are energetically performed, the irrigation fluid will pass from the posterior lens around the anterior capsule and beneath the iris. The sudden increase in fluid volume moving to exit the AC through the wound, combined with the insufficiency of iris rigidity, will bring about immediate iris prolapse. The now more flaccid iris will be more difficult to control during phaco. Additionally, the iris trauma will lead to increased postoperative inflammation in the AC.

IRIS PROLAPSE

Iris prolapse can be a frustrating problem. It has multiple causes. The predisposing factors include (1) previous iris mechanical dilation, as noted above; (2) a shallow AC secondary to a large cataractous lens, a small axial length, or a hyperopic eye; (3) a very short eye (nanophthalmos); (4) previous narrow angle glaucoma; and (5) previous uveitis with iris atrophy.

The most common cause, however, is not preexistent ocular predisposition but poorly constructed wound architecture. If a sclerocorneal incision has been created, the problem usually lies in entering the AC prematurely (i.e., too posteriorally). A similar problem can occur with clear corneal incision, particularly if the incision is too short. Prevention, by creating an architecturally correct wound is of paramount importance.6

Once prolapse has occurred, the procedure should be stopped. The incarcerated iris should be massaged back into normal position with BSS or viscoelastic. After the iris has been reposited, the AC can be carefully deepened with a small amount of viscoelastic at the wound site. If the wound is too large, placement of one or two 10-0 nylon sutures may provide adequate structural enhancement to allow resumption of phacoemulsification. If iris prolapse persists with progressive loss of pigment and increased iris friability, a small subincisional peripheral iridectomy should be helpful to equalize pressure between the anterior and posterior iris and prevent further damage.

If wound integrity is the obvious cause, prior to the development of severe iris damage, the original wound can be sutured tightly and abandoned. The procedure can be completed after a new, properly constructed, incision is produced in a different anatomic location.

Rarely, the iris is atrophic with little muscle tone. Iris prolapse my reappear in this setting. A Sheets’ glide can be utilized through a clear corneal incision to restrain the iris during phaco. It may be advantageous to temporarily suture the glide to the episclera to hold it in position during the phaco and I&A parts of the procedure. It then can be removed.1

PHACOEMULSIFICATION

All mechanical pupil-dilating techniques create a variably flaccid pupil. During phaco this flaccid tissue appears magnetically attracted to the phaco tip. If aspirated and emulsified, extraordinarily severe instantaneous iris damage is the inevitable result. To prevent this mishap, low or zero vacuum should be utilized during those phaco techniques that require sculpting. In addition, removal of segments with high vacuum should be performed above the plane of the pupil and away from the pupillary margin.

Occasionally, after a high-power encounter with the phaco tip, the iris is so damaged that it creates iris strands. These are then attracted to the phaco tip, no matter where it is in the AC, immediately with usage of foot pedal position 2. If phaco is continued, progressive iris damage ensues. It is therefore necessary to isolate iris strands with dispursive viscoelastic as well as perform phaco away from the area of the strands. Often, after instillation of a small amount of viscoelastic, cutting the persistent strands with intraocular microscissors is beneficial. Then more dispursive viscoelastic can be added to isolate the damaged area from the phaco tip (see Chapter 24).

IRIDODIALYSIS

The iris can be torn from its root during introduction of the phaco tip. This can occur at the beginning of phaco, or if the tip should be withdrawn and reinserted. The phaco tip can catch and drag the iris, causing substantial damage and hemorrhage. This is likely to occur with a crowded AC such as in high hyperopes or in a phacomorphic mature cataract, or when the iris is flaccid after stretching maneuvers. This can be avoided by creating a deep AC with dispersive viscoelastic, entering the eye with reflux, and, if necessary, gently manipulating incarcerated iris from the phaco tip with a second instrument through the paracentesis.

IRRIGATION AND ASPIRATION

Due to the iris flaccidity, a bimanual I&A may be beneficial. Separating the irrigation and aspiration, as is commonly done in Europe, decreases AC turbulence and the tendency for aspiration of iris into the 0.3-mm I&A tip.

Alternatively, using a standard coaxial I&A through the main incision and a Kuglen hook through the paracentesis, the hook can be used to push the iris away from, or hold it up over, the I&A tip so that the iris is not aspirated. Finally, putting the I&A orifice immediately adjacent to the cortex to be aspirated permits preferential aspiration of cortex rather than iris.

Most phaco machines control flow and preset the vacuum in I&A. Therefore, once the cortex is occluding the I&A tip, the vacuum will build until the cortex is aspirated with a postaspiration surge, which often aspirates the flaccid iris. Some newer machines allow variable vacuum (400 mm Hg) and preset flow (20 cc/min). This is ideal for aspiration of cortex in the presence of the iris. The cortex can be grabbed with low vacuum. The vacuum can be gradually increased until aspiration occurs, and then it can be decreased before aspiration of the iris.

INTRAOCULAR LENS SELECTION

IOL selection, as always, is determined by the condition of the capsule and surgical judgment. However, the increased iris manipulation will have a negative effect on the blood–aqueous barrier. A variable increase in the amount of postoperative inflammatory change can be expected. Therefore, one might consider one of the more biocompatible IOL materials. The hydroacrylic MemoryLens, the Alcon or Allergan acrylic lenses, or the second-generation material silicone lenses would be appropriate choices.10

Occasionally, the pupil remains dilated to a variable degree or may be partially asymmetric. To prevent IOL edge exposure and potential edge glare, an IOL with at least a 6-mm optic diameter should be used.

Once the lens has been implanted, injection of intracameral acetylcholine or carbachol may be invaluable to assess the iris and its function. In addition, if there is little iris contraction and the possibility of persistent meiosis exists, intracameral meiotics help in the decision as to whether to make use of iris sutures.

IRIS SUTURES

To create a smaller pupil, iris sutures of 10-0 Prolene can be placed in two techniques:

1.A single limbus parallel suture can be placed in the iris stroma midway between the pupil and iris root. Once tied, it will “bunch up” the iris and create a smaller pupil.

2.A circlage of the pupil can be executed by winding the suture through the iris around the pupillary margin. It is then tied with the appropriate amount of tension to create a pupil of the desired size.

POSTOPERATIVE CARE

In general the greater the iris manipulation, the greater is the anticipated postoperative inflammatory change. Therefore, increased frequency of application

CHAPTER 6 IRIS PROBLEMS • 55

of topical steroids as well as the addition of topical NSAIDs is indicated. In an effort to create a natural meiosis and prevent adhesions of iris to the anterior capsule, meiotics such as pilocarpine 1% should be used for the first few weeks on a t.i.d. to q.i.d. basis.

CONCLUSION

In the past, the small pupil was an all-too-frequent predecessor to complications during capsulorrhexis or phaco. Presently, with the appearance of successful pupil stretching techniques and the ultimate alternative procedure of iris hooks, the small pupil should be eliminated as a predisposing cause of complications.

ACKNOWLEDGMENT

This work is supported in part by a grant from Research to Prevent Blindness, Inc., New York, NY, to the Department of Ophthalmology, University of Utah.

REFERENCES

1.Fine IH. Management of iris prolapse. Presented at the Cataract Complications Panel, Maui, Hawaii, January 18, 2000.

2.Gimbel HV. Nucleofractis phacoemulsification through a small pupil. Can J Ophthalmol 1992;27:115–119.

3.Fine IH, Hoffman RS. Phacoemulsification in the presence of pseudoexfoliation: challenges and options. J Cataract Refract Surg 1997;23:160–165.

4.Osher RH, Icon RJ, Gimbel HV, Crandall AS. Cataract surgery in patients with pseudoexfoliation syndrome. Eur J Implant Ref Surg 1993;5:46–50.

5.Centurion VC, Fine IH, Lu LW. Management of the small pupil in phacoemulsification. In: Lu LW, Fine IH, eds. Phacoemulsification in Difficult and Challenging Cases. New York: Thieme; 1999:62–64.

6.Allan BD. Mechanism of iris prolapse: a qualitative analysis and implications for surgical technique. J Cataract Ref Surg 1995;21:182–186.

7.Dinsmore SC. Modified stretch technique for small pupil phacoemulsification with topical anesthesia. J Cataract Refract Surg. 1996;22:27–30.

8.Fine IH. Phacoemulsification in the presence of a small pupil. In: Steinert RF, ed. Cataract Surgery: Technique, Complications and Management. Philadelphia: WB Saunders; 1995:199–208.

9.Masket S. Preplaced inferior iris suture method for small pupil phacoemulsification. J Cataract Refract Surg 1992;18:518–522.

10.Samuelson TW. IOL selection for combined procedures: a test model for IOL biocompatability. Presented at the Royal Hawaiian Eye Meeting, physicians’ program directory, p. 137, Maui, Hawaii, January 24–29, 1999.

The hydrosteps consist of hydrodissection and hydrodelineation. Hydrodissetion is defined as the separation of cortex from adjacent cortex or from the capsular bag. It therefore is of two types—corti- cal cleaving and standard. Hydrodelineation is defined as the separation of the endonucleus from the epinucleus.

ANATOMY

The capsular bag is an elastic transparent basement membrane made up of type IV collagen. This basement membrane is laid down by the lens epithelial cells, which reside just inside the capsule. The zonules insert on the anterior capsule over an area 2 to 2.5 mm anterior to the equator. They insert on the posterior capsule 1 mm posterior to the equator. The capsule may be as thin as 2 to 4 m at the posterior pole. It is thickest (17 to 23 m) near the anterior and posterior equator where the zonular fibers attach. The anterior capsule can be as thick as 14 m in adults.1 The posterior capsule may be particularly fragile in cases with congenital posterior lenticonus and posterior polar cataract; age-related or corticosteroid-related posterior subcapsular (PSC) cataracts involve migration and enlargement of the lens epithelial cells posteriorly where the capsule is thinnest.2

The lens is a crystalline structure with an obvious lamellar pattern containing 65% water. The 35% protein matrix is composed of soluble crystalline and insoluble albuminoid portions. It is approximately 10.5 mm in diameter and 4.5 mm thick. Anatomically it is composed of an embryonic nucleus, a fetal nucleus, an adult nucleus, and cortex. The Y sutures de-

marcate the fetal and adult nucleus. With age, the lens increases in size due to continuous formation of new lens fibers. This causes the older fibers to become compressed and dehydrated. Water content decreases and the lens density increases. In addition, the accumulation of brown pigment within the lens causes discoloration1 (Fig. 7–1).

Surgically the adult cataractous lens can be separated into the endonucleus, epinucleus, and cortex. The endonucleus is connected to the epinucleus, cortex, and capsular bag by condensations of nuclear material, which are not evident on pathologic examination. These can be termed nuclear-capsular connections.

HYDRODISSECTION

In cortical cleaving hydrodissection a cannula is placed between the cortex and anterior capsule. The tip of a 27-gauge cannula attached to a 3-cc syringe, filled with BSS, is advanced under the anterior capsule until it is halfway between the anterior capsular rim and the capsular bag equator. The tip of the cannula is elevated until the anterior capsule is actually tented. A slow steady and firm stream of BSS is then injected. The stream of BSS will then advance anteriorally toward the anterior capsule and around the proximate equator. From there it passes behind the posterior pole of the nucleus and cortex and around to the opposite equator. It then progresses around the opposite equator emerging from the capsulorrhexis edge into the anterior chamber. Excess fluid then passes out the incision, thus relieving excessive pressure in the anterior chamber3 (Fig. 7–2A). If the

nucleus floats anteriorally, a common occurrence, the surgeon should cautiously push the nucleus posteriorally. This will effectively push fluid sequestered behind the nucleus around the equator (Fig. 7–2B). The surgeon is usually able to visualize the fluid flow as a wave passing around the posterior pole and then the equator. The anterior chamber is then perceived to deepen momentarily as it fills with fluid. The anterior chamber then shallows as the fluid is seen to exit through the incision. Alternately, the nucleus floats forward stretching the capsulorrhexis. The nucleus is then pushed posteriorally with the hydrodissection cannula. The chamber

deepens, and fluid and viscoelastic escape through the incision. If performed adequately, the cortex is separated or cleaved from the capsule, allowing free rotation of the endonucleus, epinucleus, and cortex as a unit, within the capsular bag.

Standard hydrodissection is performed in a similar manner, except that the cannula is placed within the substance of the cortex. This produces a cleavage plane within the cortex. Consequently part of the cortex remains attached to the capsular bag and part to the endonucleus (Fig. 7–3).

Cortical cleaving hydrodissection appears to have certain benefits over standard hydrodissection. First,