FormalPara Key Summary Points

Why carry out this study?

Each technique of scleral fixation has to ensure predictability of refractive outcomes, long-term stability of intraocular lens (IOL), and low risk of complications.

Studies on different methods of scleral fixation of IOLs help surgeons when planning the procedure and choosing the surgical technique for the best patient outcomes.

The main objective of our study was to compare the safety and efficacy of four-point scleral fixation and two-point fixation using the Yamane technique IOLs.

What was learned from the study?

Both analyzed techniques are well tolerated and have a similar safety profile.

Four-point scleral fixation ensures extremely predictable refractive results and is beneficial for young, active patients.

Introduction

Aphakia, resulting from the removal of displaced natural or artificial lens, occurring after complicated cataract surgery, trauma, intracapsular cataract removal, or lensectomy (performed because of congenital cataract), is an indication for a secondary intraocular lens (IOL) implantation.

Despite the development of surgical techniques, the absence of the lens capsule significantly complicates the implantation of a posterior chamber IOL and makes it difficult to obtain optimal results in the postoperative period. Therefore, new methods, tools, and strategies which offer surgeons a variety of techniques for surgical treatment of aphakia are being developed. Each technique should be minimally invasive, reproducible, and provide long-term IOL centration.

The transscleral fixation of the IOL, which is currently popular, was originally started by Gabor Scharioth [1, 2] and further modified by Agarwal et al. [3]. A variety of methods for scleral fixation have been described, including suture fixation and sutureless fixation methods, with or without vitrectomy [4,5,6,7]. Methods of IOL fixation to the sclera, with the use of sutures, have been previously described; however, long-term observation shows the possibility of suture breakage and slippage, resulting in subsequent lens displacement [4].

Sutureless two-point IOL fixation, proposed a few years ago by Japanese surgeon Shin Yamane, is popular partly because of the lack of use of sutures and also shortening the duration of the procedure [8]. Results of two-point sutureless flanged intrascleral fixation technique, reported by Yamane, demonstrated good visual and refractive outcomes with stable IOL location after up to 36-month follow-up. Nowadays, the application of the four-point IOL fixation method, which offers good stability and centration, is increasing. Each method of scleral fixation has its own advantages and, so far, none has strong evidence of superiority.

The purpose of our study was to compare two methods of scleral fixation of IOL: two-point fixation of AcrySof MA60AC IOL (Alcon) using the Yamane technique and four-point fixation of the Akreos AO60 IOL (Bausch & Lomb) using polypropylene sutures. We rated the best-corrected visual acuity (BCVA), refractive outcomes, intraocular pressure (IOP), and also determined intra- and postoperative complications.

Methods

The study was conducted in accordance with the tenets of the Declaration of Helsinki and has been approved by the Bioethics Committee of the Military Institute of Medicine. The ethics committee reference number is NR 11/WIM/2021. Informed consent to participate in the study was obtained from all subjects. All methods were carried out in accordance with relevant guidelines and regulations. The study was prospective and randomized. It was conducted at the Military Institute of Medicine—National Research Institute in Warsaw between 2021 and 2023. All surgeries were conducted by one surgeon (MR). The study included only adult men and women with aphakia and without capsular support in analyzed eye(s). Patients were randomly divided into two groups. The first group comprised patients who underwent four-point fixation, while the second group consisted of patients who underwent two-point fixation using the Yamane technique.

Exclusion criteria for this study included Fuchs’ dystrophy, corneal haze or scarring, history of corneal transplantation, astigmatism of more than 2.0 D (diopters), clinically active uveitis, advanced glaucoma, or macular diseases that affect visual acuity (age-related macular degeneration, diabetic maculopathy).

We compared both groups of patients in terms of age, gender, cause of aphakia, axial length, prior medical and surgical history of the eye, follow-up time, refractive status, and complications. Preoperative examination included uncorrected visual acuity (UCVA), BCVA, applanation tonometry, corneal endothelial cell density, slit-lamp anterior, posterior segment examination, and biometric values. Preoperative biometry was performed using a Zeiss IOL master 700 (Carl Zeiss Meditec, Jena, Germany) and the theoretical Sanders-Retzlaff-Kraff (SRK/T) formula was used to calculate lens power. Target refraction (TR) was − 2.5 D for patients with myopia and − 0.25 D for all others.

The patients underwent examinations at various time points, including days 1 and 7, and months 1, 3, 6, and 12. Full ophthalmic examination was performed during all postoperative visits. BCVA was collected in decimal visual acuity values and converted to logMAR for statistical analysis. Postoperative total refractive error (RE) was calculated as the difference between expected refractive and actual refractive error after surgery. Noncontact specular microscope was used for measuring endothelial cell count (ECC) before and 1 year after surgery. Clinical evaluation of inflammation included conjunctival congestion, corneal edema, cells and flare in the anterior chamber, and synechia formation. Ocular hypotension was defined as a new onset of IOP of 6 mmHg or less. Ocular hypertension was defined as a new onset of IOP of 25 mmHg or more at any postoperative visit. Corneal edema was documented if observed at any postoperative visit and was not present preoperatively. Cystoid macular edema (CME) was defined as a new onset of postoperative edema that was observed in optical coherence tomography (OCT).

All statistical calculations were carried out using the statistical package StatSoft. Inc. STATISTICA (data analysis software system) version 12.0. Significance of all conduced statistical tests was based on p values ≤ 0.05.

Intraocular Lenses

Akreos AO60 IOL (Bausch & Lomb) hydrophilic acrylic one-piece IOL with four-point haptic design was used for four-point fixation. It was fixed with a 6–0 polypropylene suture. This was one-piece acrylic IOL with biconvex aspheric front and back surfaces. The diameter of the optical part was 6 mm and had four haptics. This IOL design allowed for fixation at four points.

A three-piece AcrySof MA60AC IOL (Alcon) was used for sutureless fixation with the Yamane technique. It was an acrylic hydrophobic anterior asymmetric biconvex IOL. It had a 6-mm optic diameter and two haptics made of polymethyl methacrylate (PMMA). Haptic angle was 10° and the overall length was 13 mm. Optical diameter and haptic configuration make this IOL not only suitable for capsular and iridociliary sulcus implantation but also adjustable for scleral fixation [9].

Surgical Technique

Group 1: Four-Point Scleral Fixation of Akreos AO60 IOL

Four intrascleral tunnels were marked 2 mm from the corneal limbus, spaced 6 mm apart following retrobulbar anesthesia. Following this, corneal incisions were made, pupil-dilating solution was administered into the anterior chamber, and a viscoelastic substance was introduced. Core vitrectomy was performed if vitreous was found in the anterior chamber. An artificial lens was then implanted into the anterior chamber using an injector (Fig. 1A). The 6–0 polypropylene suture was introduced into the anterior chamber through openings in the cornea (Fig. 1B). The next stage was to perform a sclerotomy using a 30G needle. Subsequently, the needle was passed through the hole in the haptic and 6–0 polypropylene suture was inserted into the needle hole and guided outside (Fig. 1C). The opposite end of the suture, which was threaded through the opening in the haptic, was positioned in the lumen of the needle and then passed through another sclerotomy before being externalized (Fig. 1D). This maneuver was repeated with another haptic as well (Fig. 1E). Correct position of the IOL in the eye was achieved by pulling on the ends of the monofilament. Once the position was satisfactory, the ends of sutures were trimmed and cauterized to create flanges (Fig. 1F). The melted tips of the sutures were then withdrawn and fixed subconjunctivally. Next openings in the cornea were sealed and finally an antibiotic was injected into the anterior chamber.

Fig. 1
figure 1

Four-point scleral fixation of Akreos AO60 IOL. Marked locations of the intrascleral tunnels and intraocular lens (IOL) implanted into the anterior chamber (A). The 6–0 polypropylene suture introduced into the anterior chamber (B). The 6–0 polypropylene filament inserted into the needle hole and externalized (C). The same procedure was performed with the second end of the suture (D). The needle was used to externalize the second fragment of monofilament by the third and fourth sclerotomy (E). Cauterization of the tips of the 6–0 polypropylene filament (F)

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Group 2: Sutureless Scleral Fixation of AcrySof MA60AC IOL with Yamane Technique

The surgery was performed under retrobulbar anesthesia. The first step of the procedure was to mark the locations of the intrascleral tunnels, situated 2 mm from the corneal limbus, and locate them at a distance of 180° from each other. This measure aimed to prevent the lens from tilting in the eyeball (Fig. 2A). Openings in the cornea were made. Pupil-dilating solution and viscoelastic substance were injected into the anterior chamber. If vitreous was found in the anterior chamber, anterior vitrectomy was necessary. Three-piece IOL was implanted into the anterior chamber. The first sclerotomy was performed through the conjunctiva using a 30G needle 2 mm from the limbus (Fig. 2B). One of the haptics was inserted into the needle lumen and then brought out (Fig. 2C, D). The same procedure was performed with another haptic at a distance of 180° (Fig. 2E). The next step was to perform cautery of the tips of the haptics, obtaining a 0.3-mm collar that prevents the risk of the haptic coming out of the tunnel and displacing the lens inside the eyeball (Fig. 2F). The tips of the haptics were finally gently inserted into the scleral canals and covered with conjunctiva. Antibiotic was administered into the anterior chamber after sealing the corneal openings.

Fig. 2
figure 2

Sutureless scleral fixation of AcrySof MA60AC intraocular lens (IOL) with Yamane technique. Marking the locations of the intrascleral tunnels (A). The sclerotomy performed through the conjunctiva using 30G needle 2 mm from the limbus (B). The haptic insertion into the needle lumen (C). The haptic is externalized (D). The same procedure was performed with another haptic (E). Cauterization of the tips of the haptics (F)

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Typical postoperative treatment was introduced (antibiotic and anti-inflammatory topical drugs) after surgery for all patients in both groups.

Results

The study included a total of 50 eyes of 47 patients with aphakia, comprising 23 women and 24 men. Single-piece intraocular lens Akreos AO60 IOL (group 1) was implanted into 25 eyes of 23 patients. Three-piece intraocular lens MA60AC (group 2) was implanted into 25 eyes of 24 patients. The mean follow-up time in both groups was about 1 year and photographs of the patients after the surgeries are shown in Fig. 3. No statistically significant differences were found between study groups in regards to demographics. Demographic characteristics are summarized in Table 1. There were no statistically significant differences between study groups if terms of the cause of aphakia (p > 0.05). The most common cause of aphakia was complicated cataract surgery, which was found in 32% (8 cases) in group 1 and in 40% (10 cases) in group 2. Other causes of aphakia and ocular history are presented with details in Table 1.

Fig. 3
figure 3

Case report. Slit-lamp photography 1 year after scleral fixation of AcrySof MA60AC with Yamane technique (A, B). Slit-lamp photography 1 year after four-point scleral fixation of Akreos AO60 (C, D)

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Table 1 Baseline patient demographics and clinical history
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Main surgical time of scleral fixation was similar in both groups and was 24.1 min ± 8.9 (standard deviation, SD) in group 1 and 25.1 min ± 9.9 (SD) in group 2. No statistically significant differences were found in regards to the duration of the procedure (p > 0.05). There were no intraoperative complications in either group.

Improvements in visual acuity were achieved for all patients. BCVA increased at 1-year follow-up compared to the baseline (p < 0.05) in both groups. Moreover, BCVA increased significantly at visits on days 30 and 360 compared to the preoperative BCVA in both groups (p < 0.05). Mean preoperative BCVA (± SD) for group 1 and group 2 was 0.27 ± 0.26 and 0.20 ± 0.23 logMAR, respectively (Fig. 4). There were no significant differences between both groups (ns). The postoperative BCVA for group 1 and group 2 at 1 year’s observation was 0.10 ± 0.15 and 0.09 ± 0.17 logMAR, respectively (Fig. 4). There were no statistically significant differences between groups in terms of BCVA at any follow-up period (p > 0.05). Average preoperative spherical error was 9.22 ± 4.88 D in group 1 and 11.49 ± 1.40 D in group 2 (p > 0.05). The mean postoperative spherical error was − 0.32 ± 0.85 D in group 1 and 0.74 ± 0.85 D in group 2 (p < 0.05). Preoperative cylinder error was − 0.68 ± 0.86 D for group Akreos AO60 and − 0.50 ± 0.66 D for group MA60AC (p > 0.05, Fig. 4). The postoperative cylinder error 1 year after surgery was − 0.56 ± 0.87 D for group Akreos AO60 and − 0.41 ± 0.99 D for group MA60AC (p > 0.05, Fig. 4). There was no statistically significant change in cylinder error in both groups. The mean preoperative spherical equivalent (SE) refractive error was 8.88 ± 4.90 D in group 1 and 10.76 ± 2.75 D in group 2 (p > 0.05). Postoperative SE refractive error was − 0.65 ± 1.15 D in group 1 and 0.28 ± 1.13 D in group 2 (p = 0.001). The average postoperative total RE was − 0.06 ± 0.71 D for four-point scleral fixation and 0.83 ± 0.70 D for Yamane technique (p < 0.05). Total postoperative RE for TR − 0.25 D (p < 0.05) was significantly higher for group 2 compared to group 1. However, there were no statistically significant differences (p > 0.05) between groups for TR − 2.5 D.

Fig. 4
figure 4

Comparison of groups 1 and 2 in terms of best-corrected visual acuity (BCVA), cylinder (CYL), intraocular pressure (IOP) at follow-up visits

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Mean preoperative endothelial cell count was 1896.7 ± 374 cells/mm2 in group 1 and 1992 ± 563 cells/mm2 in group 2. Mean postoperative endothelial cell count was 1879.4 ± 403 cells/mm2 in group 1 and 1924 ± 367 cells/mm2 in group 2. No statistically significant differences between groups were found (p > 0.05). Endothelial cell density (ECD) loss was 0.9% in the four-point scleral fixation group and 3.5% in the Yamane technique group. No statistically significant differences between groups were found (p > 0.05). Transient corneal edema was observed in 2 eyes (8%) in group 1 and in 6 eyes (24%) in group 2, which disappeared completely for all eyes in about 2–3 weeks after the procedure. The difference was not statistically significant (p > 0.05).

Mean preoperative IOP for group 1 and group 2 was 16.0 mmHg and 16.8 mmHg, respectively. Postoperative IOP for group 1 and group 2 was 15.0 mmHg and 15.2 mmHg, respectively, at 1 year’s observation (p > 0.05, Fig. 4).

Early ocular hypertension was observed on the first few days after surgery in 8 eyes (33%) in four-point scleral fixation and in 10 eyes (40%) in the Yamane technique (Fig. 4). On the 7th day after surgery IOP was significantly higher in group 2 compared to group 1 (p = 0.025). No statistically significant differences were shown for the other postsurgery visits (p > 0.05).

Ocular hypotension was observed in 2 eyes (8%) in group 1 and in 1 eye (4%) in group 2 on the postoperative day 1. There were no statistically significant differences between groups (p > 0.05). Anterior chamber bleeding or vitreous cavity bleeding occurred in 2 cases (8%) in group 1 and in 10 cases (40%) in group 2, and it was statistically significantly more frequent in the Yamane technique group (p = 0.01). All complications were managed medically with topical therapy.

IOL displacement was found in one case (4%) in group 2 and required IOL repositioning. Suture extrusion was found in one case (4%) in group 1 at 9 months after surgery and haptic extrusion was found in one case (4%) in group 2 at 1 month after surgery. This difference was not statistically significant (p > 0.05). Conjunctival plastic surgery was performed in both cases and no re-extrusion was found at the subsequent visits. Pseudophakic reverse pupillary block (PRPB) was diagnosed in one case (4%) 1 month after the surgery in group 2 and laser peripheral iridotomy (LPI) was performed. One patient from group 1 (8%) had retinal detachment (RD) in both eyes after surgery, which might have been associated with myopia.

No cases of endophthalmitis, choroidal detachment, CME, or lens opacification were reported.

Discussion

We have described postsurgical outcomes of two scleral intraocular fixation techniques: four-point scleral fixation of the Akreos AO60 and two-point sutureless fixation by Yamane technique of the MA60AC IOL.

The literature suggests that the most common cause of secondary scleral fixation of the IOL is complicated cataract surgery [10, 11]. This was also confirmed in our study, being discovered in 40% of cases. The second most common cause of aphakia in our study was subluxation or dislocation of the IOL and was observed in 22 cases (44%). The rate of IOL decentration is between 0.1% and 3% for the 5-year observation period after cataract surgery and risk factors are pseudoexfoliation syndrome (PEX), ocular trauma, vitreoretinal surgery, myopia, and uveitis [12, 13].

Refractive outcomes after the procedure were similar in both groups. However, the refractive error was higher for patients who had surgery using the Yamane technique. Shift towards hyperopia was observed in this group. Similar refractive error results were reported in a study conducted by D’Agostino [9], which compared two fixation methods: group 1 were implanted with a three-piece MA60AC and group 2 were implanted with a newly developed single-piece foldable IOL SOLEKO FIL-SSF. In that study the mean refractive error was approximately 1 D in both groups (group 1, 1.01 D; group 2, 1.09 D). Zyablitskaya et al. reported that the postoperative refractive error for the four-point sutured scleral fixation of the Akreos was − 0.3 ± 1.03 D, which is similar to our study [14]. Refractive error was lower for the four-point fixation method, allowing for more predictable refractive results after surgery. There are numerous pre-, intra-, and postoperative factors that can influence refractive outcomes after surgery. Preoperative biometric data are necessary to determine the refractive power of the implanted IOLs [15]. Accurate IOL power calculations rely on numerous factors, such as accurate preoperative biometric measurements, precise prediction of effective lens position (ELP), appropriate IOL formula selection, and optimization of the IOL constant [16]. There were no statistical differences between the groups in our study regarding the essential biometric parameters for calculating the power of the IOLs, such as axial length (AXL), corneal power, and corneal astigmatism. We did not find a relationship between the power of the implanted IOLs and the refractive error after surgery. This study used different types of lenses for scleral fixation. We did not evaluate the effect of IOL material, which could potentially play an important role. Future studies will be needed to assess whether the differences can be explained, even in part, by the IOL material or whether there are other causes.

An increasing number of studies are evaluating the effectiveness and stability of four-point IOL fixation. In 2010 Fass and Herman described a technique using the same Akreos AO60 IOL inserted through a 3–3.4-mm incision and fixed on four points attached with a 10–0 propylene suture [17]. In our study we used 6–0 polypropylene, which is 3.5 times thicker than the 10–0 polypropylene suture, ensuring longer stability and less risk of erosion [18]. Only one case of suture erosion was recorded in 9 months after surgery. We have not recorded any cases of suture rupture during the observation period. Recently, Gore-Tex material has been used more frequently for four-point suture fixation. Gore-Tex suture has greater tensile strength and long-term durability than prolene, which has up to 27.9% suture erosion in adults at a mean follow-up of 6 years [19,20,21]. Fixation of the Akreos IOL with Gore-Tex sutures is a relatively new technique. Short-term studies have reported the accuracy of biometric calculation and favorable visual results with the IOL sutured between 2 and 3 mm from the limbus [23, 24] and a similar complication rate if compared to other scleral fixation techniques [3, 8, 25]. Studies reported good lens stability at long-term follow-up, good visual and refractive outcomes, and not a high rate of complications [14, 26]. A disadvantage of this technique is the long surgery time. Mean surgical time was approximately 72 min (range 40–180 min) in the Pardini study. The use of a 6–0 polypropylene suture and its subsequent cauterization shortened the duration of this procedure. The average time required for scleral fixation was 24.1 min ± 8.9 in our study.

Postoperative complications are similar to those described in the literature. Reports demonstrate that the incidence of postoperative ocular hypertension was 3.3–30.5% [27,28,29,30]. In our study this complication was observed on the first day after surgery in 8 eyes (33%) in four-point scleral fixation and in 10 eyes (40%) in the Yamane technique. Early ocular hypertension was the most common complication in the four-point fixation group. Probably this could have been related to the reaction of the eye to the use of steroid drops after surgery. It was necessary to include topical treatment, which was completed after about 1–1.5 months, only for some patients.

Ocular hypotony could be another possible side effect of this procedure. Khan in his study reports that hypotony was recorded in 9.4% cases after sutured scleral fixation IOL [31]. In our study it was observed in 2 eyes (4%) in group 1 and 1 eye (2%) in group 2 on the postoperative day 1.

Corneal edema rate in our study was consistent with other reports [27, 29, 30, 32] and could be explained by previous complicated cataract surgery or ocular trauma, which may have depressed the endothelial cell number before the secondary IOL implantation.

Anterior chamber bleeding was statistically significantly more frequent in the group of patients in whom the Yamane technique was performed. Postoperative bleeding in one case was probably due to IOL decentration leading to contact between the lens and iris and/or ciliary body. According to the literature, in case of three-piece suspended lens, using the Yamane technique, its displacement may occur in up to 33% of cases and the average time from suspension to its displacement is approximately 2.4 ± 1.9 months [9].

Bleeding into the anterior chamber may be accompanied by bleeding into the vitreous chamber, which has been observed in case of patients operated on according to the Yamane method. There were only two cases of postoperative isolated bleeding to the vitreous cavity observed in the group of patients operated on using the four-point fixation technique.

Moreover, in our study PRPB was found in one case, which also manifested as bleeding into the anterior chamber. This is a rare complication after implantation of three-piece IOLs, using the Yamane technique. The mechanism of PRPB is, probably, reducing the gap between the posterior surface of the iris and the optics of the lens. PRPB presents with an acute rise in IOP in the presence of a deep AC that is attributed to the increased resistance to flow of aqueous through the pupil leading to an increased pressure gradient across anterior and posterior chamber causing the characteristic posterior bowing of iris [33]. Bharathi et al. recommend either preoperative laser peripheral iridotomy or surgical iridectomy intraoperatively in eyes with a glued IOL to prevent this rare complication [33]. In this case, a laser iridotomy was used to relieve PRPB and to improve the anatomical conditions in the eye. The given results were maintained during the observation period.

Retinal detachment is a potentially sight-threatening complication following any eye surgery. This complication was found in two eyes of the same patient from the first group of our study, which was presumably related to high myopia and history of previous surgical treatment (history of cataract surgery, removal of a subluxated artificial lens). Studies show that retinal detachment may occur in 1–5% of patients after IOL scleral fixation, with higher rates occurring in patients with previous surgery, ocular trauma, myopia greater than − 1.0 D, and vitreous hemorrhage [34].

We did not record any cases of endophthalmitis, choroidal detachment, or CME in both groups after the procedure.

The long-term efficiency and safety of the two proposed methods are comparable. Our study demonstrated good visual and refractive results in both study groups, with exceptionally good results observed in the four-point scleral fixation using the Akreos AO60 IOL.

The advantages of our study were that the study was randomized, included a relatively large number of patients, the follow-up period was approximately 1 year, and all procedures were performed by one single surgeon.

There are also limitations of this study. A disadvantage of a given examination can potentially be the large number of different variables, such as comorbidities and previous surgeries, which unavoidably hinder reliable comparison of results. In such cases it is harder to predict the visual effects due to comorbidities. Therefore, further investigation is suggested with more emphasis on the possibility of selecting patients considering the variables. Besides, many further observations will help decide which method to choose.

Conclusion

The main objective of each technique of scleral fixation is to provide predictability of refractive outcomes, long-term stability of IOL centration, and low risk of complications. Both analyzed techniques are well tolerated and ensure good refractive results (extremely predictable in four-point scleral fixation) and have a similar safety profile. Four-point scleral fixation of IOLs in aphakic eyes would appear to be a safe and an effective method providing long-term stability of the IOL. This technique is beneficial for young, active patients, especially after trauma or recurrent subluxation. The choice of the method finally depends simultaneously on the surgeon’s preference, previous ocular history, and the local status of the eye.