There are several surgical techniques for intraocular lens (IOL) implantation in eyes with inadequate capsular or zonular support. Traditionally, anterior chamber IOLs (AC IOLs) have been used in such cases. However, AC IOLs are associated with some serious complications such as corneal endothelial damage, anterior synechia, and glaucoma.1–4
To avoid these complications, scleral-fixated posterior chamber IOLs (PC IOLs) have been introduced.3,5–7 A major advantage of PC IOLs is that they do not have contact with the corneal endothelium or the delicate structures of the anterior chamber angle. Disadvantages include the technical complexity of the procedure as well as erosion of suture knots through the sclera and/or the conjunctiva and suture breakage. The latter 2 are associated with IOL tilt, dislocation, and endophthalmitis.2,8–10 Nevertheless, scleral-fixated PC IOLs have become increasingly popular among surgeons during the past 20 years.11–14
Different techniques, such as rotation of the suture knots into the scleral tissue, burying the suture ends into a scleral tunnel, and scleral flaps or scleral pockets, have been described to manage suture and knot erosion.15–18 In 2010 Szurman et al.19 described a knotless technique for scleral-fixated PC IOLs using a zigzag-shaped intrascleral suture (Z-suture) obsoleting scleral flaps.
The purpose of the current retrospective study was to assess the long-term results of a large series of eyes that had an implantation of scleral-fixated PC IOLs with the Z-suture technique. We also aimed to identify risk factors associated with failure of the procedure because of suture breakage.
Patients and methods
This was a retrospective single-center interventional case series. The medical records of consecutive patients who received scleral-fixated PC IOLs using the Z-suture technique between 2004 and 2013 and had a minimum follow-up of 3 years were reviewed. All surgical procedures were performed in a tertiary referral center (University Eye Hospital Tübingen, Germany). All patients were fully informed of all aspects of the procedure and provided written informed consent. The study was performed in accordance with the tenets of the Declaration of Helsinki. The local institutional review board ruled that approval was not required for this observational outcome study.
Age, sex, previous ocular surgeries, reason for failed capsule implantation, preoperative and postoperative corrected distance visual acuity (CDVA), and postoperative complications were recorded for each patient.
Patients had a routine ophthalmic examination including CDVA, slitlamp biomicroscopy, indirect ophthalmoscopy, and intraocular pressure (IOP) measurement at baseline before surgery and 3 years, 5 years, 8 years, and 10 years after surgery.
Surgery was performed as previously described.19 Briefly, 2 conjunctival incisions were made at 180 degrees apart. The first straight needle of a double-armed 10-0 polypropylene suture was passed through the sclera 1.5 mm behind the limbus through the ciliary sulcus parallel to the iris, and it was retrieved from the posterior chamber using a hollow-bore needle inserted through the opposite scleral fixation site. Then, a clear cornea tunnel was made temporally. The polypropylene suture was then gripped at the pupillary plane and extracted through the tunnel. The suture was cut in the middle and 1 end was tied to the first haptic of a foldable 3-piece IOL (AF-1, Hoya Surgical Optics GmbH) with the IOL still in the shooter. The IOL was then implanted so that the second haptic remained outside the eye. Then, the second end of the polypropylene suture was tied to this haptic and the IOL was positioned in the posterior chamber. The scleral fixation was started with an intrascleral pass adjacent to the suture exit site parallel to the limbus at about one-fourth scleral thickness. This intrascleral pass was repeated in the respective opposite direction finally resulting in a zigzag pattern. Five passes were performed for each suture end. Last, the suture was cut without a knot and the conjunctiva was closed.
The primary outcome measure of the study was the time to dislocation of the PC IOL (failure) because of suture breakage. Secondary endpoints were the CDVA and rate of complications.
The CDVA is reported with the mean ± SD, and changes in CDVA were evaluated using a paired t test. Complications are expressed as numbers and percentages. To assess the relationship between factors for success and failure such as age, sex, and diagnoses leading to aphakia, and the risk for adverse events, odds ratios and 95% confidence intervals were calculated. The combined effect of different factors was evaluated using logistic regression analysis. Time-to-event analysis using the Kaplan-Meier method was performed to estimate the failure rate of the procedure because of breakage of the polypropylene suture. All analyses were performed with JMP software (version 11, SAS Institute, Inc.). A P value less than 0.05 was considered to reflect a statistically significant effect.
The study comprised 66 eyes of 62 consecutive patients (34 men, 28 women). Table 1 shows the demographic data of the study population. The most common reason for surgery was traumatic aphakia. In patients with pseudoexfoliation syndrome, complications during cataract surgery were the primary cause leading to the need for scleral-fixated IOLs.
The median follow-up was 64 months (range 36 to 135 months) and all 66 eyes, 60 eyes, 30 eyes, and 13 eyes had a follow-up of 3 years, 5 years, 8 years, and 10 years, respectively.
The mean preoperative CDVA was 0.71 ± 0.58 logarithm of the minimum angle of resolution (logMAR). It showed little or no change at the follow-ups, with a mean CDVA of 0.67 ± 0.54 logMAR after 3 years (P = .257), 0.73 ± 0.55 logMAR after 5 years (P = .399), 0.8 ± 0.68 logMAR after 8 years (P = .348), and 1.09 ± 0.76 logMAR after 10 years (P = .069). Patients with dislocation of the PC IOL (failure) because of suture breakage were also included in the CDVA analyses.
The time-to-event analysis was used to determine the failure rate because of breakage of the polypropylene suture (Figure 1). Eleven eyes (16.7%) failed after a mean of 7.5 years (range 5 to 10 years). Suture breakage occurred in 5 eyes (7.6%) after 5 years, in 5 eyes (7.6%) after 8 years, and in 1 eye (1.5%) after 10 years. The probability of failure because of suture breakage was estimated at 40% after 10 years (Kaplan-Meier analysis).
Table 2 shows the risk factors for failure identified in univariate and multivariate analyses. The 2 factors showing statistical significance in the univariate analysis were age under 55 years and trauma. However, in the multivariate analysis only trauma was confirmed as an independent risk factor for dislocation of the IOL, whereas age under 55 years reached only borderline significance.
Table 3 shows the postoperative complications. The use of topical medications successfully treated all the eyes that developed cystoid macular edema. Of the eyes in which corneal edema occurred, 1 eye (1.5%) had a known preoperative history of Fuchs endothelial dystrophy. Of the eyes in which an increased IOP requiring surgical intervention occurred, 2 eyes (3%) had a history of traumatic cataract with iridodialysis and peripheral anterior synechia and 3 eyes (4.5%) had exfoliative glaucoma. Six of the eyes in which retinal detachment (RD) occurred had a history of trauma and 2 had a previous RD; the retina was successfully reattached by pars plana vitrectomy and gas or silicon oil tamponade in all eyes. The eyes that developed posterior iris-chafing syndrome with microhyphema also had intermittent IOP spikes and pigment dispersion (uveitis–glaucoma–hyphema syndrome). This was treated successfully in all cases by removing the IOL.
No complications such as conjunctival suture erosion or exposure were observed.
Scleral-fixated PC IOLs have been increasingly popular to correct aphakia in patients with insufficient capsule support.11–14 Implantation behind the iris is a major advantage of scleral-fixated PC IOLs compared with AC IOLs. Thus, damage of the endothelial cells and the angle structures can be avoided.2,20,21 However, potential risks, such as endophthalmitis related to erosion of the fixation suture through the conjunctiva, spontaneous dislocation of the IOL related to degeneration or breakage of the suture, RD, and suprachoroidal or vitreous hemorrhage should be considered.
The Z-suture technique was introduced as an attempt to solve the problem with suture exposure.19 The results of our study suggest that this technique is a safe and efficient method for fixation of PC IOLs in the long term. The success rate of the procedure depends on the material properties of the 10-0 polypropylene suture.
The failure rate of PC IOL implantation because of suture breakage ranges between 1.2% and 28%.1,4,5,7,11,14,20,22,23 However, only a few studies have reported long-term results. Vote et al.7 found IOL dislocation because of breakage of the polypropylene suture occurred in 28% of their patients in a long-term retrospective study. The mean time to IOL dislocation was 50 months. In comparison, the failure rate in the current study was 16.7% after a mean of 7.5 years. Although both studies used 10-0 polypropylene sutures, the fixation techniques and study populations were different. Our study included older patients with a mean age of 59 years compared with a mean age of 41 years in the study by Vote et al.7 However, younger age might be a risk factor for long-term failure of the polypropylene suture as the results of our study suggest. The age under 55 years factor reached only borderline significance in the multivariate analysis in our study; however, it might not have been sufficiently empowered to identify age as an independent risk factor.
A major concern of scleral-fixated PC IOLs is the conjunctival suture and knot erosion, which is a potential risk factor for late-onset endophthalmitis. Solomon et al.24 reported an erosion rate of up to 73% in their retrospective series of 30 eyes over 23 months. In a larger study of 624 patients, Uthoff and Teichmann6 reported an erosion incidence of 17.9% after 1 year of follow-up. Even when scleral flaps are used to protect the conjunctiva from the knot, suture exposure can occur in 15% of cases.10 Recently, Scharioth et al.25 reported an alternative method for scleral-fixated PC IOLs without the use of a fixating suture. This technique resulted in good anatomical and functional outcomes; however, no long-term results have yet been reported. In comparison, our study used the knotless Z-suture technique described by Szurman et al.,19 and we did not observe any suture erosion in up to 10 years of follow-up.
Retinal detachment was a common complication in our study, which occurred in 10 eyes (15%). This is higher than the incidence ranging between 1% and 4% in other studies.4,7,22,23,26 However, it might be difficult to ascribe the cause for the detachment to the surgery itself, especially in eyes with a history of trauma or previous retinal surgery, which was the case in 8 of our 10 patients.5 Increased IOP requiring surgical intervention occurred in 5 eyes (7.6%) in the current study, which is comparable to previous reports.4,7,22,26 Two eyes (3%) had a history of trauma with iridodialysis and peripheral anterior synechia and 3 eyes (4.5%) had known exfoliative glaucoma.
Six eyes (9%) in our study developed postoperative macular edema, which is similar to previous reports.5,6,10,12 It has been shown that postoperative macular edema occurs more frequently in eyes with preexisting risk factors such as complicated cataract surgery, RD, or trauma.27 Corneal edema developed in 3 eyes (4.5%). However, the reason for corneal edema was not the PC IOL but Fuchs endothelial dystrophy in 1 eye and corneal trauma in 2 eyes. Although modern AC IOLs with flexible loops have a lower incidence of corneal complications compared with the older closed-loop design, corneal edema is still 1 of the most common causes for poor outcomes with AC IOLs.28,29 Consequently, AC IOLs are relatively contraindicated in patients with preexisting corneal endothelial problems.30
A major strength of our study is the long-term follow-up of up to 10 years. We acknowledge, however, that the study also has limitations inherent to its retrospective design.
In conclusion, implantation of scleral-fixated PC IOLs using the knotless Z-suture is a safe technique offering good visual outcomes in patients with aphakia. The failure rate because of suture breakage was 16.7% after a mean of 7.5 years. The probability of failure was estimated at 40% after 10 years. Traumatic aphakia was identified as a single risk factor for failure. Introducing new suture materials might increase the success rate of the technique.
What Was Known
- Correcting aphakia with PC IOLs has become increasingly popular among surgeons; however, there are only a few studies of the long-term outcomes of the procedure. The Z-suture technique for PC IOL implantation has not been studied in the long term.
What This Paper Adds
- The Z-suture technique for PC IOL implantation was safe and effective in the long term.
- The longevity of the procedure was dependent on the material properties of the suture used for scleral fixation.
- Traumatic aphakia was a risk factor for failure of the procedure.
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None of the authors has a financial or proprietary interest in any material or method mentioned.