Management of the Small Pupil for Clear Corneal Cataract Surgery

Robert M. Kershner, M.D., F.A.C.S.

Eye Laser Center

Suite 303, 1925 West Orange Grove Road

Tucson, Arizona 85704-1152 USA

Phone: (520) 797-2020 Fax: (520) 797-2235

This paper was presented at the Symposium on

Cataract, IOL and Refractive Surgery, April 28-May 2, 2001,

San Diego, California. The Perfect Pupil™ was designed and developed by John Milverton, MD of Sydney, Australia and is manufactured and distributed by Becton Dickinson Ophthalmic Surgical, Waltham, Massachusetts, USA. Perfect Pupil™ is a registered trademark of Milvella Pty Ltd. Dr. Kershner is the director of the Eye Laser Center in Tucson, Clinical Professor of Ophthalmology at the Moran Eye Center, University of Utah School of Medicine, Salt Lake City, Utah, and the IK HO Visiting Professor of Ophthalmology at the Chinese University in Hong Kong. He has authored hundreds of articles on eye microsurgical techniques and instruments and lectures to ophthalmic surgeons worldwide. Dr. Kershner has no proprietary or financial interest in the techniques or instruments described in this article.

The increased acceptance of topical anesthesia, phacoemulsification and small, foldable intraocular lenses (IOLs), have made possible the techniques of clear corneal cataract surgery (1). Operating through these small (less than 3.0 mm), corneal incisions have placed new demands on surgeons to effectively and safely remove the cataract and implant the IOL without increasing the risk of corneal, iris or capsular damage. Many patients who present for cataract removal have eyes complicated by pupils with iris sphincter sclerosis due to aging, synechiae, previous trauma or surgery, diabetes, iridoschisis, uveitis, chronic miotic therapy, pseudoexfoliation, or chronic lues. The small pupil (less than 3.0mm) can impede visualization and make instrumentation into the eye more difficult. Capsulorrhexis can be all but impossible through a small pupil. Hydrodissection and phacoemulsification of the lens nucleus can lead to an increased risk of iris sphincter tear, bleeding, iris emulsification, ruptured posterior capsule and loss of the nucleus. The postoperative result of these encounters can be an irregular and atonic pupil, photophobia and discomfort for the patient.

Present methods of dealing with a small pupil at the time of cataract surgery have all had limitations. Pharmacological therapy with the use of non-steroidal eye drops, or strong mydriatics such as 10% phenylephrine, are often associated with untoward ocular and systemic side effects and may be ineffective in dilating bound-down and scarred pupils. The surgeon can simply ignore pupil size and perform the maneuvers of small incision surgery through an unenlarged incision, but this may result in the inadvertent complications described. Many surgeons have turned to mechanical methods and devices to enlarge the pupil at cataract surgery. These include using a blade, needle or scissors to make multiple iris sphincter tears, iris hooks to retract the iris tissue through four or more corneal stab incisions (2), or introducing mechanical stretching devices to pull on the sphincter margin. All of these methods are cumbersome, require specialized instruments, difficult intraocular maneuvers, and are associated with bleeding, permanent loss of iris sphincter function, and abnormal pupil shape postoperatively.

This study was undertaken to assess the protective effect and dilating potential of a new, disposable device for small pupil cataract surgery. Developed by John Milverton, MD of Sydney, Australia, this device was aptly named the Perfect Pupil™. It is a sterile, disposable, polyurethane ring with an integrated arm that allows for easy insertion into the eye and removal at the conclusion of surgery. The device is inserted through an unenlarged clear corneal incision, with the arm remaining outside the eye to aid in easy removal. The procedures of capsulorrhexis, hydrodissection, phacoemulsification and IOL insertion are carried out with the device in place. The Perfect Pupil is then removed at the end of the surgery by reversing the steps used for insertion.

Thirty patients were selected for inclusion in the study. These patients had pupils that failed to dilate beyond 4.0mm with topical 1% tropicamide and 2.5% phenylephrine as measured at the slit lamp. All cataract patients with visually significant cataracts and a desire for surgical correction underwent a comprehensive examination, preoperative ultrasonic biometry, topography, and measurement of pupil diameter at the slit lamp. They signed an informed consent which included surgical intervention for pupil size. Institutional Review approval was not required as the device was approved for use in the United States by the Food and Drug Administration and the surgery did not require a new or different protocol than that which was routinely used for cataract surgery. All procedures were performed by a single surgeon (RMK).

Preoperatively, the patients received one drop each of topical 1% tropicamide and 2.5% phenylephrine every five minutes for fifteen minutes prior to surgery. They were transported to the operating room where a drop of 4% topical povidone iodine was instilled and surgical prep performed. The patient's eye was draped with a sterile adhesive disposable drape (Kershner Cataract Drape II- Kimberly Clark Corporation) and the Kershner reversible eyelid speculum (Rhein Medical, Tampa, Florida USA) was inserted. All procedures were performed under topical anesthesia (3). Several drops of 0.5% tetracaine hydrochloride were instilled. The pupil, as seen through the cornea, was measured through the ocular of the operating microscope and compared to a known standard pupil gauge chart in millimeters (mm).

A 2.8 mm clear corneal incision was created with either a diamond keratome or the BD disposable clear cornea incision system (Becton Dickinson Ophthalmic Surgical, Waltham, Massachusetts, USA). Astigmatism was corrected with an arcuate keratotomy incision (1, 4) or a toric intraocular lens (IOL). Intracameral sodium hyaluronate (Healon, Pharmacia, Peapack, New Jersey, USA) was injected into the anterior chamber.

The Perfect Pupil™ (figure 1) is a sterile, disposable polyurethane ring with an internal diameter of 7.0 mm. The ring is open for 45 degrees to allow for the passage of instruments. There is one 1.6m tab at the top of the device and five 4mm fenestrations in the ring for positioning. The iris is firmly held for 315 degrees by an integrated 0.24 mm flanged groove throughout the length of the ring. The material is biocompatible and flexible allowing it to be passed easily through an unenlarged corneal incision. Once in place, the device automatically expands the pupil aperture to 7 to 8 mm. It can be left in place throughout the procedure. The integral arm can be kept to the side of the corneal incision as a buttress to protect the incision, keep the device in place within the pupillary space, and to aid in removal at the conclusion of the surgical procedure. As the ring captures the entire iris sphincter, it acts not only to dilate the pupil, but it provides unparalleled protection of the iris sphincter margin avoiding the complications of iris tearing, bleeding, inadvertent sphincter damage or emulsification.

The Perfect Pupil is removed from it's sterile tray with forceps (figure 2a-step 1) and delivered to the incision. The distal end is coated with a minimal amount of hyaluronate viscoelastic. The leading edge is then dialed counterclockwise into the anterior chamber (figure 2b-step 2). A Sinsky style hook is introduced either through the corneal incision or through a sideport incision and used to engage the superior tab (step 3). The iris is engaged and the positioning holes are each used in turn until the entire pupil is captured inside the flange of the device (step 4). The pupil size is then remeasured.

Capsulorrhexis is performed with the Kershner One-Step capsulorrhexis cystotome/forceps (5) or microcapsulorrhexor (Rhein Medical, Tampa, Florida USA). Hydrodissection is performed with a Binkhorst cannula and balanced salt solution by injecting a fluid wave from beneath the sub-incisional cortex to the opposite side of the capsule until a complete wave is created loosening the cortical attachments of the lens to the capsule. Phacoemulsification is performed using a single-instrument, single-incision technique (6), with a 30 degree tip, 20% phaco power, vacuum level at 100 mm, and aspiration rate at 20 cc/minute with the Bausch and Lomb Millennium phacoemulsification machine (Bausch and Lomb, Rochester, New York, USA). Irrigation and aspiration (I&A) of residual cortex is completed with the clear cornea I&A tip (Rhein Medical, Tampa, Florida USA). The capsular bag is reinflated partially with viscoelastic and the one-piece Collamer IOL or silicone toric IOL (Staar Surgical, Monrovia, California USA) is loaded into the microinjection cartridge and inserted into the capsular bag and centered in one motion.

The residual viscoelastic is removed with gentle I&A. The Perfect Pupil is then engaged at the tab with a hook and the pupil released. The device is backed out of the incision in the reverse procedure of the insertion by grasping the arm with a forceps and gently dialing clockwise until removed (step 5). The pupil is then measured. Subtenons injection of 0.1 cc of cefazolin (Ancef, Smith Kline Beecham Pharmaceuticals) and dexamethasone (Celestone, Schering Corporation), is injected and the patient is discharged for examination the following day.

All patients underwent the procedure without complication. There were no instances of inadvertent iris sphincter damage, bleeding, or capsular rupture. Pupil size as measured at the operating microscope (figure 3) preoperatively was 3.2 mm (range 2.0 mm to 4.0mm), which expanded to 7.8 mm (range 7.0 mm to 8.0 mm) after insertion of the device, returning to 4.3 mm (range 3.0 mm to 5.0 mm) after removal.

The ease of removal of the device from it's tray, insertion of the device into the eye, and removal of the device at the end of the procedure, as determined by the surgeon, was similar to insertion of an intraocular lens. No special instrumentation or surgical techniques were required. All devices functioned as expected and there were no defects noted in the manufacture or packaging of the devices used in the study.

The patients, all of whom underwent the procedures under topical anesthesia, were comfortable during the insertion and removal of the device. There were no reported adverse effects experienced by the patients with the use of the Perfect Pupil.

Today's advanced cataract procedure is more dependent than ever on the successful execution of a meticulous series of steps from incision construction to intraocular lens implantation. Adequate pupillary dilation prior to attempting surgical removal of the cataract is of critical importance. Many patients who present for cataract removal have eyes complicated by pupils that do not adequately dilate despite several pharmacological attempts with topical mydriatic agents. The causes of pupils that fail to dilate are numerous, but include iris sphincter sclerosis due to aging, synechiae, previous trauma or surgery, diabetes, chronic lues, iridoschisis, uveitis, chronic miotic therapy, or pseudoexfoliation. When a surgeon encounters a small pupil at the time of cataract surgery, he or she is left with a decision whether to proceed with the surgery or to intervene with a procedure that will most probably effect the successful outcome. In some instances, simply leaving the pupil alone, will suffice. However, attempting the various steps of cataract surgery through an undilated pupil can be a challenging and daunting task. Visualization of the cataract can be impeded by a small pupil. This can make it difficult to see the lens capsule for a proper capsulorrhexis. Even if capsulorrhexis can be performed, attempting to phacoemulsify a cataract through an undilated pupil can result in iris sphincter tear and emulsification, bleeding, ruptured capsule, lost nucleus and breach of the vitreous cavity.

Accordingly, most surgeons will attempt to mechanically dilate the pupil at the time of cataract surgery if pharmacological agents fail to enlarge the pupil by themselves. There have been numerous techniques and instruments utilized for this task. I classify pupil dilation methods into three types. The first is the mechanical stretching method. The second is the cutting method. The third is the iris retainer method.

In the first method, the iris is mechanically stretched. The instruments of choice to perform this can be a pair of hooks introduced through two stab incisions in the cornea. The hooks engage the iris sphincter and are pulled in opposite directions. This results in one or more tears of the sphincter, which leads to an enlargement of the pupil aperture. The advantages of this procedure is that it is simple, and requires no special instruments. The disadvantage is that the iris sphincter is permanently damaged and the tear cannot be controlled, resulting in bleeding, pigment dispersion, and an abnormal and non-functional pupil postoperatively.

In the second method, sharp instruments are used to cut the iris sphincter. The instruments of choice can be a bent needle or intraocular scissors. The cutting method is more controlled but requires the use of a large instrument in the eye that can result in corneal endothelial damage. The advantages of the method are that the purposeful tears can be made small and controlled with less effect on the appearance and function of the pupil. The disadvantages are the same as the stretching method.

The third method is the iris retainer method. There have been several devices fabricated for holding the pupil in the enlarged state (7). The effect of these devices is to stretch the pupil around a ring and allow the ring to keep the pupil dilated. The advantages are these devices are sterile, and hold the pupil in the enlarged state. The disadvantages with these iris retainers are they are fixed, rigid and difficult to insert into the eye through a small incision, cumbersome to manipulate when engaging the sphincter, and they interfere with the instrumentation needed to enter the eye for the cataract procedure.

The instrument that does not share these disadvantages with existing pupil dilating methods, is the Perfect Pupil™. This device is sterile, disposable, flexible and can be easily inserted through the smallest of incisions (less than 100 microns). Because of it’s unique design, the device captures the pupillary margin, protects the sphincter, does not cause tears or stretching of the iris, bleeding or pigment dispersion. Because of the open ring design of the Perfect Pupil™, there is no interference with instrumentation of the eye. The device can be left in place for the entire procedure and following completion of the surgery, the device is just as easy to remove as it is to insert.

I am not aware of a single study that demonstrates the advantages of a pupillary dilation method that also affords the protection of the iris that this device is capable of offering. Indeed, one of the distinct benefits of the Perfect Pupil™ is it’s ability to fully protect the pupil it expands. In fact, this device not only is of benefit to the cataract surgeon encountering a small, undilated pupil, but could be of benefit to posterior segment surgeons who must often view the retina and vitreous cavity through small, bound down pupils during surgery.

The results of this study demonstrate that when small pupils are encountered (less than 4.0 mm) the Perfect Pupil™ effectively and consistently dilates the pupil to almost 8.0 mm. When removed, the pupil quickly returns to a size approximating the preoperative state (4.3mm). The resulting surgery leaves the patient with an iris that is indistinguishable from the appearance prior to surgery, and does not affect the iris function postoperatively.

Clear cornea cataract surgery offers distinct advantages over conventional cataract surgical techniques. The procedure is more efficient, requires less cutting and less instrumentation and results in faster and superior visual outcomes (1). The techniques of operating through a small, corneal incision places demands on the surgeon who must have an unobstructed view of the intraocular instruments and maneuvers to successfully complete the surgery. A small pupil (less than 4.0 mm), that fails to adequately dilate, can provide an obstruction to visualization that makes the techniques of cataract removal more difficult with added risk.

A method that adequately dilates the pupil, prevents iris sphincter damage, protects the pupil margin, and is easily performed would have decided advantages for the clear corneal cataract surgeon. The Perfect Pupil™ is just this superior device, and an excellent addition to small incision cataract surgery. When encountering pupils that do not adequately dilate, the surgeon will find the Perfect Pupil™ on the shelf, ready to use, and easy to insert and remove. The Perfect Pupil™ expands the pupil to 8mm, protects the iris sphincter during surgery, and allows the pupil to return to normal size, shape and function following the clear cornea cataract procedure. It is an excellent adjunct in the armamentarium of every clear cornea cataract surgeon.

References:

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

2. Smith GT, Liu CSC. Flexible iris hooks for phacoemulsification in patients with iridoschisis. J Cataract Refract Surg 2000; 26:1277-1280

3. Kershner RM. Topical anesthesia for small incision self-sealing cataract surgery - a prospective study of the first 100 patients. J Cataract Refract Surg1993; 19(3):290-292

4. Kershner RM. Keratolenticuloplasty - arcuate keratotomy for cataract surgery and astigmatism. J Cataract Refract Surg 1995;21(3):274-277

5. Kershner RM. A new one-step forceps for capsulorrhexis. J Cataract Refract Surg 1990; 16:762-765

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

7. Graether JM. Graether pupil expander for managing the small pupil during surgery. J Cataract Refract Surg 1996;22:530-535

Graphics:

Figure 1. Kershner-Perfect Pupil™ is an open 315º polyurethane ring with 5 positioning holes and one tab, used for insertion to expand the pupil to 7.0mm.

Figure 2a.

Kershner-Step 1-The device is removed from the sterile tray with forceps.

Figure 2b-Kershner

Step 2-Insert Perfect Pupil™ through the clear corneal incision.

Step 3-Use a hook in the positioning holes to engage the pupil edge.

Step 4-Capture the entire pupil into the groove of the ring.

Step 5-Remove Perfect Pupil™ by disengaging the ring with a hook, grasp the arm and withdraw the device through the incision.