Article Text

Quantitative evaluation of retinal and choroidal vascularity and retrobulbar blood flow in patients with myopic anisometropia by CDI and OCTA
  1. Fang Liu1,2,3,
  2. Lingling Niu1,2,3,
  3. Jie Guo1,2,4,
  4. Weijun Jian1,2,3,
  5. Jianmin Shang1,2,3,
  6. Jing Zhao1,2,3,
  7. Kang Xue1,2,4,
  8. Xingtao Zhou1,2,3
  1. 1 Department of Ophthalmology and Optometry, Eye and Ear, Nose and Throat Hospital, Fudan University, Shanghai, China
  2. 2 NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China
  3. 3 Shanghai Research Center of Ophthalmology and Optometry, Fudan University, Shanghai, China
  4. 4 Department of Ophthalmology and Shanghai Key Laboratory of Visual Impairment and Restoration, Eye and Ear, Nose and Throat Hospital, Fudan University, Shanghai, China
  1. Correspondence to Dr Xingtao Zhou, Department of Ophthalmology and Optometry, Fudan University Eye Ear Nose and Throat Hospital, Shanghai, China; doctzhouxingtao{at}163.com

Abstract

Aims To investigate the association between the myopic severity and retinal microvascular density, choroidal vascularity and retrobulbar blood flow in adult anisomyopes.

Methods This study comprised 90 eyes of 45 myopic anisomyopes who were recruited for Colour Doppler imaging (CDI) and optical coherence tomography angiography (OCTA). The superficial vessel density (SVD), deep vessel density (DVD), choroidal thickness (ChT) and choroidal vascularity, including total choroidal area (TCA), luminal area (LA), stromal area (SA) and Choroidal Vascularity Index (CVI), were measured using OCTA. Moreover, the Pulsatile Index, peak systolic velocity (PSV) and end diastolic velocity (EDV) of posterior ciliary artery (PCA), central retinal artery (CRA) and ophthalmic artery (OA) were quantified by CDI, and all parameters were compared between two eyes and the correlations among parameters were analysed.

Results The mean difference of spherical equivalent (SE) and axial lengths (AL) between eyes were −6.00±2.94 D and 2.48±1.31 mm, respectively. The SVD, DVD, ChT, TCA, LA, SA and CVI were significantly lower in more myopic eyes compared with the contralateral eyes. In more myopic eyes, CDI parameters of CRA and PSV and EDV of PCA were also significantly lower. After adjusting for age and sex, the binocular asymmetry in LA and ChT was independent risk factor affecting interocular difference in both AL and SE.

Conclusion Retinal microvascular density, choroidal vascularity and retrobulbar blood flow were simultaneously lower in adult myopic anisomyopes with more myopic eyes and disturbed choroid circulation was related to the severity of myopia. Further longitudinal study was helped to identify the effect of choroidal parameters for myopic progression.

  • Retina
  • Choroid
  • Imaging

Data availability statement

Data sharing not applicable as no datasets generated and/or analysed for this study.

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Key messages

What is already known on this topic

  • Myopia is one of the most common visual disorders worldwide, but its exact aetiology and pathogenesis remain uncertain. Recent evidences suggest that the highly vascularised choroid plays an important role in myopic development. It has been speculated that reduced ChT or blood flow leads to scleral remodelling, which promote the onset and development of myopia. Therefore, it is very important to comprehensively identify ocular vascularity parameter changes associated with myopia.

What this study adds

  • In a single cohort of adult myopic anisomyopes, retinal microvascular density, choroidal vascularity and retrobulbar blood flow were simultaneously lower in more myopic eyes. Multiple linear regression analysis results show that only choroidal parameters were significantly correlated with both AL and SE.

How this study might affect research, practice or policy

  • Comprehensive identification of changes in ocular vascularity parameters associated with myopia can help to discover potential pathophysiological changes and provide a new perspective for understanding the disease characteristics.

INTRODUCTION

Myopic anisometropia refers to the difference in myopic refractive error of at least 1.00 D between eyes,1 which is usually caused by the interocular axial length difference.2 With the increased degree of myopia and axial elongation, the tissue of the sclera, choroid and retina is stretched and thinned, increasing the risk of vision-threatening complications such as lacquer crack, posterior staphyloma, chorioretinal atrophy and choroidal neovascularisation.3 4 These complications, especially in the macular region, may cause irreversible visual impairment and even blindness. Hence, it is urgent to study the risk factors for the onset and development of myopia.

To date, the exact aetiology and pathogenesis of myopia remain unclear. Excessive axial elongation leads to macular pathological changes, which are considered to be the main cause of myopia-related visual impairment.5 And increasing evidence has shown that the choroid plays a significant role in myopic development, especially in the bidirectional change of choroidal thickness (ChT), and the release of growth factors associated with scleral remodelling.6–8 Considering that the highly vascularised choroid is the primary source of oxygen and nutrients to the sclera and reduced choroidal blood flow may promote scleral remodelling, leading to myopia. So, it is vitally important to comprehensively identify ocular vascularity parameter changes associated with myopia.

A number of invasive and non-invasive methods are used to assess changes in ocular blood parameters in myopes. Combining different methods to assess myopia may provide a new approach for better understanding myopic pathophysiological characteristic. Colour Doppler imaging (CDI) is a non-invasive and quantifiable diagnostic method, which is mostly used for the analysis of retrobulbar vessels because of its high repeatability and availability of measurement for opaque tissues.9 Optical coherence tomography angiography (OCTA) allows multilayer visualisation of the retinal vasculature, and provides more detailed information.10 Previous studies have shown that ocular vascularity was evidently disturbed in myopes.11 However, there are no studies assessing comprehensive ocular vascularity alteration and the association between these factors in a single cohort of patients with myopic anisometropia.

Myopic anisometropia, with the same genetic background and similar environmental factors, is an ideal model for studying the characteristics of myopia. This study mainly aimed to perform a quantitative analysis of ocular vascular parameters by CDI and OCTA, to determine the association among these factors in a single cohort of anisomyopes.

Materials and methods

Patients

All measurements were conducted between 13:00 to 17:0012 in constant light levels (15 lux) to control for the effect of diurnal variations and surrounding light levels on the choroid.13 14 Before formal enrolment, all patients underwent a comprehensive ocular examination, including slit lamp microscopy, visual acuity test, intraocular pressure examination (Tonemeterx-10; Canon, Tokyo, Japan), subjective refraction (Nidek RT-5100), axial length (AL; IOL Master, Carl Zeiss) and panoramic fundus photography (Daytona, Optos, UK), and have a 10-minute distance viewing15 with full distance sphere and astigmatism correction prior to OCTA imaging to wash out effects of previous environmental15 16 and optical factors.17 The inclusion criteria for myopic anisomyopes were as follows: (1) age >18 years, (2) spherical equivalent (SE) of both eyes <−0.5 D and (3) difference in SE (△SE) ≤-2.00 D (SE of the more myopic eye minus the SE of the fellow eye). None of the patients had a history of ocular or systemic diseases potentially affecting the vascular circulation such as diabetic retinopathy, age-related maculopathy or hypertension.

CDI image analysis

The HDI 5000 CDI (Philips Ultrasound, Bothell, Washington, USA) with a 7.5-MHz linear probe was used to evaluate the blood flow of the retrobulbar vessels (posterior ciliary artery (PCA), central retinal artery (CRA) and ophthalmic artery (OA)). The patients were placed in the supine position and examined by the same experienced sonographer (KX, 8 years of experience). All processes were performed in accordance with the CDI measurement protocol.18 The peak systolic velocity (PSV), end diastolic velocity (EDV) and Pulsatile Index (PI) in each vessel were measured. Resistance Index (RI) was calculated using the formula RI=(PSV−EDV)/PSV to evaluate the resistance of the peripheral vasculature. Proper angle correction was conducted for the OA measurement, as previously described.19

OCTA image analysis

One well-trained ophthalmologist (LN, 5 years of experience) assessed the retinal microvascular network using OCTA (AngioVue RTVue XR Avanti V.2018.1.0.43, Optovue, Fremont, California, USA). The OCTA images were obtained by 70 000 A-scans/s at a wavelength of 840 nm. The 6×6 mm scan area was centred on the fovea with motion correction. The split-spectrum amplitude-decorrelation angiography algorithm was used to automatically segment the superficial capillary plexus (SCP; from the inner limiting membrane to 10 µm above the inner plexiform layer (IPL)) and deep capillary plexus (DCP; from 10 µm above the IPL to 10 µm under the outer plexiform layer). The highest raw en-face images of SCP and DCP (scan quality score >6/10) were exported from the software (figure 1) and then imported into the Fiji V.1.53c software.20 The superficial vessel density (SVD) and deep vessel density (DVD) were calculated on the area percentage of the superficial and deep blood vessels in the 6×6 mm area by the binarised images, as previously described.21

Figure 1

OCTA and SD-OCT images of myopia anisometropia. (A) OCTA image of SCP in more myopic eye. (B) OCTA image of DCP in more myopic eye. (C) SD-OCT image of macular centre in more myopic eye. (D) OCTA image of SCP in less myopic eye. (E) OCTA image of DCP in less myopic eye. (F) SD-OCT image of macular centre in less myopic eye. DCP, deep capillary plexus; OCTA, optical coherence tomography angiography; SCP, superficial capillary plexus; SD-OCT, spectral-domain optical coherence tomography.

A single 9 mm horizontal line scan centred on the fovea was conducted using Optovue RTVue XR Avanti spectral-domain OCT (SD-OCT). The OCT scan images were used for further analysis when the Signal Strength Index was >40/100 (figure 2A). The range from the edge of the optic head to the temporal side at 7500 µm was manually determined by two experienced doctors (FL and LN) as the region of interest (ROI). The choroidal structure was binarised using Fiji software according to the Niblack auto local threshold method, which took into account the mean and SD of all pixels in the ROI. In summary, the image was first binarised (figure 2B). Then, using the Polygon tool, the two graders manually selected the choroidal region reaching vertically from the retinal pigment epithelium to the boundary of the choriosclera and added it to the ROI manager (figure 2C). Then the image was converted to RGB format, and the colour threshold tool was used to determine the luminal area (LA; figure 2D). Finally, the total choroidal area (TCA) and LA were automatically calculated, stromal area (SA) was TCA minus LA, and Choroidal Vascularity Index (CVI) was further calculated by dividing LA by TCA. The ChT was measured using the built-in calliper tool in OptoVue software. The vertical distance between the Bruch membrane and the chorioscleral junction in the subfovea was considered to be the ChT. All images from SD-OCT/OCTA were adjusted for differences in magnification using the Bennett formula.22

Figure 2

OCT images binarisation analysis of choroidal vasculature by Fiji software. (A) Determination of the 7500 mm choroidal area in original OCT image. (B) The binarisation image by Niblack auto local threshold method. (C) Determination of the target choroidal region by the Fiji ROI manager. (D) Overlay of the target choroidal region on the OCT image. OCT, optical coherence tomography; ROI, region of interest.

Statistical analysis

Statistical analysis was performed using the SPSS software (V.20.0) and SAS (V.9.4). All numerical data are described as the mean±SD. A paired t-test or Wilcoxon signed-rank test was used to evaluate the differences in ocular biometrics and vascular parameters between the fellow eyes, and differences between low and high myopia groups were compared using the two-sample t-test or Wilcoxon signed-rank test and χ2 test. The interclass correlation coefficient (ICC) and Bland-Altman plot were used to evaluate the interrater agreement. The correlation degree and statistical significance between variables were analysed by the Pearson and Spearman rank correlation tests for normal and non-normal distributed data, respectively. A linear mixed effects model was used to evaluate the association between interocular asymmetries in those variables of interest with p<0.1 (univariate linear regression analysis) and interocular asymmetries in AL as well as SE. A p value of <0.05 was considered statistically significant.

Results

This study recruited 45 patients (13 male and 32 female; 90 eyes) with myopic anisometropia. The mean age was 32.16±7.43 years (range: 21–48 years). For the more myopic eyes, the mean SE was −10.75±3.78 D (range: −3.75 D to −17.25 D), and that of the less myopic eyes was −4.82±2.96 D (range: 0 D to −11.38 D). The mean △SE was −6.00±2.94 D (range: −2.13 D to −15.63 D) and mean interocular difference of AL was 2.48±1.31 mm. There were significant differences between eyes with asymmetry in terms of Al, SE and best-corrected visual acuity (BCVA) (table 1).

Table 1

Baseline information of the patients with myopic anisometropia

The 95% limits of agreements within raters for ChT, TCA, SA, LA and CVI were 1.598±13.467 µm, 0.072±0.588 mm2, 0.036±0.421 mm2, 0.036±0.373 mm2 and −0.3%±23.4%, respectively. And the mean ICC value for ChT, TCA, SA, LA and CVI were 0.999 (CI 0.998 to 0.999), 0.990 (CI 0.985 to 0.994), 0.923 (CI 0.883 to 0.949), 0.993 (CI 0.990 to 0.996) and 0.917 (CI 0.874 to 0.946), respectively.

Based on a quantitative analysis, the more myopic eyes revealed lower CDI and OCTA parameters compared with the less myopic eyes (table 2). The SVD, DVD, LA, SA, TCA and ChT in the more myopic eyes were significantly lower than those in the less myopic eyes (all p<0.001). Except for these, the CVI was also lower in more myopic eyes. And there were significant decreases in CDI parameters of CRA and PSV and EDV of PCA in more myopic eyes than those contralateral eyes (all p<0.05). Whereas, there was no significant difference between eyes in the CDI parameters of OA (all p>0.05).

Table 2

Comparision of retinal, choroidal and retrobulbar parameters in more myopic eyes and less myopic eyes of myopic anisometropia

Given the wide degree of anisomyopia enrolled in the present study, the subjects were divided into low (>−6.0D) and high (≤−6.0D) myopic groups for further studies according to the SE of right eye of each subject. There was no significant difference in gender and age between the two groups. The results showed that significant difference was observed in AL, SE, all retinal, choroidal parameters and part of retrobulbar parameters (the blood flow velocity of the PCA, online supplemental table 1).

The correlation analysis results of interocular difference in CDI, OCTA parameters and interocular difference in AL and SE are presented in table 3. The interocular differences in AL and SE were significantly correlated with interocular differences in all retinal parameters, most of choroidal parameters and part of retrobulbar parameters. In terms of interocular difference in AL, the coefficients of association for SVD and DVD were −0.546 and −0.598, for TCA, LA, SA and ChT ranged from −0.400 to −0.495 and for PI and RI of PCA it was 0.330 and 0.362 (all p<0.05). That is to say, the greater interocular difference in AL between eyes, the smaller the difference in SVD and DVD, and the choroidal parameters, and the greater interocular difference in CDI parameters. As for the difference in SE between eyes, the coefficients of association for SVD and DVD were 0.477 and 0.577, for TCA, LA, SA and ChT ranged from 0.350 to 0.527 and for EDV, PI and RI of PCA it was 0.315, –0.395 and −0.442 (all p<0.05).

Table 3

Correlation analysis of the interocular differences in SE, AL, CDI and OCTA parameters

On the contrary, both interocular differences in AL and SE were not correlated with binocular asymmetry in CVI, PSV and EDV of CRA and PCA (all p>0.05). And the binocular asymmetry in ChT was only correlated with interocular differences in choroidal vascularity parameters (SA, LA, TCA and CVI, all p<0.05). In addition, we also used a mixed effects model with fixed factors to further comparison analysis, which showed the similar results (online supplemental table 2).

The correlation analysis results between retrobulbar blood flow and retinal and choroidal vascularity showed that both SVD and DVD were significantly correlated with the PSV of CRA (rSVD=0.219 and rDVD=0.217). All choroidal parameters were significantly related with both PCA and CRA parameters (rPCA ranged from 0.291 to 0.468 and rCRA ranged from 0.212 to 0.282, online supplemental table 3).

Considering the inherent correlation among variables, a linear mixed effects model was performed to adjust and further investigate the independent risk factors, which were related with the severity of myopia (interocular difference in AL and SE, table 4). Among all demographics, binocular asymmetry in CDI and OCTA parameters included in the linear mixed effects model, only LA and ChT were significantly correlated with both AL and SE. After adjusting for age and sex, the results showed that the interocular difference in SVD (β=−0.148), LA (β=1.139) and ChT (β=−0.020, all p<0.05) were the independent factors associated with interocular difference in AL, and DVD (β=0.182), LA (β=−2.028) and ChT (β=0.038, all p<0.05) were independently and significantly correlated with interocular difference in SE. And there were no significant effects identified in age and sex (all p>0.05).

Table 4

Multiple linear regression analysis of independent factors affecting interocular difference in AL and SE

Discussion

Alterations in ocular blood flow-related parameters have been found to be associated with myopia. However, the exact mechanism underlying the association between myopia and ocular circulatory disorders remains unclear. To the best of our knowledge, this study is the first to simultaneously investigate retinal microvasculature, choroidal vascularity and retrobulbar blood flow in adult myopic anisomyopes. In the current study, we found that SVD, DVD, TCA, LA, SA, CVI, the blood flow velocity of CRA and PCA were significantly lower in more myopic eyes than in fellow eyes. Additionally, most of the above parameters were closely correlated with interocular difference in AL and SE. These results suggested that retinal, choroidal and retrobulbar vascularity circulations were disordered in line with the aggravation of myopia.

In the previous literatures, numerous studies have reported similar results of SVD and DVD in myopes. Ucak et al 23 reported that SVD and DVD were lower in high myopes and negatively correlated with AL and age. Liu et al 24 analysed the results of retinal microvascular density in patient with mild, moderate, high and extreme myopia and found a stepwise induction in SVD and DVD from mild to extreme myopia, which also closely associated with AL elongation. As the degree of myopia increases and AL elongates, the eyeball continues to expand, and the retina and choroid are stretched and thinned,25 resulting in reductions in retinal function and oxygen consumption,26 which might explain the decrease in retinal microvascular circulation. Besides, all choroidal parameters (TCA, LA, SA, CVI and ChT) were significantly different between low and high myopic groups, which was inconsistent with the previous reports that stromal thinning may be greater than vascular thinning in lower degree of myopia.27 28 The reason might be that the wide degree of anisomyopia brought about both the stromal and vascular thinning.

In terms of retrobulbar blood flow, the blood flow velocity of CRA and PCA were significantly lower in more myopic eyes than in fellow eyes, which was consistent with previous reports.29 30 And only all PCA parameters showed statistically difference suggesting that PCA parameters changes might be more evident than those of CRA and OA parameters between different refractive groups. The correlation analysis showed that only the blood flow velocity of PCA were significantly related with AL and SE. Meanwhile, both SVD and DVD were mainly correlated with CRA parameters, and the choroidal parameters were more closely related to the blood flow velocity of PCA than the CRA. Considering that the CRA and PCA supply blood and nutrition to the inner retinal and choroid, respectively, it suggested that changes in the choroidal blood flow might be more closely related to the degree of myopia and the quantitative analysis of retrobulbar vascular branches is another window to evaluate the blood flow of the retina and choroid in myopes.

Next, further analysis of choroidal parameters revealed that the choroidal vascularity parameters and ChT were significantly lower in more myopic eyes. Correlation analysis showed that TCA, LA, SA and ChT were closely related to the degree of myopia. This indicated that choroidal blood flow decreases and ChT thins with the development of myopia. In 2020, Li et al 31 reported a negative correlation between LA and AL in children with low–moderate myopia. Recently, Wu et al 32 have also assessed the identical choroidal parameters in adults with anisomyopia and reported that all parameters were significantly correlated with the aggravation of myopia. Moreover, the results of choroidal parameters in paediatric anisomyopes also showed that choroidal vascularity and choriocapillaris perfusion were lower in the longer eye compare to the fellow eyes.33 All these studies suggested that there was a decline in choroidal blood flow and ChT during the development of myopia.

Recently, the role of the choroid in the onset and development of myopia has drawn significant attention. The choroid was consisted of the choriocapillaris layer, Sattler’s layer and Haller’s layer from inside out. We used the OCT image binarisation technique to reflect the conditions of Haller’s and Sattler’s layers. This method has shown good repeatability and reproducibility.31 32 In this study, we estimated the choroidal circulation by blood flow velocity of PCA and choroidal vascularity parameters and found a significant reduction in more myopic eyes than in fellow eyes. Then, the linear mixed effects model showed only LA and ChT were the independent factor affecting both AL and SE. In the last few years, more and more scholars have discovered the relationship between choroid thinning and myopia progression. Jin et al 34 have found that choroid thinned before the retina in early myopia. Deng et al 35 have also reported that ChT might be thinner than the thickness of the sclera and retina in the early stage of myopia, even in childhood. Taken together, this suggests that ChT is more sensitive than the thickness of retina and sclera in the development of myopia. In addition to this, some scholars have found that the changes in ChT in myopia are mainly caused by Haller’s large vascular layer and Sattler’s medium to small vessel layer.36 And the close relationship between ChT and choroidal vascularity (r coefficients ranged from 0.686 to 0.827, all p<0.05) in this study also supported the above results. In 2017, Gupta et al 37 first found that a decrease in LA and SA was associated with ChT thinning in highly myopic eyes. A recent study has found a simultaneous decrease in ChT and choroidal blood flow in myopia-inducing form-deprived guinea pigs and an increase in ChT and choroidal blood flow after removal from deprivation, which demonstrated the bidirectional effect of the choroid affected the ocular elongation rate.38 Given the strong association between ChT and choroidal vascularity under different condition, this may indicate that a decrease in ChT causes a decrease in choroidal blood flow or vice versa, which needs to be determined by further studies.

A previous study has shown that hypoxia was related to scleral remodelling and myopia progression,39 and actively increasing choroidal blood flow by prazosin could inhibit myopic development.40 This may be due to the reduced choroidal blood flow affecting the supply of oxygen and nutrients to the overlying sclera, leading to a relatively hypoxic environment in the sclera and ultimately promoting the myopic development.38 Currently, there is a reasonable hypothesis about myopia, that is, reducing ChT or blood flow could affect the release of growth factors and oxygen supply to the sclera, leading to scleral remodelling, which results in the onset and development of myopia. In this study, decreased PCA blood flow velocity was responsible for the changes in choroidal blood flow, which was related to the severity of myopia, supporting the hypoxia theory in myopia. However, it is not clear whether choroidal changes affect the sclera in other ways, or simply an accompanying symptom of the progression of myopia. Further analysis in combination with CDI and OCTA parameters may reveal more information and help to improve the understanding of myopia and reveal the potential pathophysiology.

Limitations

This study has several limitations. First, due to the limitations of cross-sectional studies, long-term longitudinal observation is needed to further study the association between myopia development and changes in ocular blood flow. Second, we did not evaluate choroidal vascularity in different regions because the choroidal vascularity in a single foveal scan can be considered a good substitute for the entire choroidal vascularity.41 Considering the uneven spatial distribution of ChT in the macular region,42 the topographical features of choroidal vascularity may require further evaluation. Third, the sample size was relatively small, although the CDI and OCTA parameters showed a significant difference. A larger sample size is required for further studies.

Conclusion

In brief, the more myopic eyes show lower retinal microvascular density, choroidal vascularity and retrobulbar blood flow velocity compared with the fellow eyes, and such alterations are closely correlated with the severity of myopia.

Changes in ChT and LA were the independent factors affecting both AL and SE. Combining CDI with OCTA methods to quantitatively analyse the vascular system provides a new perspective for understanding the underlying myopic pathophysiological features.

Data availability statement

Data sharing not applicable as no datasets generated and/or analysed for this study.

Ethics statements

Patient consent for publication

Ethics approval

This study involves human participants and was approved by the ethical committee of Eye and Ear, Nose and Throat Hospital of Fudan University (ID: 2016038). Participants gave informed consent to participate in the study before taking part. All procedures were conducted in accordance with the principles of the Declaration of Helsinki.

Acknowledgments

Thanks to all patients for their participation and research staff from the Eye and Ear, Nose and Throat Hospital of Fudan University for their contribution to this study.

References

Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

Footnotes

  • FL and LN are joint first authors.

  • KX and XZ contributed equally.

  • FL and LN contributed equally.

  • Contributors Conceptualisation: FL and XZ had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. FL, LN and XZ. Methodology: FL, LN and KX. Material preparation, data collection and analysis: FL, JG, WJ, JS and JZ. Software and validation, and writing the manuscript: FL and LN. Critical revision of the manuscript: FL, KX and XZ. Funding acquisition and supervision: XZ.

  • Funding This study was supported by the National Natural Science Foundation of China (grant number: 81770955), joint research project of new frontier technology in municipal hospitals (grant number: SHDC12018103), project of Shanghai Science and Technology (grant number: 20410710100), Clinical Research Plan of SHDC (grant number: SHDC2020CR1043B), project of Shanghai Xuhui District Science and Technology (grant number: 2020–015) and Shanghai Municipal Commission of Health and Family Planning (grant number: 202040285).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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