RESEARCH ARTICLE Open Access

Interocular anatomical and visual functionaldifferences in pediatric patients withunilateral cataractsErping Long†, Jingjing Chen†, Zhenzhen Liu†, Zhuoling Lin†, Qianzhong Cao, Xiayin Zhang, Xiaoyan Li, Lixia Luo,Haotian Lin*, Weirong Chen and Yizhi Liu

Abstract

Background: Congenital cataracts are often complicated by anterior segment dysgenesis. This study aims tocompare bilateral anterior segment parameters, macular thickness, and best-corrected visual acuity (BCVA) inpediatric cataract patients at 3 months after unilateral cataract extraction with intraocular lens implantation.

Methods: Fifty-three pediatric patients with uncomplicated unilateral total cataracts were included. At 3 monthspost-surgery, bilateral corneal thickness at the thinnest location (CTTL), anterior chamber depth (ACD), and anteriorchamber volume (ACV) were measured using Pentacam. Central macular thickness (CMT) was evaluated usingspectral-domain optical coherence tomography. BCVA was measured by experienced optometrists concurrently.Descriptive statistics and bivariate corrections were performed to analyze the interocular differences in bilateralanatomic parameters and their relationships with BCVA.

Results: For all 53 included patients (mean age 5.2 ± 2.3 years), the median BCVA was 10/40 in the operated eyesand 40/40 in the contralateral eyes, which indicates a significant interocular difference. BCVA values in thecontralateral eyes were significantly correlated with patient age at surgery, but this result differed for BCVA in theoperated eyes. The Pentacam analysis revealed no significant interocular differences in bilateral CTTL and ACV, butsignificant differences were found for ACD.

Conclusions: At 3 months after surgery, unilateral pediatric cataract patients exhibited no significant interoculardifferences in identified anatomical parameters (except for ACD), and these parameters were not significantlycorrelated with BCVA in bilateral eyes. Therefore, amblyopia, but not anatomical factors, might be the main causeof interocular visual functional differences in our study population.

Trial registration: ClinicalTrial.gov, NCT02765230, 05/05/2016, retrospectively registered.

Keywords: Interocular difference, Pediatric cataracts, Unilateral cataracts, Anatomical, Visual acuity

BackgroundGreat advances have been made in managing pediatriccataracts during the last several decades; these advanceshave contributed to a decrease in the incidence of post-operative complications and improvement in visual out-comes [1, 2]. Early cataract removal and replacementwith an intraocular lens (IOL) represent the most appro-priate treatments to avoid irreversible amblyopia [3].

Recent studies have been directed toward understandingthe factors associated with postoperative visual prognosisin pediatric patients with cataracts [4–7]. Althoughscreening and timely surgical intervention play a key rolein improved best-corrected visual acuity (BCVA) amongpediatric patients with cataracts, determining the prog-nosis for an individual remains difficult, particularly forunilateral cataract [8–10].Congenital cataracts are often reported to be complicated

with anterior segment dysgenesis. However, with theexception of the cloudy lens in unilateral uncomplicatedcataract patients, it remains unknown whether interocular

* Correspondence: haot.lin@hotmail.com†Equal contributorsState Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, SunYat-sen University, Guangzhou, Guangdong 510060, China

© The Author(s). 2016 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Long et al. BMC Ophthalmology (2016) 16:192 DOI 10.1186/s12886-016-0371-5

differences exist in the developmental status of the anteriorsegment [11, 12]. Gochnauer et al. reported a trend whereinthe absolute preoperative interocular axial length difference(IALD) predicted postoperative BCVA in pediatric patientswith unilateral cataracts [13]. Their finding appears to beclinically important because it indicates the possibility of acorrelation between ocular anatomy and visual function.However, the postoperative BCVA clinical outcomes ofmany pediatric patients without IALD still vary greatly [14].Few studies have focused on the interocular differ-

ences in ocular anatomic parameters other than axiallength in unilateral pediatric cataract after surgery, thesignificance of which for the possible interocular visualfunctional difference remains unclear. Therefore, weconducted this cross-sectional study to compare bilateralanterior segment parameters, macular thickness, andBCVA at 3 months after uncomplicated unilateralpediatric cataract extraction with primary IOL implant-ation and to explore any possible interocular differencesand their possible relationships.

MethodsPatientsThis cross-sectional study was performed at ZhongshanOphthalmic Center (ZOC), China’s largest eye hospital[15], which is the location of the Childhood CataractProgram of the Chinese Ministry of Health (CCPMOH)[16]. The CCPMOH is conducting a series of ongoingstudies regarding the influence of early interventionson long-term outcomes of pediatric cataract treatment[17–19]. All of the registered children of CCPMOH werediagnosed by anterior segmental photography to confirmthe morphology, location, and degree of cataract after pupildilation [17]. A flow chart of patient selection and thestudy protocol is presented in Fig. 1.

Ethical approvalThe research protocol was approved by the InstitutionalReview Board/Ethics Committee of Sun Yat-sen University(Guangzhou, China). The tenets of the Declaration ofHelsinki were followed throughout this study. To allow aconfidential evaluation of the Pentacam system, opticalcoherence tomography (OCT), Teller visual acuity (VA)cards and visual distance chart use in this study, this trialwas registered with the Clinical Research InternalManagement System of ZOC as well as ClinicalTrials.gov(NCT02765230). The authors confirm that all ongoingtrials and trials related to this study are registered.

Inclusion and exclusion criteriaInclusion criteria:

– Children with a diagnosis of pediatric unilateral totalcataracts;

– Under 10 years of age;– Underwent uncomplicated cataract surgery.

Exclusion criteria:

– History of premature birth;– Diagnosis of microphthalmia, micro- or

megalocornea, keratoconus, glaucoma, traumatic orcomplicated cataracts, or vitreous and retinal diseases;

– History of ocular trauma, past refractive surgery orother ophthalmic surgery.

Intraoperative and postoperative proceduresAll patients underwent uncomplicated cataract surgeryby two experienced cataract surgeons (Y.Z.L. and W.R.C.).General anesthesia was administered prior to surgery. Aftera temporal clear corneal incision was made, DuoVisc and asoft-shell technique were used to reform and stabilize theanterior chamber and protect the corneal endothelium. A5.5–6.0 mm central continuous curvilinear capsulorhexiswas created using a bent 26-gauge disposable needle.Hydro-dissection was performed using a balanced salt solu-tion, and a standard phacoemulsification was performed tocompletely remove the lens. A 3-piece monofocal acrylicIOL with a 6.5-mm optic diameter (Sensar AR40e, AMO,Inc. CA, USA) was placed via in-the-bag implantationfollowing lens removal.Postoperative topical therapy included the administra-

tion of 0.3 % tobramycin and 0.1 % dexamethasone eyedrops (Tobradex, Alcon Laboratories, Inc, Texas, USA)four times per day and 0.3 % tobramycin and 0.1 %dexamethasone eye ointment (Tobradex, Alcon Labora-tories, Inc, Texas, USA) every night for 1 month.

Anterior segment parameters and the pentacam systemThe Pentacam system (Oculus Inc., Wetzlar, Germany)was used for anterior segment parameter measurements at3 months after surgery. Each examination was performedthree times and reviewed by two observers to improverepeatability. At 3 months after surgery, the measurementprocedure using the Pentacam was performed according todirections provided by the Pentacam instruction manual incooperative children [20], and special requirements werefollowed for uncooperative children (described below). ThePentacam is a rotating scheimpflug camera that provides50 cross-sectional images within a few seconds and has theadvantage of generating a three-dimensional model of theanterior segment with a series of valued parameters (e.g.,corneal thickness, corneal refractive, corneal volume, anter-ior chamber depth, anterior chamber angle, and anteriorchamber volume) [21, 22]. Among the various anatomicparameters provided by the Pentacam, corneal thickness atthe thinnest location (CTTL), anterior chamber depth(ACD), and anterior chamber volume (ACV) are the most

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representative parameters for the development status ofthe anterior segment [23]. Although corneal thickness isavailable for the entire cornea and can be measured at anypoint on the cornea by manually placing the cursor at thatpoint, CTTL is defined as the corneal thickness at thecorneal vertex in the absence of keratoconus. ACD, whichis related to the anterior corneal apex position, is measuredfrom the epithelium (external = Ext.) or endothelium(internal = Int.) to the anterior surface of the lens capsuleor IOL. Therefore, the external ACD is the sum of theinternal ACD and CTTL. In this study, we chose to reportthe internal ACD.ACV is calculated as a solid bounded by the posterior

surface of the cornea (12.0 mm around the cornealvertex), iris, and lens using integral calculus. The CTTL,ACD (Int.), and ACV are reported in the summaryinformation for the Pentacam.

Macular thickness and OCTWe used spectral-domain OCT (iTVue SD-OCT; Opto-vue Inc. Fremont, CA, U.S.A.) to evaluate the bilateralcentral macular thickness (CMT) of the included chil-dren with unilateral congenital cataract at 3 monthsafter surgery [24, 25]. The macula was divided into threeconcentric circles with radii of 1, 3 and 6 mm, separ-ately. The central disc is referred to as the fovea, and theinner and outer rings were equally segmented into fourquadrants (i.e., superior, nasal, inferior, and temporal).The instrument calculated the macular thickness andsummarized the thickness results corresponding to theEarly Treatment Diabetic Retinopathy Study (ETDRS).Pupil dilation was not a mandatory requirement forCMT detection. Each subject’s eye focused on an in-ternal fixation target without blinking and eye move-ment. Good compliance was noted while the scan was

Fig. 1 Flow chart of the patient selection and study protocol. (Notes: CCPMOH = Childhood Cataract Program of the Chinese Ministry of Health,CCTL = corneal thickness at the thinnest location, ACD (Int.) = anterior chamber depth measured from the endothelium, ACV = anterior chambervolume, SD-OCT = spectral-domain optical coherence tomography, CMT = central macular thickness, BCVA = best-corrected visual acuity)

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performed. However, for the children requiring examin-ation under anesthesia, the procedure varied (describedbelow). Five scans were oversampled, and the averagefor a cross-section was displayed.

VA evaluationFor preverbal children, a complete set of Teller VACards (Stereo Optical Company, Inc., IL, USA) was usedto measure the monocular grating acuity of the operatedand contralateral eyes. The set consisted of 15 cards withgratings ranging in spatial frequency from 0.32 to 38 cy-cles/cm in half-octave steps as well as a low vision cardand a blank gray card. The infant was assessed using thestandard procedure of the operation manual [26, 27].For verbal children, BCVA was measured and recordedusing a LEA Symbols 13-Line Translucent DistanceChart (Good-Lite Co., IL, USA) according to the stand-ard procedure. To minimize the bias of BCVA in botheyes, the examiner was blinded to the operated eyes, andthe testing eyes were randomized across children. Allchildren were assessed with good compliance for BCVAin both eyes in decimal fractions at 3 months aftersurgery, and the results were translated into SnellenBCVA and LogMar BCVA for analysis [28].

Special requirements for uncooperative childrenBecause infants and young children have poor compli-ance with Pentacam and OCT examinations, we devel-oped techniques and equipment specifically for pediatricophthalmic examinations [17–19]. We performed exami-nations immediately after administering oral chloralhydrate, a retention enema with chloral hydrate as asleep aid, or intranasal dexmedetomidine to childrenwho were uncooperative for regular examinations in theclinic. This sleep-aid administration strategy has beenpreliminarily proven to be safe [29] and has beenapproved by the Institutional Review Board/Ethics Com-mittee of Sun Yat-sen University. Briefly, the sleepingchildren were placed in the right posture. Upon assist-ance from the parents, the children’s heads were placedin positions suitable for Pentacam and OCT examina-tions with our designed device. An assistant helped tosoftly open the children’s eyelids [18]. More details canbe found in our completed clinical trial (NCT02077712)regarding the sedation of pediatric cataract patients whowere uncooperative during regular examinations at theclinic [30]. Three experienced pediatric ophthalmologists(H.T.L., J.J.C. and Z.L.L.) performed all examinationsaccording to our study protocols.

Statistical analysisData for different anatomical parameters measured byPentacam examinations and OCT were entered into aMicrosoft Excel spreadsheet (Microsoft Corporation,

Redmond, WA, USA). Agreement between the readingsobtained by the two observers was calculated for eacheye of each participant using Bland-Altman limits ofagreement. All measurements were determined to havea normal distribution. The results are expressed as themean ±1 standard deviation (SD). An independent-sample-test was used to assess differences by sex, and apaired t-test was used to assess interocular differences.A bivariate correlation test (Pearson’s) was used to assessthe relationship between different anatomical parameters(i.e., CTTL, ACD, ACV, and CMT) and a functional par-ameter (i.e., BCVA). All statistical tests were two-tailed,and a p-value below 0.05 was considered statistically sig-nificant. All statistical analyses were performed usingSPSS software, version 17 (SPSS Inc., Chicago, IL, USA).

ResultsStudy populationA total of 53 registered patients (53 operated eyes and53 contralateral eyes) treated at CCPMOH were included.All patients were Han Chinese. Thirty-six patients(67.9 %) were males. The average age at surgery was 5.2 ±2.3 years, and no differences in age distributions by sexwere noted. The right eye was involved in 23 (43.4 %) ofthe 53 cases with a unilateral total cataract. All includedpatients completed the Pentacam and OCT evaluations,but only 39 (39/53) postoperative eyes and 44 (44/53)contralateral eyes completed the BCVA function evalu-ation with credible results. Seven children had credibleBCVA measured in only one eye, including 1 operated eyeand 6 contralateral eyes. All the raw data supporting theconclusions of this article is available in Additional file 1,Raw data.

Comparison between contralateral eyes and operatedeyesExcept for one operated eye with a better BCVA thanthe contralateral eye, all operated eyes displayed worseBCVA values than the contralateral eyes (Fig. 2). Themedian BCVA was 10/40 in the operated group and 40/40 in the contralateral eye group, and a significantinterocular difference was noted (p < 0.0001). Moreover,the age at surgery was significantly correlated withBCVA in the contralateral eye group (Pearson’s correl-ation = 0.356, p = 0.018) but not in the operated eyegroup (Pearson’s correlation = 0.129, p = 0.453).In the Pentacam analysis, the mean CTTL, ACV, and

ACD values in the operated eyes were compared with thecontralateral eyes (Table 1). No statistically significantinterocular differences in bilateral CTTL (p = 0.490) andACV (p = 0.145) were noted, but the ACD values in theoperated eyes were significantly increased compared withthe contralateral eyes (p < 0.0001). In the OCT analysis,the mean CMT value in the operated eyes was compared

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with the contralateral eyes (Table 1), but the interoculardifference in bilateral CMT was not significant (p = 0.708).

Linear regression of the relationship between operatedeyes and contralateral eyesTo further analyze bilateral CTTL, ACV, ACD, andCMT, we used linear regression to predict the measure-ments of operated eyes in relation to contralateral eyes.We observed a good linear relationship for bilateralCTTL, ACV, and CMT but not bilateral ACD (Fig. 3).

Pearson’s correlation analysis of the relationship betweenanatomical parameters and BCVAAnother important and interesting previously unidenti-fied relationship involves whether the analyzed anatom-ical parameters of CTTL, ACD, ACV, and CMT canpredict the functional outcome of BCVA. Pearson’s cor-relation analysis was used to assess these relationships.In the operated eye, the correlations for CTTL, ACD,ACV, and CMT with BCVA were 0.084 (p = 0.611), 0.102(p = 0.538), −0.050 (p = 0.761), and −0.273 (p = 0.092), re-spectively (Fig. 4). In the contralateral eye, the correla-tions were −0.241 (p = 0.114), −0.206 (p = 0.179), 0.059(p = 0.703), and −0.163 (p = 0.290), respectively (Fig. 5).

DiscussionIn the present study, we analyzed bilateral ocular ana-tomical values by Pentacam examination and OCT in apopulation of term-born children with uncomplicatedunilateral congenital/infantile cataract at 3 months after

cataract extraction with primary IOL implantation.Cases of preterm birth and other ocular abnormalities(e.g., microphthalmia, micro- or megalocornea, keratoconus,glaucoma, and retinal disease) were excluded [13, 14, 31].Thus, we were able to study a remarkably homoge-neous population to explore the possible relationshipbetween interocular differences of anatomy and func-tion. We found no significant interocular differences inour identified anatomical parameters, with the exception ofACD, and all identified anatomical parameters were notsignificantly correlated with bilateral BCVA. Our presentstudy helps demonstrate the significance of interoculardifferences in other ocular anatomic parameters in additionto axial length in unilateral pediatric cataracts and helpsdefine the relationships among these differences with theBCVA of the operated/contralateral eyes.In the present study, the Pentacam examination evalu-

ates the entire anterior segment from the anteriorcorneal surface to the posterior lens surface using a ro-tating Scheimpflug camera [21, 22]. These non-contactmeasurements are finished in 2 s, and the techniqueobtains 12 to 50 single captures, which is convenient forchildren with limited compliance [18, 20]. Agreementwas observed between all of the results of the anteriorsegment parameters obtained with the Pentacam andconventional methods. In the Pentacam analysis of ourpresent study, the CTTL and ACV values were increasedin the operated eyes compared with contralateral eyeswithout statistical significance. However, the ACD valueswere significantly increased in the operated eyes

Fig. 2 BCVA of contralateral and operated eyes at different age at surgery. Distribution of BCVAs between operated eyes and contralateral eyes waspresented. The BCVA of operated eyes (green rhombus) is worse than those of contralateral eyes (blue square). BCVA values in the contralateral eyeswere significantly correlated with patient age at surgery (Notes: BCVA = best-corrected visual acuity)

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compared with the contralateral eyes; these differenceswere caused by the replacement of the natural lens withthe artificial IOL and were not the basis for the intero-cular differences in BCVA [14]. However, we still cannotconclude that these identified interocular differences inthe anterior segment caused the interocular differencesin BCVA without further study.Spectral-domain OCT is a commonly used commer-

cial objective method for measuring retinal thickness,particularly CMT [25]. CMT is significantly correlatedwith VA in preterm children [32] or pediatric patientswith diagnosed retinal diseases [33]. CMT is alsocorrelated with BCVA in children with amblyopia basedon long-term follow-ups and treatments [34, 35]. Kim etal. reported that spectral-domain OCT analysis of depri-vational amblyopic eyes with unilateral pediatric cata-racts demonstrated no significant differences in macular

thicknesses compared with fellow non-amblyopic eyesand age-matched normal eyes [36]. In the present study,we also found that the mean CMT value in the operatedeyes was reduced compared with the contralateral eyes,although the differences were not significant; these find-ings are consistent with the study by Kim et al.To date, it has been difficult to predict the prognosis

of BCVA among pediatric patients with uncomplicatedunilateral cataract. In addition, the BCVA in the contra-lateral eyes are potentially significantly enhanced com-pared with the BCVA in the operated eyes in theuncomplicated unilateral cataract population [8, 10].Our results have confirmed this finding. Moreover, inour study, the relationships between the identifiedanatomical parameters and the functional outcome ofBCVA were not significantly correlated. All anteriorsegmental parameters (i.e., CTTL, ACD, and ACV) and

Table 1 The parameters and interocular differences in children with unilateral cataracts

Laterality Numbers CTTL (μm) ACV (mm3) ACD (mm)c CMT (μm)

Operated 53 547.3 (58.9)a 164.3 (35.6) 3.7 (0.7) 228.2 (21.7)

Contralateral 53 542.7 (25.1) 157.1 (28.7) 2.9 (0.4) 229.2 (23.6)

Difference N/A 4.6 [−8.7, 17.9]b 7.2 [−2.6, 17.0] 0.8 [0.6, 1.0] −1.0 [−6.3, 4.3]

Footnotes: aMean (Std. Deviation); bMean [95 % Confidence Interval]; cSignificant (p < 0.0001); CTTL corneal thickness at thinnest location, ACV anterior chambervolume, ACD anterior chamber depth, CMT central macular thickness

Fig. 3 The relationships between the operated and contralateral eyes for CTTL, ACD, ACV, and CMT. Panel a, linear relationship for bilateral CTTL(R2 = 0.332); Panel b, non-linear relationship for bilateral ACD (R2 = 6.357e-4); Panel c, linear relationship for bilateral ACV (R2 = 0.168); Panel d, linearrelationship for bilateral CMT (R2 = 0.408). (Notes: CCTL = corneal thickness at the thinnest location, ACD = anterior chamber depth, ACV = anteriorchamber volume, CMT = central macular thickness, BCVA = best-corrected visual acuity)

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CMT were not significantly correlated with BCVA ineither the operated or contralateral eyes, which indicatesthat the significant interocular differences in BCVAmight be caused by some unidentified factors. Althoughthe reasons for our findings are complicated, deprivationamblyopia in the cataract eye and visual competitiveinhibition of the contralateral eye should be considered[37, 38]. Therefore, it is crucial to conduct the long-termfollow-up study with amblyopia treatment to investigatethe therapy efficiency on our patients. Functional evalua-tions including functional magnetic resonance imaging[39–41] and visual electrophysiological techniques (forexample, visual evoked potential) [42] have been widelyused in clinical ophthalmology. We believe that theseadvanced techniques would aid in deciphering the realreasons for our findings and would also serve as a futureresearch direction to optimize unilateral cataract treat-ment and improve prognoses.Several limitations of this study should be consid-

ered. First, this study employs a cross-sectional design,which is prone to selection and measurement biases. How-ever, we excluded preterm births and other pathologiesaccompanying eye conditions, thereby allowing us to pre-cisely identify the type of patients to whom our results

might be generalized (i.e., Chinese, term-born children withuncomplicated unilateral congenital/infantile cataracts,without other pathologic eye conditions). Second, all ana-tomical and functional indices were measured at 3 monthspost-surgery; therefore, we can only evaluate postoperativevariation and draw conclusions about the development ofinterocular differences in anatomical indices and BCVAafter cataract surgery. Despite the above limitations, toour knowledge, this study is the first to compare interocu-lar differences in anterior segmental biometric and macu-lar thickness values from a homogeneous series of infantsand small children with unilateral congenital/infantilecataracts. In addition, it is also the first study to includestatistical analysis of the relationships between BCVAoutcomes and ocular anatomical parameters.

ConclusionsIn conclusion, our data on children with uncomplicatedunilateral congenital/infantile cataracts at 3 monthspost-surgery did not reveal significant interocular differ-ences in our identified anatomical parameters, with theexception of ACD. All analyzed anatomical parameterswere not significantly correlated with bilateral BCVA.These results indicate that amblyopia, but not

Fig. 4 The relationships between BCVA and CTTL, ACD, ACV, or CMT in operated eyes. No significant correlations with BCVA were identified forCTTL, ACD, ACV, and CMT. Panel a, the relationship between CTTL and BCVA; Panel b, the relationship between ACD and BCVA; Panel c, therelationship between ACV and BCVA; Panel d, the relationship between CMT and BCVA. (Notes: CCTL = corneal thickness at the thinnest location,ACD = anterior chamber depth, ACV = anterior chamber volume, CMT = central macular thickness, BCVA = best-corrected visual acuity)

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anatomical factors, might be the main cause of interocu-lar visual functional differences in our study population.Our results may contribute to the knowledge of intero-cular anatomic differences in uncomplicated unilateralcongenital/infantile cataracts and to the exploration offactors relating with operated BCVA in unilateralpediatric cataract patients. Interocular visual functionaldifferences should be assessed to determine the causes,identify related factors and monitor the prognosis ofamblyopia treatment.

Additional file

Additional file 1: Raw data. (XLSX 13 kb)

AbbreviationsACD: Anterior chamber depth; ACV: Anterior chamber volume; BCVA: Best-corrected visual acuity; CCPMOH: The Childhood Cataract Program of theChinese Ministry of Health; CMT: Central macular thickness; CTTL: Cornealthickness at the thinnest location; ETDRS: The early treatment diabeticretinopathy study; Ext.: External; IALD: Interocular axial length difference;Int.: Internal; IOL: Intraocular lens; OCT: Optical coherence tomography;SD: Standard deviation; VA: Visual acuity; ZOC: Zhongshan ophthalmic center

AcknowledgementsWe thank all the members in the CCPMOH. CCPMOH Study Group has beenfounded and developed in Zhongshan Ophthalmic Center, Sun Yat-sen

University since 2010 because of the Childhood Cataract Program of theChinese Ministry of Health.

FundingThis study was supported by the National Natural Science Foundation of China(91546101, 81300750), the Outstanding Young Teacher Cultivation Projects inGuangdong Province (YQ2015006), the Guangdong Provincial Natural ScienceFoundation for Distinguished Young Scholars of China (2014A030306030), theYouth Science and Technology Innovation Talents Funds in a Special SupportPlan for High Level Talents in Guangdong Province (2014TQ01R573). Thesponsors and funding organizations had no role in the design or performanceof this research.

Availability of data and materialsAll the raw data supporting the conclusions of this article is available inAdditional file 1, Raw data.

Authors’ contributionsConcept and design (EPL, JJC, LXL, HTL, WRC and YZL); Data acquisition,statistical analysis, and interpretation (EPL, JJC, ZZL, ZLL, QZC, XYZ, XYL andHTL); Drafting of the manuscript (EPL and HTL); Critical revision of themanuscript (JJC, ZZL, ZLL, QZC, XYZ, XYL, LXL, WRC and YZL); Securingfunding, technical support, supervision and final approval of the manuscript(EPL, JJC, ZZL, ZLL, QZC, XYZ, XYL, LXL, HTL, WRC and YZL). All authorsagreed to be accountable for all aspects of the work in ensuring thatquestions related to the accuracy or integrity of any part of the work areappropriately investigated and resolved.

Authors’ informationErping Long, Jingjing Chen, Zhenzhen Liu and Zhuoling Lin are joint firstauthors. Correspondence and requests for materials should be addressed toH.T.L. (haot.lin@hotmail.com).

Fig. 5 The relationships between BCVA and CTTL, ACD, ACV, or CMT in contralateral eyes. No significant correlations between BCVA and CTTL,ACD, ACV, or CMT were identified. Panel a, the relationship between CTTL and BCVA; Panel b, the relationship between ACD and BCVA; Panelc, the relationship between ACV and BCVA; Panel d, the relationship between CMT and BCVA. (Notes: CCTL = corneal thickness at the thinnestlocation, ACD = anterior chamber depth, ACV = anterior chamber volume, CMT = central macular thickness, BCVA = best-corrected visual acuity)

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Competing interestsThe authors declare that they have no competing interests.

Consent for publicationNot applicable.

Ethics approval and consent to participateAll study procedures were performed in accordance with the tenets of theDeclaration of Helsinki, and the study was approved by the Ethics Committee ofthe Zhongshan Ophthalmic Center. Written informed consent was obtained fromall the study participants’ parents or legal guardian. This study was registered withClinicalTrials.gov (NCT02765230).

Received: 21 June 2016 Accepted: 24 October 2016

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