Sulcus add-on intraocular lenses: Background and in vitro analyses

Incorrect intraocular lens (IOL) power remains one of the most important causes of IOL explantation, according to the tenth annual survey of members of the ASCRS/ESCRS evaluating the complications of foldable IOLs requiring explantation or secondary intervention.¹ Surgical means that have been used to deal with post-cataract surgery ametropia errors, besides IOL explantation/exchange, include implantation of a supplementary IOL (piggyback), and corneal refractive procedures.

When implantation of a piggyback pseudophakic IOL is the chosen method to deal with this problem, surgeons must be aware of the possibility of interlenticular opacification (ILO).^2,3 This is the opacification of the opposing surfaces of piggyback IOLs, which led to the explantation of pairs of lenses analysed in our laboratory. All cases analysed so far involved pairs of piggyback hydrophobic acrylic IOLs implanted in the bag, via a relatively small capsulorhexis.² Therefore, one of the surgical methods for the prevention of this complication is the implantation of the first IOL inside of the bag, and the supplementary IOL in the sulcus, so that the equatorial region of the capsular bag with residual lens epithelial cells remains sequestered.³

An IOL for piggyback implantation in the sulcus should ideally be manufactured from a soft, biocompatible material, with a relatively large optic and overall diameters, as well as round and smooth optic and haptic edges. Also, the design configuration should provide appropriate clearance with uveal tissues and the in-the-bag IOL. In collaboration with Dr Nick Mamalis, and research fellows, we have recently had the opportunity to evaluate such an IOL in our laboratory, at the John A. Moran Eye Center.⁶

The Sulcoflex is a hydrophilic acrylic IOL that was designed by Prof. Michael Amon (Vienna, Austria) specifically for piggyback implantation.⁷ The design platform, which exhibits the above-mentioned characteristics for a sulcus-fixated piggyback IOL is currently manufactured by Rayner (UK) in 3 models: aspheric, multifocal, and toric. In our study, we obtained pseudophakic human cadaver eyes from the Lions Eye Institute for Transplant & Research (Tampa, Florida, USA), as well as the San Diego Eye Bank (California, USA), which had been implanted with different IOLs in the bag. Our objective was to assess the Sulcoflex fitting, centration, tilt, haptic position and clearance with the primary IOL in eyes with different overall sizes, Soemmering's ring formation and in-the-bag IOLs.⁶

Method

Sixteen pseudophakic human cadaver eyes were obtained within 72 hours of enucleation. Each eye was measured grossly then imaged with a very-high frequency ultrasound system (Artemis, Ultralink) to access the overall position of the primary IOL and the sulcus diameter. The eyes were then injected with the Sulcoflex lens through a clear corneal incision, and the lenses were fixated in the sulcus. The ophthalmic viscosurgical device was removed by aspiration, and the incision was sutured to prevent the presence of any air bubble inside of the eye.

After fixation in formalin, the eyes were re-evaluated with the same very-high frequency ultrasound for assessment of IOL fixation, fitting, centration, tilt, haptic position, and clearance with the primary IOL and intraocular structures. Further analyses of the position of the Sulcoflex haptics in the sulcus were performed from the posterior or Miyake-Apple view, as well as from anterior and oblique views.