An ongoing challenge in complex anterior segment surgery continues to be the safe and effective management of long-term intraocular lens (IOL) fixation in the absence of capsular support. Although anterior chamber IOLs are still an option, especially with improved lens designs and relative ease in placement, complications can still occur including corneal decompensation, iris chaffing, and anterior chamber angle injury, especially when incorrectly sized or in an inadequately shallow anterior chamber.1 Therefore, additional options for posterior chamber IOL fixation in cases of capsular compromise are indicated. Posterior chamber IOLs are not only placed further from the corneal endothelium and anterior chamber angle with less risk for injury to these structures, but are also closer to the nodal point of the eye and may offer a benefit in optical outcomes.
Etiology of Loss of Capsular Lens Support
Cases of inadequate capsular support for IOL fixation can result from a multitude of causes including trauma, complicated cataract surgery, IOL exchange or replacement, and zonulopathies, such as pseudoexfoliation syndrome and, less commonly, congenital ectopia lentis (see Table 1).1,2 With the many potential causes of loss of capsular support with need for IOL fixation, the ongoing development of improved lens design and surgical techniques continues to be an ongoing challenge for surgeons.
Preoperative Considerations
Given the potential complexity of cases requiring IOL fixation when adequate capsular support is lacking, careful preoperative planning is required to determine the most appropriate technique for securing an IOL. A surgeon should also take into account their level of experience and comfort level in attempting potentially surgically demanding techniques in often challenging eyes.
A surgeon should consider whether any capsular support is present. Having some capsular support may add additional support to the IOL during manipulation during a complex case. Noting the availability of some capsular support can be particularly useful in cases when an anterior chamber IOL is not appropriate.The surgeon should also take into account whether there is sufficient iris support to consider an iris-sutured technique. In cases of absent or atrophic iris, a scleral-fixated IOL may be more appropriate for ensuring a secure IOL in the long term without inciting additional trauma to the iris.
Consideration for whether a small or large incision will be used in the case can also dictate the appropriate technique. In cases of large incisions such as combined cases with corneal transplantation with an open-sky approach, the usually more demanding scleral-fixated IOL with a polymethylmeth-acrylate (PMMA) IOL may be more accessible. When working with small incisions, an iris-sutured or scleral tunnel-glued as opposed to a scleral-sutured IOL may be more amenable when a foldable IOL may be used.
Selecting a technique that also minimizes potential complications with pre-existing ocular comorbidities should also be a priority. For example, in cases of advanced glaucoma with pre-existing or anticipated glaucoma implants or trabeculectomy surgery, an iris-sutured IOL may be desired if minimal disruption of scleral and conjunctival tissue is desired. In cases with extensive history of posterior segment pathology, care should be taken with scleral-fixation techniques, which can be wrought with more posterior segment complications (see Figure 1). Careful history and examination with appropriate preoperative testing is a necessity in these complex cases that involve multiple ocular comorbidities.
Posterior Chamber Iris-sutured Intraocular Lens
The technique for iris-sutured IOL was first described by McCannel in 1976 and has since been further refined with use of the Siepser slipknot.3,4 This technique allows for small corneal incisions with a foldable three-piece IOL. The IOL is placed in reverse optic capture with the use of a miotic agent to stabilize the IOL in the anterior chamber. Additional viscoelastic may help to drape the iris tissue over the haptics for better visualization for placement of the iris sutures. A second instrument such as a Sinskey, Kuglen, or Lester hook can be used to further tent the IOL optic as each iris suture is being placed to ensure adequate visualization and capture of the haptics. A 10-0 polypropylene suture on a long curved needle such as CIF-4 or CTC-6 (Ethicon, Somerville, NJ) needle is then passed from a clear corneal incision being sure not to inadvertently capture cornea tissue on entrance. The needle is then passed through the peripheral iris stroma to capture the lens haptic in one bite and then out through the peripheral clear cornea. A small hook instrument, such as a Sinskey, Kuglen, or Lester hook, is then used to pull the suture distal to the haptic out into a loop through the initial proximal incision site. The free proximal end of the suture is then fed through the loop several times to create a knot outside of the eye. The opposite ends of the sutures are then pulled to slide the knot into the eye creating a Siepser slipknot. The Siepser slipknot can be repeated several times to ensure a secure square knot. Intraocular scissors are then used to cut the suture tails. The same technique is repeated on the fellow haptic. Once the haptics are secured, the IOL is reposited back into the posterior chamber (see Figure 2, Video 1 available at www.touchophthalmology.com/gallery/ posterior-chamber-iris-sutured-intraocular-lens-technique-marjan-farid).
Potential limitations with this technique include the need for robust iris tissue, which can often be absent or atrophic, such as in cases of trauma, uveitis, atrophy, and aniridia. Furthermore, difficulties with technique can lead to iridodialysis, iris chafing, and unacceptable pupil shape, with
sequelae such as glare and halos. A more peripheral and smaller iris pass reduces the risk for misshapen pupil at the end of the case. The central iris also tends to be more mobile, therefore, a more peripheral iris fixation may limit iris chaffing and inflammation of the uveal tissue.1 With manipulation in the peripheral iris near the iris root, limiting excessive traction on the iris is important to reducing the risk for iridodialysis. It is important also to avoid excessively tight knots as this may also contribute to peaking of the pupil. The increased risk for corneal edema and cystoid macular edema (CME) over other techniques has been debated with irissutured IOLs as uveal irritation can occur (see Table 2).1,5
In one recent study by Soiberman et al., 72 eyes with iris-sutured IOLs for subluxated IOL were followed for a mean period of 2 years. Ninetyfour percent were found to be centered and stable with an overall
improvement in best corrected visual acuity (BCVA), including 51 eyes with a postoperative BCVA of 20/40 or better. Though there were three cases of tilted IOLs, there was no significant change in astigmatism. There were only seven cases of re-subluxation. Early re-subluxation was seen with loose sutures and late re-subluxation resulted from erosion of polypropylene suture through the iris stroma. The group discussed that polypropylene suture appeared to offer stable fixation and that suture erosions may be related to sharp edges of eyelets, rather than due to biodegradation. The final visual outcome was not worse in the cases of re-subluxation. Re-subluxation was more common in cases with a history of retinal detachment and scleral buckles. Other complications were rare and included glaucoma managed conservatively, bullous keratopathy, choroidal detachment with hypotony, self-resolving hyphema and vitreous hemorrhage, retinal detachment in one case of failed fixation, uveitis, and CME. The study was limited by the short follow-up period and the exclusion of cases of secondary IOL implantation for aphakia.6
Posterior Chamber Scleral-sutured Intraocular Lens
The most common IOL currently used for scleral-sutured fixation is a nonfoldable PMMA IOL with eyelets at the haptics for suture fixation, though foldable IOLs may be used with this technique, allowing for smaller incisions. There are many approaches to posterior chamber scleral-sutured IOLs, with the technique often divided between ab externo versus ab interno approaches. In the ab externo approach, sutures are introduced initially from the outside of the eye (see Figure 3).7 In the ab interno approach, the main incision is created first and the sutures are introduced from the inside of the eye (see Figure 4).7 Although the ab interno approach may be a more direct and faster technique, a potential advantage of the ab externo approach is accuracy and predictability of placement of fixating sutures while the eye is formed prior to creating a potentially large main incision for often nonfoldable IOLs.
Variations of technique also include how the haptics are secured, including different knot techniques (slipknot, girth hitch, standard square knot) and looping of eyelets prior to scleral fixation. The points of fixation on the haptic may also vary from 1 point up to 4 points of fixation.1,7,8 To prevent suture exposure and erosion, knots can be covered by partial thickness scleral flaps, rotated and buried within the sclera, or left with long suture tails covered by overlying Tenon’s and conjunctiva.1 Suture material also can vary including polypropylene (Prolene®), polyester (Mersilene®), and polytetrafluoroethylene (Gore-tex®) although the last is not currently US Food and Drug Administration (FDA) approved for use in the eye.2
One of the more recent modifications to the technique for scleral-sutured IOLs has been the Hoffman pocket, in which two scleral pockets are dissected posteriorly from the corneolimbal region 180° apart. The scleralfixating sutures are passed through the pockets at the ciliary sulcus space, and retrieved anteriorly by pulling the sutures out of the pockets. The sutures are then tied down and the knots are buried within the pockets.9 This technique offers easier construction of scleral flaps to prevent suture erosion and exposure with minimal disruption of adjacent tissue.
The authors of this paper commonly perform scleral-suture fixated IOLs with corneal transplantation where an ab interno approach is used. Partial thickness scleral flaps are initially created 180° apart. The CZ70BD lens (Alcon, Fort Worth, Texas) is often used in our cases, which is a nonfoldable PMMA IOL so that a large 7 mm incision is required. Each eyelet of the IOL is then looped with a double-armed 9-0 polypropylene suture. The sutures are looped in a complementary fashion on either side to minimize potential tilt. In cases where the eye is closed, a long needle, such as a CTC-6 or CIF- 4, is used to pass the distal sutures, and a standard short needle is used to pass the proximal sutures. The IOL is inserted into the eye being sure to keep the orientation of the IOL and the sutures separated. The sutures are then adjusted and tightened for centration of the IOL and tied down and secured under the scleral flaps. Alternatively, this can be performed without scleral flaps and the suture tails are left long and buried under overlying tenons and conjunctiva, or the knots are rotated into the sclera.
The many variations and innovations in posterior chamber scleral-sutured IOLs makes this technique ideal for many complex cases, but can be wrought with complications (see Table 3). Posterior chamber scleral-sutured IOLs can be limited by the need for large incisions up to 7 mm in length, which can increase the surgical difficulty of the technique when globe collapse is encountered in the context of previous vitrectomy. Though this technique places the lens closer to the nodal point, the more posterior approach also increases the risk for potential posterior segment complications. Retinal detachment and CME may result from vitreous prolapse or disruption of the anterior hyaloid face with inadequate anterior vitrectomy in eyes that may already be prone to retinal pathology. Vitreous hemorrhage and suprachoroidal hemorrhage with passage of sutures through uveal tissue can also occur. This may be avoided by passing sutures more anteriorly and avoiding the long posterior ciliary artery at the 3 and 9 o’clock position in securing haptics. Limiting intraocular pressure fluctuation including reducing incidences of hypotony from a large wound can also decrease the
Gundula et al. demonstrated in a retrospective study of 63 patients the potential concerns for posterior segment complications over a mean follow-up of about 3.5 years. Though 94 % of cases were performed safely, 20 % of postoperative complications were significant including late complications of rhegmatogenous retinal detachments (6.3 %), vitreous hemorrhage (4.8 %), choroidal hemorrhage (1.6 %), and IOL subluxation (6.3 %) requiring secondary surgeries.10
Additional challenges with the technique include suture complications. Though the thought of multiple suture passes and fixation points may lead to a more secure IOL, additional suture passes may increase the
potential risk for posterior segment injury as described above with each pass. Furthermore, with each suture pass there is potential increased risk for suture exposure and erosion, which can increase the risk for endophthalmitis.1 In addition, late suture breakage and IOL dislocation continues to be of concern. In one study, Vote et al., followed 61 eyes for a mean follow-up of 6 years with the main long-term complication being breakage of sutures leading to IOL dislocation in 28 % of cases at an average of about 4 years after surgery.11
Posterior Chamber Scleral Tunnel-glued Intraocular Lens
The technique for scleral tunnel-glued IOL was first described by Gabor et al., in 2007, and has been popularized by Agarwal et al.12,13 The main advantage of this technique is the ability to perform the surgery through small incisions with foldable IOLs with a sutureless technique, thus eliminating suture-related complications.14,15 Agarwal’s group has demonstrated promising outcomes in follow-up studies including a recent major review of 735 eyes that underwent scleral glued IOLs for insufficient capsular support with improved visual outcomes along with low rates of optic haptic-related complications.16,17 The group also discussed the application of the technique in cases of iris prosthesis, corneal transplantation, glued IOL scaffold in complicated cataract surgery, and glued endocapsular hemi-ring segments.18,19
The technique involves creating 2.5 x 2.5 mm partial thickness scleral flaps exactly 180° apart. A 23-gauge needle is then used under the flaps about 1.5 mm behind the limbus to create sclerostomy sites for haptic externalization. A small main incision is then created for insertion of a foldable IOL. While the IOL if being unfolded, a micro-incision forcep is inserted through the sclerostomy site to grasp the leading haptic, which is then externalized. The trailing haptic is then externalized using a “handshake” technique, where the micro-incision forceps are used through an incision and the sclerostomy site and the haptic handed-off between forceps walking down the haptic until the distal end is grasped and then externalized. Once both haptics are externalized, a scleral tunnel is created with at 27-gauge needle along the scleral flaps on either side in the trajectory of the haptics. The haptics are then tucked into the scleral tunnels to secure the IOL. Note that the true fixation of the IOL is a well-constructed scleral tunnel as opposed to the actual glue. The tissue glue is used to re-approximate the scleral flap and overlying tenons and conjunctiva while intrascleral fibrosis around the haptics develops for fixation (see Figure 5). Thus, a limitation of this technique may be in cases of insufficient sclera such as cases of scleromalacia and scleritis.2
The technique can be surgically demanding and may require an assistant to secure the leading haptic as the trailing haptic is being externalized. However, modifications in the technique have been made to reduce the surgical demand. The authors of this article often use a modified basket suture as originally described by Dr Samuel Masket to create a scaffold prior to introducing the IOL.20 The scaffold is created with a double-armed 10-0 polypropylene suture on a CTC-6 or CIF-4 needle docked on a 25-gauge needle and passed through the par plana in a crisscrossing fashion. This modified basket suture can then support the IOL while intraocular manipulations are ongoing (see Video 2, available at www.touchophthalmology.com/gallery/posterior-chamberscleral- tunnel-glued-intraocular-lens-marjan-farid). Beiko et al. also described the use of silicone retainer tires from iris and capsular hooks to thread onto the leading haptic to secure the haptic as the trailing haptic is being externalized.21
Due to the potential extensive manipulation of the IOL with this technique, the authors of this paper prefer the Staar AQ2010V (Staar Surgical, Monrovia, CA) and the Aaren EC-3 (Aaren Scientific, Ontario, CA) IOL, both of which have a flexible haptic span with durable material that can be manipulated with less risk for haptic distortion and breakage. The Staar AQ2010V is a silicone lens, as opposed to the Aaren EC-3 that is acrylic, and may have limitations in potential retinal cases where silicone oil may be required.
Though long-term follow-up is still pending with this technique, early reports are promising. Ganekal et al. compared visual outcomes and complications in scleral-sutured IOLs versus fibrin scleral-glued IOLs and found that visual outcomes were comparable with corrected distance visual acuity of 20/40 or better in 88 % of the scleral-sutured IOLs and 84 % of the scleral-glued IOLs. However, the complication rates including postoperative inflammation and glaucoma were nearly doubled in the scleral-sutured IOL cases.22 McKee et al., similarly demonstrated in 50 cases stable IOLs with median visual acuity improvement from 20/200 to 20/50. The patient population included complex cases of aphakia, dislocated IOLs into the vitreous, and even suture breakage in sutured IOLs. The technique was also shown to be successful with concurrent penetrating keratoplasty and staged endothelial keratoplasty in cases of corneal decompensation from anterior chamber IOLs. Complications were rare and included transient hypotony that improved with surgeon experience, self-resolving hyphema and vitreous hemorrhage, and CME. There was only one case in which the haptic–optic junction broke with rigorous postoperative eye rubbing that was revised successfully.23
Summary
In the setting of loss of capsular support, which can result from trauma, complex cataract surgeries, and zonulopathies, IOL-fixation techniques, including posterior chamber iris-sutured and scleral-fixated IOLs, may be necessary. There have not been many head-to-head studies between techniques to suggest a superior approach, and reviews comparing methods suggests that the effectiveness and safety profiles among the different techniques may be comparable.24–27 The approach to addressing these complex surgeries should therefore be evaluated on a case-by-case approach as no one technique may be suitable in all cases. Furthermore, given the surgically demanding nature of these techniques, the surgeon’s comfort level should also dictate the approach to IOL fixation. The primary goal for IOL fixation is to minimize surgical trauma and maximize IOL stability and retention for our patients. Fortunately, anterior segment surgeons have demonstrated evolving techniques over the years to achieve these goals, and continue to inspire future innovations.
