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Surgeons explain how to approach reconstruction of the iris, pupil
Tips and techniques are given for handling iris stromal loss, iris root disinsertion, pupil abnormalities and iris functional loss.
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Introduction
 Amar Agarwal |
Iris reconstructive surgery is among the most difficult operations performed by the anterior segment surgeon, especially in cases after ocular trauma. Patients in need of such reconstructive efforts, either in cases of congenital, traumatic or other causes of iris loss, often are significantly debilitated by glare and other visual disturbances resulting from a compromised iris diaphragm. My guests in this column, Robert H. Osher, MD, Michael E. Snyder, MD Christopher Khng, MD, and Scott E. Burk, MD, PhD, of the Cincinnati Eye Institute, explain how to deal with iris dysfunction or loss.
Amar Agarwal, MS, FRCS, FRCOphth
Patients with partial or total iris loss, whether from congenital, traumatic or other causes, suffer from varying amounts of visual disability. The visual dysfunction may vary from mild to severe and includes glare, photophobia, reduced visual acuity and contrast sensitivity loss. In addition, significant cosmetic issues may also be present, especially when the patient has a light-colored iris. Abnormalities of pupil size, shape and location may also be reasons for pupil reconstruction.
The following considerations for loss of iris tissue are:
- Suture repair is preferable to the use of an iris prosthesis whenever possible, although poor quality iris stroma may not be repairable.
- Create and maintain a pupil size to alleviate symptoms, yet allow adequate visualization of the fundus.
- Small-incision surgery is desirable whenever possible.
- Detailed informed consent and observation of regulatory protocol are necessary because the iris devices are not approved by the U.S. Food and Drug Administration.
Iris stromal loss
The repair options available to the surgeon depend upon the extent of iris tissue loss. This can conveniently be described in terms of clock hours or quadrants of loss.
One quadrant or less. With less than 3 clock hours of loss, the management options are straightforward. Examples of such an iris defect are iatrogenic iris atrophy with a transillumination defect adjacent to the corneal tunnel post-phaco in which iris prolapse has occurred repeatedly, a congenital iris coloboma or an excessively large surgical iridectomy. The primary repair option is with imbricating sutures to the iris leaflets or edges of the defect using Prolene 10-0 sutures with a modification of the McCannel or Siepser technique. If the operation is going to be combined with cataract surgery, implantation of both a single sector iris prosthesis such as the Morcher 96 (or single fin Ophtec Iris Prosthetic System element) and a foldable IOL, each placed into the capsular bag, may be chosen if the remaining iris stroma cannot be adequately closed. Although the sector implant affords good functional results, the cosmetic result may be suboptimal because the 96 series of implants is available only in black PMMA and the Ophtec device colors may not be an exact match at the present time. Therefore, in addition to the implant, we will often place an imbricating suture through the iris defect for cosmesis.
Between one and two quadrants. Between 3 and 6 clock hours, for example, in a case after iridocyclectomy for an iris tumor or post-traumatic iris loss, two pieces of either the partial aniridia ring (Model 96, Morcher) or the Ophtec single-element Iris Prosthetic System (IPS) may be placed into the capsular bag. If the capsular bag is absent, a full-sized prosthetic iris device may be sutured with scleral fixation. Alternately, if the iris defect is only marginally beyond 3 clock hours, imbricating sutures may be attempted depending on the elasticity or friability of the iris tissue. In the situation with iris sutures, an additional McCannel type suture may need to be placed to attach the newly created iris root to the sclera in the area of the repair.
Beyond two quadrants. Beyond 6 clock hours of iris loss, there are several good surgical options. If a small incision is possible, two multiple-fin endocapsular rings (Morcher type 50C, D or E with respective apertures of 6 mm, 5 mm, 4 mm or 3.5 mm, respectively) may be placed in the capsular bag combined with phacoemulsification and implantation of a foldable IOL.
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| Images: Osher RH, and colleagues | |
Iris root disinsertion
The surgical options for repair of iridodialysis (Figure 1) are relatively straightforward. Mattress sutures are used to reattach the iris to the sclera, the number and placement of which would depend on the extent and location of disinsertion (Figure 2).
Abnormalities of pupil size, location and shape
Abnormalities of pupil size range from an absent pupil to a large unresponsive pupil. Pupils obliterated by posterior synechiae may be abnormal in position (eccentric, corectopia) as well as in size. In this situation, synechiolysis alone or the peeling of the peripupillary membrane may restore adequate pupil size and centration. A severely displaced pupil may require the creation of a new central pupil with either a vitrector or fine intraocular scissors, followed by imbricating sutures to close the previous pupil.
A pupil may be either too small or too large. Bound-down pupils from previous anterior uveitis or long-standing pilocarpine usage may be the cause of fixed miosis. Our approach is to first attempt to lyse the posterior synechiae with a cohesive viscoelastic agent injected at the pupil edge. Any separation of tissue will allow insertion of the injection cannula, as viscodissection is highly effective. If the membrane cannot be penetrated, a flat blunt instrument such as a cyclodialysis spatula may prove more helpful in dissecting the iris edge off the lens capsule followed by viscoelastic injection. While sharp dissection is possible, care must be taken to avoid inadvertent puncture of the anterior lens capsule. A safer option is to create a small iridectomy midway between the pupil edge and the iris root through which the viscoelastic agent is injected, which by itself may lyse the posterior synechiae. Recalcitrant synechiae can be severed by either blunt or sharp dissection using the iridectomy for entry. Alternatively, 20- or 25-gauge vitreoretinal scissors can be helpful instrumentation. The iris defect can be closed by sutures. Once the pupil edge has been elevated off the lens capsule, a peripupillary membranectomy technique, as described by Dr. Osher, may prove successful in peeling the discrete ribbon-like membrane off the iris border. This often permits a significant enlargement of the pupil, once the restrictive membrane is removed. If, however, the pupil is still not an adequate size, a pupil-stretching technique may be performed with two blunt manipulating instruments followed by viscomydriasis. Other options include multiple sphincterotomies or pupil “sculpting” with either a vitrector or intraocular scissors.
At the other end of the spectrum is the dilated atonic pupil. Common causes include previous traumatic mydriasis or herpetic iris atrophy. The easiest surgical approach, as described by Dr. Osher, is to use a McCannel-like imbricating suture of 10-0 Prolene passed in each quadrant. A more elegant solution, although more technically demanding, is to use the Ogawa pupil cerclage (Figure 3 on page 61) suture. We prefer to use Prolene 10-0 on a CTC-6L needle, and the suture is placed with the needle passing just inside the
pupil margin. With this technique, the more bites of the iris the better, as too few bites cause scalloping of the pupil margin. Typically, around 20 to 24 bites are taken before the suture is tied to itself. The pupil size may be adjusted by tightening the cerclage. Once an adequate pupil size is attained, the suture is locked. The final option in a case with a fixed dilated pupil is to use two Morcher 50 series prosthetic iris rings placed into the capsular bag, an Ophtec IPS, a model 311 diaphragm prosthesis (fixated or not-fixated) or a model 67 sulcus-fixated prosthetic iris device. However, in view of the small incision, the cosmetic benefit and the regulatory availability issues, suture repair is our first choice before considering an artificial iris. A pupil that is either eccentric or severely oval can be improved by either extending the pupil into the visual axis or by creating a new centered pupil. The previous eccentric pupil can be closed by placing imbricating iris sutures.
Iris functional loss
This group of iris conditions has neither lost nor missing iris tissue, but the iris present is poorly functional. Examples include the diaphanous irides of the albino, which have missing pigment within the iris pigment epithelium, cases of chronic uveitis in which the iris tissue is poor or nonfunctional from inflammation, and the iridocorneal endothelial syndromes in which spontaneous iris holes develop as the iris tissue pulls apart, even though no actual tissue is lost. With severe transillumination defects in the albino, the functional loss may be little better than congenital aniridics. Fortunately, the same capsular fragility problems that are associated with congenital aniridia are absent. We have had mixed responses in terms of glare reduction in albinoid patients undergoing phacoemulsification and foldable lens implantation with placement of paired Morcher 50C or 50E rings or an IPS into the capsular bag (Figure 4). In the absence of adequate capsular support, an iris diaphragm IOL prosthesis such as the Morcher 67 or Ophtec 311 may be sutured to the sclera. For both the uveitic iris and cases of iridocorneal endothelial syndrome, repair of the iris using sutures may be unsuccessful because of the poor quality of iris tissue. Our patients with either uveitis or iridocorneal endothelial syndrome have enjoyed a significant reduction in glare with a prosthetic iris device.
For More Information:
- Amar Agarwal, MS, FRCS, FRCOphth is director of Dr. Agarwal’s Group of Eye Hospitals. Prof. Agarwal is author of several books published by SLACK, Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery, and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; fax: 91-44-28115871; e-mail: dragarwal@vsnl.com; Web site: www.dragarwal.com.
- Michael E. Snyder, MD, can be reached at msnyder@cincinnatieye.com.
- Christopher Khng, MD, can be reached at chriskhngeye@yahoo.com.sg.
- Scott E. Burk, MD, PhD, can be reached at sburk@cincinnatieye.com.
- Robert H. Osher, MD, can be reached at Cincinnati Eye Institute, 10494 Montgomery Road, Cincinnati, OH 45242; 513-984-5133; fax: 513-936-4881; e-mail: rhosher@cincinnatieye.com.
References:
- Agarwal A. Handbook of Ophthalmology. Thorofare, NJ: SLACK Incorporated; 2005.
- Agarwal A. Phaco Nightmares: Conquering Cataract Catastrophes. Thorofare, NJ: SLACK Incorporated; 2006.
- Agarwal A, et al. Two Volume Textbook on Phacoemulsification. New Delhi, India: Jaypee Brothers; 2004.
- Agarwal A, Agarwal A, Agarwal S. Four Volume Textbook of Ophthalmology. New Delhi, India: Jaypee Brothers; 2000.
- Ogawa GS. The iris cerclage suture for permanent mydriasis: a running suture technique. Ophthalmic Surg Lasers. 1998;29(12):1001-1009.
- Osher RH. Peripupillary membranectomy. Video J Cataract Refract Surg. 1991;Volume VII, Issue 4.
- Osher RH. Surgical repair of the fixed, dilated pupil. Consultation Section. J Cat Refract Surg. 1994;20(6):665-666.