Iridectomy and Sphincterotomy
Sharon F. Freedman, MD
Maria Gomez-Caraballo, BA
SURGICAL IRIDECTOMY AND SPHINCTEROTOMY
Surgical procedures on the iris in children fall into three main categories:
Peripheral iridectomy to treat or prevent pupillary block glaucoma.
Optical iridectomy to make a visual axis, usually in settings where a central opacity of the cornea prevents the central visual axis from being adequate and where one wishes to avoid penetrating keratoplasty (See Chapter 19).
Manipulations of the iris in the course of other surgery. Discussion of the topic here is limited to sphincterotomy.
PERIPHERAL IRIDECTOMY
One or more openings are made in the peripheral iris, specifically avoiding involvement of the pupillary sphincter, to treat or to prevent angle-closure glaucoma from pupillary block mechanism. Note that, in some instances, a laser iridotomy may be effective in older and cooperative children, but caution is recommended in using laser iridotomy in cases where cooperation is in question or likelihood of reclosure is high (eg, uveitis, see others below).
Indications:
Acute closed-angle glaucoma with or without elevated IOP: Acute closed-angle glaucoma usually occurs secondary to iris bombe with uveitis, after surgery (aphakic or occasionally pseudophakic eye after childhood cataract removal), in eyes with a history of severe retinopathy of prematurity, and less often with spherophakia or lens subluxation.
Narrow closeable angles (eyes in which there is a higher risk for acute close-angle glaucoma and pupillary block): Narrow closeable angles can present in patients noted above before the angle is completely closed and in addition may be noted in eyes with microphthalmia, spherophakia, and selected other developmental abnormalities.
Prophylactically in high-risk situations for angle-closure despite a deep anterior chamber angle and open angle. Examples include high-risk cataract cases (ie, eyes with a history of retinopathy of prematurity), eyes with silicone oil after retinal detachment surgery (iridectomy must be placed inferiorly), rarely in cases of iris cyst, and other nonmalignant space-occupying lesions of the anterior segment.
Comparing laser iridotomy and peripheral iridectomy:
Consider laser iridotomy in select cases. This technique can be difficult in the pediatric population as some children are not able to remain still during the laser iridotomy procedure.
Nonsurgical management (temporizing and preoperative preparations):
The goals of preoperative medications are to decrease intraocular pressure pending more definitive iridectomy, to decrease inflammation in cases of uveitis or where the angle closure has caused inflammation, and to help clear the view in cases of corneal edema to improve technical ease of surgery. Useful medications include aqueous suppressants such as timolol and dorzolamide, and apraclonidine 0.5% for pressure reduction (with oral acetazolamide in severe cases), prednisolone acetate 1% topically (and systemic steroid in cases of severe inflammation or known uveitis); sodium chloride 5% topically in cases of corneal edema (see Chapter 9).
Pilocarpine can be used in cases where the pupil is able to react, but caution is recommended in cases where there may be a component of “posterior pushing” from a relatively anteriorly positioned crystalline lens or uveitis, which may be made worse with pilocarpine.
Procedure:
Equipment needed:
Number 64 microsurgical blade with a handle.
A 15-degree Super Sharp blade or equivalent for paracentesis.
Forceps.
Colibri or very fine toothed forceps.
Utrata forceps in special cases.
Westcott (or micro Westcott) scissors.
Iris or Vannas scissors.
Surgical steps:
Choose a limbal site: Superotemporal and superonasal sites are usually preferred in order to conceal the iridectomy underneath the superior lid; although in adult cases with laser iridotomy, the current recommendation is in the horizontal meridian to reduce diplopia risk.
Placement of a traction suture under the superior rectus is recommended, but not mandatory.
Make a small conjunctival peritomy (˜2-2.5 mm) at the intended site of iridectomy.
Make a groove with a Super Sharp blade (˜2 mm long) in the anterior surgical limbus and very vertically oriented (to at least ˜ 2/3-3/4 depth).
Consider performing another paracentesis at another convenient location (eg, temporal) with a Super Sharp blade and inserting a small amount of viscoelastic if there is a shallow anterior chamber.
Enter the anterior chamber at the base of the groove with a Super Sharp blade. If needed, add more viscoelastic to allow safe enlargement of the entry site to the full 2 mm. CAUTION—watch carefully to avoid iris injury.
Grasp peripheral iris with Colibri forceps. Use Utrata forceps if friable iris is suspected.
Carefully lift peripheral iris through the wound; cut flush with iris or Vannas scissors. CAUTION—watch to be sure that the iris sphincter muscle is still inside the eye.
Ensure that enough iris is in forceps to include iris pigment epithelium (this ensures it is a full-thickness iridectomy).
Inspect the specimen to ensure that the removed iris contains iris pigment epithelium.
Reposition the iris if necessary and look for red reflex and confirmation of iridectomy patency. CAUTION—avoid adding too much viscoelastic, which may expel more iris out the limbal opening; use a small amount of Miochol or Miostat if needed to pull iris back in and constrict pupil.
Irrigate the wound with balanced salt solution if there is some pigment remaining.
Deepen the anterior chamber through the previously performed paracentesis if necessary, to avoid iris entrapment in the wound.
Irrigate viscoelastic from the eye through the paracentesis.
Place a small filtered air bubble if desired.
Close the primary opening with 10-0 polyglactin (Vicryl) suture (use two interrupted or one figure-of-8-style suture).
Close the conjunctiva with the same suture.
Close the side paracentesis if needed (often can hydrate this closed).
Standard subconjunctival antibiotics and steroid therapy (see Chapter 3).
Place standard patch and eye shield.
Additional procedures like lysis of posterior synechiae may be needed in eyes with uveitis or in postcataract eyes.
Lysis of posterior synechiae in some cases of iris bombé patients: Sometimes these cases may require anterior vitrectomy in addition to iridectomy (eg, in cases of aphakic, postcataract eyes with synechial pupillary block).
In these cases, consider performing the surgery with a 23G vitrectomy device through two standard ports in a closed chamber. The vitrector is used port down to engage and cut the iris making a small peripheral iridotomy.
Postoperative care:
It is helpful to rub the specimen on the surgeon’s surgical glove and look for pigment unless the specimen needs to be sent to pathology.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
