Stretching the Pupil in Cataract Surgery
Tips for expanding the pupils of glaucoma patients.
Using a pharmacologic agent is the first choice for dilating the pupil. Prior to cataract surgery, ophthalmologists typically use 1% tropicamide and 2.5% phenylephrine. If these agents do not produce sufficient dilation, good results can often be achieved by increasing the strength of the pharmacologic agents (eg, 10% Neo-Synephrine [Bayer Corporation, West Haven, CT] and 2% Cyclogyl [Alcon Laboratories, Inc., Fort Worth, TX]). In some cases, patients can take the agents home and begin dilation before they come to the surgery center.
If the pupil still does not dilate adequately, a viscoelastic agent may be helpful. Viscosurgical devices with high molecular weights such as Healon5 (Advanced Medical Optics, Inc., Santa Ana, CA) work well. If posterior synechiae are present, then the surgeon should perform lysis prior to pupil dilation with a dispersive agent like Viscoat (Alcon Laboratories, Inc.). Healon5 may be used thereafter to dilate the pupil. Particularly in glaucoma patients, it is imperative that all of the viscoelastic be removed from the eye after surgery, because residual Healon5 can cause pressure increases.
MECHANICAL PUPILLARY STRETCHING
If pharmacologic and viscoelastic agents are unable to dilate the pupil, two Lester hooks (Katena Products Inc., Denville, NJ) are an option. One hook is inserted through the main incision, and the second hook is inserted through the paracentesis. The hooks engage the pupillary margin at opposite points. They are then pulled apart, moved 90º, and pulled again to manually dilate the pupil (Figure 1).
Figure 1. The surgeon uses two Lester hooks to stretch the pupil.
The Beehler Pupil Dilator
Instead of hooks, our favorite technique in these cases is to use the Beehler pupil dilator (Moria, Antony, France), which comes in two- and three-pronged versions. The two-pronged version is inserted through a 2.5-mm incision, and the three-pronged version is inserted through a 3.0-mm incision. In both designs, one hook wraps around the subincisional pupillary margin. The surgeon then pushes a plunger, and either two or three prongs emerge from the tip (Figure 2). The prongs feature small hooks that engage the distal pupillary margin. In one motion, the whole pupil is dilated.
Figure 2. A three-pronged Beehler pupil dilator expands the pupil.
Because the Beehler pupil dilator creates more even dilation by distributing tension on all sides of the pupil, eyes will frequently have a better cosmetic appearance at the end of the case than after the use of two Lester hooks.
When employing the Beehler pupil dilator for the first time, surgeons should make sure to introduce and remove the proximal hook, which goes under the subincisional pupillary margin, in a sideways fashion so it does not accidentally tear the incision in the cornea. While dilating the pupil, surgeons must be careful not to put downward pressure on the lens, especially in eyes with pseudoexfoliation glaucoma, because these patients have weak zonules.
Iris retractors are another option for small pupils. The surgeon makes four small paracenteses, through each of which he inserts the retractors. The devices create a square pupil, and the paracenteses allow fluid to egress out of the eye, which can affect the fluidics. Iris retractors are therefore not ideal.
If the pupil is stretched but will not remain dilated, a pupil ring may be helpful. One available option is the type 5S Morcher pupil dilator (Morcher GmbH, Stuttgart, Germany). This solid PMMA ring is placed at the pupillary margin, and it expands the pupil through 300º with even tension all the way around (Figure 3). The ring also protects the pupillary margin by preventing floppy irides from entering the phaco tip. The ring is inserted through the 2.5-mm incision, and it is easily placed using hooks. The surgeon manipulates the central segment of the ring into position, in apposition to the distal pupillary margin, and then places the ends of the ring with the aid of its eyelets. After implanting the IOL, the surgeon removes the ring by freeing its ends from their point of apposition with the pupil by means of a small hook, again placed in each eyelet. The ring then may be withdrawn from the anterior chamber with a forceps. An injector for the ring is available from Geuder AG (Heidelberg, Germany).
Figure 3. A pupil ring is placed.
Another available pupil ring is the Perfect Pupil (Milvella Pty Ltd, Epping, Australia). This polyurethane device functions similarly to the Morcher ring, but it has a safety arm that sticks out of the incision and prevents it from becoming lost in the eye. An injector is available from the company.
Although pupil rings work well, inserting them in the eye can be intimidating. Additionally, they remain in the eye during the cataract procedure.
Although most surgical techniques for expanding the pupil have fallen into disuse because of the development of the aforementioned instruments, pupillary membrane dissection is sometimes still necessary.1 Certain small pupils have a fibrotic membrane around the pupillary margin that can prevent them from dilating. Surgeons can peel the membrane off with a Fine forceps (American Surgical Instruments Corporation, Westmont, IL).
Postoperatively, the pupil may not constrict. It is important to address this problem soon after surgery, because a pupil dilated to 6 or 7 mm is not cosmetically pleasing and can cause glare. Instilling Miochol-E (Novartis Ophthalmics, Inc., Duluth, GA) can help. Additionally, surgeons can stroke the pupil into place with a hook or spatula. Pilocarpine instilled postoperatively can also constrict the pupil and improve cosmesis.
I. Howard Fine, MD, is Clinical Professor at Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University, and he is in private practice at Drs. Fine, Hoffman, & Packer in Eugene, Oregon. He is a paid consultant for Advanced Medical Optics, Inc., and he receives research and travel support from Alcon Laboratories, Inc. Dr. Fine may be reached at (541) 687-2110; email@example.com.
Richard S. Hoffman, MD, is Clinical Associate Professor at Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University, and he is in private practice at Drs. Fine, Hoffman, & Packer in Eugene, Oregon. He stated that he holds no financial interest in the products and companies mentioned herein. Dr. Hoffman may be reached at (541) 687-2110; firstname.lastname@example.org.
Mark Packer, MD, FACS, is Clinical Assistant Professor at Casey Eye Institute, Department of Ophthalmology, Oregon Health & Science University, and he is in private practice at Drs. Fine, Hoffman, & Packer in Eugene, Oregon. He is a paid consultant for Advanced Medical Optics, Inc., and he has received travel support and honoraria from Alcon Laboratories, Inc. Dr. Packer may be reached at (541) 687-2110; email@example.com.
1. Osher RH. Pupillary membranectomy [videotape]. Audiovisual Journal of Cataract and Implant Surgery. 1991;7(3).