Dr. Kershner has no financial or proprietary interest in any of the techniques or instruments described in this article.

Introduction

Lens extraction with the implantation of an IOL is the most commonly performed refractive procedure in the world today. Since the invention of the IOL by the late Sir Harold Ridley in 1949, lens implantation has been the primary correction of the most common refractive error, aphakia, which occurs as a result of cataract extraction. In 1995, I published my results on the technique of clear corneal cataract surgery with the simultaneous correction of myopia, hyperopia, and astigmatism. The results then, as today, demonstrated that we could do a good job of improving patients’ visual acuity with the cataract procedure. Today, cataract surgery is looked upon more often as a refractive procedure that is used to improve preexisting refractive error and optimize uncorrected visual acuity than it is used solely to treat a clouded crystalline lens.

The increasing acceptance of refractive procedures to eliminate or reduce the need for spectacle and contact lens correction for patients with ametropia first gained acceptance with the radial keratotomy (RK) technique of the late S. N. Fyodorov of Moscow, Russia. In the early 1990s, the development of the excimer laser enabled surgeons to correct a larger array of refractive errors. Used in combination with the automated keratome to create a corneal flap under which a small layer of cornea is removed by the laser, laser in situ keratomileusis (LASIK) has gained in popularity over the past decade. The difficulty of using a mechanical device to create a consistent corneal flap and the limitations of removing corneal tissue without compromising the corneal integrity has lead surgeons to embrace an additional approach to the correction of high orders of refractive error. Today’s cataract procedure with IOL implantation can fill the need. Much work has been undertaken on the use of refractive implantable lenses for cataract surgery and now for phakic refractive correction, either in the anterior chamber, iris supported, or in the posterior chamber. This approach has held promise also for the correction of presbyopia, the natural loss of accommodative ability that comes with age.

The application of laser technology and implantable lenses has fallen short of expectations for patients who have high degrees of refractive error. In addition, patients who have corneal abnormalities, such as irregularity, keratoconus, corneal dystrophies, or scars, may be ineligible for corneal surgery. What do we offer those for whom corneal alteration procedures cannot be pursued? For these patients and those for whom the visual quality of an IOL with the simultaneous correction of refractive error may prove superior, the choice of lens surgery may be a more acceptable alternative.

Today’s cataract procedure has enabled the use of small (less than 3 mm) incisions. With the development of laser phaco, phakonit, and newer technologies, these incisions are rapidly decreasing to 1 mm or less. These small microincisions are placed through the clear corneal architecture precluding the need for conjunctival dissection, cautery, sutures, injection anesthetics, bandaging, and restriction of normal postoperative activities. Microincision cataract surgery has all but eliminated the complications of wound leak, uveal prolapse, and surgically induced astigmatism. These advances have paved the way for faster, more efficient surgery, with less instrumentation, less intervention, and faster visual recovery for the patient.

Slide 1

In 1994, I coined the term keratolenticuloplasty (KLP) to better reflect what cataract surgeons were accomplishing with the simultaneous reshaping of the cornea by tailoring the incision (Slide 1) and replacing the abnormal lenticular architecture with an artificial IOL to correct refractive error. Smaller incision surgery has motivated the IOL industry to develop newer intraocular materials to replace the rigid PMMA lenses of yesterday with newer acrylic, thermoplastic, and hydrogel materials that can be injected through microincisions.

Slide 2

Slide 3

Coincident with these advances in microincision cataract surgery has been the increasingly superior visual results that patients have achieved. Myopia and hyperopia are eliminated with the IOL and astigmatism can be corrected with the use of a toric IOL with or without arcuate keratotomy incisions (the so-called limbal or peripheral corneal relaxing incisions). Smaller incision surgery has meant better results for the patient and less complications and worry for the surgeon.

Slide 4

I have developed and adhered to a single incision-single instrument approach to cataract surgery that has benefited my patients over the years. This approach utilizes a clear corneal microincision, in-the-bag phacoemulsification with a mini-phaco flip maneuver, and injection of the IOL through the unenlarged incision. The patient’s visual results are illustrated in Slide 2, Slide 3, and Slide 4. Eighty-nine percent of patients are spectacle-free for most tasks and 29% can read without the need for a near correction. The refractive outcome achieved by following these techniques are the best we have ever achieved. With incision sizes approaching 1 mm, this technology holds promise for even greater advances in the not too distant future.

Slide 5

Preoperative Evaluation and Surgical Plan

All patients who present for cataract surgery undergo a comprehensive ophthalmic evaluation that includes dilated fundoscopy. In devising the surgical plan, cycloplegic refraction combined with corneal topography (Slide 5), and ultrasonic biometry are used to select the best IOL power for complete refractive correction. The strategy is to correct the sphere fully for distance, eliminate less than 1 D of astigmatism with a single incision that doubles as the cataract incision (KLP), and supplement the astigmatic correction for more than 1 D with the toric IOL. The goal of astigmatic treatment is to fully correct or slightly undercorrect the cylinder, and not overcorrect or shift the cylinder axis. To achieve the proper correction a preoperative surgical plan is developed (see worksheets #1, #2, #3, and #4).

The surgeon has few surgical options at this time to correct presbyopia. I am not a proponent of monovision unless the patient has lifetime success with monovision contact lenses. The multifocal or bifocal IOLs cause optical aberrations and loss of contrast sensitivity and, therefore, are to be used only in the simplest and non-demanding cases. As such, most patients who need refractive correction for near tasks use a low power reader, at least until a high quality refractive correction for both near and far vision can be achieved.

The Procedure

I encourage almost any surgeon who is currently using scleral tunnel incisions to consider switching to topical anesthesia and clear corneal incisions. This surgical approach saves time. Patients prefer the fact that their eyes are fully functional and appear normal almost as soon as they leave the operating room. Clear corneal incisions require that that the surgeon observes a different set of rules than those that apply to scleral incisions. The surgical team will need to make changes in the way patients are prepared for surgery, the manner in which the surgeon creates and manipulates the incision, and how the surgeon operates through that incision.

1. Use topical anesthesia
With topical anesthesia, patients can feel that which they could not feel with anesthetic blocks. Always inform the patient that although they will feel pressure, see the light of the operating microscope, and feel the surgeon touching them, they will not have pain. I always tell the patient when I am going to begin the phaco (infusion causes a proprioceptive sensation of pressure) and when I am about to inject the IOL (as the bag distends, pressure is felt). As long as a patient is informed, he or she will not startle or move or feel discomfort.

After performing a cycloplegia and a surgical scrub, instill several drops of proparacaine 2.5% or tetracaine 2.5%. Avoid the longer acting anesthetics such as bupivacaine as these drops are hyperosmotic, burn, and last much longer than required. Following this, apply 1 drop of hydroxypropyl methylcellulose (HPMC) 2.5%, rather than balanced salt solution irrigation. I coat the cornea with HPMC instead of forcing the scrub technicians to direct a stream of balanced salt solution over the ocular surface to keep it clean and moist. Several ophthalmic products contain HPMC including Ocucoat (hydroxypropyl methylcellulose 2%, Bausch & Lomb), Celluvisc (carboxymethylcellulose sodium 1.0%, Allergan), Refresh (Allergan) artificial tears, and Goniosol (hydroxypropyl methylcellulose 2.5%, Novartis Ophthalmics). In our practice, my colleagues and I typically transfer a bottle of Goniosol (maintaining sterility) into TB syringes on the morning of surgery. Goniosol is the most viscous, is optically clear, coats the cornea well, and even provides 1.5X magnification. After applying 1 drop onto the center of the cornea, the scrub technician can do something else. The ocular surface is protected.

2. Pay attention to the incision
Unlike scleral tunnel incisions, corneal incisions are not very forgiving. Corneal incisions distort, tear, or stretch easily and as a result, these incisions will leak, induce unwanted astigmatism, and heal more slowly. Following are a few basic rules:

Size. The most common error inexperienced surgeons make when constructing clear corneal incisions is using a keratome that is too small for the instruments they plan on passing through the incision. This causes stretching or tearing of the incision and striae that can obscure visualization during the procedure. It can also cause postoperative healing problems. Unlike scleral incisions, corneal incisions do not snap back into place after stretching. If your incision is too small, you will likely distort the incision when passing instruments through it, causing it to gape like a fish mouth rather than seal shut like a paper cut. The easiest way to avoid this distortion is to use a keratome that is properly sized to accommodate your largest instrument.

Typically, corneal incisions wider than 3.2 mm will induce flattening and unwanted aberration in the refractive power of the central cornea. These incisions usually do not self-seal and require suturing. Incisions 3 mm wide or less seal appropriately.

Slide 6

Slide 7

Blades. Standard disposable steel keratomes used routinely for scleral tunnel incisions do not work for clear corneal incisions. Only very sharp keratomes can atraumatically penetrate the Descemet membrane. Many clear corneal surgeons use diamond blades because of their unrivaled sharpness. The cutting edges can be made as thin as 1 µm, enabling these knives to pass through the corneal lamella smoothly and easily, leaving behind an incision as smooth as a paper cut.

Slide 8A

Slide 8B

However, many surgeons lack the trained surgical team necessary to maintain these expensive instruments. For these surgeons, there is an alternative. A new clear corneal incision system developed by Becton Dickinson Ophthalmic Surgical in Waltham, Mass., (Slide 6) features a blade that rivals a diamond’s sharpness, contour, and geometry, yet is made from surgical steel. The disposable kit also includes a fixation ring to keep the eye stable and an inkless marker that helps to mark the proper size, location, and configuration of the ideal clear corneal incision. The marking device creates two marks, a curved mark where the entrance to the incision should be and a linear mark for the entrance into the eye through the Descemet membrane. By simply fixing the globe in place with the fixation ring (Slide 7) and marking the incision with the inkless marker (Slide 8A and Slide 8B), the surgeon can properly position the keratome for the ideal incision.

To ensure proper geometry and architecture, place the tip of the corneatome on the incision entrance line, aim and line the blade up with the second line mark, then pass the blade into the cornea until it reaches the laser mark on the blade. At this point, the tip will enter the eye at the proper angle and the ideal tunnel length will be achieved automatically. The length:width ratio will be maintained at 3:2, which has been proved to be stable (Slide 9). The keratomes are available in a variety of widths to accommodate a surgeon’s preferred phacoemulsification tip and lens insertion method. The knife has a specially designed double-bevel slit blade in either angled or straight form for proper clear corneal incision construction. An accurate depth blade preset to 550 µm or 600 µm by the manufacturer is used to construct the two-step arcuate keratotomy incision (Slide 10).

Slide 9

Slide 10

3. Correct astigmatism — Do not make it worse
The location of the incision is just as important as how it is made. Before surgery, note in the chart the position of the patient’s steepest meridian on the cornea (see worksheets #1, #2, #3, and #4). As all transverse or arcuate corneal incisions flatten the corneal architecture, always locate your incision on the steepest meridian. If the steepest meridian cannot be determined, simply refract the patient in plus cylinder or analyze a corneal topographic map. Placing the incision anywhere other than the steepest part of the cornea will make the astigmatism worse. Since most elderly patients have against-the-rule astigmatism, temporal incisions typically work well for most, but not all, patients. These ncisions are also best if a patient has a spherical cornea. The temporal limbus is located further away from the optical center than is the superior limbus, such that temporal incisions will create lens-induced corneal astigmatism. Patients with significant preexisting astigmatism will benefit from astigmatic keratotomy (keratolenticuloplasty) at the time of surgery.

4. Avoid corneal injury.
The best defense against corneal burns and incision leaks is to construct a properly sized corneal incision. Incisions that are too small will crimp the irrigation sleeve on the phaco tip, causing the probe’s temperature to rise. Using thick, cohesive viscoelastics also increases the incidence of wound burn. I advise the use of thinner viscoelastics such as sodium hyaluronate for all these cases.

5. Prevent capsule complications
If you are a beginning clear corneal surgeon, you will most likely discover that your access and ability to maneuver through the small incision is much less than you are used to. Because of this, you may find it useful to make a few alterations in your technique.

Slide 11

The first challenge is making a good capsulorrhexis (Slide 11). This is critical to prevent problems during phaco and IOL implantation. Use the instrumentation with which you are most comfortable. I prefer two devices made by Rhein Medical (Tampa, Fla). The One-Step Capsulorrhexis cystotome/forceps is a forceps of my own design that allows a surgeon to open the capsule and conduct the tear with a single instrument. The microcapsulorhexer allows passage through a 100-µm paracentesis incision.

It is not uncommon to have the capsulorrhexis tear as it starts to head off toward the equator. If tearing occurs, stop, inject viscoelastic to tamponade the lens, and push the lens-iris diaphragm posteriorly. This reduces the stress on the capsule from the peripheral zonules. Then, regrasp the flap and pull it toward the center of the eye to bring it back into line. Then you can complete the tear. Even if the anterior capsule has a small tear, you can still proceed as planned, just do not inadvertently turn an anterior capsule tear into a zonular dehiscence that will result in a posterior capsular tear. If this happens, you must change your plan.

When emulsifying the nucleus, keep the phaco tip within an imaginary triangle in the central portion of the cataract, as far away as possible from the iris, posterior capsule, and corneal endothelium. This will help prevent damage to any of these three structures.

If the capsule breaks before the nucleus has been removed, you will need to stop, perform a vitrectomy and then remove the remaining lens fragments, if any. There are two options. You can abandon your clear corneal incision and make a new scleral incision through which to continue the case, or you can use your clear corneal incision along with a left-handed instrument through a paracentesis incision to remove the lens and implant the IOL.

6. Use an IOL that can be injected through the clear corneal incision without enlarging it.
I prefer plate-haptic single-piece lenses, either in silicone or collamer, a collagen copolymer. These IOLs are fully injectable which makes it possible to use a 2.4-mm or smaller incision. If the lens tears or becomes damaged with the injection method, I use another, the Utrata lens snare and forceps (Rhein Medical). This instrument pair allows a surgeon to cut the lens into two or more pieces and remove the pieces without enlarging the incision.

If three-piece silicone or acrylic lenses tear or become damaged, you will generally have to enlarge the incision to remove them. Any incision larger than 3.2 mm should be sutured.

The clear corneal incision is here to stay. More surgeons are mastering the finesse of the technique and more and more patients are demanding the rapid recovery and clear uncorrected vision that this technique provides. By incorporating these six tips into your approach to cataract surgery, you will save time and avoid complications.

Performing Phacoemulsification for the Clear Cornea Refractive Procedure

Today’s new techniques of topical anesthesia, clear corneal cataract surgery, and injection of elastic IOLs through small microincisions have placed new constraints on the ability of the surgeon to perform phacoemulsification.

Introducing the phacoemulsification tip through a small clear corneal refractive microincision limits access to the cataract and can restrict the surgeon’s ability to manipulate the lens within the capsular bag. As a result of the challenge and demands of smaller incision cataract surgery, surgeons have adopted several new approaches to the strategy for phacoemulsification.

All methods of cataract removal have essentially one goal in common: to take a large anatomic structure (the lens) and dismantle it into smaller pieces for ease of removal through an incision smaller than the overall size of the lens. Whether one adopts a divide and conquer technique, a quadratic phacoemulsification method, a chip and flip, or a stop and chop method, the goal remains the same. One can either mechanically divide the cataract into segments and remove the individual segments, or chip away at the larger structure and remove it piece by piece.

Many surgeons use two incisions through the cornea and two instruments for phaco, one for the phaco tip and one for a sideport lens-manipulating instrument. I do not believe that a second-handed instrument is necessary for effective and efficient phacoemulsification of the cataract. There are distinct advantages of maintaining the phaco incision as one incision. Placing an additional incision in the eye is not only unnecessary but it increases the likelihood of synechiae and incisional leaks, an additional portal for infection, and encourages excessive instrumentation of the eye.

Single Incision Phaco: The Three-Step Keyhole Technique

Early in its development, phacoemulsification was performed entirely through a single incision. This single incision/single instrument phacoemulsification technique has previously been called a one-handed phaco technique. The name is a misnomer, as two hands are required to successfully perform phaco. The maneuvers of lens rotation and segmental removal of the cataract can be performed with a single hand on the instrument thus freeing the left hand for manipulating the eye, stabilizing the globe, retrieving instruments, or stabilizing the phacoemulsification handle and tubing.

It is important that a surgeon adopt an efficient method of phacoemulsification through today’s small corneal microincisions prior to adopting a single incision technique. Although the single instrument phaco technique is efficient, easy to learn, and less traumatic to the eye, it requires a strategy and a masterful technique.

Incision Construction
The clear corneal microincision has placed new demands on the surgeon for evacuating the cataract through a single small corneal incision. These incisions can be unforgiving — they must not be distorted, torn or heated during the procedure lest they create profound refractive effects in the eye.

Incision construction is critical to a successful phacoemulsification procedure. The incision must be accurately sized for the size of the phacoemulsification tip to be used. Current microincision corneal procedures use an incision of 2.5 mm or smaller that must accommodate a micro phaco tip. Following fabrication of the clear corneal incision with a blade specifically designed for the clear corneal incision such as a diamond keratome or the new disposable clear corneal incision system developed by Becton Dickinson Ophthalmic Surgical, the anterior chamber is entered and a viscoelastic placed to deepen the chamber.

Slide 12

In early phacoemulsification methods, it was important to maintain the position of the cataractous lens within the capsular bag to stabilize it. Following the introduction of capsulorrhexis, it was found that the limited access into the capsular bag created difficulties in rotating the lens for emulsification and removal. To facilitate these maneuvers, hydrodissection was adopted to cleave the strong cortical attachments between the lens capsule and the cortex of the cataract (Slide 12). Slipping a curved, 27-gauge cannula through the incision and positioning it beneath the subincisional anterior lens capsule can create a fluid wave created across the posterior lens. This maneuver prematurely loosens the cortex beneath the incision making it easier to remove with irrigation and aspiration later in the procedure.

Slide 13

Parameters
A phacoemulsification machine is preferred with individual parameters that are controlled by the surgeon. Phacoemulsification power should be set to a reasonable level, which allows the surgeon adequate control with the phaco pedal. I will rarely use phaco powers greater than 20% to 30%. With single incision phacoemulsification, a higher head of pressure is required to maintain the chamber, allowing the delicate maneuvers with the phaco tip without danger of collapsing the capsular bag or injuring the corneal endothelium (Slide 13). I keep the irrigation bottle at a height of 115 mm.

Slide 14

Step 1. Central sculpting
When performing central sculpting (Slide 14), occlusion of the phacoemulsification tip rarely occurs. The goal of central sculpting is to remove the densest, hardest part of the nucleus at the beginning of the procedure when it is easiest to do so. The lens is kept entirely within the capsular bag. Using the phacoemulsification tip, gentle sculpting of the central nucleus is completed. If the lens nucleus is dense, a deep and wide sculpting is performed. If the lens is soft, a narrow and shallow sculpting is performed.

Slide 15

Step 2. Segmental removal of the cortical rim
Once central sculpting is completed, the surgeon is left with a cortical bowl. To remove the cortical bowl (Slide 15), a notch is aspirated to release the tension on the cortical ring of the cataract in the peripheral cortex. Using the phacoemulsification tip as a fulcrum, the remaining cortical rim can be gently rotated clockwise. Two clock hours of cortical rim are then gently aspirated into the central triangle of safety and are removed with minimal phacoemulsification.

Slide 16

Step 3. Removal of the nuclear plate
Following complete removal of the cortical rim, a small flat section of posterior nucleus remains. To remove this without risking injury to the posterior capsule (Slide 16), I use a mini phaco flip technique. The phacoemulsification tip is used to push the tip of the nucleus plate against the equator of the capsule and flip it over. The surgeon should allow the piece to come to the tip rather than chase it around the posterior chamber. Using short bursts of phaco power, the final piece can be safely elevated off the posterior capsule and removed.

Slide 17

Slide 18

IOL Insertion
The capsular bag should be filled with viscoelastic, with caution not to overfill the chamber but inflating it just enough to open the capsulorrhexis (Slide 17). The single-piece injectable lens is carefully loaded into the injector and inserted into the capsular bag in one maneuver. If a toric IOL is used (Slide 18), it is aligned with the steep meridian by placing the anterior lens marks at the proper location. The lens is then injected in one simple maneuver into the capsular bag at the proper meridian (Slide 19). This carefully controlled procedure results in the cornea being reshaped into a spherically and optically sound structure (keratolenticuloplasty) with the proper IOL fully correcting the spherical error (keratolenticuloplasty) (Slide 20).

Slide 19

Slide 20

The single instrument phacoemulsification procedure is quick, requires only one incision and one instrument, and is less traumatic to the eye. Following are some benefits of this technique:

• A consistent microincision
• Less unwanted astigmatism
• Better control at correcting preexisting refractive error
• A more predictable refractive outcome

As a result, patients have a rapid visual recovery. Any difficulties a surgeon may encounter when using a single instrument technique are outweighed by the benefits of the technique and satisfied patients.

The ultimate goal of outpatient cataract surgery is less intervention and better visual results. This approach offers the best opportunity for the optimum refractive outcome.

The Strategy to Achieve the Best Refractive Outcome from the Clear Cornea Procedure.

Most surgeons have been slow to accept the techniques of astigmatism management with their cataract procedure because of a resistance to acquire new skills or the need for new instrumentation. Some surgeons wrongly assume that there is no real benefit to creating better uncorrected vision after patients’ cataract procedures. In the United States, there is no extra reimbursement for taking time to create a better visual outcome for the patient, so some feel there is no benefit for the surgeon. Astigmatism should be managed, however, because it is better for our patients and because it can be predictably and easily corrected with today’s techniques. Simply by adopting a few sound fundamental principles and investing in additional instrumentation, a surgeon can offer a better refractive result for patients. The surgical correction of astigmatism along with full refractive correction of the spherical error reduces the need for spectacle correction postoperatively which translates into increased patient satisfaction and more patients. To ensure a precise method to achieve better refractive outcomes, a surgeon needs a philosophy of refractive correction and the discipline to follow a set of rules:

1. Do not overcorrect the cylinder or shift from the preexisting axis.
2. To accurately correct astigmatism, accurately measure it.
3. Always apply the astigmatic correction on the proper meridian.

Measuring Astigmatism

A full and accurate cycloplegic refraction will allow a surgeon to determine the magnitude and the orientation of the cylinder axis. Corneal topography and other corneal scanning measurements can allow us to properly analyze the origin of the astigmatism. A patient who has a refractive cylinder that does not appear topographically would not require corneal alteration to correct it. Simply removing the cataract will suffice. If the topographic astigmatism, which is usually measured as less than the refractive astigmatism, significantly differs from the power or the orientation of the cylinder, then the surgeon must make a judgment of what refractive error to correct. Here is where the art of astigmatic correction with cataract surgery departs from the science. A cookbook approach for every patient will not work. It is always better not to attempt a correction rather than perform the incorrect treatment.

Topography is valuable in both determining the qualitative appearance of the astigmatism and the location of the cylinder (Slide 5) for choosing whether to use symmetrical or asymmetrical incisions. Newer methods of corneal and intraocular analysis utilizing wavefront analysis may further provide insight into higher order aberrations that could affect postoperative refractive result. If the astigmatic correction is regular, clear and present on a single meridian, then it is correctable. Irregular astigmatism, keratoconus, corneal scars, and higher order aberrations are best left uncorrected rather than to attempt a correction that may result in an undesirable postoperative irregular cornea.

Correcting Astigmatism

Early methods of astigmatic control at the time of surgery were limited to elaborate suturing techniques and corneal wedge resection. Although this was effective in instances where large corneal incisions were utilized for cataract surgery, it has had little role with today’s techniques. All incisions placed onto the dome of the cornea will act as if tissue is added where they are placed. We can use this principle to intentionally flatten the steep areas of the cornea to create a more spherical result. Small, arcuate corneal incisions work best when surgeons want to flatten the cornea at a given location. Arcuate incisions, which closely follow the corneal curvature, placed on the proper latitude of the globe, can flatten in the meridian in which they are placed. This can be utilized to neutralize preexisting corneal astigmatism. The flattening in one meridian usually results in a steepening of the meridian 90º away; this coupling ratio is approximately 1:1 for arcuate clear corneal incisions. Surgeons need not take into account a change in the spherical power of the eye when they perform astigmatic surgery. Biometry is carefully preformed preoperatively. The spherical correction required can be calculated and the lens selected without attention to whether the astigmatism will contribute to an alteration in the lens power.

We can maximize the effect of the clear corneal cataract incision to correct astigmatism by inducing intentional flattening in the meridian in which it is placed. Simply by operating on the steepest meridian, we can improve the refractive results for our patients. Operate more than 15º off axis, and you will make the postoperative refractive result worse. That is why it is critical to know on which meridian to operate. In evaluating the patient for refractive cataract surgery, I consider the cycloplegic refraction, review the topography, and look at the A-scan result. The proper IOL is chosen; the location of the steep meridian is marked on the chart. To identify the proper meridian in the operating room, surgeons can make a note in the chart (see the worksheets #1, #2, #3, and #4) of the presence of a small nevus or corkscrew vessel, which may help identify the 12 o’clock meridian. Using this mark as a guide, the proper meridian for the astigmatic correction can be selected. I prefer to use an ocular reticule in the operating microscope that allows me to align the proper axis with the microscope. Alternatively, the surgeon can use a hand-held degree gauge to determine the proper meridian. Taking into account any rotational movement of the eye when the patient is supine is usually not an issue when topical anesthesia is used. If a peribulbar block is used, however, this must be taken into account when determining the proper location for correction. It is often best to mark the proper axis before administration of the block if one is used.

We can maximize the effect of the clear corneal incision to flatten the cornea by designing its architecture with the goal of intentionally flattening the incision.

For astigmatically neutral, clear corneal incisions, a one-step plane parallel clear corneal incision is used (Slide 1). A 2.4-mm disposable keratome can be used to create the proper architecture for a clear corneal incision that will be self-sealing and maintain a width to length ratio of 3:2. If the width of the incision is 3 mm, the tunnel length through the cornea should be approximately 2 mm. In the KLP technique, I utilize the cataract incision for all the subsequent steps of the surgery to optimize its refractive result. The cataract incision itself can correct up to 1.5 D of astigmatism alone when used in a length of approximately 3 mm or less. For an astigmatically neutral incision (Slide 1A) a single-plane incision is created with the keratome. For less than 1D of astigmatism (Slide 1B) a two-step clear corneal incision is utilized to flatten in the meridian in which it is placed. By using an accurate d epth blade set at a depth of 550 µm to 600 µm, the incision is made vertically, perpendicular to the cornea. Position the blade handle toward the center of the globe to create a deep groove approximately 85% of corneal depth. The corneatome selected for the phaco tip and the IOL injector (I usually use a 2.6 mm) is positioned at the base of this keratotomy and enters the eye in a plane parallel fashion. In this fashion, a two-step clear corneal self-sealing incision is created with the maximum flattening effect.

To correct larger degrees of astigmatism (Slide 1C) the incision is coupled with an additional arcuate incision on the opposite meridian from the cataract incision at an optical zone of 9 mm, 10 mm, or 11 mm to induce further flattening, or combined with the implantation of a toric IOL (Staar Surgical, Monrovia, Calif.). The toric IOL is presently available in two cylinder powers with the anterior surface of the lens delivering the refractive torus. The 2 D lens will deliver approximately 1.4 D of astigmatic correction at the spectacle plane, and the 3.5 D will provide approximately 2.3 D of correction.

The incisions are constructed utilizing the disposable BD limbal relaxing incision system which consists of a hinged fixation ring, an inkless marker to mark the proper location for the incision, the accurate depth blade to make the vertical component of the incision, and a slit blade to make the proper architecture for corneal entry (Slide 6).

The Operative Procedure

Topical tropicamide 1% in combination with phenylephrine 2.5% drops are administered into the operative eye, 1 drop every 5 minutes for three administrations, 15 minutes before surgery. On call to surgery, patients receive a single drop of topical povidone-iodine 4% suspension. The surgical scrub is performed and a sterile adhesive drape applied to exclude the eyelids and lashes. Several drops of tetracaine 2.5% anesthetic are instilled (if anesthetic drops are used before the procedure, there may be excessive drying or sloughing of the corneal epithelium making visualization difficult). The Kershner reversible eyelid speculum (Rhein Medical) is positioned under the eyelids and can be rotated out of the way so as to not interfere with the various steps of the procedure. The cornea is kept dry while the proper meridian of the cylinder is identified and marked with the inkless marker. The globe can be fixated with the disposable fixation ring, if necessary, and the incisions created. Next, the cornea is coated with several drops of HPMC 2.5%, which covers and protects the cornea, keeps it moist, eliminates the need for irrigation during the procedure, and provides 1.5X magnification. Hyaluronate viscoelastic is instilled into the anterior chamber.

The Kershner one-step forceps (Rhein Medical) are utilized to create a 5-mm round central capsulotomy. Hydrodissection is carried out with a Binkhorst cannula and balanced salt solution irrigation beginning with the subincisional cortex to ensure that this is loosened before the phaco procedure. Next, an in-the-bag, three-step phacoemulsification technique is performed with a 30º tip. Phaco power is set at 20%, maximum vacuum at 500 mm Hg, and an aspiration rate of 25 cc/min. Central sculpting is performed deeply and widely before the lens is rotated.

After central sculpting and removal of cortical rim, the phaco tip is utilized to press on the superior pole of the nucleus until it flips inside the capsular bag. The remainder of the nuclear plate can then be safely removed well separated from the posterior capsule with gentle emulsification and an aspiration. The clear corneal irrigation and aspiration tip is then introduced to remove residual cortex and irrigate the capsular bag. The capsular bag is then inflated with viscoelastic to open the capsular rim without over inflating the anterior chamber of the eye.

Next, the collamer hydrogel IOL (for spherical correction) or the silicone toric IOL is selected, loaded into the injector cartridge, and passed through the incision into the capsular bag at the proper meridian, where it is allowed to position itself without additional manipulation. The injector is then withdrawn from the incision margin. Irrigation and aspiration is used to remove residual viscoelastic. The lens position is checked for proper centration, the eye is reinflated to 20 mm Hg and sub-Tenon injections of 0.1 cc of betamethasone and 0.1 cc of cefazolin are placed. The patient uses artificial tears as needed. No bandage is provided. The patient is given a pair of sunglasses for use when outdoors and is seen postoperatively on the first day, at 2 weeks, 3 months, 6 months, and 1 year intervals. If an Nd:YAG laser capsulotomy is required, it is not performed until the 3-month postoperative visit is completed.

I have had good refractive results of clear corneal cataract surgery (Slide 2). Both the sphere (Slide 3) and the cylinder (Slide 4) can be predictably corrected with these techniques. The majority of patients have spectacle-free vision following the procedure and can return to normal activities the same day. Because the incision size is so small, the need for long-term postoperative eye drop therapy is unnecessary. This saves both on cost and patient inconvenience, and creates a more satisfied patient.

Conclusion

Today’s modern techniques of microincision cataract surgery have enabled surgeons to fully correct refractive error with cataract removal and IOL implantation. Smaller, more flexible injectable IOLs, combined with more efficient methods of phacoemulsification, have made it possible to keep incision sizes less than 2.5 mm and as small as 1 mm. Judicious selection of the IOL and careful attention to astigmatic correction, incision construction combined with toric IOLs can maximize the full refractive correction for the cataract patient. This translates into a more satisfied patient with fewer postoperative complications and minimal postoperative care after surgery.

Surgeons have within their grasp today the techniques for optimizing the refractive results of their cataract procedure. Full refractive correction at the time of cataract surgery can and should be accomplished, and must be the goal of every cataract surgeon.

This article received the "Best Paper of Session" award at the 2001 American Society of Cataract and Refractive Surgery Symposium held in San Diego, Calif.

Bibliography

Kershner RM, ed. Refractive Keratotomy for Cataract Surgery and the Correction of Astigmatism. Thorofare, NJ: Slack; 1994.

Kershner RM. Keratolenticuloplasty: Arcuate keratotomy for cataract surgery and astigmatism. J Cataract Refract Surg. 1995;21:274-277.

Kershner RM. One-step forceps for capsulorhexis. J Cataract Refract Surg. 1990;16:762-765.

Kershner RM. Embryology, anatomy and needle capsulotomy. In: Koch PS, Davison JA, eds. Textbook of Advanced Phacoemulsification Techniques. Thorofare, NJ: Slack; 1991:35-48.

Kershner RM. Sutureless one-handed intercapsular phacoemulsification: The keyhole technique. J Cataract Refract Surg. 1991;17(suppl):719-725.

Kershner RM. Topical anesthesia for small incision self-sealing cataract surgery: A prospective study of the first 100 patients. J Cataract Refract Surg. 1993;19(3):290-292.

Kershner RM. Capsular rupture at hydrodissection. J Cataract Refract Surg. 1992;18:201.

Kershner RM. Antibacterial prophylaxis before, during and after routine cataract surgery. J Cataract Refract Surg. 1993;19(1):110.

Kershner RM. Topical anesthesia cataract surgery. Ophthalmic Practice. 1993;11(4):160-165.

Kershner RM. Clinical consultation: Single instrument phaco and continuous curvilinear capsulorhexis. Ophthalmic Practice. 1994;12(1):39.

Kershner, RM. How to be a hero to your patients: Refractive cataract surgery. Review Ophthalmol.1996(June):50-4.

Kershner RM. Clear corneal cataract surgery and the correction of myopia, hyperopia and astigmatism. Ophthalmology. 1997;104(3):381-389.

Kershner RM. Patient’s adaptation to cataract surgery. Ophthalmology. 1998;105(1):6-7.

Kershner RM. Refractive cataract surgery. Curr Opin Ophthalmol. 1998;9(1):46-54.

Kershner RM. The case for one-handed clear corneal cataract surgery. Review of Ophthalmology. 1998;5(3):68-73.

Kershner RM. Six tips to clear cornea cataract surgery. Review of Ophthalmology. 1999;7(4):120-124.

Kershner RM. Toric lenses for correcting astigmatism in 130 eyes. Ophthalmology. 2000;107:1776-1782.

Worksheet 1. Advance the Greenbaum cannula until the conjunctiva/Tenon fits snugly over the expanded hub.

Kershner Operative Worksheet
Eye Laser Center Robert M. Kershner, MD, PC, FACS 1925 W. Orange Grove Road · Suite 303 Tucson, AZ 85704-1152
Patient Name:____________________________________ Age:_______ Occupation:__________________________ Dominant Eye:_______ Date:______________________
V R20/___ V         R20/___         J R_____ sc L20/___ cc         L20/___         L_____ C R     .     +     .     X           L     .     +     .     X        K R     .     V     .     H      °    L     .     V     .     H       °
WEARS: R     .     +     .     X           Glasses: L     .     +     .     X           ADD:              Last Rx              WEARS: R     .     +     .     X           Glasses: L     .     +     .     X           Last Rx:
O.D. O.Z.     .     mm     ARC LENGTH     .     mm AXIS:
O.S. O.Z.     .     mm     ARC LENGTH     .     mm AXIS:                 OPERATIVE EYE:____________ IOL Style                    Power
PACHYMETRY__________________	PACHYMETRY _________________

Worksheet 2.

Worksheet 3.

Worksheet 4.