PERIPHERAL IRIS IOL FIXATION

RATIONALE AND RESULTS

Garry P. Condon, MD

Rationale

The most appropriate intraocular lens (IOL) and method of fixation in the absence of capsular support remains one of the most controversial topics in ophthalmic surgery. Aphakia requiring correction with spectacles or contact lenses can frequently be problematic and poorly tolerated, making it a suboptimal result after cataract surgery. For several decades, the 3 broad categories of secondary IOL fixation have included:

1. Angle support of an anterior chamber IOL (ACIOL)
   
2. Iris suture fixation of a posterior chamber IOL (PCIOL)
   
3. Transscleral fixation of a PCIOL

Each of these broad categories of fixation has advantages and disadvantages in terms of technical difficulty and complications. Despite modern open-loop ACIOL designs, ongoing concerns with the close proximity of their haptics to the cornea and angle have reduced their popularity. Aside from the required larger incision, even the latest flexible ACIOLs continue to pose sizing problems, resulting in the potential for iris compression or IOL movement, which increases the risk for corneal endothelial compromise, glaucoma, and uveitis.^1,2 Methods for the scleral support of a PCIOL are numerous and continue to evolve. The potential devastating complication of endophthalmitis related to scleral suture erosion has led to the introduction of several different IOL types and fixation techniques for the scleral support of these PCIOLs.³ We often see a surge of enthusiasm for each newly suggested scleral fixation technique until later term results and problems direct us toward newer approaches and variations within this broad category. Although technically more difficult, techniques to suture PCIOLs to the sclera avoid some of the complications specific to ACIOLs, and common indications for this approach include young age, glaucoma, abnormal iris/angle anatomy, and an increased risk of corneal endothelial decompensation.⁴

The one factor common to all forms of IOL fixation outside of an intact capsular bag is some degree of uveal tract violation or compromise. This is the most likely underlying element responsible for complications such as uveitis, hemorrhage, elevated intraocular pressure, and cystoid macular edema, which are associated with noncapsular bag fixation of IOLs.^5,6 The implantation of suture and or rigid plastic materials within and adjacent to uveal tissue has the potential to cause irritation and inflammation that can result in both early- and late-term breakdown of the blood-aqueous barrier. Normal eyelid and ocular motility as well as eye rubbing could exacerbate the process. Related clinical findings can range from minimal pigment dispersion to frank intraocular hemorrhage necessitating further medical or surgical intervention. Minimizing the initial and persistent disruption of uveal tissue is likely to be the major key for successful long-term tolerability of IOL fixation in the absence of capsule support.

Using the iris as an IOL fixation platform dates back to some of the first available iris-supported IOL designs. McCannel’s idea for a retrievable suture in 1976 popularized using peripheral iris tissue for stabilizing subluxated IOLs.⁷ Using modifications of his technique and a long curved needle, it has now become routine to use the peripheral iris to stabilize and fixate 3-piece PCIOLs located outside the capsular bag. This approach only requires clear corneal incisions as small as 1 mm and leaves the suture entirely within the eye. A peripheral iris suture occupies a relatively immobile location where minimal long-term stress would be placed on the sutures and surrounding iris tissue (Figure 26-1). The introduction of the 3-piece hydrophobic acrylic IOL in the 1990s allowed the adaptation of this fixation method for secondary IOL suture fixation in aphakic patients.^8–11 Through a small incision, this type of IOL can be unfolded inside the eye in a slow, controlled fashion that readily allows capture of the optic by the pupil for temporary stabilization while the haptics are sutured to the peripheral iris (Figures 26-2 through 26-5). This form of secondary IOL implantation for aphakia or IOL exchange offers the advantages of a small clear corneal incision with minimal associated astigmatism, no disruption of the conjunctiva, and no externalized suture or IOL material that can be associated with an increased risk of endophthalmitis.

While not readily available in North America, the Artisan iris claw ACIOL has been used successfully in several countries as an alternative option for secondary IOL implantation.¹² It too relies on the peripheral iris for support using haptic enclavation of the same area of iris that polypropylene suture fixation requires. The reported long-term success with the Artisan IOL lends further support for the safety and efficacy of using peripheral iris for IOL support.

Secondary IOL implantation using peripheral iris fixation has raised some concerns from the outset. Reported cases of polypropylene suture breakage where the fixation suture was passed through the positioning hole of a polymethylmethacrylate (PMMA) IOL raised concerns over whether the same suture would be durable enough to support iris fixation of a lens haptic. In the 5 cases of late polypropylene suture breakage reported by Price and coauthors, all were broken at the site at which the suture came in contact with the edge of the positioning hole of the PMMA optic.13 The absence of any sharp edge and minimal movement of the peripheral iris during normal pupil movement might explain the rarity of suture breakage when a small-diameter, round polypropylene haptic is sutured to the peripheral iris. This is despite the use of smaller gauge 10-0 polypropylene suture. While some peripheral iris fixation cases reveal some degree of pseudophacodonesis, the final IOL position appears to be more stable than anticipated due to the interaction of the distal portion of the haptics with the ciliary body. Ultrasound biomicroscopy after peripheral iris fixation of secondary 3-piece IOLs demonstrated that the final haptic location is often within the ciliary body. This may contribute to the more posterior final IOL position in the majority of cases.¹⁴ Indeed the average IOL position approximated that of a capsular bag–placed IOL. Thus, it is appropriate to use an IOL power calculated for inthe-bag implantation. The angulated haptics and their position within the ciliary body may keep the optic edges far enough away from the posterior iris to explain the low frequency of hemorrhage and secondary pigmentary glaucoma associated with this form of IOL fixation.¹⁵

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