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Refractive Surgery | May 2014

Meticulous Incision Construction

Pointers for creating main and sideport incisions for cataract surgery.

Jorge L. Alió, Md, PhD

Following selection of a case for cataract surgery, my first priority is to determine how I can obtain a perfect outcome with quick visual recovery. Among other ancillary elements of the preoperative clinical workup, I base my decision for incision location on the patient’s anterior corneal topography. I always sit at the 12-o’clock position and place two 1-mm incisions in the oblique quadrants. I also mark the steepest meridian of the corneal topography, as this is where I will place the main incision for the IOL at the time of implantation ((see IOL Insertion and Closure, pg 71).


Careful incision construction implies a perfect understanding of the anatomy of the specific eye undergoing surgery. A few factors should be taken into account. An unusually thin or thick cornea often makes the incision shorter or longer than intended, respectively, thus affecting later wound closure, increasing or decreasing the incision’s effect on astigmatism, and sometimes reducing visibility during surgery. The limbal anatomy may have been impaired by previous surgery, trauma, or disease. Localized corneal thinning can lead to incision gaping and should suggest selecting a different location for incision construction. A shallow anterior chamber or risk of a floppy iris requires a more central corneal incision to avoid iris prolapse.

In standard eyes, I prefer a near-to-clear corneal incision: that is, at the limbus, near clear cornea (Figure 1). Although an incision at this location will produce some bleeding and conjunctival chemosis, it is expected to heal faster than a clear corneal incision. My incision is 2.2 mm wide and created with a calibrated bevel-down steel blade. As this incision induces about 0.25 D of corneal astigmatism, it is not necessary to locate it at the steepest topographic meridian. Only in oval corneas do I abandon the 11-o’clock meridian and move the incision temporally.

My sideport incision (about 1 mm wide) is located about 90° apart from the main incision and is created with a 22.5° blade. I prefer this blade to one that is 15° or 30º; the former is too narrow and may touch and cut the anterior capsule, and the latter is too wide and may inadvertently enlarge the incision, especially if the patient’s eye moves.

To stabilize the eye, I use a cotton swab instead of forceps (Figure 1) because it is not felt by the patient. The pressure exerted on the eye must be released as the blade enters the anterior chamber to avoid aqueous humor exit. In my opinion, a meticulously constructed incision will not lose aqueous humor.


When I operate, I aim to do as little as possible. That is why, when a colleague commented on a well-respected surgeon’s successful yet slow performance, saying, “He does not do anything but sit there staring at the cataract long enough for it to get so embarrassed it decides to get out by itself,” I could only laugh. My colleague’s slightly humorous description of an atraumatic surgery may have been accurate, but this should be what every surgeon aims for.

We sometimes talk about and admire fast surgery, but I prefer to think only in terms of efficiency. For me, the goal is to conclude each surgery with as few movements as possible. This process begins with incision creation.

The concept of microincision cataract surgery (MICS) is to use incisions of less than 2 mm in order to induce minimal (if any) astigmatism and, more important, to increase anterior chamber stability by minimizing fluid leakage from the anterior chamber. I prefer a coaxial MICS technique, and I use the same 1.8-mm steel blade for both the sideport and main tunnel incisions. This tool is sharp enough to allow me to create the incisions with little to no counterforce. If gentle counterforce is necessary, I place the back end of the capsulorrhexis microforceps handle in my nondominant hand, just touching the sclera opposite the incision.

For optimal wound tightness after surgery, a tri-planar architecture is used for both incisions. The sideport is made as small as possible; as soon as I can see the tip of the blade glitter inside Descemet membrane, I retract the knife (Figure 2). The shape of the single-beveled slit knife leaves a wider outer opening of the sideport, making it easier to insert and move the instruments.

I create the phaco tunnel 90º away from the sideport. When the blade exits the incision, I make the smallest movement to one side in order to ensure that the outer opening is 0.1 to 0.2 mm wider than the rest of the incision. This facilitates the introduction of phaco and I/A tips. The rest of the tunnel remains at 1.8 mm, thus optimizing fluidics.


At the end of surgery, I like to have a perfect self-sealing incision. Because precalibrated knives sometimes create an incision size larger or smaller than predicted, I use calipers to measure the incision (Figure 3).

My routine technique is MICS, performed with a 21-gauge phaco tip. To use this tip most effectively and ensure that the anterior chamber is stable during the entire procedure, I construct a 1.8-mm incision in two steps. In the first, I approach the corneal limbus from the top, and then I enter the anterior chamber by directing the blade toward the center (Figure 4). The length of the tunnel must be one-third or one-quarter of the incision size. If the tunnel is too long, insertion of the phaco tip can create corneal folds and lead to difficult phacoemulsification; if the incision is too short, it can decrease the self-sealing effect after surgery.


Before I get into incision creation, I would like to share my surgical preparatory process. At our center, we use povidone-iodine for preoperative disinfection of the surgical field exclusively. The conjunctival sac is irrigated with povidone-iodine 5%, and the lid margins and skin are scrubbed and wiped with separate cotton tip applicators soaked with the same solution. The solution is then allowed to dry, providing sufficient exposure time.

A drape with integrated adhesive foil is pressed firmly over the widely opened lid fissure, with the lashes reflected over the lid skin; when the foil is incised in the middle of the lid fissure, two flaps are generated, and these can be wrapped around the lid margins.

This process is the best available combination of measures for preventing contamination of the surgical field, and it has near-unanimous international acceptance and practice. On the other hand, perioperative antibiotic regimens have, especially in the recent past, been shown to cause more bacterial resistance than infection prophylaxis. With our current knowledge base, there is no rationale for forensic panic-driven antibiotic use perioperatively.

My preferred incision is posterior limbal. The argument for this location has been discussed extensively, and adequate argumentation is beyond the scope of this article. However, Paul H. Ernest, MD, has researched this topic extensively and exhaustively; we summarized the arguments together almost 2 decades ago.1

I prefer a temporal location for the posterior limbal incision. Here, the conjunctiva fixa—where conjunctiva, Tenon capsule, and episclera are fused—is usually relatively wide, so that the subconjunctival space cannot be opened with the incision. Locating the incision here prevents irrigation fluid from leaking into the subconjunctival space and subsequent conjunctival ballooning, the only potential disadvantages of the posterior limbal incision location.

As I perform it, a posterior limbal incision created temporally does not induce more than 0.25 D of astigmatism. Therefore, I have no major incentive to place this incision in the steep meridian. I will do so, however, in eyes with no more than 0.75 D of with-the-rule (WTR) astigmatism— if the patient wishes—because superior incisions, by default, are closer to the optical center of the cornea than temporal incisions and there is almost no coniunctiva fixa. In this position, the incision will be less posterior than with a temporal location and, therefore, less square. This may reduce the WTR astigmatism by approximately 0.25 to 0.50 D, but not reliably. Any reliable and meaningful astigmatism correction requires a toric IOL and, for that matter, a reliably astigmatically neutral incision.

Finally, I perform an old-fashioned stepped incision, not just a paracentesis, for optimal apposition and self-sealing. Paracenteses are performed between 80° and 70° to either side of the main incision.

  1. Ernest PH, Neuhann T. Posterior limbal incision. J Cataract Refract Surg. 1996;22:78-84.


In all patients, I prefer to perform a temporal limbal incision in three steps. The stability and integrity of such an incision is essential to achieve rapid postoperative recovery. Compared with a clear corneal incision, a limbal incision heals faster (6 days vs 6 weeks),1 and it does not leave a scar. To ensure reproducibility, I use a special diamond knife that, if the precise dimensions are known, allows meticulous incision construction in every case. Assuming that an angled Zaldivar trapezoidal knife is used, the length of the blade will be 3 mm, with a width of 0.7 mm at the tip and 1.2 mm at the base. Below is a step-by-step description of my incision-creation technique.

Step No. 1. A 0.7-mm vertical incision is made using the tip of the trapezoidal knife, following the natural curve of the limbus for about 3 mm; the diamond blade allows both sizes. Even if the true opening of the temporal limbal incision is only 2.4 mm, I prefer to have a longer precut of about 3 mm in order to avoid radial tearing of the wound edge during phacoemulsification or IOL implantation.

Step No. 2. This step is the horizontal preparation of the cut, namely the pocket. Ideally it should be 1.5 mm long (requiring exactly half the length of the diamond blade) before sinking the tip of the knife in toward the anterior chamber to open it.

Step No. 3. The internal incision is increased to 2.4 mm parallel to the limbus. This is easy to reproduce, as the base width of the diamond blade is 1.2 mm. The double width at the posterior end of the diamond blade permits an incision of exactly 2.4 mm.

The resulting incision, best visualized with corneal optical coherence tomography, will be similar to an incision created with a femtosecond laser.


For me, a strong, safe wound that does not require stromal hydration at the end of surgery is condition sine qua non.

I prefer a superior wound with a two-step configuration. First, I pressurize the eye with an ophthalmic viscosurgical device (OVD), injected through a sideport incision prior to constructing the main incision. This always renders the eye with appropriate hardness to create a perfect incision. After an approximately half-depth near-clear corneal groove, I create a 1.5-mm tunnel with a single-bevel knife, bevel-up, which provides the best control for the exact tunnel length. Keeping the entire knife against the tunnel roof during cutting prevents it from early entry into the anterior chamber, inadvertently creating a short incision.

With this technique, and by not stretching the incision during IOL injection, I rarely have to hydrate the incision to obtain a watertight wound. I can even press on to the posterior wound lip without any fluid egress.


I prefer to use a temporal approach for microcoaxial phacoemulsification. I make sure that the head and eye are aligned parallel to the microscope eyepiece.

I use a 1-mm angled dual-bevel slit knife to make a paracentesis, as it is compatible with the width of the Grieshaber I/A handpiece (Alcon), thus preventing a mismatch that could lead to a leaky or an overtight incision. The angle on the knife makes it easy to enter the anterior chamber parallel to the iris plane. The knife is placed just anterior to the vascular arcades, 3 clock hours away from the proposed site of the main incision. Once the widest part of the keratome enters the internal entry site, the keratome is removed via the same track without making a sidecut for enlargement. I first inject 0.1 mL of preservative-free intracameral lidocaine 1%, keeping the cannula in the internal entry. Care is taken not to point the fluid toward the iris, pupil, or endothelium.

Using the Arshinoff soft-shell technique, the anterior chamber is partially filled with Viscoat (Alcon) close to the endothelium and with Provisc (Alcon) over the central capsule, so that it uniformly pastes Viscoat to the endothelium. After the anterior chamber is filled with OVD, the risk of anterior chamber collapse leading to inadvertent anterior capsule split is minimized.

A second paracentesis is made diagonally opposite to the first to facilitate chopping action; placing it closer than 3 clock hours from the main incision may make maneuvers awkward for the surgeon. Finally, a single-plane, temporal, clear corneal incision is made with a 2.2-mm keratome. The eye is rotated nasally by introducing the spatula, held in the nondominant hand, through the second paracentesis. The keratome is placed just anterior to the conjunctival vascular arcades, and the tip is introduced so that it reaches two-thirds stromal thickness. The eye is then held in place firmly with the spatula while the keratome travels parallel to the corneal dome for approximately 1.5 mm. The wrist holding the keratome is then realigned (ie, lifted) so that the blade enters parallel to the iris plane.