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This paper was presented at a symposium on Cataract, IOL, and Refractive Surgery, April 28-May 2, 2001, San Diego, California.
Dr. Kershner has no proprietary or financial interest in the techniques or instruments described in this tutorial.
The increased acceptance of topical anesthesia, phacoemulsification, and small foldable IOLs has prompted the development of clear corneal cataract surgery techniques.1 Operating through small corneal incisions that are less than 3 mm requires that cataract surgeons effectively and safely remove the cataract and implant an IOL without increasing the risk of corneal, iris, or capsular damage. Many patients who undergo cataract removal have pupils with iris sphincter sclerosis due to aging, synechiae, previous trauma or surgery, diabetes, iridoschisis, uveitis, chronic miotic therapy, pseudoexfoliation, or chronic lues. A pupil smaller than 3 mm can impede visualization and cause difficulty when inserting instruments into the eye. Performing a capsulorrhexis is nearly impossible through a small pupil, and hydrodissection and phacoemulsification of the lens nucleus can lead to an increased risk of an iris sphincter tear, bleeding, iris emulsification, a ruptured posterior capsule, and loss of the nucleus. As a result, postoperatively, a patient may experience an irregular and atonic pupil, photophobia, and discomfort.
Current methods of managing a small pupil during cataract surgery have limitations. Pharmacological therapy with nonsteroidal eye drops or strong mydriatics, such as phenylephrine10%, is often associated with untoward ocular and systemic side effects and may be ineffective in dilating bound down and scarred pupils. A surgeon can ignore pupil size and perform small incision surgery through an unenlarged incision, but this may result in the inadvertent complications described above. Many surgeons have turned to mechanical methods and devices to enlarge the pupil during cataract surgery. These methods 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 incisions2; or mechanical stretching devices to pull on the sphincter margin. All of these methods are cumbersome, require specialized instruments and difficult intraocular maneuvers, and are associated with bleeding, permanent loss of iris sphincter function, and an abnormal pupil shape postoperatively.
Most surgeons will attempt to mechanically dilate the pupil during cataract surgery if pharmacological agents fail to enlarge. Numerous techniques and instruments have been used. I classify pupil dilation methods into the mechanical stretching, cutting, and iris retainer methods.
Mechanical Stretching
A pair of hooks introduced through two stab incisions in the cornea can be used to mechanically stretch the iris. 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.
An advantage of this technique is that it is simple and requires no special instruments. Disadvantages of mechanical stretching are the permanent
damage of the iris sphincter and an uncontrolled tear. This may result in bleeding, pigment dispersion, and an abnormal and nonfunctional pupil
postoperatively.
The Cutting Method
In the cutting method, sharp instruments such as a bent needle or intraocular scissors are used to cut the iris sphincter. The cutting method is more
controlled than mechanical stretching but requires the use of a large instrument in the eye that can result in corneal endothelial damage. The
advantages of cutting 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 — permanent damage of the iris sphincter and an uncontrolled tear.
Iris Retainer Method
There have been several devices fabricated for holding the pupil in an enlarged state.3 These devices stretch the pupil around a
ring to keep the pupil dilated. The advantages of these devices include instrument sterility and the ability to hold the pupil in an enlarged state. The
disadvantages of iris retainers are that they are fixed, rigid, and difficult to insert into the eye through a small incision; they are cumbersome to
manipulate when engaging the sphincter; and they interfere with the instrumentation required for the cataract procedure.
A new device that does not share the disadvantages of the mechanical stretching, cutting, and iris retainer pupil dilating methods is the Perfect Pupil (Becton Dickinson Ophthalmic Surgical, Waltham, Mass), which has recently been developed by John Milverton, MD, for small pupil cataract surgery. The Perfect Pupil is a sterile, disposable, and flexible polyurethane ring with an integrated arm designed to allow for easy insertion and removal through the smallest of incisions (less than 100 µm). The device is inserted through an unenlarged clear corneal incision, with the arm remaining outside the eye to aid in easy removal. Capsulorrhexis, hydrodissection, phacoemulsification, and IOL insertion are performed with the device in place. The Perfect Pupil is then removed at the end of the surgery by reversing the steps used for insertion. Because of its unique, open ring design, the device captures the pupillary margin, protects the sphincter, and does not cause tears or stretching of the iris, bleeding, or pigment dispersion.
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The Perfect Pupil (Slide 1) has an internal diameter of 7 mm and a 45° opening to allow for the passage of instruments. There is one 1.6-mm tab at the top of the device and five 4-mm fenestrations in the ring for positioning. The iris is firmly held for 315° by an integrated 0.24-mm flanged groove throughout the length of the ring. The material is biocompatible and flexible, which allows easy passage through an unenlarged corneal incision. Once in place, the device automatically expands the pupil aperture to 7 mm to 8 mm. The Perfect Pupil can remain 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 aid in removal at the conclusion of the surgical procedure. As the ring captures the entire iris sphincter, it not only dilates the pupil, but also provides protection of the iris sphincter margin, thereby avoiding the complications of iris tearing, bleeding, and inadvertent sphincter damage or emulsification.
A study of 30 patients was performed to assess the protective effect and dilating potential of the Perfect Pupil. Patients in the study had pupils that failed to dilate more than 4 mm with topical tropicamide 1% and phenylephrine 2.5% as measured at the slit lamp. All 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 U.S. Food and Drug Administration (FDA) and the surgery did not require a new or different protocol from that which was routinely used for cataract surgery. I performed all procedures.
Preoperatively, patients received 1 drop of topical tropicamide 1% and phenylephrine 2.5% every 5 minutes for 15 minutes before surgery. In the operating room, 1 drop of topical povidone-iodine 4% was instilled and the patients were prepared for surgery. Each patient’s eye was draped with a sterile adhesive disposable drape, and the Kershner reversible eyelid speculum (Rhein Medical, Tampa, Fla) was inserted. All procedures were performed under topical anesthesia.4 Several drops of tetracaine hydrochloride 0.5% were instilled. The pupil, as seen through the cornea, was measured through the ocular of the operating microscope and compared to a standard pupil gauge chart.
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). Astigmatism was corrected with an arcuate keratotomy incision1,5 or a toric IOL. Intracameral sodium hyaluronate was injected into the anterior chamber.
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Procedure
The following standard procedure was used for all patients in the study. The Perfect Pupil is removed from its sterile tray with forceps
(Slide 2) and delivered through 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 (Slide 3). A Sinskey hook is introduced through either a corneal
incision or a sideport incision and used to engage the superior tab (Slide 4). The iris is engaged and the positioning holes are used in
turn until the entire pupil is captured inside the flange of the device (Slide 5). The pupil size is then remeasured.
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Capsulorrhexis was performed with the Kershner One-Step capsulorrhexis cystotome/forceps6 or microcapsulorhexor (Rhein Medical). Hydrodissection was performed with a Binkhorst cannula and balanced salt solution by injecting a fluid wave from beneath the subincisional cortex to the opposite side of the capsule until a complete wave was created loosening the cortical attachments of the lens to the capsule. Phacoemulsification was performed using a single-instrument, single-incision technique,7 with a 30° tip, 20% phaco power, vacuum level at 100 mm, and aspiration rate at 20 cc/minute with the Millennium phacoemulsification machine (Bausch and Lomb, Claremont, Calif). Irrigation and aspiration (I&A) of residual cortex was completed with a clear cornea I&A tip. The capsular bag was reinflated partially with viscoelastic and the one-piece Collamer IOL or silicone toric IOL (Staar Surgical, Monrovia, Calif) loaded into the microinjection cartridge, inserted into the capsular bag, and centered in one motion.
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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 (Slide 6). The pupil is then measured. A 0.1-cc sub-Tenon injection of cefazolin and dexamethasone is administered. The patient is discharged and required to return for examination the next day.
No patients who underwent the procedure experienced complications. There were no instances of inadvertent iris sphincter damage, bleeding, or capsular rupture. Patients 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.
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Pupil size as measured preoperatively at the operating microscope (Slide 7) was 3.2 mm (range 2 mm to 4 mm), which expanded to 7.8 mm (range 7 mm to 8 mm) after insertion of the device, returning to 4.3 mm (range 3 mm to 5 mm) after removal.
I found that the ease of the Perfect Pupil’s removal from its tray, insertion into the eye, and removal from the eye at the end of the procedure was similar to insertion of an IOL. No special instrumentation or surgical techniques were required. All devices functioned as expected and no defects in the manufacturing or packaging of the devices used in the study were observed.
The results of this study demonstrate that when pupils smaller than 4 mm are encountered, the Perfect Pupil effectively and consistently dilates the pupil to almost 8 mm. When removed, the pupil quickly returns to approximately the preoperative size (4.3 mm). The surgery does not affect the function of the iris, and, postoperatively, the appearance of the iris is indistinguishable from its appearance before surgery.
I am unaware of a study that demonstrates the advantages of a pupillary dilation method that also affords the protection of the iris that the Perfect Pupil offers. One of the benefits of the Perfect Pupil is its ability to fully protect the pupil. The device is beneficial not only to a cataract surgeon encountering a small, undilated pupil, but also to a posterior segment surgeon who must often view the retina and vitreous cavity through small, bound down pupils during surgery.
Today’s advanced cataract procedure is highly dependent on the successful execution of a meticulous series of steps from incision construction to IOL implantation. Adequate pupillary dilation prior to attempting surgical removal of the cataract is critical. Many patients who present for cataract removal have pupils that do not adequately dilate despite several pharmacological attempts with topical mydriatic agents. The causes of a pupil’s failure to dilate 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 must decide whether to enlarge the pupil. Attempting cataract surgery through an undilated pupil can be a daunting task. A small pupil can impair a surgeon’s visualization, which can make it difficult to see the lens capsule for a proper capsulorrhexis. Attempting to emulsify a cataract through an undilated pupil can result in iris sphincter tear or trauma, bleeding, ruptured capsule, lost nucleus, and breach of the vitreous cavity.
Clear corneal cataract surgery offers distinct advantages over conventional cataract surgery techniques. Clear corneal surgery is more efficient, requires less cutting and less instrumentation, and results in faster recovery 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 pupil smaller than 4 mm that fails to adequately dilate can provide an obstruction to visualization that makes 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. When encountering pupils that do not adequately dilate, the Perfect Pupil is ready to use and easy to insert and remove. The Perfect Pupil expands the pupil to 8 mm, 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 clear corneal cataract surgeons.
