Patients with iris defects do not present very often in routine clinical practice. The average ophthalmologist may encounter only a handful of these patients in a year. But when they present, they are usually quite light- and glare-sensitive and they present a significant therapeutic challenge.
Indications
Patients with iris defects do not present very often in routine clinical practice. The average ophthalmologist may encounter only a handful of these patients in a year. But when they present, they are usually quite light- and glare-sensitive and they present a significant therapeutic challenge.
Most iris defects result from penetrating and nonpenetrating trauma. Penetrating iris injuries are often associated with iris tissue loss. Many patients with significant trauma histories have other ocular injuries including corneal scars, corneal decompensation, retinal scarring, and retinal detachment histories. Another common cause of acquired aniridia is surgical trauma. Posttraumatic and postoperative aniridia is further classified as partial or complete.
In routine clinical practice, congenital forms of aniridia are less common. Congenital forms include colobomas and hereditary aniridia. Hereditary forms of aniridia can also be partial or complete. Hereditary aniridia is often associated with corneal thinning, glaucoma, loose zonules, and poor visual potential. Current Availability of Prosthetic Iris Devices
At this time, there are no FDA-approved artificial iris devices in the United States. While many companies have plans to enter the prosthetic iris market, only a Dutch company, Ophtec, and a German company, Morcher, have actually manufactured devices for worldwide distribution.
Ophtec manufactures a variety of artificial iris devices, and their model 311 iris reconstruction lens is in phase 3 clinical trials in the United States. Ophtec hopes the model 311 lens will be approved by the FDA by the second or third quarter of 2008. Morcher has no plans to pursue clinical trials of its devices in the United States. Morcher implants are available on a case-by-case compassionate-use basis through the FDA.
Preoperative Planning
If an aniridic patient presents with a clear lens, the lens should not be sacrificed to correct an iris defect. Patients with clear lenses should be instructed to wear dark glasses or tinted contact lenses. Artificial iris contact lenses are also available.
The most important question a surgeon asks in planning the implantation of an artificial iris device is, “Does the patient have a cataract?” If yes, and the zonules are reasonably strong, my preference is to implant 1 or 2 Morcher capsule tension ring (CTR) devices to recreate an artificial iris. If the iris defect is sectoral, a sectoral or coloboma ring can be implanted. If the defect extends 360 degrees, 2 or more CTR devices can be implanted to reconstruct an entire iris, as shown in Figure 1. The most common devices I implant are the 96F coloboma ring and the 50F pupil reconstruction ring. Two 50F rings are needed to reconstruct a complete iris.