22 Iris Claw Lens
Summary
Implantation of intraocular lens (IOL) inside the capsular bag is the “standard of care” to correct aphakia. However, when we are dealing with complex situations involving anterior segment reconstruction and lens implantation, the capsular bag may either be not available at all or be inadequate or some other clinical situation makes it difficult, precarious, or impossible for posterior chamber lens implantation. It could be a case of inadvertent posterior capsule rupture during phacoemulsification, grossly subluxated capsular bag due to trauma, congenital, aphakia, traumatized iris, or any other condition with absent or deficient capsular support. Angle-supported IOLs have historically been known to cause a lot of problems in the long term but end up getting implanted for lack of a popular alternative. 1 , 2 Scleral-fixated lens implantation techniques are generally time-consuming and require a lot of instrumentation and manipulation. 2 , 3
In such conditions, the Artisan lens, also known as the iris claw lens, may come to the rescue of the surgeon. All that the iris claw lens requires is available iris tissue that may provide for two points where the claws of the lens may be anchored. Implantation of the iris claw lens may be done on the anterior surface of the iris (classical way of fixation) or the posterior surface of the iris, also known as the retropupillary implantation. 4 , 5 Long-term results with iris claw lens implantation are very encouraging. Every anterior segment surgeon needs to have a backup system in case a posterior chamber lens implantation is not possible. The iris claw lens is the best design for this purpose. In this chapter, we shall learn about the iris claw lens design, instrumentation, and technique of implantation of this unique lens in a variety of clinical situations.
22.1 Introduction
Iris claw lens or the Artisan lens is an entirely unique genre of IOLs, which does not need the angle of the anterior chamber, the ciliary sulcus, the sclera, or the capsular bag for support. Instead, it is fixated to the iris muscle either to the front surface or to its back surface. Fixation to the back surface of the iris is referred to as retropupillary fixation. Classically, this lens had been designed to be fixated to the anterior surface of the iris. In this chapter, we shall be discussing the versatility of implantation of the iris claw in a variety of situations, both on anterior as well as on the posterior surface of the iris according to the situation at hand.
22.2 History and Design of the Iris Claw Lens
Before we say anything else, it is important that we briefly delve into the history of the lens. Designed by legendary Dutch ophthalmologist Dr. J. G. F. Worst in the early 1970s, the basic design of the iris claw lens has remained unchanged for nearly four and a half decades. This lens has weathered the eventful years of revolution in cataract surgery technology from the era of primitive lens designs to the present day. The iris claw lens is a single-piece all-polymethyl methacrylate design (▶Fig. 22.1 and ▶Fig. 22.2). It is a planoconvex lens with an optic in the center and two oval openings in the haptic on either side of the optic, which are split in the middle to form a pincer-/claw-like mechanism, which the surgeon uses to fixate the lens to the iris tissue. Dr. Daljit Singh of India modified this design, which was known as the Singh–Worst design, in which the claws instead of being at 180° were positioned at 45 and 135°. We shall be discussing primarily about the original design of the iris claw lens with claws at 180° in this chapter.
22.3 Size of the Iris Claw Lens
The design of iris claw lens is primarily of the same as the original Artisan lens that Prof. Dr. J. G. F. Worst designed. However, the comparison ends here. The overall dimensions of the original lens manufactured by Ophtec, Netherlands (8.5-mm overall length and 5-mm optic diameter) are much bigger than the lenses currently being used. The larger size of the lens was meant to achieve peripheral iris fixation and to avoid distorting the pupil. However, this brought the haptic of the lens perilously close to the endothelium. Perpetual iridodonesis and pseudophacodonesis led to intermittent endothelial touch and persistent cell loss.
However, if the lens is fixated to the iris tissue just outside the collarette (both anterior and posterior), pupillary distortion does not occur and this also does not impede the dilatation of the pupil; hence, smaller sized lenses were chosen over the original sized lenses.
The sizes of iris claw lenses (▶Fig. 22.3) used are manufactured in India and are available in the following dimensions:
Size 1: Overall length 7.25 mm × 4.20-mm optic diameter.
Size 2: Overall length 6.4 mm × 4.00-mm optic diameter.
Size 3: Overall length 5.5 mm × 3.50-mm optic diameter.
Size 4: Overall length 4.0 mm × 2.00-mm optic diameter (special order).
The only reason why these lenses can be implanted in small sizes is because this lens does not require the support of the external shell of the eyeball for its fixation. This is also precisely the reason that implantation can be carried out in eyes of all diameters ranging from microcornea to megalocornea.
22.4 Implantation of the Iris Claw Lens
All lens designs in principle derive their fixation support by way of their springy haptics, which lean against the angle of the anterior chamber, the ciliary sulcus, the capsular bag, or the sclera. The iris claw lens is the only design that uses the iris tissue for its fixation. As the name implies, the lens is fixed to the iris. The lens can be implanted horizontally, vertically, or obliquely to suit any clinical situation according to the availability of the iris tissue, the accessibility of the surgeon, or the availability of an optical window. The lens can be implanted centrally over the pupil or eccentrically, something which is unique to this lens design. The iris claw lens can be fixated to the anterior surface as well as to the posterior surface of the iris.
22.4.1 Biometry
IOL power calculation is done using the standard calculation formulae. For implantation of the iris claw lens to the anterior surface of the iris, a constant of 115.5 is used and for posterior fixation, a constant of 116.5 is used with the SRK/T formula.
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