Management of Posterior Synechiae Causing Small Pupil
Small pupil may be encountered with posterior adhesions (synechiae) between the iris and the crystalline lens. As isolated pathology, it is usually a result of long-term use of miotics, pseudoexfoliative syndrome, or neurological disorders. Posterior synechiae is a result of uveitis, acute angle closure glaucoma, ocular trauma, or previous surgery. Removal of a cataract through such a pupil is challenging. The situation is recognized preoperatively by failure to achieve dilation after instillation of mydriatics such as cyclopentholate 1%, tropicamide 0.5%, and phenylephrine 10%. Posterior synechiae may be released before surgery following subconjunctival injection of Mydricaine. Patients using miotics are advised to discontinue them 3 weeks before surgery.
Pharmacological Management of Small Pupil
In surgery several steps can be employed to dilate and maintain pupil dilation throughout the procedure. If posterior synechiae exist, they may be released with a spatula following injection of a viscoelastic agent into the anterior chamber or with an anterior chamber maintainer. This may be done by releasing the synechiae with a viscoelastic cannula passed between the iris and the lens parallel to the lens to avoid injury to the anterior capsule while injecting viscoelastic agent under the iris. The cannula is swept circumferentially. Further injection of the viscoelastic agent in the center of the miotic pupil causes the iris to stretch, deepening the anterior chamber and improving pupil dilation. This is also fairly effective in the absence of posterior synechiae. Alternatively, to dilate or maintain the dilated pupil, a pledget sponge soaked with dilating agents may be placed in the conjunctival sac for 10 to 20 minutes before surgery. Mydriatics such as epinephrine (0.3-0.5 ml of 1:1,000) may be added to the irrigation or the infusion bottle if an anterior chamber maintainer is placed. Otherwise, 0.5 to 1 ml sulfite and preservative-free epinephrine 1:1,000 diluted 1:3 in 1:3 xylocaine 4% and BSS-plus or 0.1 ml mixture of cyclopentholate 0.1%, phenylephrine 1.5% and xylocaine 1% may be injected into the anterior chamber before adding the viscoelastic agent. Epinephrine is especially effective in floppy iris syndrome.
Surgical Management of Small Pupil
Several mechanical maneuvers are available if the above fail. All of them cause stretching of the iris margin resulting in microsphincterotomies. They may be used in conditions other than small pupil such as iridoschisis. They are best performed with viscoelastic material. Care should be taken to avoid injury to the corneal endothelium and the anterior lens capsule. The key element in using these techniques and instruments is to dilate the pupil slowly. Overstretching should be avoided because it may result in an atonic pupil, chronic inflammation, cystoid macular edema, pigment deposition, or pupillary intraocular lens capture.
Stretching maneuvers are better avoided, if possible, in patients with iris rubeosis, chronic uveitis, or coagulopathy because of the risk of bleeding and in floppy iris syndrome. If bleeding does occur, it may be controlled by raising the intraocular pressure by means of increasing the height of the infusion bottle or by digital pressure. It may also be partially compartmentalized with a viscoelastic agent.
The first stretching technique involves 2 instruments such as iris hooks or Lester's lens manipulators that are introduced into the anterior chamber. Both may be inserted through the main incision, or one of them may be introduced through a paracentesis at 1 to 2 o'clock from the incision.1 The instruments also may be inserted through 2 paracenteses. One instrument retracts the pupil margin toward the entry port while the other pushes the opposite side of the pupil margin. The maneuver is performed slowly for a period of 10 to 20 seconds. The stretched position is maintained for 5 to 10 seconds, and the maneuver is repeated perpendicular to the original maneuver.
In a second maneuver, a 2-pronged pupil dilator (Keuch Pupil Dilator, Katena, Denville, NJ) and 3or 4-pronged pupil dilator (Beehler Pupil Dilator, Moria, Antony, France) may be introduced into the anterior chamber to hook the iris margins and stretch it slowly. The Beeler dilator has 2 or 3 movable prongs for the distal iris margin and a fixed one for the proximal iris margin. The prongs should be hooked into the margin and the plunger pushed slowly, causing the distal prongs to expand the iris. The Beeler dilator is cruder than others and may cause iris tears, hyphema, and corneal edema if not used properly, so it is better avoided if the anterior chamber is crowded.
In another technique, an iris ring made of hydrogel (Grieshaber & Co., Schaffhausen, Switzerland) is used. It is a compact oval instrument in its dehydrated form. It is inserted through the main incision and placed in the pupillary plane. On contact with the aqueous humor, it expands and captures the iris margin, causing the pupil to expand. Other flexible pupil expanders made of silicone (Graether Pupil Expander, Eagle Vision, Memphis, TN), polyurethane (Perfect Pupil Injectable, Milvella, Sydney, Australia), polypropylene (Malyugin Ring, MicroSurgical Technology, Redmond, WA) and polymethylmethacrylate (5S Morcher Pupil Expander, Morcher GmbH, Stuttgart, Germany) are available. They all are grooved rings with some differences between them. They are inserted through the main incision at the beginning of the surgery and removed at its completion after filling the anterior chamber with a viscoelastic agent.
Another option is the Graether Pupil Expander, an incomplete ring with an internal diameter of 6.3 mm bridged by a slender strap that facilitates access through the pupil. It may be inserted after retraction of the proximal pupil margin with an iris glide retractor.4 The folded expander is loaded on an insertion spatula so that its folded end extends just beyond the spatula tip. The spatula is placed into the anterior chamber on its side and then rotated 90 degrees. The folded tip of the expander engages the distal margin of the iris, and the bulged tabs of the folded expander engage the proximal stretched side of the pupil. The insertion instrument is then withdrawn and leaves the Graether to expand. An iris spatula is inserted through the paracentesis to hold the expander in place while the iris glide is removed. Two hooks are placed in the 2 tabs at the base of the expander to stretch the strap. After insertion of the intraocular lens (IOL), the strap is folded inward by an iris hook, lifting the expander and removing it from the eye.
The Perfect Pupil is an incomplete ring with an integral arm bulging toward the incision and a 7-mm internal diameter. The arm facilitates the removal of the ring and the 45° opening part of the ring allows insertion of the phacoemulsification tip. It can be placed with or without an injector system (No. PP70-Inj, PP70-Inj-1, Geuder AG, Heidelberg, Germany).
Malyugin Ring is a rectangular ring with an internal diameter of 6 mm. It has 4 coiled corners through which the iris margins are engaged. It is inserted with an inserter that is placed at the pupil center. The ring is released by pushing the inserter knob so its distal scroll engages the distal iris margin. As the device is injected, the other scrolls will engage the iris margin except of the proximal one that would lye on the iris surface. This one is inserted to engage the proximal iris margin by an iris hook inserted through a paracentesis. It is removed in a reverse manner using the inserter.
The Morcher Pupil Expander is an incomplete ring with internal diameter of 5.0 mm. It lacks an integral arm or strap and is therefore more difficult to insert and remove. It may be inserted with or without an injector (Geuder Pupil Dilator Injector No. G-32970, Geuder AG, Heidelberg, Germany).
Another option is iris retractors that can be positioned in 4 quadrants.2, 3 They are used to engaged the iris margins in miotic pupils and floppy iris syndrome and to release reverse pupillary block in highly myopic or vitrectomized eyes. They can also be placed in the capsulorhexis edge in cases of zonular weakness. The flexible nylon retractors with adjustable silicone retaining sleeves are easier to manipulate than rigid titanium ones. The retractors are introduced into the anterior chamber through 4 paracenteses to retract the pupil margin. The paracenteses are made at the limbus with slight posterior declination so that when the retractors are introduced into the anterior chamber, they point to the pupil margin. The pupil is slowly retracted to a diameter of 5 to 5.5 mm. The retractors provide a constant pupillary diameter and protect the pupillary margin from the phacoemulsification tip. These devices as well as iris rings are preferred over stretching techniques for floppy iris syndrome.
When different devices were compared, it was found that the largest pupil was obtained with the Morcher Pupil expander, followed by iris hooks, the Beeler Pupil Dilator, and bimanual stretching (5.9 ± 0.6 mm, 5.6 ± 0.6 mm, 5.5 ± 0.8 mm, and 4.9 ± 0.7 mm respectively), however, the postoperative pupil size was not statistically different.5 The least time-consuming techniques for pupil dilation employed the Beeler Pupil Dilator and bimanual stretching.
If the anticipated postoperative intraocular inflammation is high, such as with pediatric cataract, acute or chronic uveitis, or after trauma, 40 mg of enoxparine (Clexan®), a low-molecular heparin may be added to an infusion bottle of 500 ml BSS6 or triamcinolone acetonide 1 mg may be injected into the anterior chamber although the later may cause high postoperative intraocular pressure and may be devastating if endophthalmitis develops. Subconjunctival corticosteroids (betamethasone disodium phosphate 3 mg) with antibiotics also may be added at the completion of the surgery. Postoperatively, more vigorous treatment with topical corticosteroids is warranted.
References
- Shepherd DM. The pupil stretch technique for miotic pupil in cataract surgery. Ophthalmic Surg. 1993;24(12):851-852.
- Nichamin LD. Enlarging the pupil for cataract extraction using flexible nylon iris retractors. J Cataract Refract Surg. 1993;19(6):795-796.
- Masket S. Avoiding complications associated with iris retractor use in small pupil cataract extraction. J Cataract Refract Surg. 1996;22(2):168-171.
- Graether JM. Graether pupil expander for managing the small pupil during surgery. J Cataract Refract Surg. 1996;22(5):530-535.
- Akman A, Yilmaz G, Oto S, Akova YA. Comparison of various pupil dilation methods for phacoemulsification in eyes with small pupil secondary to pseudoexfoliation. Opthalmology. 2004;111(9):1693-1698.
- Rumelt S, Stolovich C, Segal IZ, Rehany U. Intraoperative enoxaparin minimizes inflammatory reaction after pediatric cataract surgery. Am J Ophthalmol. 2006;141(3):433-437.
Author Disclosure
Dr. Rumelt states that he has no financial relationship with the manufacturer of any product discussed in this article or with the manufacturer of any competing product.