Lhasa childhood eye study: the rationale, methodology, and baseline data of a 5 year follow-up of school-based cohort study in the Tibetan plateau region of Southwest China

Assessment of macular choroidal and retinal thickness: a cohort study in Tibetan healthy children

This research investigates the distribution, progressive changes, and contributing factors of macular choroidal and retinal thickness in Tibetan children utilizing swept-source optical coherence tomography (SS-OCT). The Lhasa childhood study recruited 1632 students from seven primary schools in Lhasa. These participants underwent OCT and ophthalmological evaluations, encompassing retinal and choroidal thickness measurements, refractive error, axial length (AL), and systemic examinations. The median age of the scholars was 8.57 ± 0.50 years with a median spherical equivalent (SE) of 0.19 ± 1.28D. Multivariate regression analysis revealed that thinner macular choroid thickness was correlated with lower value of SE, worse best-corrected visual acuity, higher mean arterial blood pressure (MABP) and boys, while retinal thickness was associated with better image quality and lower value of SE. The choroid and retina were significantly thinner in myopic children. SE was positively related to the thickness of all choroidal and full retinal subregions. In comparison to baseline data from 20 months prior, most regions of the full retina had significantly thinned. Choroidal thickness of Tibetan children is thinner than that of same-age children from other regions. Thinning of retina, the outer-sector GCC and GCIPL may be specified as a follow-up and prognostic indicator for myopia.

Evaluation of childhood developing via optical coherence tomography-angiography in Qamdo, Tibet, China: A prospective cross-sectional, school-based study

BACKGROUND

Optical coherence tomography angiography (OCTA) is a new and reliable machine used to evaluate retinal structure and macular perfusion in children. The use of OCTA under bad condition such as high altitude, low atmospheric oxygen, and low humidity, in children is rarely.

AIM

To quantify the macular micro-vasculature in healthy children of various ages using OCTA in Qamdo.

METHODS

Design: Prospective cross-sectional, school-based study. Three hundred and forty-seven normal students from 9 schools in 4 different areas in Qamdo were included. OCTA was performed on a 3 mm × 3 mm area centered on the macular region and macular cube 512 × 128 showed details in macular. Early treatment of diabetic retinopathy study Vessel Flow Density (VD) of the macular central vascular plexus density (CVD), inner vascular plexus density (IVD), full vascular plexus density (FVD), and the size of the foveal avascular zone (FAZ) were measured. All these results corrected by t/s = 3.382 × 0.01306 × (axial length-1.82). The differences were compared among various ages, sexes and living environments.

RESULTS

The mean FAZ area in all eyes was 0.27 mm2 ± 0.12 mm2. The mean foveal thickness (MFT) in the macular cube was 227.64 μm ± 23.51 μm. Compared with girls, boys had a lager FAZ (P = 0.0029). Among the different age groups, MFT (P < 0.001) and FVD (P < 0.0001), IVD (P < 0.0001), and CVD (P = 0.0050) increased with age. FAZ areas were not correlated with age (P = 0.8853) or others (MFT, area).

CONCLUSION

OCTA can use to evaluate macular perfusion in children. Our data bridge the gap between structural OCT and perfusion density in children in high altitude. Even though these were not a longitudinal study, it may provide us with hints about retina development during puberty and clinical implications of OCTA in children.

Baseline Refractive Error, Habitual Accommodative Tone, and Its Association With Myopia in Children: The Lhasa Childhood Eye Study

PURPOSE

The purpose of this study was to describe the baseline refractive error, habitual accommodative tone (HAT) in Tibetan children and its longitudinal association with incident myopia and myopia progression.

METHODS

This was a prospective cohort study. From 7 elementary schools, 1440 children with mean age of 6.83 ± 0.46 years were included with full noncycloplegic and cycloplegic refraction data at baseline, 1-year and 2-year follow-up in the Lhasa Childhood Eye Study. Noncycloplegic and cycloplegic automated refraction were performed at baseline and annually over the next 2 years. HAT was measured as the difference in spherical equivalent (DSE) between noncycloplegic and cycloplegic refraction.

RESULTS

The mean HAT decreased from a baseline value of 0.92 ± 0.82 diopters (D) to 0.55 ± 0.65 D, P < 0.0001 at 2 years. In multivariable logistic regression models, only baseline spherical equivalent (SE; P < 0.0001) was significantly (negatively) associated with 1- and 2-year incident myopia. Among 1386 children without myopia at baseline, 271 developed myopia over 2 years. For hyperopic children, baseline HAT was significantly associated with the incidence of myopia over 2 years (odds ratio [OR] = 0.43, P < 0.001), and the incidence of myopia was significantly lower with baseline HAT ≥0.5 D, compared to children <0.5 D. For 54 (3.75%) children who were myopic at baseline, SE was significant positively associated with myopic progression in univariable (P = 0.03) and multivariable general mixed linear regression analysis (P = 0.03).

CONCLUSIONS

Baseline SE was an independent influencing factor for the incidence of myopia and its progression. The incidence of myopia was significantly higher with lower baseline HAT among hyperopic children, indicating that lower HAT was potentially associated with myopic development.

Paediatric vision screening in Urban Lhasa from the Tibetan Plateau of Southwest China

PURPOSE

Few studies of vision screening in school-aged children were reported in Tibetan Plateau. We herein summarize the results of a mandatory vision screening conducted in young children in the Tibetan Plateau of Southwest China.

METHODS

The Lhasa Childhood vision Screening (LCVS) performed uncorrected distant visual acuity (UCVA) test on primary school students in urban Lhasa from July to September 2019. Pin-hole corrected VA (PCVA) was obtained for individuals with the UCVA less than 20/25. Decreased VA was defined for UCVA based on the American Academy of Pediatrics guidelines 2016 (UCVA < 20/32 for over 60 months). Visual impairment (VI), Mild VI, and moderate VI to blindness, defined as a PCVA less than 20/40, less than 20/40 to 20/63 and less than 20/63 in the better eye, respectively.

RESULTS

Overall, 34,848 children aged 9.03 ± 1.87 years fulfilled the screening with a response rate of 98.5%. 18,412 (52.8%) of the participants were males, and 30,531(87.6%) were Tibetan. The prevalence of decreased VA, VI, Mild VI, and moderate VI to blindness was 35.6%, 4.4%, 3.5%, and 1.0%, respectively. The prevalence of decreased VA in grade 1-6 students was 28.8%, 20.8%, 26.9%, 40.7%, 50.8%, 59.5%, respectively. The prevalence of VI in grade 1 to 6 students was 1.5%, 1.4%, 2.4%, 5.6%, 7.7% and 9.9%, respectively.

CONCLUSION

This study documented a relatively low prevalence of decreased VA and VI in Tibetan primary school students than other urban populations in China. An increasing trend of poor vision with grades was found.

Pinhole does not increase screening accuracy of detecting decreased best corrected visual acuity in schoolchildren

Background

Decreased best corrected visual acuity among children should be treated early in life, and vision screening in schoolchildren is an efficient and feasible selection for developing countries. Thus, the screening accuracy of different visual acuity tests is the key point for making vision screening strategies. The present study aims to explore the screening accuracy of uncorrected visual acuity (UCVA) and pin-hole corrected visual acuity (PCVA) using different vision chart in the detection of decreased best-corrected visual acuity (BCVA) among schoolchildren.

Methods

Grade one primary schoolchildren in urban Lhasa with data of UCVA using tumbling E chart (UCVAE), PCVA using tumbling E chart (PCVAE), UCVA using Lea Symbols chart (UCVAL), PCVA using Lea Symbols chart (PCVAL) and BCVA using Lea Symbols chart were reviewed. Decreased BCVA was defined as BCVA≤20/32(≥0.2 logMAR). Difference, reliability, and diagnostic parameters in the detection of decreased BCVA of different visual acuity results were analyzed.

Results

Overall, 1672 children aged 6.58 ± 0.44 years fulfilling the criteria. The prevalence of decreased BCVA was 6.8%. Although no significant differences were found between UCVAE vs UCVAL (p = .84, paired t-test) as well as PCVAE vs PCVAL (p = .24), the ICC between them was low (0.68 and 0.57, respectively). The average difference between BCVA and UCVAE, UCVAL, PCVAE, PCVAL was logMAR -0.08 (− 0.37, 0.21), − 0.08 (− 0.29, 0.17), − 0.05 (− 0.30, 0.19), − 0.06 (− 0.23, 0.12) using Bland–Altman method. The area under the receiver operating characteristic curve of UCVAE, PCVAE, UCVAL, PCVAL for the detection of decreased BCVA was 0.78 (0.73, 0.84), 0.76 (0.71, 0.82), 0.95 (0.94, 0.96), 0.93 (0.91, 0.95), respectively.

Conclusion

Pinhole does not increase the screening accuracy of detecting decreased BCVA in grade one primary schoolchildren. Visual acuity test using Lea Symbols is more efficient than Tumbling E in the screening of that age.

Trial registration

Data were maily from the Lhasa Childhood Eye Study which has finished the clinical registration on (ChiCTR1900026693).

Prevalence and pattern of refractive error and visual impairment among schoolchildren: the Lhasa childhood eye study

Background

Early and effective ocular screening may help to eliminate treatable eye disorders. The Lhasa Childhood Eye Study (LCES) revealed the particular prevalence of refractive error and visual impairment in grade one schoolchildren (starting age of 6 years old) in Lhasa.

Methods

This is a cross-sectional part of school-based cohort study. One thousand nine hundred forty-three children were enrolled (median age, 6.78 years, range, 5.89 to 10.32). Each child underwent general and ocular examinations, including logarithm of the minimum angle of resolution (logMAR) visual acuity, cycloplegic autorefraction, and slit-lamp biomicroscopy evaluation. Multivariate and correlation analyses were performed to evaluate the association between refractive error with gender and ethnics.

Results

The prevalence of visual impairment (logMAR visual acuity ≥0.3 in the better-seeing eye) of uncorrected, presenting and best-corrected visual acuity (BCVA) was 12.2, 11.7 and 2.7%, respectively. Refractive error presented in 177 (78.0%) out of 227 children with bilateral visual impairment. Myopia (spherical equivalent refractor [SER] ≤ − 0.50 diopter [D] in either eye) was present in 4.7% children when measured after cycloplegic autorefraction. Hyperopia (SER ≥ + 2.00 D) affected 12.1% children. Hyperopia was significantly associated with female gender (P<0.001). Astigmatism (cylinder value ≤ − 0.75 D) was present in 44.8% children. In multivariate regression and correlation analysis, SER had no significant difference between ethnic groups.

Conclusion

The Lhasa Childhood Eye Study is the first school-based cohort study to reveal the prevalence and pattern of refractive error and visual impairment in Lhasa. Effective strategies such as corrective spectacles should be considered to alleviate treatable visual impairment.

Stereoacuity and its determinants in 7-year-old children: the Lhasa Childhood Eye Study

PURPOSE

To explore the distribution of stereoacuity and to examine its determinants in school-age children in Tibetan plateau, Southwest China.

METHODS

This is the cross-sectional part of a school-based cohort study of 7-year-old children in Lhasa, Tibet Autonomous Region, Southwest China. Children in first year of primary school were invited to undergo a comprehensive examination, including height, weight, visual acuity, cycloplegic autorefraction (1% cyclopentolate), anterior segment, cover and uncover test, and stereoacuity (Titmus Stereo Test).

RESULTS

A total of 1833 eligible subjects were included, with a mean age of 6.82 ± 0.46 years. Mean stereoacuity was 1.78 ± 0.21 in log units (median: 60 arcsec). Children with stereoacuity equal to 40 arcsec and stereoacuity worse than 100 arcsec accounted for 29.24% and 8.18% of the cohort, respectively. Tibetan ethnicity (OR = 1.98; 95%CI, 1.30-3.03), astigmatism (OR = 1.65; 95%CI, 1.26-2.17), strabismus (OR = 2.92; 95%CI, 1.38-6.18), and amblyopia (OR = 3.77; 95%CI, 1.14-12.49) were risk factors for normal stereoacuity (= 40 arcsec). Shorter height, younger age, strabismus, and worse BCVA (P < 0.05 for all) were both related to lower stereoacuity in Spearman correlation analysis and associated with lower stereoacuity in multivariate regression analysis.

CONCLUSION

Stereoacuity maturation does not appear fully completed in 7-year-old children, while few children present stereoacuity worse than 100 arcsec (8.18%). Lower stereoacuity was associated with younger age, shorter height, strabismus, and lower best-corrected visual acuity.