Commentary on: A modern outlook on scleral-fixated intraocular lens implantation

Scleral-fixated intraocular lenses (SFIOLs) are proving to be a great choice for the management of aphakia and loss of ample capsular support. The optimal technique for treating aphakia without capsular support remains uncertain.[1,2] Sutured, glued, and sutureless glueless techniques have evolved, each having advantages and caveats.[3] Sutured SFIOLs have classically utilized diametrically opposite 10-0, 9-0, or 8-0 polypropylene sutures tied with eyelets in specialized haptics of polymethylmethacrylate (PMMA) IOLs at one end and with the sclera extraocularly. The extraocular knots were classically made under rectangular or triangular partial-thickness scleral flaps, taking a bite of the scleral bed for fixation. Exteriorization of the sutures was achieved by “rail-roading” through a 26G needle introduced ab externo through the floor of the scleral flaps, while equal tension on the two sutures prevented intraocular lens (IOL) decentration and tilt. The flaps were then closed using interrupted 10-0 nylon sutures covering the knots.[4] Modifications of this technique described passage of the extraocular suture end through a scleral bite in the roof of the flap, thereby making the subsequently tied knot buried under a closed flap without the need for additional 10-0 nylon sutures.[5] A single-point fixation technique has been described for patients with partial capsular support, wherein the suture knot is accommodated within the 6-mm corneoscleral tunnel used to insert the IOL, made in the region of deficient capsular support.[6,7] The sutures could also be exteriorized under separate diametrically opposite scleral grooves[8] or corneoscleral (Hoffman) pockets,[9] eliminating the need to suture the flaps. Additional knots at both ends positioned as internal fixation markers have been described as check valves against the scleral wall, while pulling the polypropylene suture to fixate onto the sclera (“in and out technique”).[10] In an effort to prevent displacement of sutured IOLs, 9-0 nylon or 8-0 expanded polytetrafluoroethylene (Gore-tex; WL Gore, Newark, DE, USA)[11] sutures, which have greater tensile strength, may be used. Presently, any IOL with diametrically opposite holes can be fixed to the sclera. This technique is also applicable for foldable single-piece acrylic IOLs with haptic holes (e.g., enVista MX60; Bausch and Lomb, Laval, Canada), which can be injected into the eye with the sutures passing through the IOL cartridge.[12] It is also possible to pierce the suture needles through single-piece hydrophilic acrylic IOL haptics, thereby making these IOLs a viable option for scleral fixation regardless of the IOL design. Exteriorization of multipiece IOL haptics and their insertion into intrascleral tunnels were described. This could be done with rigid and foldable multipiece IOLs.[13] Initially, exteriorization was achieved through microforceps introduced through 19G/20G paracenteses made in the floor of the scleral flaps using microvitreoretinal (MVR) knives. The use of 25G vitreoretinal trocar-cannula systems for the sclerotomy[14] and a loop retinal scraper or suture lasso for catching the haptic[15] have also been described. Exteriorization of haptics without the need for disproportionate scleral cutdown was facilitated with the ab externo introduction of bent 26G needle to accommodate the IOL haptics introduced into their opening intraocularly using microforceps, although this required skillful intraocular manipulation. IOL haptic exteriorization led to good IOL centration and reduced IOL tilt without the need for manual adjustment of suture length and tightness. The limbus-parallel tunnels were initially made using MVR knives and 24G trocar-cannulas,[16] but were made later using 26G needles. These tunnels were located initially beneath scleral flaps, which were closed in the usual manner. Later, surgeons attempted to glue the scleral flaps back into place using fibrin glue. When glue was applied to reappose the scleral flaps, it also percolated into the intrascleral tunnels and caused adhesion of the haptics inside the tunnel. The use of fibrin glue was thought to be more physiological, allowing healing using natural adhesive components. However, it was soon realized that glue was an optional adjunct, and that stability of IOL was comparable whether the glue was used or not and was actually due to scar tissue formation around the haptics. Sutureless glueless scleral fixation of multipiece IOLs was popularized by doing away with the scleral flaps altogether.[17] Localized conjunctival peritomy was followed by direct introduction of 26G needles through an L-track consisting of a short intrascleral horizontal pass, which was followed by a transscleral penetration. The exteriorized haptics were introduced into intrascleral tunnels made close to the depth of the intrascleral pass of the needles. This was done by creating the tunnels starting near the exit point of the haptic using the MVR knife or 26G needle, followed by pushing of the exteriorized part of the haptic into the tunnel using plain forceps. Although this technique resulted in a very short length of the haptics remaining on the scleral surface, long-term results were good. As an improvement, another short perforating intrascleral pass of the 26G needle was used to create the tunnel, exiting close to the exit point of the haptic. The haptic was introduced into the lumen of 26G needle using plain forceps, followed by pulling on the needle, which released the IOL haptic inside the scleral tunnel thus created.[18] Oftentimes, slippage of an exteriorized haptic by inadvertent loosening of its hold by the surgical assistant resulted in unnecessary prolongation of the surgery. This was prevented by threading silicone stoppers of iris hooks or small pieces of scleral buckle through them. Very soon, a pre-sterilized device incorporating silicone stoppers on 26G needles – the X-NIT – was innovated. A modification of this technique also involved use of a 30G needle.[19] The X-NIT technique involved the use of pars plana continuous fluid infusion, passing the needle into the eye from the fixation point and out through the 6-mm sclerocorneal tunnel, followed by extraocular insertion of the IOL haptic into the needle, pulling onto which carried the haptic with the needle out of sclerotomy. X-NIT still utilized pushing the haptic ends into intrascleral tunnels. Even this was deemed cumbersome, and further developments ensued. X-NIT was further modified using S-FIX – a novel device using a 380-µm spatulated needle attached to a short piece of 5-0 nylon suture and a polyimide tube. The technique entails insertion of the exteriorized haptic into the polyimide tube, pushing the docked polyimide tube into the eye, suture bite starting from the point of sclerotomy, and pulling the suture thread, thereby causing the haptic along with the polyimide tube to come out and the haptic getting fixed into the narrow suture track.[20] The exteriorized haptics of multipiece lenses were modified into flanges after exteriorization to prevent their slippage into the vitreous cavity.[21] Cut ends of the haptics were subjected to heat cautery to melt the ends into bulbous masses, which would prevent their passage back through the needle ports or intrascleral tunnels. The flanges could be buried at the outer ends of the tunnels or scleral grooves, or could even be left as such under the episclera.[2] Some workers also performed this maneuver transconjunctivally.[14] Although the latter risked erosion of the overlying tissue, the results were comparable. Thicker polypropylene sutures (e.g., 5-0 or 6-0) have also been used to anchor PMMA IOLs to the sclera. One end of the suture was passed through the PMMA IOL haptic eyelet, and the other passed through the 26G needle in the L-track intrascleral tunnel. Both ends were modified to make flanges to hold the IOL in place (four-flange technique). The flanges were made by heat (after Canabrava[22]) or argon laser (after Agrawal and Raju[23]). Recently, four-flanged scleral fixation through the dialing hole of a standard PMMA IOL has also been described, which enabled scleral fixation of any PMMA IOL.[24] Multi-point fixation was described for complex designs of foldable IOLs with two, three, or four closed-loop haptics, apart from those with eyelets. These techniques prevented the need for a suture knot or flange at the IOL haptics. The individual sutures could be made to loop inside the holes of the haptics and pass extrasclerally through ab externo needle sclerotomies fashioned at a very short distance from each other, either horizontally apart[25] or radially outward, so that one suture end passed anteriorly and the other one posteriorly. The sutures could also be made to pass through multiple haptics intraocularly, coming out from different needle sclerotomies a few clock hours apart (e.g., for the Akreos AO60, Bausch and Lomb, Laval, Canada, which has four haptics).[26] Any of the techniques could be used separately or in combination, the latter especially for IOLs with an odd number of closed-loop haptics (e.g., the Bigbag IOL, or CT Asphina 603P, Carl Zeiss, Jena, Germany).[27] Extrasclerally, the suture ends could be tied or made into flanges. For tying, the suture ends could be made to pass over the sclera or through additional intrascleral passes, thereby eliminating suture exposure. The suture knots could be rotated inside the eye to prevent their erosion.[3] Knotless zigzag suture fixation techniques have also been described, although the rates of IOL displacement may be more with these techniques.[28] Scleral fixation of IOLs is also applicable for in-the-bag IOLs subluxated or dislocated, wherein the IOL, with the bag, is repositioned and fixed to the sclera.[29] Fibrosis of the capsular bag and anteroposterior looping of the suture around the IOL haptic and any capsular tension ring incorporated provide adequate countertraction to the suture. This is especially useful for traumatic IOL dislocation, wherein minimal manipulation is the key to success.[30] Many IOLs, if dislocated or subluxated, can be scleral fixated in a minimally invasive manner. Recently, transscleral plug IOLs have been introduced, which are single-piece IOLs made of soft foldable material with preformed T-shaped haptics. These dedicated scleral-fixated IOLs may or may not have scleral counterpressure points, for example, Carlevale IOL (Soleko, Rome, Italy)[31] and CMT-Flex IOL (Appasamy Associates, Chennai, India), respectively. The introduction of this unique haptic design has done away with the hassle of making flanges altogether. Secondary IOL implantation can be combined with endothelial keratoplasty in case of low specular cell density, providing rapid, sustained visual recovery. Intraoperative microscope-integrated optical coherence tomography is another tool in the armamentarium, which reduces the chances of tilting of the SFIOL by providing quick intraoperative feedback for revision of the sclerotomies if required.[30] With progressive improvement in scleral fixation techniques, patients undergoing SFIOL now have the opportunity to enjoy reduced dependence on spectacles for optimum vision. Toric[32] and multifocal IOLs can also be fixed to the sclera.[33] Innovative capsular bag substitutes like the Jagat-Bala IOL supporting system now allow any IOL to be implanted in patients with inadequate capsular support. Scleral fixation of this device during the primary surgery can make any secondary IOL surgery as simple as a primary IOL insertion.[34] Thus, the modern view of SFIOL implantation is not merely the creation of flanges by one method or the other. It now encompasses a vast body of literature which is rapidly evolving, with new innovations overtaking the existing ones by the day. The ophthalmologist has to keep advancing him/herself, challenging his/her surgical limits and choosing the best techniques in the interest of the patient.

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