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Intraocular lens (IOL) intrascleral fixation using the double-needle technique was introduced in 2017 by Shin Yamane as a simple and minimally invasive method for achieving good centration and a firm fixation of a 3-piece IOL when no capsular support was present. The novelty was the use of a cautery to create a flange at the tip of each haptic and no sutures.1 Since then, numerous modifications have been explored to achieve easier and safer haptics manipulation.2–7 As some reports of exposed flanges and late endophthalmitis have appeared, every surgeon should be advised that whenever a flange technique is used, it carries an intrinsic risk of erosion/extrusion through the Tenon and conjunctiva.8–10 For that reason, we decided to study whether there was a difference in flange depths between 2 techniques, with or without scleral pockets, for flange burying.11
METHODS Patients and MeasurementsIn this prospective, randomized, comparative, single-surgeon, observational study, 36 patients (36 eyes, 72 flanges) who underwent intrascleral IOL fixation at Instituto de Oftalmología Santa Fe (Argentina) from September 2019 to September 2022 were selected. Patients with preoperative aphakia and no capsular support were randomly divided into a Yamane technique with no scleral pocket group (NSP group; 18 cases, 18 eyes, 36 flanges) and a scleral pocket modified technique group (SP group; 18 cases, 18 eyes, 36 flanges).
Preoperatively, surgical technique assignment was achieved when the data analyst randomly selected each patient for either the NSP or SP group. Throughout the research study, patients and examiners were masked to treatment assignment, and the surgeon was blinded to the group allocation until surgery day.
All patients received a complete eye examination both preoperatively and postoperatively including uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) (obtained in a decimal scale and converted to logMAR units for statistical analyses), manifest refraction, slitlamp photography of the anterior segment, intraocular pressure, and fundus examination were routinely performed.
IOL power was calculated with the IOL Master 500 using the SRK-T formula, aiming for a −0.25 diopter (D) refractive target. Scleral thickness was measured preoperatively 2 mm from the limbus at positions 3′ and 9′ with ultrabiomicroscopy (Compact STS Quantel Medical). Flange depth was assessed postoperatively from the conjunctival surface to the upper point of the flange using the RTVue OCT system (Optovue, Inc.) with an anterior segment lens adapter by an independent operator (L.H.).
Differences in visual acuity (UDVA and CDVA), spherical equivalent (SEQ), and flange depth at 1 month, 3 months, 6 months, and 12 months postoperatively were compared between groups.
All patients were adequately informed about the study, risks, and benefits of the surgery and provided signed informed consent to participate. The study protocol followed the tenets of the Declaration of Helsinki and was approved by an independent Ethical Review Board of the Instituto Universitario Italiano de Rosario.
The inclusion criteria were as follows: at least 18 years of age, a clear cornea, aphakia, and no capsular support. The exclusion criteria were as follows: concurrent ocular diseases and/or systemic diseases that could affect conjunctival or scleral tissues and pregnancy.
The data that support the findings of this study are available from the corresponding author on reasonable request.
Surgical MethodsAll surgeries were performed by the same experienced physician (S.A.) under retrobulbar anesthesia. Either a TECNIS ZA9003 (Abbott Medical Optics, Inc.) or a Focus Acrylic 600 (EyePx) were randomly implanted upon availability.
NSP TechniqueThe procedure was started with a 2-port vitrectomy. The midline was identified with ink marks made on the limbal conjunctiva at the 3 o'clock and 9 o'clock positions. A second set of marks was made 2 mm from the limbus and then 2 mm inferior or superior to the first marks. A 3.2-mm corneal incision was made at the 12 o'clock position. A 2 mm long, angled 5 degrees to 10 degrees downward from the iris plane and 20 degrees from the limbus, scleral tunnel was made at the 3 o'clock position. A 3-piece IOL was partially inserted into the anterior chamber, and the leading haptic of the IOL was directly threaded into a 30-gauge thin wall (TW) needle. The IOL optic was injected into the anterior chamber while the trailing haptic was left securely into the main incision. A second 2-mm intrascleral tunnel was created 180 degrees from the first tunnel. A 23-gauge micro forceps (Microsurgical Technology) was used to guide the trailing haptic into the second 30-gauge TW needle. The needles were externalized, once at a time, the trailing haptic being the first. A specially designed forceps (Perfect Flanger Forceps, Rumex International Corp.) and low-temp cautery (Accu-Temp Cautery, Beaver-Visitec International) were used to melt 1 mm of each haptic end.12 Burying of the flanges into the scleral tunnel was performed. Ophthalmic viscosurgical device (OVD) removal was accomplished with a dual-port irrigation/aspiration (I/A) cannula. An iridotomy was made at the 12 o'clock position with a vitrector.
SP TechniqueThe procedure was started with a 2-port vitrectomy. The midline was identified with ink marks made on the limbal conjunctiva at the 3-o'clock and 9-o'clock positions. Two small peritomies were created next to them. A second set of marks was made 2 mm from the limbus and then 2.5 mm inferior or superior to the first marks (Figure 1, A). A 3.2-mm corneal incision was made at the 12-o'clock position. With a 1 mm wide gradable diamond knife set at 400 μm, a scleral incision was made (Figure 1, B). Next, a Sinskey hook was used to create a 400 μm long scleral pocket from the incision. A 30-gauge TW needle (TSK Laboratories) was introduced while holding up the roof of the scleral pocket with the hook (shoehorn technique) (Figure 1, C). A 2.5 mm long, angled 5 degrees to 10 degrees downward from the iris plane and 20 degrees from the limbus, scleral tunnel was made at the 3 o'clock position. A 3-piece IOL was partially inserted into the anterior chamber, and the leading haptic of the IOL was directly threaded into the 30-gauge needle. The IOL optic was then completely injected into the anterior chamber while the trailing haptic was left securely into the main incision. A second 2.5-mm intrascleral tunnel was created 180 degrees from the first tunnel. A 23-gauge micro forceps was used from the main incision to guide the trailing haptic into the second 30-gauge needle. The needles were externalized, once at a time, the trailing haptic being the first. A forceps (Perfect Flanger Forceps) and low temp cautery (Accu-Temp Cautery) were used to melt 1 mm of each haptic end for a suitable flange creation (Figure 1, D). Burying of the flanges into the scleral pockets was performed (Figure 1, E and F). OVD removal was accomplished with a dual-port I/A cannula. An iridotomy was made at the 12 o'clock position with the vitrector. The conjunctiva was closed with fibrin glue (Video 1).
Figure 1.: Shoehorn technique. A: Ink guiding marks for 2.5 mm long scleral tunnels. B: 400-μm preset scleral incision. C: Lifting the roof of the pocket. D: Flange creation with a Perfect Flanger forceps. E and F: Complete flange burying inside scleral tunnels.
,,]}All patients were instructed to use topical instillation of gatifloxacin 0.3% 4 times a day for 2 weeks, ketorolac 0.4% twice a day for 4 weeks, and prednisolone acetate 1% 4 times a day for 2 weeks and then twice a day for another week. Both groups were controlled at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months postoperatively (Figure 2).
Figure 2.: A and B: Box plot indicating postoperative UDVA and CDVA at 1 month, 3 months, 6 months, and 12 months in the NSP group and SP group. Not statistically different. NSP = no scleral pocket; SP = scleral pocket
Statistical AnalysisThe sample size was calculated using the EPIDAT v. 3.1 software (Xunta de Galicia) with a confidence level of 95%, power of 90%, and significance level of 0.05. All data were statistically analyzed using IBM SPSS software (v. 26.0, IBM Corp.). The normality of data was verified with the Shapiro-Wilk test. Continuous variables were expressed as means with their respective SDs, whereas categorical variables were expressed in percentages. Between-group differences were determined using the paired t test for the normally distributed data; non-normally distributed data were analyzed using the Mann-Whitney U test and Kruskal-Wallis test. The Pearson chi-square or Fisher exact test was used to compare categorical variables. A P value less than 0.05 was considered statistically significant.
RESULTS Demographic Data, Causes of Aphakia, and Implanted IOLEach group comprised 18 eyes, resulting in 36 flanges per group. The NSP group included 12 women (66.6%) and 6 men (33.3%) and 10 right eyes (55.5%) and 8 left eyes (44.5%). The SP group included 11 women (61.1%) and 7 men (38.9%) and 7 right eyes (38.9%) and 11 left eyes (61.1%). Groups were not statistically different preoperatively according to age, scleral thickness, IOP, SEQ, UDVA, and CDVA according to the paired t test and Mann-Whitney U test (Table 1). Causes of aphakia included intraoperative cataract surgery complications in 25 cases (69.44%), late surgical complications in 6 cases (16.67%), and ocular trauma in the remaining (5) cases (13.89), demonstrating a significantly younger population when trauma was the cause of aphakia (P < .05, Kruskall-Wallis test) (Table 2).
Table 1. - Demographics: implanted IOL Parameter NSP groupNSP = no scleral pocket; SEQ = spherical equivalent; SP = scleral pocket; ST = scleral thickness
ICSC = intraoperative cataract surgery complication; LSC = late surgical complication; OT = ocular trauma
*Statistically significant
Either an AMO TECNIS z9003 (poly(methyl methacrylate) [PMMA] haptics) or a Focus Acrylic 600 (polyvinylidene fluoride [PVDF] haptics) IOL was implanted upon availability (randomly provided by the patient's health insurance company): 5 PMMA and 13 PVDF haptics IOLs in the NSP group and 4 PMMA haptics IOLs and 14 PVDF haptics IOLs in the SP group (P = .585, Pearson chi-square test) (Table 1).
Postoperative Visual Acuity and Spherical EquivalentAt 12 months postoperatively, mean UDVA for the NSP group was 0.40 logMAR (SD ± 0.19) and for the SP group was 0.35 logMAR (SD ± 0.14) and mean CDVA for the NSP group was 0.17 logMAR (SD ± 0.14) and for the SP group was 0.16 logMAR (SD ± 0.14) (P = .333; P = .446, respectively, Mann-Whitney U test). The results at 1 month, 3 months, 6 months, and 12 months for both groups were not statistically different and are listed in Table 2. At 12 months, mean SEQ for the NSP group was −0.50 D (SD ± 0.81) and for the SP group was −0.23 D (SD ± 0.68), not significantly different (P = .078, Mann-Whitney U test).
Flange Depth for Surgical Groups and Type of Implanted IOLAS-OCT confirmed a significantly deeper flange position for the group with a scleral pocket (SP) at 1 month, 3 months, 6 months, and 12 months postoperatively (P < .05, paired t test and Mann-Whitney U test) (Table 3). Mean flange depth at 12 months for the NSP group was 120.61 μm (SD ± 18.73) and for the SP group was 330.78 μm (SD ± 27.26) (Figure 3A). At 12 months, the NSP group mean depth for nasal flanges was 119.61 μm (SD ± 17.49) and for temporal flanges was 121.61 μm (SD ± 20.36); in the SP group, nasal flanges had a mean depth of 330.89 μm (SD ± 28.75) and temporal flanges 330.67 μm (SD ± 26.54). There was no statistical difference for mean flange depth between nasal or temporal flange location (P = .933, Mann-Whitney U test) (Figure 3B). At 12 months postoperatively, in the NSP group, IOLs with PMMA haptics had a mean flange depth of 115.20 μm (SD ± 14.38) and for PVDF haptics was 122.69 μm (SD ± 20.02); in the SP group, PMMA haptics mean flange depth was 326.25 μm (SD ± 16.58) and for PVDF haptics was 332.07 μm (SD ± 29.74). There was no statistical difference for mean flange depth between the 2 different IOLs implanted for both groups (P = .367, Mann-Whitney U test; P = .602, paired t test, respectively).
Table 3. - Postoperative visual acuity, spherical equivalent, flange depth, and complications Parameter NSP groupNSP = no scleral pocket; SEQ = spherical equivalent; SP = scleral pocket
*Statistically significant
Figure 3.: A: Box plot representing mean flange depth for the NSP group and SP group at 1 month, 3 months, 6 months, and 12 months*. B: 1 month postoperative AS-OCT in the NSP technique. C: 1 month postoperative AS-OCT showing details of incision, scleral pocket, and flange location. Flange depth measured from the conjunctival surface to the upper point of the flange. *Statistically significant. NSP = no scleral pocket; SP = scleral pocket
Subconjunctival:Transconjunctival FlangesFor the NSP group, 3 flanges (8.33%) were subconjunctivally located at 1 month, 3 months, and 6 months postoperatively and 4 flanges (11.11%) at 12 months postoperatively. No flanges were subconjunctivally located in the SP group at 1 month, 3 months, 6 months, and 12 months postoperatively. There was a significantly higher presence of subconjunctival flanges in the NSP group at 12 months (P = .04, Pearson chi-square test). No cases of transconjunctival flanges were detected for both groups 12 months postoperatively.
ComplicationsIn the NSP group, there were 2 postoperative complications (11%). One case presented with a rhegmatogenous retinal detachment 5 weeks postoperatively, but this patient had a severe blunt trauma as the cause of aphakia associated with a peripheral retinal tear; we think this might have caused the rhegmatogenous retinal detachment and not the IOL implantation surgery itself. A mild transient vitreous hemorrhage was detected in the second case, which spontaneously resolved after 3 weeks.
In the SP group, there was 1 postoperative complication (5.5%), a small vitreous hemorrhage, which spontaneously resolved after 2 weeks.
For both groups, there were no flange-related complications at 12 months postoperatively (no dislocations, conjunctival erosion, or endophthalmitis).
DISCUSSIONFlanged fixation techniques (IOL haptics or sutures) are becoming increasingly popular, and indeed, some authors describe inserting them into scleral tunnels as a fundamental part of their technique while others describe that covering them with Tenon or conjunctiva may be sufficient, provided appropriate flange shape, size, and tension are obtained.11,13,14
Canabrava et al. reported 7.5% to be in the sub-Tenon and 2.89% exposed in their flange cohort; we found 4 flanges (11.11%) located subconjunctivally (sub-Tenon), but no conjunctival erosions. By contrast, their study involved the use of 5-0 and 6-0 polypropylene sutures instead of different haptics materials (PVDF and PMMA) as in our study.15
Obata et al. and Karaca et al. described cases of endophthalmitis secondary to an exposed haptic after an intrascleral IOL fixation using the Yamane technique.10,16 We had no transconjunctival flanges or endophthalmitis cases after a 12-month period of follow-up.
Our study is the first to demonstrate that creating a previous scleral pocket permits a significantly deeper flange position compared with the (no pocket) intrascleral fixation technique originally described by Shin Yamane.1 A key feature of our study is the standardization of the scleral pocket dimensions, given that we used a preset diamond knife (as described by Valvecchia) for a 400 μm deep and 1 mm wide scleral incision and the length of the pocket was attained by a 400 μm long Sinskey hook (personal modification).17 In addition, lifting the roof of the pocket before inserting the 30-gauge needle (Shoehorn technique) results in less risk of engaging scleral tissue, therefore, ensuring the tunnel pathway begins at the desired depth.12 It is important to keep in mind that inadequate flange position can be caused by poor technical steps, such as a superficial, short, or excessively vertical tunnel, which may generate insufficient tension between the sclera and the IOL haptic.18
At this point, we would like to discuss a new concept which, to the best of the authors' knowledge, has not been reported to date and should be added as a cause of superficial flange location. The concept refers to inadequate flange/tunnel entrance ratio (FlaTER), meaning a poor relation between flange diameter vs the scleral tunnel entry diameter, preventing a complete burying of the flange into the scleral tunnel.
To clarify the concept, we will set the following example: Ma et al. found that PVDF haptic melting of 0.5 mm produces an approximately 377-μm flange and the melting of 1 mm produces a 445-μm flange diameter, taking a mean 400-μm flange diameter and put against a 300-μm tunnel entrance diameter for a 30-gauge needle, we obtain in this case a FlaTER >1 (1.33). As expected, a 400-μm diameter flange is unlikely to be completely buried into the 300-μm tunnel, unless a wider (>400 μm) opening is used to balance the equation (FlaTER ≤1).19 This could be the reason why some flanges, despite a correct scleral tunnel construction technique (but no pocket), remain located in the sub-Tenon/subconjunctival space.
Reasonably, we only need an entrance ≥400 μm wide for a small fraction of the tunnel, long enough to perfectly nest the flange (approximately 200 μm long according to Kronschläger et al.), but the rest of the tunnel must remain of the same 300 μm diameter so that the flange does not slip into the eye; the use of a larger 27-gauge or 25-gauge tunnel to balance the equation may compromise flange stability/biomechanical forces (except the tip of the needle is partially inserted to open the entrance but at risk of damaging the haptic).20 Therefore, we suggest making tunnels 2.5 mm long, permitting an entrance pocket of 400 μm deep, 1 mm wide, and approximately 400 μm long to obtain a FlaTER ≤1 and, still, providing a remaining 2 mm long and 30-gauge in diameter scleral tunnel to keep tension on the haptic (preventing internal slipping of the flange).
It could be argued that a significant advantage of the Yamane technique, which is saving surgery time, is lost with a scleral pocket technique. In the author's opinion, making a conjunctival peritomy and cauterizing the episcleral blood vessels in that area, allowed an excellent visualization throughout pocket construction and certainty of complete burying of the flange into the scleral tunnel (deeper location), often obscured by blood when transconjunctival piercing was performed.
The biggest strength of this study is the prospective, double-blind (patient-examiner), randomized controlled study design, which offers comparability and validity. However, there are still some potential limitations to it. First, the population enrolled was small, so a randomized multicenter study with a large sample may be necessary to confirm our findings. Another inherent limitation was that each surgical technique could not be blinded for the surgeon during the operation, but in order not to bias the results, the surgeon did not participate in the subsequent examinations and data analysis. In addition, implantation of IOLs with 2 different haptics materials (PMMA and PVDF) was due to availability issues in our country, but it was randomly provided by the health insurance company and no statistical difference in flange depth was found between IOLs used. Finally, we think that a period of 12 months is long enough to allow for refractive stabilization and conjunctival scarring to be completed postoperatively; however, studies with a longer follow-up should be performed for exploring the long-term outcomes, possible flange position changes, and complications related to them.
In conclusion, when performing flanged intrascleral IOL fixation with no capsular support, a scleral pocket provides a significantly deeper flange position than no pocket techniques, achieving similar visual acuities and refractive outcomes at 12 months postoperatively.WHAT WAS KNOWN Flanged IOL fixation is one of the most effective ways to fixate an intrascleral IOL without using suture or glue. Several postoperative flange-related complications (IOL decentration/luxation, hypotony, vitreous hemorrhages, endophthalmitis) have been reported. Inadequate flange position can be caused by poor technical steps, such as short or excessively vertical tunnels.
WHAT THIS PAPER ADDS AS-OCT revealed a significantly deeper flange position for the scleral pocket (SP) group at 1 month, 3 months, 6 months, and 12 months postoperatively (P < .05) with no differences in CDVA or spherical equivalent. There were no flanges subconjunctivally located in the SP group at 12 months postoperatively. A 400 μm deep, 1 mm wide, and 400 μm long pocket provides adequate flange/tunnel entrance ratio (≤1) enabling complete scleral burying of PVDF and PMMA flanges. AcknowledgmentsTo Santiago Cueto, PhD, for his assistance with statistics.
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