Comparison of the efficacy of the patented anterior chamber maintainer method and traditional method for implantable collamer lens implantation in myopic eyes: A clinical study

Abstract

Objective

To evaluate the clinical efficacy of a novel ophthalmic viscosurgical device-free method using an anterior chamber maintainer for intraocular collamer lens implantation in eyes with myopia.

Methods

Forty patients underwent bilateral intraocular collamer lens implantation, with one eye receiving the traditional implantation method using an ophthalmic viscosurgical device and the other eye undergoing the anterior chamber maintainer method. Preoperative and postoperative parameters, including uncorrected distance visual acuity, best-corrected distance visual acuity, spherical equivalent, intraocular pressure, aberrations, subjective visual quality, corneal endothelial cell density, operation time, and complications, were compared between and within the two groups.

Results

In the traditional group, 10% of eyes had intraocular pressure >22 mmHg at 2 h postoperatively, compared with 0% in the anterior chamber maintainer group (P < 0.001). The anterior chamber maintainer group showed better uncorrected and best-corrected distance visual acuity, spherical equivalent, total and low-order aberrations, and defocus at 1 day postoperatively (all P < 0.05), as well as shorter operation time (2.85 ± 0.30 vs. 4.37 ± 0.66 min, P < 0.001). No complications were observed except early intraocular pressure elevation in the traditional group.

Conclusion

The anterior chamber maintainer intraocular collamer lens implantation method provides faster visual recovery, a shorter operation time, and more stable intraocular pressure. It offers a convenient alternative to the traditional approach, avoiding ophthalmic viscosurgical device-related complications without introducing new ones.

Keywords

Anterior chamber maintainer intraocular collamer lens implantation traditional intraocular collamer lens implantation intraocular pressure ophthalmic viscosurgical device-free method visual quality

Introduction

Myopia, a refractive error characterized by the focusing of parallel light rays in front of the retina under relaxed accommodation, affects approximately 600 million individuals in China, with approximately 10% classified as having high myopia.¹ Corneal refractive surgery is contraindicated for some individuals with myopia and insufficient corneal thickness, making posterior chamber phakic intraocular lens (PIOL) implantation a primary therapeutic option. The EVO implantable collamer lens (ICL) with a central hole, a type of posterior chamber PIOL, has become a preferred intervention for myopia—particularly high myopia—owing to its favorable outcomes in postoperative visual acuity, optical quality, and reversibility.^2,3

Traditional ICL implantation requires the use of ophthalmic viscosurgical devices (OVDs) to maintain anterior chamber stability and protect intraocular structures. However, residual OVDs can cause acute postoperative intraocular pressure (IOP) elevation,⁴ prolong surgical duration, and increase costs.⁵ To address these limitations, our team developed a technique using an anterior chamber maintainer (ACM) with continuous balanced salt solution (BSS) irrigation through a side incision. This method has demonstrated preliminary safety in previous studies.⁶ The Bianchi^7,8 technique enables the implantation of implantable phakic contact lens (IPCL) V2.0 without viscoelastic agents, using BSS to maintain anterior chamber pressure and stability. This approach eliminates the risks associated with residual viscoelastic material, such as IOP elevation or endothelial damage. Clinical evidence supports the safety and efficacy of this method, establishing it as a significant technological advancement in the field of IPCL implantation.

The present study aimed to evaluate the clinical efficacy of a novel OVD-free method using an ACM for ICL implantation in eyes with myopia.

Methods

This was a comparative, single-center, nonrandomized clinical study. From 2023 to 2024, 160 eyes of 80 patients (38 men and 42 women) underwent EVO ICL implantation at Nanjing Drum Tower Hospital. All patient details were de-identified. Each patient had one eye treated using the ACM method and the other eye treated with the traditional method. The study established clear inclusion and exclusion criteria for patient selection, as described below.

For inclusion, patients were required to have a stable refractive status and to be either unsuitable for or unwilling to wear spectacles or contact lenses, while expressing a desire to undergo refractive surgery. Individuals with high refractive errors or those with moderate refractive errors combined with thin corneas, who are typically unsuitable candidates for corneal refractive surgery, were also eligible for inclusion. Eligible participants were aged between 21 and 40 years. Key ocular parameters included a corneal endothelial cell density (ECD) of ≥2200 cells/mm², normal intraocular pressure, an anterior chamber angle greater than 30°, an anterior chamber depth of at least 2.8 mm, and the absence of iris or ciliary body abnormalities.

Exclusion criteria included the following: (a) a history of ocular surgery; (b) severe dry eye; (c) progressive corneal degeneration; (d) cataract; (e) retinal detachment; (f) uveitis; (g) other ocular diseases; (h) compromised corneal endothelial cell function; (i) preexisting corneal degeneration or trauma-induced corneal morphological abnormalities; (j) abnormally large pupil diameter; or (k) systemic conditions such as diabetes mellitus or autoimmune disorders.

The study included a 12-month follow-up period.

Ethical approval

The study was approved by the Ethics Committee of Nanjing Drum Tower Hospital (approval number: 2024-JS-30, approval date 9 August 2024). Written informed consent was obtained from all participants. The study was conducted in accordance with the principles of the Declaration of Helsinki (1975), as revised in 2013. The reporting of this study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.⁹

Treatment

Parameters to be evaluated

Preoperative evaluations included uncorrected and best-corrected distance visual acuity (UDVA/BCVA), scotopic pupil measurement, slit-lamp anterior and posterior segment examination, non-contact tonometry (TX-20; Canon, Japan), cycloplegic and subjective refraction (CV-5000; Topcon, Japan), anterior chamber (AC) depth and corneal curvature assessed by Pentacam (OCULUS, Germany), and sulcus-to-sulcus (STS) distance measured by ultrasound biomicroscopy (UBM; SW-3200L, Suoer, China) for ICL sizing (STS + 0.7 mm). Wavefront analysis (i-Trace; Tracey, USA) was used to evaluate total aberrations (TA), total high-order aberrations (tHOAs), spherical aberration, coma, trefoil, total low-order aberrations (tLOAs), defocus, and astigmatism. All aberration values were expressed as root mean square (RMS). Before examination, all participants underwent at least 30 min of dark adaptation to ensure a pupil diameter greater than 5.0 mm. Corneal ECD (SP-1P; Topcon, Japan) and National Eye Institute Refractive Error Quality of Life–42 (NEI-RQL-42) scores were recorded preoperatively and at 1 year postoperatively. Surgical procedures were standardized, with a single surgeon performing all cases. Prophylactic topical levofloxacin (0.5%) was administered preoperatively. Postoperative care included levofloxacin and fluorometholone (0.1%) four times daily for 2 weeks.

ACM

A custom ACM developed by our group, with a 0.4-mm diameter, 1.5-mm length, and a 60° beveled tip, was used through a side incision to stabilize intraoperative AC dynamics (Figure 1) (https://pss-system.cponline.cnipa.gov.cn/retrieveList?prevPageTit=changgui).

Figure 1.

Anterior chamber maintainer. (a) Complete picture of the ACM. (b) The length of the ACM tip is 1.5 mm, and the head is beveled at a small angle (60°) and (c) patent certificate. ACM: anterior chamber maintainer.

Surgical procedures

Traditional ICL implantation

Mydriasis was achieved using compound tropicamide (four times daily), and topical anesthesia was administered with proparacaine. A right-side assisted incision was created, and an appropriate amount of OVD (1.7% hyaluronate) was injected into the AC through this incision. A 3.0-mm clear corneal primary incision was then performed. The ICL was inserted into the AC through the main incision. The footplates were positioned beneath the iris with OVD assistance, followed by manual BSS to remove residual OVD.

ACM ICL implantation

Mydriasis and topical anesthesia were performed as in the traditional method. Only BSS was placed in the implant container. Bilateral symmetrical 0.4-mm assisted incisions were created, with the left incision used for ACM placement. A 3.0-mm clear corneal incision allowed ICL insertion without an OVD, with ACM used to stabilize the AC.

Management of early acute IOP elevation

Early postoperative IOP elevation was defined as an increase in IOP exceeding 22 mmHg within 2 h after surgery. When such elevation occurred, slit-lamp examination was performed to rule out pupillary block or malignant glaucoma due to excessive vaulting. Mild IOP elevation (<25 mmHg) was managed with close observation. For moderate elevations (25–30 mmHg), topical anti-glaucoma medications were administered. In cases of marked IOP elevation (>30 mmHg), AC drainage was performed through the side incision, either alone or combined with topical anti-glaucoma treatment, to reduce IOP to 10–13 mmHg. After treatment, IOP was measured every 2 h until normalization.

Statistical analysis

One of the primary outcome measure in this study was IOP on postoperative day 1. Based on data from previous literature, the anticipated mean IOP in the ACM group was 15.33 mmHg standard deviation (SD = 2.27) and 20.68 mmHg (SD = 1.98) in the traditional group. Sample size estimation was performed using a two-sided t-test with a significance level of α = 0.05 and a statistical power of 80%. Assuming an equal allocation ratio (1:1) between the two groups, 80 eyes per group were required. Considering an estimated dropout rate of 10%, the final sample size was adjusted to 88 eyes per group, for a total of 176 eyes. All sample size calculations were performed using Power and Sample Size (PASS) 15 software. Data were analyzed using Statistical Package for the Social Sciences (SPSS) 26. The Shapiro–Wilk test was used to assess normality. Normally distributed data were analyzed using t-tests, whereas non-normally distributed data were evaluated using the Mann–Whitney U test for between-group comparisons and the Wilcoxon signed-rank test for pre-vs. post-treatment analyses. Categorical variables were analyzed using the chi-squared test. Repeated measures were evaluated using analysis of variance (ANOVA). Statistical significance was set at P < 0.05.

Results

General data

No significant differences were observed between the two groups in age, sex, or preoperative spherical equivalent (SE), UDVA, or BCVA (Table 1).

Table 1.

Comparison of baseline data between the groups.

Variable	ACM method (n = 80)	Traditional method (n = 80)	P-value
Age	25.20 ± 3.48	24.98 ± 3.70	0.780
Sex	Male/Female = 38:42	Male/Female = 38:42	–
LogMAR (UDVA)	1.30 (1.10, 1.50)	1.25 (1.08, 1.40)	0.256
LogMAR (CDVA)	0.20 (0.10, 0.20)	0.20 (0.10, 0.30)	0.444
SE	−11.25 (−12.25, −10.25)	−11.50 (−12.75, −10.50)	0.302

ACM: anterior chamber maintainer; LogMAR: logarithm of the minimum angle of resolution; UDVA: uncorrected distance visual acuity; CDVA: corrected distance visual acuity; SE: spherical equivalent.

Comparison of IOP between the two groups

The mean IOP values in the ACM group were 13.72 ± 2.17, 15.55 ± 2.44, 14.15 ± 2.07, 13.88 ± 2.27, 13.62 ± 2.62, and 13.40 ± 2.20 mmHg at the preoperative, 2-h, 1-day, 1-week, 3-month, and 1-year postoperative assessments, respectively. The corresponding values in the traditional group were 13.55 ± 2.34, 20.57 ± 2.80, 14.28 ± 1.95, 13.78 ± 2.30, 13.38 ± 2.91, and 13.40 ± 2.93 mmHg. Preoperative IOP values were within the normal range for both groups, with no significant difference (P = 0.730). A significant difference in IOP changes over time was observed between the two groups. At 2 h postoperatively, no patients in the ACM group (0%) had IOP > 22 mmHg, whereas eight patients (10%) in the traditional group exhibited elevated IOP. One patient in the traditional group developed mild ocular pain and corneal edema, with an IOP of 31 mmHg at 2 h postoperatively. Following AC drainage and administration of carteolol hydrochloride eye drops twice, the symptoms resolved within 24 h, and the IOP decreased to 17 mmHg. The remaining seven patients with elevated IOPs had values of 23, 25, 23, 24, 25, 23, and 26 mmHg; three of these patients (25, 25, and 26 mmHg) received carteolol hydrochloride twice. At 1 day postoperatively, all eyes in both groups had IOP < 22 mmHg. At 2 h after surgery, the IOP in the ACM group was significantly lower than that in the traditional group (P < 0.001). No significant between-group differences were observed at 1 day, 1 week, 3 months, or 1 year postoperatively (P = 0.782, 0.845, 0.687, and 0.999, respectively; Figure 2). A significant difference in IOP was detected between the preoperative and 2-h postoperative time points in both groups and between the preoperative and 1-day postoperative measurements in the traditional group (P < 0.001). No other significant differences were found between time points (Figures 3 and 4). The differences between postoperative and preoperative baseline IOP values in the ACM group were 1.82 ± 0.96, 0.42 ± 1.55, 0.15 ± 2.02, −0.10 ± 1.58, and −0.33 ± 1.56 mmHg at 2 h, 1 day, 1 week, 3 months, and 1 year postoperatively, respectively. The corresponding differences in the traditional group were 7.03 ± 2.91, 0.72 ± 1.41, 0.23 ± 2.01, −0.17 ± 1.84, and −0.15 ± 2.06 mmHg. The change in IOP from baseline to 2 h postoperatively was significantly smaller in the ACM group than in the traditional group (P < 0.001). No significant differences were observed between groups at 1 day, 1 week, 3 months, or 1 year after surgery (P = 0.369, 0.868, 0.845, and 0.669, respectively; Figure 5).

Figure 2.

Comparison of intraocular pressure between the two groups at different time points.

Figure 3.

Comparison of intraocular pressure within the ACM method group before the operation and at 1 day, 1 week, 3 months, and 1 year postoperatively. ACM: anterior chamber maintainer.

Figure 4.

Comparison of intraocular pressure within the traditional group before the operation and at 1 day, 1 week, 3 months, and 1 year postoperatively.

Figure 5.

Comparison of postoperative IOP changes between groups relative to baseline. IOP: intraocular pressure.

Comparison of visual acuity and refractive power between the two groups

At 1 year postoperatively, both groups demonstrated significant improvements in UDVA and BCVA compared with preoperative values. Postoperative SE values were significantly reduced relative to baseline. On postoperative day 1, the ACM group exhibited better UDVA and BCVA than the traditional group (P < 0.001 and P = 0.002, respectively). The SE in the ACM group was also significantly lower on day 1 (P = 0.006), although no significant differences were observed at subsequent time points (Table 2).

Table 2.

Time courses of visual and refractive outcomes between the ACM and traditional groups.

Group	Preoperative period	Postoperative period				P-value
Group	Preoperative period	1 day	1 week	3 months	1 year	P-value
LogMAR (UDVA)
ACM method	1.30 (1.10, 1.50)	0.00 (0.00, 0.00)	0.00 (−0.10, 0.00)	0.00 (−0.10, 0.00)	0.00 (−0.10, 0.00)	P₀ < 0.001
Traditional method	1.25 (1.08, 1.40)	0.10 (0.00, 0.10)	0.00 (−0.10, 0.00)	0.00 (−0.10, 0.00)	0.00 (−0.10, 0.00)	P₀ < 0.001
P-value	P₁ = 0.256	P₁ < 0.001	P₁ = 0.440	P₁ = 0.782	P₁ = 0.389
LogMAR (CDVA)
ACM method	0.20 (0.10, 0.20)	0.00 (0.00, 0.00)	−0.10 (−0.10, 0.00)	−0.05 (−0.10, 0.00)	−0.10 (−0.10, 0.00)	P₀ < 0.001
Traditional method	0.20 (0.10, 0.30)	0.10 (0.00, 0.10)	0.00 (−0.10, 0.00)	0.00 (−0.10, 0.00)	−0.10 (−0.10, 0.00)	P₀ < 0.001
P-value	P₁ = 0.444	P₁ = 0.002	P₁ = 0.121	P₁ = 0.937	P₁ = 0.983
SE
ACM method	−11.25 (−12.25, −10.25)	−0.12 (−0.25, 0.00)	−0.25 (−0.25, 0.00)	−0.25 (−0.25, 0.00)	−0.25 (−0.25, 0.00)	P₀ < 0.001
Traditional method	−11.50 (−12.75, −10.50)	0.00 (0.00, 0.25)	0.00 (−0.25, 0.00)	−0.25 (−0.25, 0.00)	−0.25 (−0.25, 0.00)	P₀ < 0.001
P-value	P₁ = 0.302	P₁ = 0.006	P₁ = 0.308	P₁ = 0.475	P₁ = 0.657

P₀ = P-value for the difference between preoperative and 1-year values; P₁ = P-value for the difference between the ACM ICL implantation and traditional ICL implantation groups; *P < 0.05 indicates a significant difference.

ACM: anterior chamber maintainer; ICL: implantable collamer lens; LogMAR: logarithm of the minimum angle of resolution; UDVA: uncorrected distance visual acuity; CDVA: corrected distance visual acuity; SE: spherical equivalent.

Comparison of aberrations between the two groups

In the ACM group, TA, tLOAs, and defocus values before surgery were significantly higher than those at all postoperative time points (P < 0.001). The TA value on postoperative day 1 was higher than that at 1 year after surgery (P < 0.001). No significant differences were observed in astigmatism, tHOAs, coma, spherical aberration, and trefoil across the postoperative time points (Table 3).

Table 3.

Time courses of aberrations after ACM ICL implantation.

ACM method	Preoperative period	Postoperative period
ACM method	Preoperative period	1 day	1 week	3 months	1 year
TA	5.39 ± 0.21	1.66 ± 0.10	1.60 ± 0.09	1.47 ± 0.03	1.46 ± 0.02
P-value		P₁ < 0.001	P₁ < 0.001	P₁ < 0.001	P₁ < 0.001, P₂ < 0.001
tLOAs	5.33 ± 0.23	1.86 ± 0.09	1.83 ± 0.07	1.79 ± 0.09	1.79 ± 0.07
P-value		P₁ < 0.001	P₁ < 0.001	P₁ < 0.001	P₁ < 0.001, P₂ > 0.999
Defocus	5.23 ± 0.11	1.47 ± 0.12	1.42 ± 0.07	1.38 ± 0.08	1.38 ± 0.07
P-value		P₁ < 0.001	P₁ < 0.001	P₁ < 0.001	P₁ < 0.001, P₂ = 0.155
Astigmatism	0.41 ± 0.11	0.43 ± 0.08	0.41 ± 0.08	0.41 ± 0.09	0.40 ± 0.08
P-value		P₁ > 0.999	P₁ > 0.999	P₁ > 0.999	P₁ > 0.999, P₂ > 0.999
tHOAs	0.45 ± 0.11	0.43 ± 0.09	0.42 ± 0.10	0.42 ± 0.09	0.41 ± 0.08
P-value		P₁ > 0.999	P₁ > 0.999	P₁ > 0.999	P₁ > 0.999, P₂ > 0.999
Coma	0.26 ± 0.04	0.28 ± 0.03	0.28 ± 0.02	0.28 ± 0.04	0.28 ± 0.02
P-value		P₁ = 0.227	P₁ = 0.569	P₁ = 0.482	P₁ = 0.545, P₂ > 0.999
Spherical aberration	0.22 ± 0.01	0.22 ± 0.01	0.22 ± 0.01	0.22 ± 0.02	0.22 ± 0.01
P-value		P₁ > 0.999	P₁ > 0.999	P₁ > 0.999	P₁ > 0.999, P₂ > 0.999
Trefoil	0.26 ± 0.04	0.26 ± 0.01	0.26 ± 0.01	0.26 ± 0.01	0.26 ± 0.02
P-value		P₁ > 0.999	P₁ > 0.999	P₁ > 0.999	P₁ > 0.999, P₂ > 0.999

P₁ = P-value for the difference in aberration before surgery and at 1 day, 1 week, 3 months, and 1 year after surgery; P₂ = P-value for the difference in aberration between 1 day and 1 year after surgery; P < 0.05 indicates a significant difference.

ACM: anterior chamber maintainer; ICL: implantable collamer lens; TA: total aberration; tLOAs: total lower-order aberrations; tHOAs: total higher-order aberrations.

In both groups, preoperative TA, tLOAs, and defocus values were significantly higher than those measured postoperatively (P < 0.001). Similarly, TA, tLOAs, and defocus values on postoperative day 1 were higher than those at 1 year after surgery (P < 0.001). No significant intergroup differences were found for astigmatism, tHOAs, coma, spherical aberration, or trefoil at any time point (Table 4).

Table 4.

Time courses of aberrations after traditional ICL implantation.

Traditional method	Preoperative period	Postoperative period
Traditional method	Preoperative period	1 day	1 week	3 months	1 year
TA	5.39 ± 0.21	2.16 ± 0.32	2.01 ± 0.29	1.47 ± 0.04	1.47 ± 0.03
P-value		P₁ < 0.001	P₁ < 0.001	P₁ < 0.001	P₁ < 0.001, P₂ < 0.001
tLOAs	5.33 ± 0.23	2.15 ± 0.34	1.84 ± 0.27	1.79 ± 0.24	1.79 ± 0.34
P-value		P₁ < 0.001	P₁ < 0.001	P₁ < 0.001	P₁ < 0.001, P₂ < 0.001
Defocus	5.22 ± 0.36	1.53 ± 0.17	1.43 ± 0.09	1.38 ± 0.15	1.38 ± 0.14
P-value		P₁ < 0.001	P₁ < 0.001	P₁ < 0.001	P₁ < 0.001, P₂ < 0.001
Astigmatism	0.41 ± 0.14	0.43 ± 0.13	0.41 ± 0.11	0.41 ± 0.11	0.40 ± 0.12
P-value		P₁ > 0.999	P₁ > 0.999	P₁ > 0.999	P₁ > 0.999, P₂ > 0.999
tHOAs	0.45 ± 0.13	0.44 ± 0.13	0.42 ± 0.13	0.42 ± 0.12	0.41 ± 0.12
P-value		P₁ > 0.999	P₁ > 0.999	P₁ > 0.999	P₁ > 0.999, P₂ > 0.999
Coma	0.26 ± 0.04	0.28 ± 0.05	0.27 ± 0.04	0.28 ± 0.04	0.28 ± 0.04
P-value		P₁ = 0.007	P₁ = 0.579	P₁ = 0.566	P₁ = 0.447, P₂ > 0.999
Spherical aberration	0.22 ± 0.03	0.22 ± 0.03	0.22 ± 0.02	0.22 ± 0.03	0.22 ± 0.03
P-value		P₁ > 0.999	P₁ > 0.999	P₁ > 0.999	P₁ > 0.999, P₂ > 0.999
Trefoil	0.26 ± 0.02	0.26 ± 0.02	0.26 ± 0.02	0.26 ± 0.02	0.26 ± 0.02
P-value		P₁ > 0.999	P₁ > 0.999	P₁ > 0.999	P₁ > 0.999, P₂ > 0.999

ICL: implantable collamer lens; TA: total aberration; tLOAs: total lower-order aberrations; tHOAs: total higher-order aberrations.

Table 5 presents the comparison of RMS values of total ocular aberrations between the ACM and traditional groups. No significant preoperative differences were observed between the two groups. On postoperative day 1, the traditional group exhibited higher TA, tLOAs, and defocus values than the ACM group (P < 0.001). At 1 week postoperatively, TA remained significantly higher in the traditional group (P < 0.001). No significant differences were found at later time points or for astigmatism, tHOAs, coma, spherical aberration, or trefoil (P > 0.05).

Table 5.

Time courses of aberrations in the ACM and traditional groups.

Group	Preoperative period	Postoperative period
Group	Preoperative period	1 day	1 week	3 months	1 year
TA
ACM method	5.39 ± 0.21	1.66 ± 0.10	1.60 ± 0.09	1.47 ± 0.03	1.46 ± 0.02
Traditional method	5.39 ± 0.21	2.16 ± 0.32	2.01 ± 0.29	1.47 ± 0.04	1.47 ± 0.03
P-value	P = 0.987	P < 0.001	P < 0.001	P = 0.942	P = 0.783
tLOAs
ACM method	5.33 ± 0.23	1.86 ± 0.09	1.83 ± 0.07	1.79 ± 0.09	1.79 ± 0.07
Traditional method	5.33 ± 0.23	2.15 ± 0.34	1.84 ± 0.27	1.79 ± 0.24	1.79 ± 0.34
P-value	P = 0.985	P < 0.001	P = 0.852	P = 0.974	P = 0.988
Defocus
ACM method	5.23 ± 0.11	1.47 ± 0.12	1.42 ± 0.07	1.38 ± 0.08	1.38 ± 0.07
Traditional method	5.22 ± 0.36	1.53 ± 0.17	1.43 ± 0.09	1.38 ± 0.15	1.38 ± 0.14
P-value	P = 0.925	P = 0.048	P = 0.933	P = 0.910	P = 0.963
Astigmatism
ACM method	0.41 ± 0.11	0.43 ± 0.08	0.41 ± 0.08	0.41 ± 0.09	0.40 ± 0.08
Traditional method	0.41 ± 0.14	0.43 ± 0.13	0.41 ± 0.11	0.41 ± 0.11	0.40 ± 0.12
P-value	P = 0.826	P = 0.864	P > 0.999	P = 0.982	P = 0.981
tHOAs
ACM method	0.45 ± 0.11	0.43 ± 0.09	0.42 ± 0.10	0.42 ± 0.09	0.41 ± 0.08
Traditional method	0.45 ± 0.13	0.44 ± 0.13	0.42 ± 0.13	0.42 ± 0.12	0.41 ± 0.12
P-value	P = 0.972	P = 0.497	P = 0.991	P = 0.999	P = 0.941
Coma
ACM method	0.26 ± 0.04	0.28 ± 0.03	0.28 ± 0.02	0.28 ± 0.04	0.28 ± 0.02
Traditional method	0.26 ± 0.04	0.28 ± 0.05	0.27 ± 0.04	0.28 ± 0.04	0.28 ± 0.04
P-value	P = 0.928	P = 0.378	P = 0.897	P = 0.870	P = 0.984
Spherical aberration
ACM method	0.22 ± 0.01	0.22 ± 0.01	0.22 ± 0.01	0.22 ± 0.02	0.22 ± 0.01
Traditional method	0.22 ± 0.03	0.22 ± 0.03	0.22 ± 0.02	0.22 ± 0.03	0.22 ± 0.03
P-value	P = 0.791	P = 0.962	P = 0.807	P = 0.845	P = 0.497
Trefoil
ACM method	0.26 ± 0.04	0.26 ± 0.01	0.26 ± 0.01	0.26 ± 0.01	0.26 ± 0.02
Traditional method	0.26 ± 0.02	0.26 ± 0.02	0.26 ± 0.02	0.26 ± 0.02	0.26 ± 0.02
P-value	P = 0.882	P = 0.274	P = 0.556	P = 0.910	P = 0.884

ACM: anterior chamber maintainer; ICL: implantable collamer lens; TA: total aberration; tLOAs: total lower-order aberrations; tHOAs: total higher-order aberrations.

Subjective visual quality assessment

Patients completed the NEI-RQL-42 before surgery and at 1 year postoperatively. Scores were calculated as instructed: the average value for each domain equaled the total score divided by the number of questions in that domain. As shown in Table 6, both groups demonstrated significant improvement (P < 0.05) in most domains 1 year after surgery compared with baseline, except for decreased glare scores and no significant improvement in near vision. BCVA for distance vision and asthenopia remained stable.

Table 6.

NEI-RQL-42 scores before and 1 year after surgery in the ACM and traditional groups.

	ACM method		P-value	Traditional method		P-value
	Pre	Post 1 year	P-value	Pre	Post 1 year	P-value
Total score	61.89 ± 2.70	82.63 ± 3.46	P < 0.001	61.61 ± 2.38	82.12 ± 3.22	P < 0.001
Clarity of vision	64.23 ± 2.83	88.66 ± 3.22	P < 0.001	64.31 ± 2.85	88.60 ± 4.05	P < 0.001
Expectation	30.36 ± 3.35	81.31 ± 3.91	P < 0.001	30.24 ± 3.36	81.18 ± 3.39	P < 0.001
Near vision	81.04 ± 2.97	81.08 ± 3.08	P = 0.957	82.08 ± 3.08	82.10 ± 3.64	P = 0.971
Far vision	81.62 ± 3.26	82.15 ± 2.91	P = 0.431	81.46 ± 3.09	82.07 ± 3.07	P = 0.345
Visual fatigue	73.49 ± 3.22	73.06 ± 3.74	P = 0.553	73.16 ± 3.73	74.43 ± 3.64	P = 0.073
Activity limitations	42.09 ± 2.44	88.76 ± 2.34	P < 0.001	42.55 ± 2.98	88.95 ± 2.44	P < 0.001
Glare	72.72 ± 2.42	68.93 ± 3.06	P < 0.001	73.30 ± 1.95	69.47 ± 3.36	P < 0.001
Symptoms	73.60 ± 2.78	78.08 ± 4.02	P < 0.001	72.27 ± 3.17	77.89 ± 5.08	P < 0.001
Dependence on correction	29.04 ± 3.20	98.66 ± 0.72	P < 0.001	28.88 ± 3.32	98.68 ± 0.71	P < 0.001
Worry	49.14 ± 3.18	74.81 ± 2.79	P < 0.001	48.46 ± 2.91	74.56 ± 3.00	P < 0.001
Suboptimal correction	74.68 ± 2.80	89.52 ± 2.98	P < 0.001	74.48 ± 2.67	89.28 ± 3.32	P < 0.001
Appearance	49.02 ± 3.47	89.22 ± 3.42	P < 0.001	49.21 ± 3.54	89.83 ± 3.35	P < 0.001
Satisfaction with correction	58.17 ± 3.44	91.00 ± 3.33	P < 0.001	57.86 ± 2.77	90.82 ± 3.75	P < 0.001

ACM: anterior chamber maintainer; NEI-RQL-42: National Eye Institute Refractive Error Quality of Life Instrument-42.

Preoperative symptom scores were significantly higher in the ACM group than in the traditional group (P < 0.05). No other significant between-group differences were observed in any domain at either time point (Table 7).

Table 7.

NEI-RQL-42 scores before and 1 year after surgery between the ACM and traditional groups.

	Pre			Post 1 year
	ACM method	Traditional method	P-value	ACM method	Traditional method	P-value
Total score	61.89 ± 2.70	61.61 ± 2.38	P = 0.619	82.63 ± 3.46	82.12 ± 3.22	P = 0.498
Clarity of vision	64.23 ± 2.83	64.31 ± 2.85	P = 0.900	88.66 ± 3.22	88.60 ± 4.05	P = 0.945
Expectation	30.36 ± 3.35	30.24 ± 3.36	P = 0.867	81.31 ± 3.91	81.18 ± 3.39	P = 0.872
Near vision	81.04 ± 2.97	82.08 ± 3.08	P = 0.131	81.08 ± 3.08	82.10 ± 3.64	P = 0.179
Far vision	81.62 ± 3.26	81.46 ± 3.09	P = 0.828	82.15 ± 2.91	82.07 ± 3.07	P = 0.904
Visual fatigue	73.49 ± 3.22	73.16 ± 3.73	P = 0.677	73.06 ± 3.74	74.43 ± 3.64	P = 0.101
Activity limitations	42.09 ± 2.44	42.55 ± 2.98	P = 0.450	88.76 ± 2.34	88.95 ± 2.44	P = 0.724
Glare	72.72 ± 2.42	73.30 ± 1.95	P = 0.244	68.93 ± 3.06	69.47 ± 3.36	P = 0.453
Symptoms	73.60 ± 2.78	72.27 ± 3.17	P = 0.049	78.08 ± 4.02	77.89 ± 5.08	P = 0.857
Dependence on correction	29.04 ± 3.20	28.88 ± 3.32	P = 0.834	98.66 ± 0.72	98.68 ± 0.71	P = 0.882
Worry	49.14 ± 3.18	48.46 ± 2.91	P = 0.317	74.81 ± 2.79	74.56 ± 3.00	P = 0.697
Suboptimal correction	74.68 ± 2.80	74.48 ± 2.67	P = 0.747	89.52 ± 2.98	89.28 ± 3.32	P = 0.733
Appearance	49.02 ± 3.47	49.21 ± 3.54	P = 0.806	89.22 ± 3.42	89.83 ± 3.35	P = 0.420
Satisfaction with correction	58.17 ± 3.44	57.86 ± 2.77	P = 0.657	91.00 ± 3.33	90.82 ± 3.75	P = 0.825

ACM: anterior chamber maintainer; NEI-RQL-42: National Eye Institute Refractive Error Quality of Life Instrument-42.

Comparison of ECD before and after operation within and between the two groups

There were no significant differences in corneal ECD between the ACM and traditional groups either before or 1 year after surgery (P = 0.610, P = 0.472). No significant changes were observed within each group over time (P = 0.373, P = 0.071) (Table 8).

Table 8.

Comparison of corneal endothelial cell density within and between the ACM and traditional groups.

ECD	ACM method	Traditional method	P-value
Pre	2671.65 ± 133.94	2654.93 ± 157.25	0.610
Post 1 year	2667.50 ± 128.62	2643.30 ± 141.31	0.472
P-value	P = 0.373	P = 0.071

ACM: anterior chamber maintainer; ECD: endothelial cell density.

Operation time and complications

The ACM group had a significantly shorter mean operation time (2.85 ± 0.30 min) than the traditional group (4.37 ± 0.66 min, P < 0.001). Postoperative vault measurements remained within 0.5–1.5 corneal thickness in all eyes at all follow-up time points. Although some patients experienced transient IOP elevation, no serious intraoperative or postoperative complications—including corneal layer detachment, cataract, pupil block, iris injury, or pigment dispersion—were observed during the 1-year follow-up.

Discussion

With continuous advancements in ICL implantation techniques, the ICL with a central hole has become the preferred option for intraocular refractive surgery. This technique is particularly suited for patients with high myopia or other refractive errors who are unsuitable for or dissatisfied with corneal laser procedures.¹⁰ The safety and efficacy of ICL implantation have been well established.¹¹ In traditional ICL surgeries, OVDs are injected into both the ICL implant container and the eye to protect the corneal endothelium and crystalline lens while maintaining sufficient AC space for surgical maneuvers. However, residual OVDs have been associated with complications such as elevated or abnormal IOP, lens opacification, and delayed visual recovery.¹² Several researchers, including Blumenthal et al.,¹³ Tak,¹⁴ Özcura and Çevik,¹⁵ and Bardoloi et al.,¹⁶ have explored various ACM devices to eliminate the need for OVDs during phacoemulsification cataract extraction or intraocular lens implantation. Pan et al.¹⁷ introduced an ICL implantation technique that combines continuous infusion with single-handed ACM, which has demonstrated both safety and efficacy. To date, Pan’s study remains the only reported application of ACM in ICL implantation. However, Pan’s ACM technique requires one-handed operation, which limits bimanual coordination during maneuvers such as stabilizing ocular movement. Therefore, we developed a hands-free, operationally efficient ACM device. Under continuous infusion, this device allows ACM ICL implantation that not only shortens operation time but also promotes early visual recovery, helps control IOP elevation, and minimizes complications associated with residual OVDs. Overall, ACM ICL implantation shows excellent efficacy and holds strong potential for broader clinical application.

In traditional ICL implantation procedures, the use of OVDs plays a critical role by providing filling, protection, and lubrication for the AC.¹⁸ In this study, we introduced an ACM technique using BSS infusion, which facilitates faster ICL deployment and minimizes contact with ocular tissues. This approach eliminates the need for postoperative rinsing, shortens surgery time to approximately 3 min, reduces the risk of corneal injury, lowers costs, and enhances both patient and surgeon satisfaction.

Several studies^19–21 have reported that early postoperative IOP elevation is a common complication associated with residual OVDs following traditional ICL implantation. The choice of OVD during surgery may significantly influence IOP recovery. Gonzalez-Lopez et al.²² observed that among 100 eyes implanted with V4c ICL, 5 experienced elevated IOP 3–6 h postoperatively. This increase was attributed to residual OVDs (2% hydroxypropyl methylcellulose) obstructing the trabecular meshwork or the central hole of the ICL. Almalki et al.²³ reported that among 534 patients who underwent ICL implantation, 58 exhibited postoperative IOP elevation. Of these, 23 cases occurred on the first postoperative day, in which 1% sodium hyaluronate was used as the OVD. Senthil et al.²⁴ found that among patients who experienced elevated IOP after ICL implantation, 27% of cases attributed to residual OVD (2% hydroxypropyl methylcellulose), including two cases of pupil block caused by OVD remnants. In our study, 2 h after surgery, a significantly higher proportion of patients (10%) in the traditional group showed IOP > 22 mmHg compared with the ACM group (0%). These findings are consistent with previous research regarding postoperative IOP elevation associated with traditional ICL implantation.

In our study, the ACM group exhibited smaller IOP increases at 2 h postoperatively compared with the traditional group. Both groups demonstrated normal IOP levels at 1 day, 1 week, 3 months, and 1 year after surgery, with no significant intergroup differences. The ACM group maintained stable IOP values relative to baseline, whereas the traditional group showed a significant IOP elevation at 2 h postoperatively. Statistically significant differences between preoperative and 1-day postoperative IOP were observed in the traditional group. These findings suggest that avoiding OVD use facilitates early IOP control and recovery.

This study assessed visual quality after refractive surgery using both objective and subjective parameters. On the first postoperative day, the traditional group exhibited significantly higher TA, tLOAs, and defocus values compared with the ACM group. At 1 week postoperatively, the traditional group continued to show a higher TA value. The ACM group achieved superior UDVA and corrected distance visual acuity (CDVA) on postoperative day 1. These differences were primarily attributed to transient IOP elevation, residual OVDs, and longer surgical duration in the traditional group, which may have contributed to AC inflammation. By 1 year postoperatively, both groups achieved comparable and excellent visual outcomes.

The cornea plays a crucial role in the ocular refractive system, with its thickness and transparency preserved through the structural and functional integrity of corneal endothelial cells.²⁵ Excessive endothelial cell loss can result in decompensation of corneal function, leading to irreversible corneal edema and significant visual impairment.²⁶ During ICL implantation, corneal endothelial cells are exposed to nonphysiological conditions and may directly interact with perfusion fluids, viscoelastic agents, surgical instruments, and the ICL itself, increasing their vulnerability to mechanical and metabolic stress. Previous EVO ICL studies using OVDs have reported variable endothelial cell loss rates, ranging from approximately 2% at 6 months (Cao et al.²⁷) to 1.7% at 12 months (Lisa et al.²⁸), and 4.6% at 3 months (Pan et al.¹⁷) postoperatively. In the present study, the ACM group demonstrated a corneal endothelial cell loss rate of approximately 1.5%, compared with 4% in the traditional group at 1 year after surgery. No significant pre- to postoperative changes were observed within either group. These findings indicate that the ACM technique does not induce additional damage to corneal endothelial cells, achieving outcomes comparable to those obtained with OVD use. The reduced corneal injury observed in the ACM group may be attributed to its shorter operation time (2.85 ± 0.30 min), which was nearly half that of the traditional approach. This shorter duration helps maintain AC stability and minimize mechanical trauma during surgery. Furthermore, BSS possesses a physicochemical composition similar to that of aqueous humor, is noncytotoxic, and effectively preserves AC pH and osmotic pressure. In this study, the brief and controlled BSS perfusion maintained appropriate IOP and effectively cleared intraoperative exudates, tissue fragments, and microhemorrhages, thereby reducing the risk of corneal endothelial injury and postoperative inflammation. No intraoperative or postoperative transparent lens changes were observed in either group during the 1-year follow-up, confirming that ACM ICL implantation safely eliminates OVD-related complications such as corneal endothelial cell loss and lens damage.

This study was limited to a single ophthalmologist at one institution, which may restrict the generalizability of the findings. Future multicenter studies involving multiple surgeons across different institutions are warranted to further validate the safety and efficacy of the ACM technique.

Conclusion

The ACM ICL implantation technique significantly reduces early postoperative IOP elevation and shortens surgical duration while maintaining visual acuity and safety outcomes comparable to those of the traditional method. By eliminating OVD-associated risks, this approach provides a safer and more efficient alternative for myopia correction.

Supplemental Material

sj-pdf-1-imr-10.1177_03000605251397305 - Supplemental material for Comparison of the efficacy of the patented anterior chamber maintainer method and traditional method for implantable collamer lens implantation in myopic eyes: A clinical study

Supplemental material, sj-pdf-1-imr-10.1177_03000605251397305 for Comparison of the efficacy of the patented anterior chamber maintainer method and traditional method for implantable collamer lens implantation in myopic eyes: A clinical study by Weiwei An, Yinru Wang, Yan Li, Zifang He, Feifei Chen, Yajun Liu and Qin Qin in Journal of International Medical Research

Footnotes

Acknowledgments

The authors thank all patients who participated in this study.

Author contributions

WWA and QQ collected and analyzed the data and drafted the manuscript. YRW, YL, ZFH, FFC, and YJL analyzed the data and critically reviewed and approved the final version. QQ supervised the study, analyzed the data, and approved the final manuscript. All authors read and approved the final version of the manuscript.

Data availability statement

The datasets generated and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Declaration of conflicting interest

The authors declare no potential conflicts of interest.

Funding

This work was supported by the Medical Research Key Project of the Jiangsu Provincial Health Commission of China (ZD2022022); the Clinical Trials Project from the Affiliated Drum Tower Hospital, Medical School of Nanjing University (2023-LCYJ-MS-30); and the New Medical Technology Development Project of Nanjing Drum Tower Hospital (XJSFZLX202330).

ORCID iD

Qin Qin

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