Introduction: The aim of this study was to investigate the features of imaging differences between Clarus and Optomap ultra-widefield imaging systems after implantable collamer lens (ICL) implantation. Methods: This was a non-randomized controlled study. Ninety-two eyes of 46 consecutive patients were enrolled. Full-scale ophthalmological examinations were conducted preoperatively. All patients underwent Clarus (CLARUS 500; Carl Zeiss, Dublin, USA) and Optomap (Daytona; Optos, UK) ultra-wide imaging sequentially under the same circumstance preoperatively and 1 month after EVO-ICL implantation. A single image was acquired from each. Dx was defined as the distance between the upper furcation of the central retinal artery and the central fovea of macula. Pixels of the optic cup and disc and Dx as well as the optic cup/disc ratio were calculated and compared on each machine before and after surgery. Results: All surgeries were uneventful without complications. Safety and efficacy indices were both 100% at 1 month. Values of both optic cup and disc areas were in decrease after surgery with statistically significant differences (p < 0.001), while the cup/disc ratio remained the same (Clarus mean of differences = −0.0028, p = 0.83; Optomap mean of differences = −0.0016, p = 0.76). Dx of images captured with either machine was statistically significantly decreased (p < 0.001). Differences of both optic cup (p = 0.057) and disc (p = 0.041) areas of Clarus were more obvious than that of Optomap, while only the latter was with statistical significance. Difference of Dx of Clarus was statistically significantly larger than Optomap. Conclusions: Display ranges tend to be broadened after EVO-ICL implantation in both Clarus and Optomap ultra-widefield imaging systems, while Clarus shows a wider display range of the two, which encourages the application of Clarus when it comes to the detection of more peripheral retinal lesions.

Ultra-widefield (UWF) imaging has been widely used and has shown great clinical application value over the past decade. UWF imaging is superior in providing a view of up to 240° of the fundus without pupil dilation. With development of technology, several UWF imaging systems have appeared, among which is the Optomap imaging system (Daytona; Optos, UK). Optomap imaging is one of the most extensively used UWF imaging systems. It contains an ellipsoidal mirror with two focuses, which allows light source to travel at a wide angle without mydriasis [1]. A 532-nm green laser is installed as autofluorescence, while a 633-nm red laser is installed as an information displayer of deep retina. Not only has Optomap imaging been applied to normal subjects for contrast [2] but also to detection of macular degeneration [3], diabetic retinopathy [4], anterior uveitis [5], myopia [6], etc., as well.

CLARUS 500 (Carl Zeiss, Dublin, USA) was first introduced in 2017. It can provide a single image of 133° or an auto-merge image of 200°. Multiple modalities, including true color, RGB channel separation, fundus autofluorescence, infrared, and external, meet different requirements. Clarus provides a UWF view with high resolution.

Myopia has become a worldwide public health issue. Considering its tendency toward blindness, it is believed that myopia deserves global intervention before it affects overall social productivity [7]. Implantable posterior chamber phakic intraocular lens (implantable collamer lens [ICL]) implantation has been widely accepted as one of the managements of high myopia [8]. A 1-year observation indicated that ICL implantation showed equivalently satisfying outcomes in both low-to-moderate and high myopia [9]. A 7-year study stated that despite slight myopic shift over the long term, no visual quality debasement was discovered [10]. The implantable posterior chamber phakic intraocular lens is composed of hydrophilic collagen polymer and is located ahead of the crystalline lens in the posterior chamber [11]. Since fundus diseases such as myopic macular degeneration and retinal detachment occur as common complications of high myopia [12], regular fundus examinations are essential and highly recommended.

While several studies have compared Clarus and Optomap UWF imaging systems [13, 14], how implantable posterior chamber phakic intraocular lens affect imaging of the two systems still remains unexplored. This study aimed to reveal the optical effects of implantable posterior chamber phakic intraocular lens on Clarus and Optomap UWF imaging systems.

Subjects

This case control study is in compliance with the tenets of the Declaration of Helsinki and the request of the Ethics Committee of the Eye and ENT Hospital of Fudan University. Ninety-two eyes of 46 consecutive patients (male, 12; female, 34) who were scheduled for preoperative examination of ICL implantation at the Eye and ENT Hospital of Fudan University (Shanghai, China) from November 2021 to January 2022 were recruited.

The inclusion criteria were as follows: age between 18 and 45 years, refractive error change within 0.50 D per year for at least 2 years, anterior chamber depth no less than 2.8 mm, and endothelial cell density no less than 2,000 cells/mm2. The exclusion criteria were as follows: history of systematic diseases and other ocular diseases, trauma, or surgery history.

Surgical Procedure

All surgeries were performed by the same surgeon (X.Z.). After full-scale pre-operation examination, patients used levofloxacin eye drops for 3 days. 1 h before operation, the pupil was dilated with 2.5% norepinephrine. Afterward, surface anesthesia was applied. An ICL was inserted through a 3-mm temporal corneal incision with a one-step technique. The pupil was contracted with 0.005% carbachol. The details of surgery procedures were elaborated in a previous study [15]. All surgeries were uneventful. No complications were observed in follow-up examinations.

Main Examinations

Preoperatively, patients underwent thorough ophthalmologic examinations including slit-lamp examination, uncorrected distance visual acuity, spherical equivalent (SE), corrected distance visual acuity, intraocular pressure (Canon, Japan), axial length (IOL Master, Carl Zeiss, Germany), anterior chamber depth (Pentacam), endothelial cell density (SP-2000P, Topcon Corporation, Japan), horizontal corneal diameter and ciliary sulcus diameter (WTW and STS, UBM, Quantel Medical, France). Patients underwent follow-up visits 1 month postoperatively.

Clarus and Optomap Image Acquisition and Analysis

All images were obtained with pupils fully dilated. Images of Clarus were acquired with a true color fundus imaging facility (CLARUS 500, Carl Zeiss). Single-imaging mode was applied with an imaging angle of 133° and the angular vertex at the center of the eyeball. Images of Optomap were acquired with an ultra-wide laser scanning ophthalmoscope (Daytona; Optos). The imaging angle was 133° with the angular vertex at the center of the eyeball. Distance between the upper furcation of central retinal artery and the central fovea of macula was defined as Dx. Pixels of Dx, optic cup, and disc were collected, while the optic cup/disc ratio was calculated. Parameters were compared on both machines pre- and postoperatively. All images were viewed and processed on Photoshop (v23.5.1) by two ophthalmologists (X.H. and Y.X.) simultaneously and separately, both of whom were masked to the other examination data of patients recruited.

Statistical Analysis

Statistical analysis was performed using R version 4.0.5 (R Project for Statistical Computing, http://cran.rproject.org). Continuous variables were presented as mean ± standard deviation, and categorical variables were presented as frequency and percentage. The eye-level continuous variables at different time points were compared using linear mixed models. A two-sided p value less than 0.05 was considered statistically significant.

A total of 92 eyes of 46 patients (12 male and 34 female) were enrolled in this study, whose mean age was 27.46 ± 5.13 years. The preoperative spherical equivalent was −8.41 ± 2.49 D and ranged from −6.00 D to −12.25 D. Detailed preoperative demographic characteristics are listed in Table 1.

Table 1.

Clinical information of patients enrolled

Demographic characteristicsSizeRange
Sample 92 eyes of 46 patients  
Gender Male 12; female 34  
Age, years 27.46±5.13 18–42 
SE, D −8.41±2.49 −12.25–−6.00 
Spherical error, D −7.86±2.50 −12.25–−6.50 
Cylindrical error, D −1.09±0.79 −4.00–0 
Axial length, mm 26.71±1.23 24.08–30.15 
IOP, mm Hg 15.20±3.28 9.60–24.70 
Demographic characteristicsSizeRange
Sample 92 eyes of 46 patients  
Gender Male 12; female 34  
Age, years 27.46±5.13 18–42 
SE, D −8.41±2.49 −12.25–−6.00 
Spherical error, D −7.86±2.50 −12.25–−6.50 
Cylindrical error, D −1.09±0.79 −4.00–0 
Axial length, mm 26.71±1.23 24.08–30.15 
IOP, mm Hg 15.20±3.28 9.60–24.70 

SE, spherical equivalent; IOP, intraocular pressure.

All surgeries were successful without complications. Fundus pictures of the same eye captured with Clarus and Optomap before and after EVO-ICL surgery are shown in Figure 1, and intraclass correlation coefficients between two graders are listed in Table 2. The average optic cup area captured with Clarus was 1,059.15 ± 277.71 px before surgery and 941.24 ± 266.07 px after surgery, while mean value of the optic disc area was 6,406.28 ± 1,307.18 px and 5,880.14 ± 1,335.32 px. There appeared to be a statistically significant decrease in value postoperatively (p < 0.001). The mean difference of the optic cup/disc ratio before and after surgery was −0.0028 with no statistically significant difference (p = 0.83). Average value of Dx was 238.41 ± 15.01 px preoperatively and 232.06 ± 15.17 px after. The difference was statistically significant (p < 0.001).

Fig. 1.

Fundus pictures of the same eye captured with Optomap and Clarus before and after EVO-ICL surgery. a Optomap pre-operation. b Optomap post-operation. c Clarus pre-operation. d Clarus post-operation.

Fig. 1.

Fundus pictures of the same eye captured with Optomap and Clarus before and after EVO-ICL surgery. a Optomap pre-operation. b Optomap post-operation. c Clarus pre-operation. d Clarus post-operation.

Close modal
Table 2.

Intraclass correlation coefficients between 2 graders (p < 0.05)

Clarus pre-operationClarus post-operationOptomap pre-operationOptomap post-operation
Optic cup area 0.955 0.909 0.996 0.941 
Optic disc area 0.972 0.996 0.976 0.996 
Optic cup/disc ratio 0.988 0.996 0.989 0.854 
Dx 0.957 0.934 0.905 0.983 
Clarus pre-operationClarus post-operationOptomap pre-operationOptomap post-operation
Optic cup area 0.955 0.909 0.996 0.941 
Optic disc area 0.972 0.996 0.976 0.996 
Optic cup/disc ratio 0.988 0.996 0.989 0.854 
Dx 0.957 0.934 0.905 0.983 

The average optic cup area captured with Optomap was 389.49 ± 112.20 px preoperatively and 336.62 ± 104.86 px postoperatively. The mean value of the optic disc area was 2,906.44 ± 738.09 px before operation and 2,536.32 ± 796.47 px after operation. There was a statistically significant decrease in value postoperatively (p < 0.001). The mean difference of the optic cup/disc ratio before and after surgery was −0.0016 with no statistically significant difference (p = 0.76). Average value of Dx was 199.29 ± 16.60 px preoperatively and 189.97 ± 18.45 px after. The difference was statistically significant (p < 0.001).

The means of difference of both optic disc (p = 0.041) and Dx (p = 0.021) of Clarus between before and after surgery were larger than that of Optomap and statistically significant. While the mean of difference of optic cup of Clarus was also more notable compared to Optomap, it appeared no statistical significance. Main outcomes were displayed in Figure 2.

Fig. 2.

Statistical facts before operation and in follow-up visits. The means of difference of the optic cup/disc ratio of both Clarus (p = 0.83) and Optomap (p = 0.76) before and after surgery were not statistically significantly different, while average values of Dx of both machines preoperatively and postoperatively were (p < 0.001).

Fig. 2.

Statistical facts before operation and in follow-up visits. The means of difference of the optic cup/disc ratio of both Clarus (p = 0.83) and Optomap (p = 0.76) before and after surgery were not statistically significantly different, while average values of Dx of both machines preoperatively and postoperatively were (p < 0.001).

Close modal

With EVO-ICL implantation on trend, life quality of numerous patients with high myopia has been improved. High myopia often comes with various complications including macular degeneration, posterior scleral staphyloma, and retinal choroid atrophy [16], which could lead to blindness without intervention. Therefore, regular fundus examination should be brought to spotlight. How the implantation of intraocular lens alters the fundus imaging system has been one of the common concerns. To our knowledge, this is the first study to investigate the differences between Clarus and Optomap UWF imaging systems before and after EVO-ICL implantation, which is of utility value.

It was revealed in our study that the values of distance between the midpoint of diameter transversa of the optic disc and the central fovea of macula of both machines were in decrease after EVO-ICL implantation. Eye movement of the model may cause false change of length in fundus in two-dimension, while the advantage of extended depth of field of UWF imaging systems makes that deviation negligible. With the size and parameters of images fixed, the result above suggested enlargement of the display range. This could be related to the implantation of the concave lens, on the one hand, which has scatter effect over the incident light. The scattered light reached more peripheral retina, leading to a broadened display range. On the other hand, EVO-ICL implantation serves as an addition to the optic media, leading to a potentially minor shift of fundus observation postoperatively. Moreover, there is a small degree of tilt and decentration of EVO-ICL after implantation with positive effect on subjective visual quality, which could contribute to the inconsistency of the fundus display range before and after surgery [17, 18]. Much as previous studies have probed into the application and comparison of Clarus and Optomap on peripheral retina lesions [19, 20], diabetic retinopathy lesions [13, 21, 22], and neovascular age-related macular degeneration [23], EVO-ICL implantation-related research studies have not yet been investigated. Kumar et al. [20] reported higher sensitivity in detecting peripheral retinal breaks of Optomap than Clarus, and Maruyama-Inoue et al. [23] indicated higher specificity in identifying neovascular age-related macular degeneration of Optomap than Clarus. While discrepancies between the two devices were reported in most studies, the abilities of detecting diseases remained quite close, and the differences of display range variation were negligible. The extended display range on the retina after EVO-ICL implantation provides a more ideal observing scope.

It was discovered in our study that the optic cup/disc ratio remained static after surgery on both machines, which implies that instead of being distorted, images changed proportionally after EVO-ICL implantation. In our study, all three of the parameters (pixels of optic cup, disc, and Dx) were taken from the central area of the fundus. The area of a normal optic disc is similar to that of an ICL V4c central hole. Measured by two machines, the changes of parameters before and after surgery were highly consistent in all patients, which reflect that the central hole of ICL V4c has no influence on imaging stability to a large extent. It is mutually corroborated by previous studies [24, 25].

There are several limitations to our study. First, the sample size is relatively small. Second, as much as single image mode has been investigated, other imaging modes such as four-direction montaged image mode remain to be revealed. Further investigations are necessary.

In conclusion, in both Clarus and Optomap UWF imaging systems, the display range tends to expand after EVO-ICL implantation. Clarus shows a broader display range of the two, which indicates a wider application of Clarus when it comes to the detection of more peripheral retinal lesions.

The authors appreciate the contributions of all patients who participated in this study, as well as the staff in the Eye and ENT Hospital of Fudan University for their support.

This study protocol was reviewed and approved by the Ethics Committee of the Eye and ENT Hospital of Fudan University, approval number 2020107. Written informed consent was obtained from participants.

The authors have no conflicts of interest to declare.

The study received funding from the following sources: National Natural Science Foundation of China (Grant No. 81770955); Project of Shanghai Science and Technology (Grant No. 20410710100); Clinical Research Plan of SHDC (SHDC2020CR1043B); Project of Shanghai Xuhui District Science and Technology (2020-015); Project of Shanghai Xuhui District Science and Technology (XHLHGG202104); Shanghai Engineering Research Center of Laser and Autostereoscopic 3D for Vision Care (20DZ2255000); and construction of a 3D digital intelligent prevention and control platform for the whole life cycle of highly myopic patients in the Yangtze River Delta (21002411600).

Xiaosong Han collected the data with Yijia Xu and drafted the manuscript. Zhi Chen contributed to design of methodology. Ruoyan Wei analyzed the data. Weiming Yang, Zhiqiang Yu, and Xiaoying Wang supervised and revised the manuscript for critical review. Meiyan Li and Xingtao Zhou contributed to the conceptualization.

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.

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