Modified Four-Flanged Intrascleral Fixation of Foldable Intraocular Lenses Using a 1-Inch, 30-Gauge Needle for Extraocular Suture Threading
Article information
Abstract
Purpose
To evaluate the efficacy and safety of modified four-flanged intrascleral fixation of foldable intraocular lenses (IOLs) using a 1-inch 30-gauge needle for extraocular suture threading.
Methods
This retrospective case series included 20 eyes of 20 patients who underwent four-flanged intrascleral IOL fixation using a 1-inch 30-gauge needle, with at least 6 months of follow-up. We modified the original Canabrava technique by inserting a foldable IOL through a 2.4-mm clear corneal incision with a standard injector and performing extraocular suture threading with a 1-inch 30-gauge needle. Collected data included uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), intraocular pressure, spherical equivalent (SE), prediction error (PE), and corneal and lens astigmatism. Postoperative complications and IOL centration were also evaluated.
Results
Visual acuity improved significantly over the 6-month follow-up; mean preoperative logMAR UCVA was 1.25 ± 0.66 (Snellen equivalent, 20 / 355) and improved to 0.35 ± 0.19 (20 / 45), and logMAR BCVA improved from 0.53 ± 0.38 (20 / 70) to 0.15 ± 0.09 (20 / 30) (p < 0.05). The mean postoperative SE at 6 months was −0.61 ± 1.08 diopters, and PE was −0.25 ± 0.86 diopters. No significant changes in endothelial cell density were observed. Corneal astigmatism remained stable, and lens astigmatism was reduced after surgery, although not significantly. Postoperative complications included one case each of hypotony and vitreous hemorrhage, both resolved with medical therapy. No IOL redislocation, decentration, tilt, or flange-related issues occurred.
Conclusions
Modified four-flanged intrascleral IOL fixation using a 1-inch 30-gauge needle provides stable IOL fixation by pairing a robust suture with the smallest suitable needle. Extraocular suture threading reduces intraocular manipulation, simplifying the procedure and resulting in favorable visual outcomes and low complication rates.
Conventional scleral fixation of intraocular lenses (SFIOLs) typically involves conjunctival dissection, large corneal or scleral incisions, and suture fixation of the IOL to the sclera [1,2]. These procedures are associated with prolonged operative time, surgically induced astigmatism, suture-related complications (e.g., exposure, erosion, or breakage), and delayed visual recovery [3,4]. To overcome these limitations, minimally invasive techniques have been developed to avoid large incisions, sutures, or adhesives [5–7].
Among these, Yamane’s double-needle flanged intrascleral fixation has gained popularity for its sutureless design and stable haptic fixation through small incisions [5]. However, two-point fixation may predispose to IOL tilt or decentration, and the technique requires significant surgical expertise, particularly for threading the trailing haptic into the needle lumen. To improve IOL stability and simplify the procedure, Canabrava introduced a four-flanged intrascleral IOL fixation technique using polypropylene sutures [6,7]. Although simple in concept, this method remains technically demanding, especially the step of threading the suture into a small-gauge needle with the non-dominant hand.
In this study, we describe a modified four-flanged intrascleral IOL fixation technique using a 1-inch, 30-gauge needle, longer than the conventional half-inch type (Fig. 1), which enables needle externalization through the opposite side-port incision. This permits extraocular suture threading, minimizing intraocular manipulation and simplifying the procedure.
Comparison of conventional (top) and 1-inch 30-gauge needles (bottom). The conventional needle measures 0.5 inch (1.27 cm) in length, while the needle used in this study measures 1 inch (2.54 cm), enabling external suture threading and minimizing intraocular manipulation.
Materials and Methods
Ethics statement
This study was approved by the Institutional Review Board of Wonkwang University Hospital (No. WKUH 2025-04-019). The requirement for informed consent was waived due to the use of deidentified data and the retrospective nature of the study. All patient data were anonymized before analysis to ensure confidentiality and ethical compliance. The study was conducted in accordance with the principles outlined in the Declaration of Helsinki.
Study participants
We retrospectively reviewed the medical records of patients who underwent four-flanged intrascleral IOL fixation at Wonkwang University Hospital between February and October 2024. The procedure used a 1-inch, 30-gauge, regular-wall hypodermic needle (Sungshim Medical). Per manufacturer confirmation (ISO 9626–compliant), the conventional 0.5- and 1-inch 30-gauge needles have identical outer and inner diameters and differ only in shaft length (outer diameter, 0.312–0.315 mm; inner diameter, 0.170 mm). Indications for surgery included aphakia, dislocated crystalline lens or IOL, or inadequate capsular support. Patients were excluded if they had a history of ocular disease affecting central vision or if their follow-up duration was less than 6 months.
Surgical technique
All surgeries were performed by a single surgeon (JYH) and are illustrated in Fig. 2A–2H and Supplementary Video 1. A standard three-port, 23- or 25-gauge pars plana vitrectomy (PPV) was performed using the Stellaris Elite vitrectomy system (Bausch + Lomb) under sub-Tenon anesthesia. In cases of zonular dialysis or traumatic cataract, the crystalline lens was removed by phacoemulsification, extracapsular cataract extraction (ECCE), or pars plana lensectomy. Dislocated foldable IOLs were explanted via a 2.8-mm clear corneal incision, while polymethylmethacrylate (PMMA) IOLs required a 6.0-mm incision. Foldable IOLs with four eyelets were implanted: Akreos AO60 (Bausch + Lomb) or Artis PL E (Cristalens Industrie). We modified the original Canabrava four-flange intrascleral IOL fixation technique [7] by inserting a foldable IOL using standard cartridge and injector through a 2.4-mm clear corneal incision and passing a 1-inch, 30-gauge needle through the haptic eyelets, externalizing it through the opposite side-port incision, and threading the suture into the needle outside the eye, thereby eliminating intraocular threading.
A modified four-flanged intrascleral intraocular lens (IOL) fixation surgical technique. (A) Two sclerotomy marks, 4 mm apart, were made at 3 and 9 o’clock, positioned 2 mm posterior to the limbus. A 2.4-mm clear corneal incision was created at 12 o’clock, with side-port incisions at 3 and 9 o’clock. The IOL was inserted and horizontally aligned over the iris. (B) A bent 1-inch, 30-gauge needle was inserted at the inferior mark at 9 o’clock, passed through the corresponding haptic eyelet, and externalized across the anterior chamber via the opposite side-port incision using a viscoelastic cannula. A 6-0 polypropylene suture was threaded into the externalized needle, which was then withdrawn to deliver the suture outside the eye. (C) The needle was reinserted at the superior mark, passed through the opposing haptic eyelet, and externalized again through the contralateral side-port. The suture’s free end at this port was threaded into the externalized needle and extracted from the eye. (D) One side of the haptics was secured. (E, F) The same procedure was repeated at 3 o’clock. (G) All four haptics were secured, and the sutures adjusted to ensure IOL centration. (H) Then, each suture was trimmed 1 mm from the end, flanges were created with thermocautery, and all flanges were buried within the scleral tunnels and covered by conjunctiva.
Surgical steps
After drying the ocular surface, reference marks were placed 2.0 mm posterior to the limbus at the 3 and 9 o’clock positions. From each reference, additional marks were placed 2.0 mm superior and 2.0 mm inferior, yielding two points 4.0 mm apart per side. We set the inter-flange distance to 4.0 mm because the original Canabrava used 3.5 mm spacing and subsequent modified method have predominantly adopted 4 mm; in our experience, 3.5 mm is difficult to mark symmetrically on both sides, whereas 4 mm provides stable and reproducible four-point support [8–10]. A 2.4-mm clear corneal incision was created at 12 o’clock, and side-port incisions were made at 3 and 9 o’clock. The IOL was inserted and aligned horizontally over the iris. A bent 1-inch, 30-gauge needle was inserted at the inferior mark at 9 o’clock position, passed through the corresponding haptic eyelet, and externalized across the anterior chamber through the opposite side-port incision using a viscoelastic cannula. A 6-0 polypropylene suture was threaded into the externalized needle, which was then pulled out to deliver the suture. The needle was reinserted at the superior mark, passed through the corresponding haptic, and externalized again through the opposite side-port. The free end of the suture at the opposite side-port was threaded back into the externalized needle and pulled out. One side of the haptics was then secured. The procedure was repeated at the 3 o’clock position. After securing all four haptics and centering of IOL, the sutures were cut 1 mm from the ends, and flanges were created using thermocautery. All flanges were buried within scleral tunnels and covered by conjunctiva. To secure the flanges, slight hypotony was induced by temporarily halting infusion and egressing aqueous. McPherson forceps were used to gently depress the sclera while pinching the suture before flange creation. Finally, the vitrectomy trocars were removed, and triamcinolone was injected into the subconjunctival space.
Clinical evaluation
All patients underwent comprehensive ophthalmologic evaluation, including uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), intraocular pressure (IOP) measured with a Goldmann applanation tonometer, slit-lamp biomicroscopy, and dilated fundus examination. Axial length and keratometry were obtained preoperatively using Lenstar LS 900 (Haag-Streit), and IOL power was calculated using the device software. Intraocular lens power was calculated with the SRK/T formula, assuming an in-the-bag lens position and targeting slight myopia (mean target −0.30 ± 0.25 diopters [D]). Spherical equivalent (SE) and corneal astigmatism were measured using an autorefractor- keratometer (HRK-9000A, Huvitz). Total refractive astigmatism from manifest refraction and corneal astigmatism from autokeratometry were used to calculate the lens astigmatism as the vector difference between total refractive and corneal astigmatism in power-vector space (J0, J45) following the approach of Munoz-Escriva and Furlan using standard spherocylindrical notation S/C×axis (α) [11]. The prediction error (PE) was defined as the achieved postoperative SE minus the preoperative predicted SE. Corneal endothelial cell density (ECD) was assessed with the CellChek 20-1 specular microscope (Konan Medical). Postoperative follow-up was conducted on day 1 and at 1 week, 1 month, 3 months, and 6 months. At each visit, patients underwent visual acuity and IOP measurements, slitlamp biomicroscopy, dilated fundus examination, autorefractive testing, and corneal ECD evaluation. Snellen visual acuity was converted to the logarithm of the minimal angle of resolution (logMAR) for statistical analysis. Counting fingers and hand motion were assigned logMAR values of 2.10 and 2.40, respectively.
Statistical analysis
Data were reported as means ± standard deviation or counts (%). The Wilcoxon signed rank test was used to compare preoperative and postoperative values. A p-value less than 0.05 was considered statistically significant. All statistical analyses were performed using IBM SPSS ver. 26 (IBM Corp.).
Results
Table 1 summarizes baseline characteristics and surgical indication. Twenty eyes of 20 patients were included in this study. Of the 20 patients, 16 (80.0%) were male and 4 (20.0%) were female, with a mean age of 63.55 ± 11.23 years. Indications for surgery included IOL dislocation in 12 eyes (60.0%), surgical aphakia in 2 (10.0%), acute angle closure from crystalline lens subluxation in 2 (10.0%), and inadequate capsular support during cataract surgery in 4 eyes (20.0%). Of the 20 eyes, 19 (95.0%) were implanted with Akreos AO60 and 1 (5.0%) with Artis PL E. The average axial length was 23.48 ± 0.61 mm.
Baseline characteristics of the included patients
Visual outcomes
The UCVA improved significantly at all postoperative visits, increasing from 1.25 logMAR (Snellen equivalent, 20 / 355) preoperatively to 0.35 (20 / 45) at 6 months (p < 0.05). The BCVA improved from 0.53 (20 / 70) at baseline, with statistically significant gains observed at 3 months (0.22, 20 / 35; p = 0.04) and 6 months (0.15, 20 / 30; p = 0.01) (Table 2).
Changes in visual acuity, refractive outcome, IOP, and ECD after surgery
Refractive outcomes
The mean SE improved from +6.24 ± 6.38 D preoperatively to mild myopia at 6 months (−0.61 ± 1.08 D, p < 0.05). At 6 months, the mean PE was −0.25 ± 0.86 D, indicating a slight myopic shift than the target refraction (−0.30 ± 0.25 D). Corneal astigmatism showed a transient increase up to 1 month and stabilized thereafter; no statistically significant differences were detected at any visit (all p > 0.05). In addition, calculated lens astigmatism decreased and remained around 1.3 D from 1 week to 6 months, without reaching statistical significance (all p > 0.05) (Table 2).
Intraocular pressure and corneal endothelial cell density
The IOP decreased from 22.32 ± 11.79 mmHg preoperatively to 14.58 ± 3.32 mmHg at 6 months, with significant reductions at most follow-up visits. The ECD remained stable without significant change during the 6-month follow-up (Table 2).
Complications
Two postoperative complications occurred. One patient developed hypotony with a soft globe and choroidal folds on postoperative day 1, which resolved with topical steroids and cycloplegics within 2 weeks. Another patient experienced intraoperative ciliary body hemorrhage during needle passage; vitreous hemorrhage occurred postoperatively but resolved spontaneously. No cases of IOL tilt, decentration, optic capture, redislocation, or flange-related complications were observed.
Discussion
This study evaluated the efficacy and safety of modified four-flanged intrascleral IOL fixation technique using a 1-inch, 30-gauge needle. All 20 patients demonstrated significant improvements in UCVA and BCVA over the 6-month follow-up. No significant changes in corneal or lens astigmatism or ECD were observed. Postoperative complications included one case of hypotony and one case of vitreous hemorrhage, both of which resolved with medical therapy and did not require surgical intervention. No IOL-related complications, such as redislocation, decentration, or tilt, were observed. Likewise, no flange-related issues, including internal flange slippage or exposure, were reported during follow-up.
In Canabrava’s four-flanged IOL fixation technique, one of the most challenging steps is inserting the suture into a fine-gauge needle with the nondominant hand. Although several modifications have been proposed [9,12,13], these approaches often require additional IOL preparation, such as passing the suture through the haptics or folding the lens—steps that increase surgical complexity and may lead to suture entanglement or prolonged surgical time. To minimize intraocular manipulation and simplify the procedure, we used a 1-inch, 30-gauge needle (longer than the standard 0.5-inch version) to externalize through the opposite side-port incision, enabling extraocular suture threading. When a scrub nurse stabilizes the syringe attached to the needle, the surgeon can insert the suture into the externalized needle using both hands, providing an accessible solution for novice surgeons. In addition, our method does not require specialized materials (e.g. ultrathin-wall needles or off-label Gore-Tex sutures) or additional IOL preparation before insertion. Additionally, the 1-inch, 30-gauge needle is cost-effective and widely available. We also attempted external threading using a conventional 0.5-inch needle bent at its proximal site, but in eyes with a long axial length, the needle often failed to reach the opposite side-port, making external suture insertion difficult and compromising the surgical view. These technical limitations led us to adopt the current long-needle approach.
Based on the 5-year study by Canabrava and Carvalho [8], four-flanged intrascleral IOL fixation is most reliable when it employs the following: (1) a robust suture (5-0 or 6-0 polyprolene); (2) the smallest needle that still allows smooth suture passage; (3) long scleral tunnels (≥2 mm); and (4) flanges that are appropriately sized and fully buried. Accordingly, we used 6-0 polypropylene with a 30-gauge needle, which provides small sclerostomies, less scleral trauma during tunnel creation, a high flange-to-needle diameter ratio, and a low risk of flange exposure. Clinical studies report fewer complications with 30-gauge than with 27-gauge needles [14], and experimental models show higher haptic disinsertion forces with 30-gauge compared with 27-gauge [15]. Regarding suture strength, 10-0 polypropylene has a low breaking force (approximately 0.52 N) and has been linked to late suture breakage in SFIOL, whereas 6-0 and 5-0 polypropylene demonstrate markedly higher tensile strength (range, 4.8–9.8 N) [3,16,17]. In flanged stability testing, combinations such as 30-gauge/6-0 polypropylene or 27-gauge/5-0 polypropylene generate higher disinsertion forces than very fine sutures (e.g., 33-gauge/8-0 polypropylene) [16]. Taken together, these data support using comparatively thick polypropylene (5-0 or 6-0) with the smallest needle that can pass the suture (30-gauge needle); although 5-0 polypropylene can theoretically pass through a 30-gauge needle (suture thickness 0.143 mm vs. 0.16 mm inner diameter of needle), the cut tip tends to flatten and the material’s strong memory hampers insertion and handling; 6-0 polypropylene offers adequate tensile strength with more favorable handling.
We selected the SRK/T formula because it is relatively independent of anterior chamber depth, and in-the-bag IOL calculation has been reported to yield reliable refractive outcomes even in four-flanged intrascleral IOL fixation [10,18,19]. In our study, the mean PE at 6 months was −0.25 ± 0.86 D, indicating a milder myopic shift compared with previous studies employing IOL fixation 2 mm behind the limbus, such as Dubinsky-Pertzov et al. [10] (−0.75 ± 0.32 D) and Su et al. [20] (−1.35 ± 1.32 D). The mean axial length in this study was 23.48 ± 0.61 mm, with only two eyes longer than 24 mm, which may partially account for the smaller myopic shift. Although the IOL position remains relatively constant regardless of axial length in SFIOL, longer eyes tend to show a myopic PE, whereas shorter eyes tend to show a hyperopic PE [21]. In addition to axial length, numerous factors, such as biometry accuracy, suture material and suture tension, and combined PPV, can influence postoperative refraction [18,22]. Nevertheless, the refractive predictability in our study was acceptable, with 8 of 20 eyes (40.0%) within ±0.50 D, 17 of 20 eyes (85.0%) within ±1.00 D, and all eyes (100%) within ±1.50 D of the predicted refraction.
Compared with baseline, corneal astigmatism showed no statistically significant differences at any visit. Postoperatively, it increased by 0.6 D at 1 week and then settled to 0.3 D at 6 months, comparable to that 2.4-mm clear corneal incision phacoemulsification. Notably, two eyes requiring a 6-mm corneal incision for ECCE and PMMA IOL explantation developed 3.00 and 2.50 D of astigmatism at week 1, respectively, which both improved to approximately 1.50 D by 6 months. In addition, calculated lens astigmatism at 6 months in our study was 1.29 ± 0.37 D, similar to values of other studies of four-point scleral fixation (1.17 ± 0.70 and 1.31 ± 0.49 D) and two-point fixation (2.23 ± 0.98 D) [22,23]. Given that pronounced IOL tilt or decentration typically increases internal astigmatism, these findings are consistent with the absence of clinically meaningful IOL malalignment following our technique.
In this study, the mean preoperative logMAR UCVA (Snellen equivalent) was 1.25 ± 0.66 (20 / 355), improving to 0.35 ± 0.19 (20 / 45), while BCVA improved from 0.53 ± 0.38 (20 / 70) to 0.15 ± 0.09 (20 / 30) at 6 months. These outcomes are comparable to the 5-year results of Canabrava and Carvalho [8], where UCVA improved from 0.95 ± 0.22 (20 / 178) to 0.45 ± 0.35 (20 / 56), and BCVA from 0.27 ± 0.12 (20 / 37) to 0.25 ± 0.32 (20 / 35). In the 5-year series by Canabrava and Carvalho [8], among 71 eyes, retinal detachment occurred in three eyes (4.2%), cystoid macular edema in three eyes (4.2%), and flange-related complications in five eyes (7.0%)—including one exposed flange (1.4%) and four internalized flanges (5.6%)—with no cases of endophthalmitis, resulting in an overall complication incidence of approximately 15.5%. In our study, during a 6-month follow-up, two postoperative complications were observed among 20 eyes (10.0%): one case of transient hypotony and one case of intraoperative ciliary body hemorrhage. Although our short-term safety outcomes appear favorable, additional cases and longer follow-up are warranted to fully assess the long-term complication profile of this technique. Additionally, a significant reduction in postoperative IOP was observed, driven mainly by three patients, two with angle-closure glaucoma from crystalline lens subluxation and one with vitreous prolapse and IOL dislocation. In patients with lens subluxation from zonular weakness, this fixation method may offer a dual benefit of IOP control and reliable SF-IOL placement.
This study has several limitations, including its retrospective design, single-center setting, small sample size, short follow-up period, and the absence of a control group—particularly a direct comparison with the conventional four-flanged intrascleral IOL fixation using 0.5-inch 30-gauge needle. Nevertheless, many studies cited in our Discussion used conventional four-flanged intrascleral IOL fixation using 0.5-inch 30-gauge needles [9,10,21], and our outcomes for visual acuity, refractive results, and complications were broadly comparable. The mean operative time in our study was 88.56 ± 27.10 minutes (range, 50–140 minutes), which was slightly longer than in previous reports—for example, 71 minutes in a large study of Yamane intrascleral haptic fixations [24] and 72 minutes (range, 40–180 minutes) for combined PPV with four-point scleral fixation in another study [25]. In our study, early cases required about 130 to 140 minutes, whereas later cases decreased to 50 to 60 minutes; given that the primary surgeon was a second-year vitreoretinal surgeon, this trend suggests a modest learning curve and supports the feasibility of this technique for less-experienced surgeons.
In conclusion, four-flanged intrascleral IOL fixation using a 1-inch, 30-gauge needle ensures stable IOL fixation by pairing a robust suture with the smallest suitable needle. Extraocular suture threading reduces intraocular manipulation, simplifying the procedure and providing favorable visual outcomes and low complication rates.
Notes
Conflicts of Interest:
None.
Acknowledgements:
None.
Funding:
None.
Supplementary Materials
Supplementary Video 1. Modified four-flanged intrascleral fixation of IOL using a 1-inch, 30-gauge needle. Available at: https://youtu.be/JOFhcH2bmVs