplasia and become fibroblasts, and that took over 30 days to happen,” he said.

Devgan takes a similar approach, with care taken to slightly nick the limbal blood vessels to ensure stronger long-term sealing of the incisions.

Wound extension and manipulation

Phacoemulsification can be performed through incisions smaller than 1 mm. In phakonit, developed by Agarwal, bimanual phacoemulsification is performed with 0.9-mm phaco needles and irrigating choppers. Microphakonit involves bimanual phacoemulsification with 0.7-mm tip instruments.

Both phakonit and microphakonit involve a side-port incision and a main incision that is extended to allow IOL insertion.

In a study published in the Journal of Cataract and Refractive Surgery in 2008, Agarwal and colleagues analyzed wound architecture in 700-µm microphakonit surgery. Five eyes underwent surgery with a 700-µm phaco tip with no IOL insertion. Seven eyes had surgery with IOL implantation after the main-port incision was extended with a 2.8-mm keratome.

Wound healing and resolution of coaptation loss or endothelial realignment occurred earlier in wounds that were not extended.

Agarwal said there is a need for IOLs that can be inserted through incisions smaller than 1 mm.

“I don’t have an intraocular lens which is going through a sub-1 mm incision. That is the biggest disadvantage right now,” he said. “The surgery is through a sub-1-mm incision, but the IOL implantation is still larger.”

Agarwal noted that when two sub-1-mm incisions are placed 90° apart, astigmatism created by one wound is neutralized by the other wound.

“Normally, in coaxial phaco, one incision is large, 3 mm. The second is for a chopper, which is small. So, there is an imbalance between the two sides,” Agarwal said. “But if I have two equal sub-1-mm incisions 90° apart, what will happen will be that any astigmatism which one creates, the other will neutralize.”

Saidel said that smaller incisions do not necessarily reduce surgically induced astigmatism.

“The reason for that nuance is that, the smaller the wound is, the less astigmatism it will induce based on the wound alone,” Saidel said. “However, what happens inside the wound matters a great deal. For example, if a lens is forced through a wound that is too small, it may cause some wound tearing or wound gape and induce astigmatism that otherwise would not have been created with a larger wound.”

Smaller wounds that are not manipulated induce less astigmatism, Saidel said.

“Smaller wounds where there’s a lot of manipulation of the wound, perhaps causing a wound tear or even a phaco wound burn or any number of complications, will induce astigmatism, sometimes in an unpredictable fashion,” he said. “That is to say that making larger wounds is not necessarily going to induce more astigmatism. It’s a combination of the size of the wound and what you do in the wound.”

Sutures vs. sealant

The advent of clear corneal incisions saw an increase in postoperative endophthalmitis. A study published in Ophthalmology in 2003 explored a possible link between sutureless clear corneal incisions, poor wound apposition and subsequent risk of endophthalmitis. McDonnell and colleagues attributed the development of endophthalmitis to a transient reduction in IOP that may lead to gaping of the incision and admission of fluid into the anterior chamber.

Liquid polymer corneal sealants are a good substitute for sutures in cases in which wound leakage is suspected or identified, Hovanesian said.

“For many of the cases where we now use sutures, it would probably be a better fit,” he said. “Not all incisions are created equal. Some are not as well constructed as others. Some eyes are not as prone to fast healing as others.”

Sutures are time-consuming, may cause irritation for patients and may allow infection into the wound, Hovanesian said, noting that testing incisions with compressive force may cause leakage.

Sutures are called for in cases in which wound healing may take longer than 5 days, Hovanesian said.

“Sealants last about 5 days or so, and then they’re gone. If you need holding power for long, then a suture is your best bet. If you need it during the usual period of concern, which is 3 to 5 days, then a sealant is more than adequate,” he said.

Hovanesian said a sealant such as ReSure (Ocular Therapeutix) can be used on any type of cataract incision.

Sealants are not needed to seal posterior limbal incisions, Ernest said.

“If you make your architecture a little more posterior, you don’t need ReSure to seal a clear corneal incision,” he said. “But I think for other techniques like DSAEK and other things where you can’t afford to have any kind of leak or shallowing, ReSure is great. I don’t need it with the placement of my incision and the architecture that I use.”

Devgan said stromal hydration can be used to help temporarily close wounds, but any persistent leakage of an incision is best addressed with a suture.

“The hydration kind of swells the stroma of those incisions, which makes it seal tighter,” Devgan said.

However, stromal hydration is not a long-term method of wound closure.

“What actually keeps the incision closed in the long term is the corneal endothelial pump function. That’s the same thing that keeps a LASIK flap stuck on the eye without any stitches,” Devgan said.

Devgan said that sealants have a role, but they should be used only on dry wounds and they do not eliminate the need for sutures.

“Glue is not going to stick to anything wet. If your incision is absolutely dry, the sealant works pretty well. But if your incision is actively, even minimally, leaking, you’re best off putting a suture in,” Devgan said.

Sclerotomies

Wound closure is critical in sclerotomy, and a sutured corneal wound may have an impact on future sclerotomy, according to Seenu M. Hariprasad, MD, OSN Retina/Vitreous Board Member.

As with clear corneal incisions, polyethylene glycol-based sealants have been shown to be useful in closing sclerotomies performed in pars plana vitrectomy. In a cadaveric eye study published in 2011, a polyethylene glycol hydrogel polymer sealant significantly increased leak pressure among eyes that underwent 23-gauge sclerotomies; the sealant was found to be equivalent to sutured 20-gauge incisions, Hariprasad and colleagues said.

In another study, Hariprasad and colleagues showed that a polyethylene glycol-based hydrogel bandage was successful in closing sutureless sclerotomies, providing a barrier to India ink ingress into wounds with various IOP manipulations.

“These implications in the surgical setting would be very useful in eyes that have thin sclera, repeat vitrectomy and leaking wounds,” Hariprasad said. “In cataract surgery cases where vitrectomy surgery is anticipated, such as retained lens fragment cases, corneal closure with a sealant would be very useful to the retina surgeon as we apply a lot of pressure when inserting cannulas into the eye and we often perform depression during our surgery, which distorts the corneal wound and can cause leakage of anterior chamber fluid.”

Hovanesian said that suturing a corneal wound generally has a minimal effect on future sclerotomy.

“I don’t think it has a great impact on retina specialists,” he said. “For a suture to affect the retina specialist’s view, I would think it would need to be right in the visual axis or causing so much distortion that the patient would complain about it. Usually, it’s not the retina specialist’s view that guides our decisions on what to do with sutures.” – by Matt Hasson

References:

Agarwal A, et al. J Cataract Refract Surg. 2008;doi:10.1016/j.jcrs.2008.05.027.

Calladine D, et al. J Cataract Refract Surg. 2007;doi:10.1016/j.jcrs.2007.04.011.

Hariprasad SM, et al. Arch Ophthalmol. 2011;doi:10.1001/archophthalmol.2011.13.

McDonnell PJ, et al. Ophthalmology. 2003;doi:10.1016/S0161-6420(03)00733-4.

Singh A, et al. Am J Ophthalmol. 2010;doi:10.1016/j.ajo.2010.04.002.

For more information:

Amar Agarwal, MS, FRCS, FRCOphth, can be reached at Dr. Agarwal’s Eye Hospital and Eye Research Centre, 19 Cathedral Road, Chennai-600 086, India; 91-44-28116233; email: dragarwal@vsnl.com.

Uday Devgan, MD, FACS, FRCS, can be reached at Devgan Eye, 11600 Wilshire Blvd., Suite 200, Los Angeles, CA 90025; 800-337-1969; email: devgan@gmail.com.

Paul H. Ernest, MD, can be reached at TLC Eye Care of Michigan, 1116 W. Ganson St., Jackson, MI 49202-4240; 517-782-9436; email: paul.ernest@tlcvision.com.

Seenu M. Hariprasad, MD, can be reached at Department of Ophthalmology and Visual Science, University of Chicago, 5841 S. Maryland Ave., MC 2114, Chicago, IL 60637; 773-795-1326; email: retina@uchicago.edu.

John A. Hovanesian, MD, FACS, can be reached at Harvard Eye Associates, 24401 Calle De La Louisa, Suite 300, Laguna Hills, CA 92653; 949-951-2020; email: johnhova@gmail.com.

Michael A. Saidel, MD, can be reached at Cornea Service, University of Chicago, 5841 S. Maryland, MC 2114, Chicago, IL 60637; 773-702-3937; email: msaidel@bsd.uchicago.edu.

Disclosures: Agarwal has no relevant financial disclosures. Devgan has served as a consultant for i-Therapeutix (Ocular Therapeutix) and is an active consultant for Alcon. Ernest is a consultant for Alcon. Hariprasad has been a consultant for Alcon, Allergan, Genentech, Baxter, OD-OS, Ocular Therapeutix, Optos and Bayer and has participated in speakers bureaus for Alcon, Allergan and Genentech. Hovanesian is a consultant for Abbott Medical Optics, Bausch + Lomb and Ocular Therapeutix and has a small equity interest in Ocular Therapeutix. Saidel is on the speakers bureaus of Alcon and Bausch + Lomb.

 

Do you prefer sutures or sealant to close a clear corneal incision in a high-risk case?

Sutures prevent leaks and damage

Having experience with incisions such as femtosecond, clear corneal, scleral tunnel, radial transverse, 8-mm limbal and von Graefe, along with sealants, I can speak from the long-term perspective. There is no doubt which tools I would pull from my surgical armamentarium for an eye that was about to sustain the possibility of extreme pressure and distortion: sutures. I did not always feel this way nor will I in the future. However, there is nothing as strong as a well-placed individual 10-nylon suture closure to fully secure a wound.

Don’t get me wrong: For well-opposed shelving, 2-mm clear corneal incision sutures can be a problem. A wound of that size and composition is best left alone. This is even more true for the perfectly constructed and controlled femtosecond clear corneal incision I find with our laser platform. I am a big fan of sealant, but it is more about leaky wounds that might suck in debris from the tear film than about secure closure. Using sealant is like trying to seal a leaky tire by putting your palm over the leak. An internal patch will self-seal with far more strength. Sealant (ReSure, Ocular Therapeutix) is needed far more commonly than we believe. Until there is something that truly binds the wound, I will stick (no pun intended) with sutures, which not only close the wound but also prevent leaks and damage from torsion and high pressures. There is no reason not to add sealant over a sutured wound. It will provide further protection, akin to adding a belt when wearing suspenders.

Steven B. Siepser, MD, FACS, is an OSN Cataract Surgery Board Member. Disclosure: Siepser has no relevant financial disclosures.

Sealant secures incisions

Sealant is a viable alternative to sutures in complex IOL cases or in cases in which additional surgery may be required, given normal small-incision clear corneal wound size and architecture are maintained. Although corneal sutures have been standard of care in cases such as these, data from routine cataract surgery support decreased wound leakage when compared with suture. We know the risk of endophthalmitis is increased in complex cases requiring vitrectomy, so in theory risk may be minimized with a well-sealed wound. It stands to reason that based on the data supporting superiority of sealant to suture in routine cases, it would apply to complex cases as well. Furthermore, potential advantages of sealant to suture in complex cases would be less pressure applied to the lips of the corneal wound compared with placing a suture. This may be beneficial in complex cases with poor iris tone, sulcus or secondary IOL placement, or vitreous loss in which chamber fluctuation due to wound manipulation can lead to iris or vitreous prolapse or IOL malposition.

George O. Waring IV, MD, FACS, is director of refractive surgery and assistant professor of ophthalmology, Medical University of South Carolina. Disclosure: Waring has no relevant financial disclosures.