IRIS CLAW IOL FOLLOWING SUBLUXATED IOL EXCHANGE

Thomas Kohnen, MD, PhD, FEBO

Intraocular lenses (IOLs) have been the treatment of aphakia since Harold Ridley first implanted the first IOL into a human eye in 1949. In the vast majority of patients nowadays, the IOL is implanted into the capsular bag, which is considered the optimal location for the artificial lens. In cases where capsular bag implantation is not possible, sulcus IOL implantation is performed when residual capsular support is sufficient.

In the absence of sufficient capsule, noncapsular IOL fixation options must be considered. These options include anterior chamber IOLs,¹ such as angle- or iris-supported IOLs, and posterior chamber IOLs with iris or scleral fixation.^2,3 This fixation is done either with sutures or with specially designed IOLs.

When explanting a subluxated IOL, the location of the replacement IOL also depends on the status of the remaining capsular bag. If zonular disruption is minimal (eg, fewer than 3 clock hours), then the IOL can be implanted into the capsular bag with the haptics orientated pointing toward the meridian of the zonular defect. If the zonular disruption is larger, options include:

• Ciliary sulcus implantation, possibly with scleral or iris fixation of one or both haptics
  
• Insertion of one haptic into the capsular bag and suturing of the second haptic after it is placed into the sulcus
  
• Endocapsular ring implantation to stabilize the capsular bag or a Cionni-type ring to suture the capsular bag/ring complex to the sclera
  
• Anterior chamber lens implantation (angle supported or iris fixated); an angle-supported anterior chamber lens is acceptable if no angle pathology, glaucoma, or uveitis is present
  
• Posterior chamber lens implantation (eg, iris-fixated retropupillary Artisan/Verisyse-type IOL or scleral-sutured IOL)

Which IOL fixation method for aphakia without adequate capsular support is best remains the subject of great debate. In this chapter I would like to focus on the option of iris claw IOLs.

Worst et al introduced the first iris claw IOLs in 1972.^4–6 This type of fixation can be chosen for cases with aphakia, posterior capsule defects, or zonular weakness. The main advantage of iris-fixated IOLs is that no capsular support is needed for fixation. The Artisan/Verisyse IOLs have haptics that terminate in claws that fixate on the IOL to the midperipheral iris stroma. The most common indications are aphakia, pseudoexfoliation, or other causes of severe zonulopathy.

The Artisan/Verisyse aphakia IOL is made of polymethylmethacrylate with an 8.5-mm length, a 1.04-mm maximum height, and a 5.0-mm optical zone. The IOL power is calculated using the SRK/T formula.

The IOL can be implanted into the anterior chamber as a prepupillary IOL or into the posterior chamber as a retropupillary IOL (Figure 58-1). Prepupillary IOLs have occasionally been associated with endothelial cell loss, bullous keratopathy,⁷ macula edema, secondary glaucoma, and uveitis.

Mohr et al showed the advantages of the retropupillary location as a new approach in 2002,⁸ and several studies reported outcomes using this approach.^6,9 The most important benefits of retropupillary, iris-fixated IOLs are that they better preserve the anatomy of the anterior segment and improve endothelial cell safety. The vaulting of iris claw IOLs provides enough clearance to avoid iris chafing10 and precludes the need for an iridectomy to prevent a pupillary block glaucoma.

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