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Iridectomy of the anterior iris stroma using the vitreocutter during phacoemulsification in patients with iridoschisis

Ghanem, Vinícius Coral MD*,a,b; Ghanem, Emir Amin MDa,b; Ghanem, Ramon Coral MDa,b

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Journal of Cataract & Refractive Surgery: November 2003 - Volume 29 - Issue 11 - p 2057-2059
doi: 10.1016/S0886-3350(03)00336-5
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Abstract

Iridoschisis is a rare condition characterized by separation of the anterior and posterior iris layers. It is usually bilateral but can be asymmetric. The affected fibers may bow forward, leading to anterior synechias and angle-closure glaucoma in up to 50% of patients.1,2 Endothelial touch and corneal decompensation can also occur.3,4 As most of these patients are older than 60 and 70 years, there is also a high probability of cataract. The use of flexible iris hooks5 or the Graether pupil expander6 has been reported to help keep fibrillar material out of the pupil area during phacoemulsification. These can solve the surgeon's intraoperative problem but cannot prevent long-term postoperative complications due to the anterior bow of the iris fibers. We describe a technique in which the affected anterior iris stroma is removed using a vitreocutter just before cataract extraction. This makes phacoemulsification easier and prevents the formation of anterior synechias and damage to the endothelial cells.

Surgical Technique

Pupil dilation is performed using 4 drops of tropicamide 0.5% and phenylephrine 10% at 15-minute intervals 1 hour prior to surgery. Peribulbar anesthesia is then applied.

A superior limbal peritomy is performed, and a 2.75 mm wide scleral tunnel with 2.00 mm of extension is made approximately 1.50 mm from the limbus. A 15-degree blade is used to make a paracentesis. Dispersive viscoelastic material is injected through the paracentesis to inflate the anterior chamber and prevent its collapse. A vitreocutter (Alcon Series 20000 Legacy) is inserted in the anterior chamber and used to cut the iris strands at the site of the iridoschisis, making an anterior sector stromal iridectomy. The iris pigment epithelium is preserved. The vitreocutter parameters are 300 cpm for cut rate, 200 mm Hg for vacuum level, 25 cc/minute for aspiration, and 5.00 cm for bottle height. An anterior continuous curvilinear capsulorhexis is performed between 4.00 mm and 6.00 mm. Hydrodissection is completed with a flat cannula. The nucleus is removed by the divide-and-conquer technique, and the residual cortical material is aspirated. The incision is enlarged to 4.10 mm, and a 3-piece 6.00 mm acrylic foldable intraocular lens (IOL) is implanted in the capsular bag. The residual viscoelastic material is aspirated.

Carbacol is used to constrict the pupil. Remnants of the loose anterior iris fibers are excised with the vitreocutter, and the scleral incision is sutured. The vitreocutter parameters are the same as above. At the end of surgery, a subconjuntival injection of 0.2 mL dexamethasone 4 mg/mL (Ariston®) and 0.2 mL gentamicin 40 mg/mL (Gentaron®) is administered. The eye is padded and a shield applied.

Case Report

A 79-year-old white woman was examined for complaints of pain and decreased visual acuity over an 8-month period in the right eye. Medical and family history were unremarkable.

On examination, best corrected visual acuity (BCVA) was counting fingers in the right eye and 20/100 in the left eye. There was intense corneal edema in the right eye with bullous keratopathy. Both eyes had extensive splitting of the anterior layers of the iris with fibrillar degeneration extending from 3 to 9 o'clock, being more intense at 6 o'clock and confirming a classic iridoschisis case. The bowing forward of the iris narrowed the anterior chamber, but intraocular pressure was normal at 17 mm Hg in the right eye and 16 mm Hg in the left eye. Gonioscopy was not possible in the right eye but showed a slit angle in the left eye without peripheral anterior synechias (PAS). There was approximately 3+/4+ nuclear sclerosis in the right eye and 2+/4+ in the left. Diffuse atrophy of the retinal pigment epithelium was evident on ophthalmoscopy in the left eye. The left eye endothelial cell count was 1210 cells/mm2. Surgery was performed as described in the left eye. Postoperative BCVA improved to 20/25. The patient's last visit was 18 months after surgery (Figure 1). Despite the iatrogenic iridectomy, the patient had no complaints of photophobia or diplopia.

F1-20
Figure 1.:
(Ghanem) A postoperative aspect after iridectomy of the affected anterior iris stroma with the vitreocutter. The pigment epithelium is intact except for the small iatrogenic holes made by the vitreocutter.

Discussion

Patients with iridoschisis usually present other ocular pathologies that may or may not be related. For example, cataract is likely related to the older age of these patients and can be removed by phacoemulsification. However, glaucoma and corneal decompensation are more difficult to treat and must be prevented.

The etiology of endothelial damage or glaucoma is unknown but is likely related to the brushing of loose iris fibers against the corneal endothelium and PAS formation in the angle.2,4 Initially, there is focal endothelial damage overlying the iridoschisis area.3 With time, it spreads over the entire endothelium and leads to corneal decompensation, as noted in our patient's right eye. Prompt action was required to avoid this same complication in the left eye. If surgery is postponed, the angle can be progressively occluded by the PAS and glaucoma develops.

In our technique, the removal of the affected anterior iris stroma is easy to perform and requires only a vitreocutter. Full-thickness holes do not spontaneously develop as the disorder is limited to the iris stroma, but it is a potential risk when performing the anterior iridectomy with the vitreocutter. If the iridectomy is done prior to cataract extraction, care should be taken not to damage the anterior capsule, which can compromise phacoemulsification. Thus, complete removal of the affected iris stroma can be postponed to the end of the surgery after IOL implantation. To avoid excising the iris pigment epithelium, the vitreocutter tip should be kept upward or slightly turned at all times, but not turned sideways or downward.

Another potential complication of the anterior iridectomy is bleeding from the small arterioles of the disintegrating iris stroma, although this did not occur in our case. We believe hemorrhage is more likely to occur if traction is exerted on the fibers attached to the iris root by the phacoemulsification tip or aspiration cannula, damaging the major arterial circle of the iris; their removal prior to cataract extraction can avoid this complication. As the dilator and sphincter iris muscles are still functional, reasonable intraoperative dilation and miosis can be achieved.7 If the pupil is not wide enough to perform safe surgery, flexible iris hooks5 or the Graether pupil expander6,8 can be helpful. In our case, the iris pigment epithelium showed no signs of atrophy after 18 months of surgery, neither the iatrogenic iris holes were larger, however it can happen in a longer follow-up. We had the same experience in a similar case, but the patient missed a 1-month postoperative follow-up. However, no intraoperative or early postoperative complications were found. We believe that the removal of the iris strands also has a postoperative protective effect against glaucoma and corneal decompensation and can be performed prophylactically in patients without cataracts.

References

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2. Salmon JF, Murray ADN. The association of iridoschisis and primary angle-closure glaucoma. Eye 1992; 6:267-272
3. Weseley AC, Freeman WR. Iridoschisis and the corneal endothelium. Ann Ophthalmol 1983; 15:955-956, 958–959, 963–964
4. Rodrigues MC, Spaeth GL, Krachmer JH, Laibson PR. Iridoschisis associated with glaucoma and bullous keratopathy. Am J Ophthalmol 1983; 95:73-81
5. Smith GT, Liu CSC. Flexible iris hooks for phacoemulsification in patients with iridoschisis. J Cataract Refract Surg 2000; 26:1277-1280
6. Castanera J. Pupil management during phacoemulsification in patients with iridoschisis [letter and reply by GT Smith, CSC Liu]. J Cataract Refract Surg 2001; 27:797-799
7. Albers EC, Klien BA. Iridoschisis; a clinical and histopathologic study. Am J Ophthalmol 1958; 46:794-802
8. Graether JM. Graether pupil expander for managing the small pupil during surgery. J Cataract Refract Surg 1996; 22:530-535
© 2003 by Lippincott Williams & Wilkins, Inc.