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Avoiding iris trauma from phacoemulsification in eyes with iridoschisis

Rozenberg, Israel MD*; Seabra, Fabíola P MD

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Journal of Cataract & Refractive Surgery: April 2004 - Volume 30 - Issue 4 - p 741-745
doi: 10.1016/j.jcrs.2003.09.042
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Abstract

Iridoschisis is a rare disease with few cases reported.1 It is characterized by a split or schisis between the posterior pigmented iris layer and the iris stroma. The pigmented layer appears normal, but many of the stromal fibers go through a degenerative process in which they detach and free float in the anterior chamber,1 creating a shredded wheat appearance that primarily affects the inferior iris quadrants.2 The disease has been associated with other ocular conditions such as syphilitic interstitial keratitis,3 keratoconus,4 and most frequently, glaucoma.5 It has even been considered a consequence of the intermittent or acute intraocular pressure (IOP) elevation associated with unusual manifestations of iris stromal atrophy.5 Because iridoschisis is associated with aging,6 cataract is often a concomitant issue. Lens extraction is difficult because the free-floating iris fibrils are immediately attracted to the phaco tip and the irrigation/aspiration (I/A) needle by the fluidic negative forces present during phacoemulsification and aspiration. If the loose iris fibrils become entrapped in the aspiration port, the cataract extraction process is impaired and there is a strong chance of complications such as bleeding, iris tears, loss of mydriasis, and disruption of the blood–aqueous barrier.2

Two methods have been described to ease iris and pupillary management in the presence of iridoschisis. Both are based on mechanical restraint of the diseased portion of the iris. One technique uses multiple iris hooks, and the other uses the Graether pupil expander.2,7 These methods are unable to maintain the stability of the fibrils along the anterior surface of the iris. By allowing free contact between the circulating balanced salt solution (BSS®) and the exposed iris stroma, the techniques above may facilitate the iris being drawn in by the streams of BSS that flow from the phacoemulsification handpiece irrigation holes. We describe a case in which the iris fibrils were restrained by another technique.

Surgical Technique

The patient had phacoemulsification in both eyes on different days under peribulbar anesthesia performed with bupivacaine 0.75%. Pupillary dilation was achieved with tropicamide 1% and phenylephrine 10%, with 1 drop each given 3 times preoperatively. Traditional preoperative prophylactic measures were performed immediately (eg, the instillation of povidone–iodine 5% on the conjunctival surface, placement of an adhesive plastic drape to cover the eyelashes, and vigorous flushing of the conjunctival sac with BSS).

A paracentesis incision was made at the 3 o'clock meridian with a 22-gauge injection needle. The main incision was made in the clear cornea at the 12 o'clock meridian with a 2.5 mm diamond blade keratome. Different ophthalmic viscosurgical devices (OVDs) were used in each eye to facilitate safe surgical maneuvers. In 1 eye, after the main incision was made, sodium hyaluronate 1.4% (Healon GV®) was injected in the anterior chamber angle to push the free iris strands posteriorly, away from the main incision at 12 o'clock. The amount of Healon GV injected covered the areas of the iris affected by iridoschisis. Approximately a quarter of the lower part of the anterior chamber was filled with an arc of Healon GV (Figure 1, A). The remaining space in the anterior chamber was filled with methylcellulose 2% (Visicrom®) until it began to extrude from the main incision (Figure 1, B). In the second eye, Healon GV was replaced with sodium hyaluronate 2.3% (Healon®5) and Visicrom was replaced with sodium hyaluronate 3%–sodium chondroitin sulfate 4% (Viscoat®) in approximately the same amounts as in the first eye.

Figure 1.
Figure 1.:
(Rozenberg) A: The first OVD is injected into the lower portion of the anterior chamber. B: The second OVD is injected and fills the anterior chamber. C: The capsulorhexis is formed in an elliptical fashion and does not extend beyond the center of the pupil.

The initial capsulotomy was made with a disposable 27.5-gauge needle bent at the midportion of the bevel. An elliptical capsulorhexis was made from 3 to 9 o'clock with a capsulorhexis forceps; it did not extend beyond the center of the pupil (Figure 1, C). Hydrodissection was performed with a flat, 25-gauge cannula (4025 Hurricane Medical) using small bursts of BSS to avoid expelling the OVDs from the eye. Nuclear fracture was performed with a Fine-Nagahara phaco chopper (#08 14503, Rhein Medical) and a bent-tip, 22-gauge injection needle instead of the commonly used phaco tip (Figure 2, A). The nucleus was fractured into more than 4 pieces to ease removal from the eye. The nuclear fracture process was done inside the capsular bag.

Figure 2.
Figure 2.:
(Rozenberg) A: The nucleus is chopped with a bent-tip, 22-gauge needle in the right hand and a Fine-Nagahara chopper in the left hand. B: Loss of iris restraint can be seen at 5 o'clock. C: Final cortical remnants are manually aspirated with the Simcoe cannula. D: After complete cortical aspiration, the elliptical capsulorhexis is evident.

Phacoemulsification was performed using a Protegé unit (Storz) and a MicroFlow 30-degree phaco tip (DP 8230, Bausch & Lomb). If iris fibril movement was noticed (Figure 2, B), the 6 o'clock region of the anterior chamber was refilled with the second OVD that had been injected. With an aspiration rate no higher than 100 mm Hg and the BSS bottle lowered to 150 cm, slow phacoemulsification was performed to reduce turbulence in the anterior and posterior chambers.

After nuclear emulsification, the cortical remnants were mechanically aspirated with an I/A cannula and the remaining strands were manually aspirated with a Simcoe cannula (Figure 2, C). After complete cortical aspiration, the elliptical capsulorhexis was evident (Figure 2, D). The anterior chamber and capsular bag were filled with a sodium hyaluronate 1% solution (Biolon®), and a single-piece acrylic intraocular lens (IOL) (AcrySof® SA30AL, Alcon) was implanted in the bag.

The portion of the anterior capsule in front of the IOL optic was removed to complete a partially circular capsulorhexis (Figure 3, top). The final shape of the capsulorhexis was asymmetric (Figure 3, bottom).

Figure 3.
Figure 3.:
(Rozenberg) Top: After IOL insertion, the portion of the anterior capsule in front of the IOL optic is removed in a continuous curvilinear fashion. Bottom: The final shape of the capsulorhexis is asymmetric, and the IOL is in the bag.

Remnants of OVD were carefully aspirated mechanically beginning at 12 o'clock and ending around 6 o'clock; special care was given to OVD remnants behind the IOL optic. When the iris fibrils began to move toward the I/A tip, the process was stopped and the small amount of OVD remaining was left in the eye around 6 o'clock. The incisions were sealed with BSS injections.

Diluted carbachol 0.01% (Miostat®) was injected in the anterior chamber at the end of the procedure. Antibiotic agents and povidone–iodine 5% were instilled in the conjunctival fornix. The patient took 1 tablet of acetazolamide 250 mg (Diamox®) on leaving the operating room and 1 tablet 12 hours later because OVD remnants in the eye could lead to a posterior ocular hypertensive peak.

Case Report

A 72-year-old white woman presented with a best corrected visual acuity (BCVA) of 6/20 in the right eye and 6/15 in the left eye. The IOP was 8 mm Hg in both eyes. Slitlamp examination showed iridoschisis in both eyes and light blue irises. In the right eye, there was a larger and more severely affected area that covered 40% of the lower anterior surface of the iris (Figure 4, left). The left eye had a 25% affected area in the iris, also around 6 o'clock. The corneas showed normal specular microscopy and steeper vertical meridians on topography. Grade 3+ nuclear sclerotic cataracts were present in both eyes.

Figure 4.
Figure 4.:
(Rozenberg) Left: In the right eye, 40% of the iris was affected by iridoschisis. Right: After surgery, the iris surface remains remarkably untouched.

The patient's medical history was unremarkable. Fundoscopy was not performed with dilation because it was thought the loose iris fibrils might induce angle closure. Ultrasound (US) evaluations of the posterior segment of the eye were normal. The less affected left eye was the first one to have phacoemulsification; the total US time was 2:48 minutes with a mean final rate of 10% of potency. With the OVD combination used in this eye (Healon GV and Visicrom), a loss of the protective effect was observed during surgery. Visicrom was reinjected 3 times to inhibit iris fibril movement with the BSS stream. On the fourth postoperative day, the uncorrected visual acuity (UCVA) in this eye was 6/10.

The procedure was performed in the right eye 3 weeks later. After the main incision was made, small iris fragments detached from the diseased areas and floated out of the incision. A similar surgical procedure was performed, but Healon5 and Viscoat were used instead. Although the iridoschisis in this eye was severe, phacoemulsification was accomplished with only the initial load of the OVD. The iris fibrils remained immobile during the procedure. The total US time was 4:37 minutes with an average rate of potency of 9%. On the fourth postoperative day, the UCVA was 6/15 and the iris presented an unmodified aspect compared with the preoperative situation (Figure 4, right). No IOP spikes were noted during recovery. Four weeks after the second procedure, the BCVA was 6/7.5 in the right eye and 6/6 in the left eye.

Discussion

The disorganized anterior layer of the iris in iridoschisis cases has a tendency to become drawn in by the suction of the I/A cannula and phaco tip during phacoemulsification. Previous techniques use mechanical restraint of the fibrils with hooks or pupillary expanders.2,7

The use of specific OVDs in cataract surgery in eyes with iridoschisis has been superficially reported elsewhere, as has the use of a slightly eccentric capsulorhexis.2 However, application of the soft-shell technique with the use of more than 1 OVD during surgery8 has not been described before. The placement of an arcuate mattress of a high-viscosity OVD covering the diseased area of the iris prevents iris fibril movement under the BSS stream, but this product can easily wash away as surgery evolves because of its cohesive nature. Filling the remaining space of the anterior segment with a dispersive substance will shield the highly viscous OVD from being dislodged from the diseased iris surface by the BSS flow.

We used 2 combinations of OVDs, Healon GV and Visicrom, and Healon5 and Viscoat. The second combination was more resistant to the BSS flow as it kept the iris fibrils steady during phacoemulsification. The placement of OVDs in the eye does not guarantee that no iris tissue will be lost, as shown by our patient's second eye. In that case, aqueous drained out of the main incision with a few detached iris fragments as soon as the anterior chamber was entered.

A capsulorhexis is traditionally round and centered in cataract surgery. In our technique, we used an elliptical one that did not extend vertically beyond the middle of the pupil. We thought that a wide and round capsulorhexis would allow the phaco tip and floating fibrils to move too close together. With the elliptical shape, we were able to fracture the nucleus and perform almost all lens emulsification within the capsular bag. The nucleus was fractured with a phaco-chop technique, but instead of using a phaco chopper and the phaco tip, we opted to break the nucleus in slices with the phaco chopper and a 22-gauge, bent-tip needle. Expertise with the chopping process was required; the idea was to use the minimum possible amount of US energy and BSS flow when it was safe. Otherwise, we would have used traditional chopping instruments.

The main incision should preferably be made at 12 o'clock, as this allows phacoemulsification to occur as far from the floating fibrils as possible. Even in cases in which the steeper meridian is horizontal, safety should be emphasized over refractive outcomes.

In conclusion, proper management of OVDs using the principles of the soft-shell technique along with an elliptical capsulorhexis and cautious in-the-bag phacoemulsification can provide consistently safe results in cataract extraction in eyes with iridoschisis.

References

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© 2004 by Lippincott Williams & Wilkins, Inc.