Clinical characteristics analysis of patients who underwent lens exchange or explantation after implantable collamer lens implantation

doi:10.21203/rs.3.rs-4958183/v1

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Research Article

Clinical characteristics analysis of patients who underwent lens exchange or explantation after implantable collamer lens implantation

https://doi.org/10.21203/rs.3.rs-4958183/v1

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Background

This study aims to analyze the clinical characteristics of patients receiving secondary lens exchange or explantation after implantable collamer lens (ICL) implantation.

Methods

This retrospective study included 2347 eyes of 1175 consecutive patients receiving ICL or toric ICL (TICL) implantation. Clinical characteristics and ocular biometric measurements of patients who underwent secondary lens exchange or explantation (Group Ex) were analyzed. Visual outcomes and safety indices of secondary surgery were compared with the control group (Group C).

Results

The overall exchange or explantation rate was 1.11%. Eight eyes (0.34%) exhibited an excessive vault height, which was corrected after exchange surgery. Seventeen eyes (0.72%) exhibited a low vault, of which one eye underwent explantation, 11 eyes achieved a vault > 250 µm after exchange surgery, and five eyes had a vault ≤ 250 µm. One eye (0.04%) experienced repeated vertical TICL rotation and was exchanged with a nontoric lens. The clinical characteristics associated with an insufficient vault included a higher crystal sagittal height, smaller ciliary processes, and a wide iris-ciliary angle (ICA). The efficacy index at one month postoperatively was significantly higher in Group C (1.20 ± 0.20) than in Group Ex (1.10 ± 0.19) (P < 0.05). The safety index was 1.16 ± 0.17 and 1.22 ± 0.18 in Group Ex and Group C (P > 0.05), respectively.

Conclusions

Abnormal vault height after ICL implantation is the main reason for secondary exchange or explantation surgery. Biometric characteristics, including higher crystal sagittal height, smaller ciliary processes, and wider ICA, were associated with low vault height.

Trial Registration:

Registration number: ChiCTR2100051739. Prospectively registered: 01 October 2021.

Implantable Collamer Lens

Exchange

Explantation

Vault height

Implantable collamer lenses (ICLs) with a central port (Model V4c; STAAR Surgical, Monrovia, CA, USA), are widely utilized for correcting refractive errors, especially in cases of high myopia. While patients are often motivated by significant improvements in visual acuity and quality of life offered by ICL implantation, it is crucial to consider the potential risks associated with the procedure. Proper vault height, which is critical for postoperative safety of ICL implantation, depends on the selection of a lens of appropriate size. An oversized ICL may result in excessive vault height (> 1000 µm), increasing the risk of pupillary block, elevated intraocular pressure, angle closure, and glaucoma.¹ Conversely, an undersized ICL may lead to insufficient vault height (< 100 µm), increasing the risk of anterior subscapular cataract.² The V4c ICL, featuring a 0.36 mm central hole, facilitates the physiological flow of aqueous humor and maintains crystalline lens epithelium cell metabolism, thereby reducing the incidence of pupillary block and cataracts. Previous reports suggest that the ideal vault height ranges from 250 to 750 µm.^1.3 When the vault height is suboptimal, secondary explantation and exchange surgeries are required. However, such secondary surgeries not only increase the incidence of endophthalmitis and corneal endothelial cell loss but also impose mental stress on both doctors and patients. Thus, the identification of risk factors associated with secondary surgery after ICL implantation is important to reduce the incidence of such surgery.

This study analyzes the incidence and risk factors for ICL explantation or exchange following ICL/toric ICL (TICL) implantation. Additionally, this study examines the clinical characteristics of eyes requiring secondary surgery and the safety of secondary surgeries.

Subject

This retrospective study included 2347 consecutive eyes (1175 patients) that underwent ICL/TICL (Model V4c) implantation for refractive error correction. All procedures were performed by a single surgeon (JHY) between January 2018 and March 2023. The study adhered to the principles of the Declaration of Helsinki and was approved by the Institutional Review Board of the Ethics Committee of Second Affiliated Hospital, School of Medicine, Zhejiang University (Approval No: 20210744). Informed written consent was obtained from all patients. This study was registered at the Chinese Clinical Trial Registry (http://www.chictr.org.cn) (Registration No: ChiCTR2100051739). Inclusion criteria included age ≥ 18 years, absence of ocular and systemic diseases, and stable refraction for at least one year. Among the patients, 54 right eyes of 54 consecutive patients who underwent ICL implantation in 2022 served as the control group (Group C), while 26 eyes of patients who underwent ICL/TICL exchange formed the exchange/explantation group (Group Ex). Exchange/explantation surgery effectiveness and safety were evaluated using the efficacy index (postoperative uncorrected distance visual acuity (UDVA)/preoperative corrected distance visual acuity (CDVA) and safety index (postoperative CDVA/preoperative CDVA).⁴

Preoperative examination

Preoperative examinations included UDVA, CDVA, manifest refractions, slit-lamp anterior segment examination and fundus examinations, eye axis and lens thickness (IOL-master 700, Carl Zeiss Mediated AG, Germany), endothelial cell density (ECD, Tomey Corporation, Japan), intraocular pressure (IOP), white-to-white (WTW) distance (Pentacam, HR, Oculus GmbH, Wetzlar, Germany), anterior chamber depth (ACD, Pentacam), horizontal sulcus-to-sulcus (STS) distance, vertical STS distance, and the morphology of the ciliary body (ultrasound biomicroscope (UBM), BME-MEDA, China).

The EVO ICL power was calculated using the Online Calculation and Ordering System (OCOS^™, Staar Surgical, USA) provided by STARR Surgical. The ICL size was selected based on ACD (Pentacam), WTW distance (Pentacam), and STS distance (UBM) measurements.

Surgical techniques

All surgeries were performed per standard procedures. Prior to surgery, patients received pupil dilation using tropicamide phenylephrine eye drops (UniVision, China) and topical anesthesia with 0.5% proparacaine hydrochloride (Alcon, Fort Worth, TX, USA). Following a 3.0 mm clear corneal incision, a V4c ICL loaded in an injector cartridge (STARR Surgical) was inserted into the anterior chamber. Subsequently, a viscoelastic agent (Qi Sheng Biologics Co., Ltd, China) was injected to maintain the depth of the anterior chamber, and ICL haptics were adjusted into the posterior chamber and rotated to the intended position using an ICL manipulator (Mingren Eye Instruments, Suzhou, China). Finally, the remaining viscoelastic agent was thoroughly washed out.

Currently, there is no widely accepted indication for ICL exchange surgery. The indication for surgery often relies on the surgeon's clinical experience. In this retrospective study, the vault height was measured by corneal and anterior segment optical coherence tomography (CAS-OCT, SS-1000, Tomey Corporation, Japan). In this study, exchange surgery was deemed necessary when: (1) vault height exceeding 1200 µm, accompanied by shallow anterior chamber angle of less than 15 degrees (Pentacam); (2) vault height less than 250 µm; (3) ICL in direct contact with the anterior surface of the crystalline lens. Patients with excessive vault which decreased after re-alignment surgeries were not included in this study.

For the ICL/TICL exchange surgery, the new ICL size was determined based on the ACD, WTW distance, STS distance, and the vault height of the previously implanted ICL. If the secondary surgery proceeded shortly after the implantation (less than one month), the previous incision would be reopened. If the interval was longer than one month, a new incision was made. A viscoelastic agent was injected to maintain the depth of the anterior chamber, and an ICL manipulator was used to rotate the lens haptics and remove them from the posterior chamber. The ICL was then removed using forceps (Mingren Eye Instruments) through the incision. The new ICL was subsequently inserted as previously described. Finally, the viscoelastic agent was thoroughly washed out. Postoperatively, topical tobramycin and dexamethasone eye drops (S.A. Alcon-Couvreur) were administered four times a day for one week, and pranoprofen was administered four times a day for one month.

Statistical analysis

This is a retrospective study. Statistical analysis was performed using SPSS software (version 18.0, SPSS, Inc.). Clinical data were assessed for normal distribution using the Kolmogorov–Smirnov test and are presented as mean ± standard deviation (SD). The independent samples t-test was employed to analyze and compare differences in UCVA, efficacy index, and safety index at one month after surgery between Group Ex and Group C. A P value less than 0.05 was considered statistically significant.

Incidence and causes of secondary ICL exchange or explantation surgery

Among the 2347 eyes of 1175 patients who underwent ICL/TICL implantation, 26 eyes (1.11%) of 22 patients required ICL exchange or explantation (Table 1). Of these patients, six (seven eyes, 0.30%) were male, and 16 (19 eyes, 0.81%) were female. Among these 26 eyes, nine (0.38%) were implanted with TICL, 17 (0.72%) were implanted with nontoric ICL. 21 (0.89%) were right eyes, and five (0.21%) were left eyes. Eight eyes (0.34%) of seven patients underwent ICL exchange due to excessive vault height (> 1200 µm), and 17 eyes (0.68%) of 13 patients underwent ICL exchange due to low vault height (< 250 µm), of which one eye (0.04%) of one patient underwent ICL explantation due to low vault height and declined exchange surgery with a larger sized ICL lens due to worries about related risks. One eye (0.04%) of one patient underwent TICL exchange with a nontoric ICL due to repeated vertical rotation (the rotation angle was nearly 90°), despite a normal vault height of 596 µm. Patient characteristics and duration between primary and secondary surgeries are shown in Table 2.

Table 1

The proportion of eyes underwent ICL exchange/explantation after ICL implantation surgery
Characteristics		Total eyes
Eyes (n, %)	26 (1.11%)	2347
Gender (M/F, %)	7 (0.30%) / 19 (0.81%)	632 / 1715
OD / OS (%)	20 (0.85%) / 6 (0.26%)	1177 / 1170
ICL/ TICL (%)	17 (0.72%) / 9 (0.38%)	1554 / 793
Excessive / Insufficient Vault Height (%)	8 (0.34%) / 17 (0.72%)
M = male; F = Female; OD = right eye; OS = left eye; D = Diopter

Table 2

Characteristics of patients who underwent ICL exchange/explantation surgeries.
Causes	Patient number	Gender	Age	ICL/ TICL	Eye	Original ICL Size	Secondary ICL Size	Original Vault Height (µm)	Vault Height after Secondary Surgery (µm)	Time of Secondary Surgery
Excessive Vault Height	1	M	27	T	OD	13.2	12.6	1450	740	1W
	2	M	20	Non-T	OD	13.2	12.6	1351	1102	10D
	3	F	23	T	OD	12.6	12.1	1290	546	2M
	3	F	23	T	OS	12.6	12.1	1310	467	2M
	4	F	32	Non-T	OD	13.2	12.6	1400	814	2D
	5	F	26	T	OD	13.2	12.6	1447	862	1M
	6	F	20	T	OD	13.7 V	13.2 H		873	Immediately After
	7	F	28	Non-T	OD	12.6	12.1		420	Immediately After
Insufficient Vault Height	8	F	25	Non-T	OD	12.1	12.6	150	265	6M
	8	F	25	Non-T	OS	12.1	12.6	190	394	6M
	9	M	38	Non-T	OD	12.6	13.2	159	238	1M
	10	F	26	Non-T	OD	12.1	12.6	235	304	2M
	10	F	26	Non-T	OS	12.1	12.6	117	264	2M
	11	F	43	Non-T	OD	12.6	13.2		215	Immediately After
	12	M	37	Non-T	OD	12.6		196		Removal after 2D
	13	F	25	Non-T	OD	12.1	12.6		635	Immediately After
	14	F	22	T	OD	12.1 V	12.1 H	137	245	1W
	14	F	22	T	OS	12.1 V	12.1 H	118	254	1M
	15	F	19	T	OD	12.6 V	12.6 H		430	Immediately After
	16	F	30	Non-T	OD	12.6	13.2		326	Immediately After
	17	F	29	Non-T	OD	12.6	13.2	205	313	1W
	18	M	33	Non-T	OD	12.6	13.2	76	306	1W
	18	M	33	Non-T	OS	12.6	13.2	98	220	10D
	19	F	32	Non-T	OD	12.6	13.2	127	352	4D
	20	M	19	Non-T	OD	12.1	12.6		164	Immediately After
TICL Rotation	21	F	38	T	OD	12.6 T	12.S	596	636	2D
M = male; F = Female; OD = right eye; OS = left eye; T = toric ICL; Non-T: non-toric ICL; H = horizontal implantation; V = vertical implantation; W = week; D = day; M = month

Characteristics of eyes undergoing ICL/TICL exchange/explantation

Among the 26 eyes, eight eyes of seven patients underwent exchange due to excessive vault height (vault range: 1290 to 1450 µm). Among these eyes, 3 underwent ICL exchange, and 5 underwent TICL exchange. After exchanging the original ICL with a smaller-sized ICL, the average vault height decreased by 601 µm (from 1359 µm ± 64 to 758 µm ± 255). Patients with excessive vault height typically exhibited acute iris-ciliary angle (ICA) and longer ciliary process on ultrasound biomicroscopy (UBM) examination (Fig. 1A). In contrast, 17 eyes of 13 patients underwent exchange due to low vault height (vault range:76 to 235 µm). Among these 17 eyes, 14 underwent ICL exchange, and 3 underwent TICL exchange. After exchanging with a larger-sized ICL, the average vault height increased by 143 µm (from 140 µm ± 45 to 284 µm ± 54). Patients with insufficient vault height exhibited obtuse ICA accompanied by smaller and shorter ciliary process on UBM examination (Fig. 1B). UBM examination shows the ICL haptics positioned beneath the ciliary process after the secondary exchange surgery (Fig. 2A). Figure 2B demonstrates shorter ciliary process prior to ICL implantation.

Efficacy and Safety of ICL/TICL exchange

Figure 3 shows the comparison of postoperative UDVA and CDVA between Group Ex and Group C. The efficacy of the two groups was presented as the cumulative percentage of Snellen visual acuity at one-month follow-up (Fig. 3A). At the one-month follow-up, 88% (25 eyes) and 100% (54 eyes) reached 20/20 or better in Group Ex and Group C, respectively. No eyes in either group lost two or more lines of CDVA at one month postoperatively. In Group Ex, 40% of eyes gained one line of CDVA, 20% of eyes gained two lines or more of CDVA, and 36% of eyes had no change in CDVA. In Group C, 37% of eyes gained one line of CDVA, 33% of eyes gained two lines or more of CDVA, and 22% of eyes had no change in CDVA (Fig. 3B). The efficacy index at one month was 1.10 ± 0.19 in Group Ex and 1.20 ± 0.20 in Group C, showing statistical significance between the two groups (t = 2.062, P < 0.05). The safety index at one month was 1.16 ± 0.17 in Group Ex and 1.22 ± 0.18 in Group C, lacking a statistically significant difference between the groups (t = 1.554, P > 0.05). All surgeries were uneventful, with no intraoperative or postoperative complications observed. No eyes showed obvious corneal endothelial cell loss (Table 3).

Table 3

Comparisons of patient characteristics between group-Ex and group-C (mean ± SD and range)
	Group Ex(n = 26)	Group C (n = 54)	t Value	P Value
Age(years)	27.65 ± 6.29 (19 to 43)	27.02 ± 5.72 (19 to 44)	-0.435	0.665
Sphere (D)	-9.44 ± 2.08 (-6.00 to -15.00)	-9.26 ± 2.07(-6.25 to -17)	0.360	0.720
Cylinder (D)	-1.05 ± 0.90 (0.00 to -3.75)	-1.05 ± 0.84(0.00 to -2.50)	0.008	0.993
SE (D)	-9.97 ± 2.14 (-6.88 to -15.25)	-9.79 ± 2.27(-6.25 to -18.25)	0.345	0.732
IOP (mmHg)	15.81 ± 2.46 (11.00 to 20.50)	14.69 ± 3.26(9.00 to 22.5)	-1.709	0.092
ECD-preop (cells/mm²⁾	2673.19 ± 232.62(2302 to 3268)	2649.70± 177.31(2333 to3155)	-0.445	0.652
WTW (mm)	11.46 ± 0.40 (10.80 to 12.50)	11.58 ± 0.36 (10.90 to 12.40)	1.292	0.203
ACD (mm)	3.09 ± 0.24 (2.77 to 3.71)	3.26 ± 0.23(2.70 to 3.84)	3.009	0.004*
Horizontal STS (mm)	11.59 ± 0.40 (10.86 to 12.66)	11.72 ± 0.35 (11.05 to 12.50)	1.486	0.144
Vertical STS (mm)	12.03 ± 0.47 (11.19 to 12.90)	12.13 ± 0.38 (11.31 to 12.82)	0.913	0.367
Safety index	1.16 ± 0.17	1.22 ± 0.18	1.554	0.126
Efficacy index	1.10 ± 0.19	1.20 ± 0.20	2.062	0.044*
ECD-postop (cells/mm²⁾	2669 ± 218.13	2678.74 ± 175.97	0.192	0.848
SD = standard deviation; D = diopters; IOP = intraocular pressure; SE = spherical equivalent; STS = sulcus-to-sulcus distance; WTW = white-to-white distance; ACD = anterior chamber depth; ECD = Endothelial Cell Counts; Group Ex = exchange/explantation; group; Group C = control group; *Statistically significant difference

Previous studies suggested that ICL V4c implantation for myopia correction is a safe and effective procedure, with stable refractive outcomes and low adverse event rates.^{3, 5} Most adverse events are related to excessive or insufficient postoperative vault height, which is the main reason for secondary exchange or explantation surgeries. Zeng et al.² outlined the criteria for exchange/explantation surgeries as follows: (1) a vault height less than 100 µm at the center or direct contact between the ICL and the anterior surface of the crystalline lens; (2) vault height greater than 1000 µm, shallow anterior chamber accompanied by angle closure in any quadrant, or vault height exceeding 1000 µm with postoperative pupil diameter larger than preoperative and unrelieved patient-reported glare. In their study, the ICL exchange or explantation rate was 2.6% (16 of 616 eyes). Rayner et al. ⁶ reported the criteria for insufficient vault was 50 µm (with a visible gap), with no specific upper limit as long as the angle structure and function remain normal. Some other studies reported ICL/TICL exchange/explantation incidence ranging from 0.09%⁷ to 2.00%⁸ to 3.80%.⁹ In the present study, ICL exchange was deemed necessary if the vault height exceeded 1200 µm, accompanied by shallow anterior chamber angle of less than 15 degrees, or vault height of less than 250 µm. The overall exchange/explantation rate was 1.11%.

Many factors influence the postoperative vault height. First, the lack of precise biometric measurements is one of the main reasons for choosing ICLs of inappropriate sizes. According to the Online OCOS™ recommendation provided by STARR Surgical, ICL size was usually chosen based on ACD and horizontal WTW distance measurements. Currently, there are several commonly used methods to measure WTW distance, including manual calipers, imaging devices such as anterior segment analyzer with Scheimpflug imaging devices (Pentacam), slit scanning topography devices (Orbscan II), and IOLMaster biometric analyzer. However, discrepancies remain between the measurements with different methods. In this study, WTW distance was measured by Pentacam, which may be overestimated in cases with more obvious limbal pigmentation, pinguecula, and neovascularization, especially in high-myopic contact lens wearers.^{5, 9} An overestimated WTW distance can lead to the selection of a larger ICL and, subsequently, excessive postoperative vault height. Second, the manufacturer only provides four sizes of ICL (12.1, 12.6, 13.2, and 13.7 mm) for selection, which may not always satisfy the clinical needs of patients. Third, ACD and horizontal WTW distance measurements do not provide sufficient information about the structure of the ciliary sulcus. It is known that the ICL haptics are designed to be positioned in the ciliary sulcus, which would provide proper fixation and compression to achieve a proper vault height.¹⁰ In the earlier stage, ICL size selection is primarily based on WTW distance measurement. However, WTW distance was found to be a poor predictor of sulcus diameter in some cases.^{5, 11} As a result, UBM was used to provide a direct measurement of the sulcus diameter.¹² UBM showed that the sulcus exhibited an oval shape, with the vertical diameter exceeding the horizontal diameter.¹³ Matarazzo first proposed that rotating the ICL from a horizontal orientation to a vertical orientation effectively reduced the vault, avoiding secondary surgery to exchange with a small ICL size,¹⁴ and that vertical implantation reduced vault height by nearly 300 µm compared to horizontal implantation.¹⁵ Therefore, precise UBM measurements can help to select ICL of a proper size. Nevertheless, UBM examination is a time-consuming method that is not widely used in clinical practice.^{3, 14} Moreover, the accuracy of UBM measurements depends on the skill of the technician. In addition, higher crystalline lens protrusion and a thicker lens also play a role in a low vault height, which would occupy more intrinsic space in a bulging ICL.¹⁶ Finally, the malposition of ICL haptics can lead to an unsatisfactory vault height, which is a common phenomenon in clinical practice.

Theoretically, ICL haptics should be positioned in the ciliary sulcus to achieve the intended vault height.¹² However, studies have indicated that there are various types of ICL haptic positions, including within the ciliary sulcus, on the ciliary body, and beneath the ciliary.^{12, 17–19} These malpositions of ICL haptics were associated with uneven vault height distribution.¹² In a study of 134 eyes by Zhang et al., 21.6% of eyes had ICL haptics positioned in the ciliary sulcus, and 12.0% of eyes had two or more types of haptic positions.²⁰ Ye et al. found that 51.4% of eyes had haptics positioned above the ciliary process plane.¹² The causes of ICL haptic malposition and inappropriate vault height are miscellaneous. First, ciliary body morphology influences the prediction of vault height and haptic position. Maximum ciliary body thickness (CBTmax), which represents the distance from the innermost point of the ciliary processes to the inner wall of the sclera, influences the haptic position. A substantial CBTmax volume can provide a stable fixation of the haptics. A study by Chang et al.¹⁸ revealed that when CBTmax was less than 1.3 mm, only 14.7% of eyes had three or four haptics in the ciliary sulcus. Second, the ciliary sulcus angle (CSA) (or ICA) also plays an important role in predicting vault height and haptic position. A narrow angle (CSA < 30°) often leads to a high postoperative vault height (> 750 µm), while a wide angle (CSA > 90°) is associated with a low vault height (< 250 µm); however, a normal angle (CSA = 30–90°) leads to a normal vault height (250–750 µm).¹⁶ Finally, the length of the ciliary process (CPL) influenced ICL haptic malposition.²¹ A longer ciliary process with a narrow CSA is usually a risk factor for an excessive ICL vault height. However, a shorter and nearly diminished CPL and a diminished CBTmax were found to contribute to a lower vault height.^{12, 18} In the present study, we found that patients who underwent ICL exchange due to a low vault height commonly had shorter ciliary processes and obtuse ICA (CSA > 90°) and were usually accompanied by haptic positions beneath the ciliary body. Even after exchanging with a larger ICL, the average vault height of the eye only increased by nearly 140 µm, which is not consistent with the results of previous studies with changes in vault height of 542 ± 187 µm.²² Those results demonstrated that preoperative ciliary morphology examination with UBM is important because shorter ciliary processes and obtuse ICAs may indicate a postoperative low vault height, which needs more consideration of the ICL size and more communication with patients before surgery. Furthermore, eyes with shorter ciliary processes and obtuse ICAs may exhibit little increment in vault height after exchanging with a larger ICL, which indicates that ICL exchange may not be necessary for those eyes.

This study has some limitations. First, this was a retrospective study, and in earlier cases, some patients were lost to follow-up after surgery, resulting in a reported follow-up time of one month. Second, in the earlier cases, the lack clinical experience may overestimate the need for secondary surgeries. For example, in cases with excessive vault height after ICL horizontal implantation, the vault height could be reduced through vertical implantation, yet we chose to replace the ICL lens. Third, the selection of ICL size was based on WTW measured by Pentacam, with risks of overestimation, which we became aware of in the later stages of the study. Fourth, a study indicates that the incidence of cataract formation due to low vault is extremely low.⁵ Some studies pointed out the “generally accepted” lower vault limit was 50 µm ⁶ or 150 µm.²³ Therefore, the relatively more encompassing indications for ICL lens exchange led to an increased rate of secondary exchange surgery in our report. With increasing clinical experience, the probability of secondary surgery has decreased significantly.

In conclusion, abnormal vault height after ICL implantation is the main reason for secondary exchange or explantation surgery. Biometric characteristics, including higher crystal sagittal height, smaller ciliary processes, and wider ICA, were associated with low vault height. Accurate measurements of WTW distance and ACD before surgery, and detailed biometric measurements of CBTmax, CSA (ICA), and CPL with UBM, are critical to the selection of ICLs with appropriate size.

ICL implantable collamer lens

TICL toric implantable collamer lens

ICA iris-ciliary angle

ECD endothelial cell density

IOP intraocular pressure

WTW white-to-white

ACD anterior chamber depth

STS sulcus-to-sulcus

UBM ultrasound biomicroscope

OCOS Online Calculation and Ordering System

CAS-OCT corneal and anterior segment optical coherence tomography

SD standard deviation

CBTmax maximum ciliary body thickness

CSA. ciliary sulcus angle

CPL. length of the ciliary process

Ethics approval and consent to participate

This study was approved by the Institutional Review Board of the Ethics Committee of Second Affiliated Hospital, School of Medicine, Zhejiang University (Approval No: 20210744). Informed written consent was obtained from all patients.

Consent for publication

Not applicable.

Availability of data and materials

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests

The authors declare no competing interests.

Funding

This study was funded by Zhejiang Provincial Natural Science Foundation of China (No. LY20H120010, LGC20H120001), National Natural Science Foundation of China (No. 81870558);

Authors' contributions

HYJ contributed to the conception of the study. HYJ and TW contributed to the data collection and data synthesis. The manuscript was drafted by HYJ and TZH. All authors reviewed and approved the manuscript.

Acknowledgements

Not applicable.

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No competing interests reported.

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Clinical characteristics analysis of patients who underwent lens exchange or explantation after implantable collamer lens implantation

Status:

Version 1

Abstract

Background

Methods

Results

Conclusions

Trial Registration:

Figures

BACKGROUND

PATIENTS AND METHODS

Subject

Preoperative examination

Surgical techniques

Statistical analysis

RESULTS

Incidence and causes of secondary ICL exchange or explantation surgery

Characteristics of eyes undergoing ICL/TICL exchange/explantation

Efficacy and Safety of ICL/TICL exchange

DISCUSSION

Abbreviations

Declarations

References

Additional Declarations

Status:

Version 1