Hong Kong Med J 2022 Apr;28(2):152–60 | Epub 25 Mar 2022
© Hong Kong Academy of Medicine. CC BY-NC-ND 4.0
ORIGINAL ARTICLE (HEALTHCARE IN MAINLAND CHINA)
Teacher-to-parent communication and vision care–seeking behaviour among primary school students
K Du, PhD Candidate1; J Huang, PhD Candidate2; H Guan, PhD1; J Zhao, PhD1; Y Zhang, PhD Candidate1; Y Shi, PhD1
1 Center for Experimental Economics in Education, Shaanxi Normal University, Xi’an, China
2 College of Economics and Management, China Agricultural University, Beijing, China
Corresponding author: Dr H Guan (firstname.lastname@example.org)
Introduction: To determine the associations between teacher-to-parent communication and vision care–seeking behaviour among students.
Methods: This cross-sectional study included 19 934 students from 252 primary schools in two prefectures in western China. Information regarding the sampled students was collected through questionnaires and vision examinations. Eligible students with uncorrected refractive error were allocated to four groups according to whether and how parents were informed about vision problems in their children: uninformed, informed by only teachers or only students, or informed by both. The relationship between teacher-to-parent communication and vision care–seeking behaviour was analysed by multiple logistic regression.
Results: Among valid responses (n=2922) analysed, 42.3% (n=1235) of parents were not informed about vision problems in their children. Teacher-to-parent communication enabled 35.9% (n=1050) of parents to learn about vision problems in their children. When only teachers informed parents, the odds of students having refraction examinations (odds ratio [OR]=1.499; P=0.002) and spectacles ownership (OR=1.755; P=0.002) were significantly higher than for students in the uninformed group. When both students and teachers informed parents, the odds of students having refraction examinations (OR=5.565; P<0.001) and spectacles ownership (OR=7.935; P<0.001) were highest.
Conclusions: Knowledge of vision problems is an essential step in vision care for students. Teacherto- parent communication concerning vision problems is positively associated with the rate of vision care–seeking behaviour. Teacher-to-parent communication provides an important route for parents to learn about vision problems in their children.
New knowledge added by this study
- Knowledge of vision problems is an essential step in vision care for students. More than 40% of parents were not informed by students or teachers about vision problems in their children.
- Teacher-to-parent communication is significantly associated with students having refraction examination and spectacles ownership.
- Teacher-to-parent communication provides an important method for parents to learn about vision problems in their children; it also reinforces the effects of students informing their parents.
- Policymakers should carefully consider the role of teachers in vision care for students; teacher-to-parent communication is a cost-effective way to enhance vision care–seeking behaviour among students.
- Teachers should participate in vision care for students, at least in the form of communication with parents.
Uncorrected refractive error is the leading cause of visual impairment among children worldwide; it affects nearly 13 million children under the age of 16 years, half of whom live in China.1 Uncorrected refractive error can lead to various broader issues if not treated in a timely manner.2 Uncorrected refractive error in school-aged children reportedly has negative effects on academic performance,3 physical and mental health, and quality of life.4 Fortunately, over 80% of refractive error can be easily and safely corrected by accurately prescribed spectacles.5 However, the correction rate in rural areas in China is very low.6 A study in 2014 revealed that in rural China, as few as one in six children needing spectacles actually wears them.7
The lack of vision problem awareness at the family level is an important contributing factor in the low rate of refractive correction in rural areas.8 There are two main ways for parents to learn about vision problems in their children: from the children themselves and from their teachers. Information conveyed by a teacher is more likely to receive parental attention and cause parents to take action.9 Teacher-to-parent communication (TPC) allows parents and teachers to exchange information, strengthen feelings of mutual obligation and trust, and coordinate efforts to help students thrive in terms of mental health, school engagement, and school performance.10 11
However, the relationship between TPC and vision care–seeking behaviour among students is not well-investigated, particularly in more realistic settings. Researchers have indicated that teachers have an important role in vision care for students. Chinese rural teachers can perform vision screening accurately for students with only moderate training.12 Teachers can help to improve the uptake of spectacles and the use of spectacles among students who participate in free spectacles distribution programmes.13 Considering the potentially important role of teachers in vision care for students, further analyses are needed regarding the interactions between TPC and vision care–seeking behaviour among students.
In this study, our overall goal was to identify the associations between TPC and vision care–seeking behaviour among students. Specifically, when teachers informed students’ parents that their children could not see the blackboard clearly, we assessed whether the information sharing interacted with vision care–seeking behaviour among students, including refraction examinations and spectacles ownership. To meet this goal, we had three specific objectives. First, we documented the rates of vision care–seeking behaviour in four groups, according to whether and how the parents were informed about vision problems in their children. Second, we explored the relationship between TPC and refraction examination history. Third, we investigated the association between spectacles ownership and TPC.
The data analysed in this study were collected in two adjacent provinces (Gansu and Shaanxi) of western China in September 2012. In each of the provinces, one prefecture that is of the province was chosen for this study: Tianshui prefecture in Gansu and Yulin prefecture in Shaanxi. For sample selection, we obtained a list of all rural primary schools in each prefecture. We randomly selected 252 townships, then randomly selected one school per township for inclusion in the study. Within each school, one class was randomly chosen in each of the fourth and fifth grades. This cross-sectional study was approved by Stanford University (No. ISRCTN03252665, registration site: http://isrctn.org).
The data collected in this study included three parts: a standardised maths test, questionnaires, and a vision screening. The standardised maths test was timed (25 min) and proctored by two study enumerators at each school. Mathematics testing was conducted to reduce the effect of home learning on performance; this facilitated greater focus on classroom learning.7 We standardised the baseline maths score, such that the mean score was 0 and the standard deviation was 1.
Questionnaires were used to collect data from students, including grade, gender, boarding status, the main caregivers, parental education, and siblings. A parental questionnaire asked whether any family members wore spectacles and whether the parents thought spectacles were useful. Family wealth was calculated by summing the values, as reported in the China Rural Household Survey Yearbook,14 of the items on the list of 13 durable consumer goods owned by the family. A parental questionnaire asked about ownership of 13 selected items as an index of family wealth. The distance from the school to the county seat was approximated using Google Maps (Google LLC, Mountain View [CA], United States).
Vision care–seeking behaviour was measured via self-reporting on the questionnaires administered to students; it included refraction examination history (defined as undergoing a refraction examination in a professional institution before the day of questionnaire administration) and spectacle ownership (defined as the possession of spectacles before the day of questionnaire administration). To reduce the measurement error, we also asked these two questions to each student’s parents. Individuals with inconsistent answers were excluded from the study.
Teacher-to-parent communication was measured by asking parents whether they had been informed by teachers that their children could not see the blackboard clearly. Students were also asked whether they had informed their parents about their vision problems. Based on the responses to these two questions, we allocated all students with vision problems into four groups: neither teachers nor students informed parents (uninformed group), only students informed parents, only teachers informed parents, and both teachers and students informed parents (Fig).
Visual acuity assessment and refraction
After completion of the maths test and questionnaires, a two-part eye examination was administered to students by a team of qualified optometrists who followed a prescribed protocol to ensure standardisation and quality.
First, visual acuity screenings were administered using Early Treatment Diabetic Retinopathy Study eye charts, which are regarded as the worldwide standard for accurate visual acuity measurement.15 Visual acuity values, measured by the Early Treatment Diabetic Retinopathy Study eye charts, were transformed into logarithm of the minimum angle of resolution (logMAR) units; logMAR is one of the most commonly used continuous scales in the field of ophthalmology/optometry.3 15 Students who failed the visual acuity screening test (using a visual acuity cut-off of ≤6/12 in either eye) were enrolled in a second vision test.
The second vision test was conducted by a team of one optometrist, one nurse, and one staff assistant. Children with uncorrected visual acuity ≤6/12 in either eye underwent cycloplegia with up to 3 drops each of cyclopentolate 1% and proparacaine hydrochloride 0.5%. To ensure that vision problems among the students could be treated using spectacles, the students were examined via automated refraction (Topcon KR 8900; Topcon, Tokyo, Japan) and subjective refinement by a local optometrist who had previously been trained by experienced optometrists from Zhongshan Ophthalmic Center.
Vision problems in the students could be corrected using spectacles if they met the following criteria: first, an uncorrected (ie, without spectacles) visual acuity of ≤6/12 in either eye and refractive error within the limits associated with significantly greater improvement in visual acuity upon correction (myopia ≤-0.75 dioptres, hyperopia >=2.00 dioptres, or astigmatism [non-spherical refractive error] >=1.00 dioptres)7; second, visual acuity improvement to >6/12 in both eyes was possible with spectacles.
Descriptive statistical analyses were performed to summarise the demographics of the students and to compare the proportions of students who had undergone refraction examination and owned spectacles among four groups by using the Chi squared test and one-way analysis of variance. Refraction examination and spectacle ownership were both regarded as dummy variables that equalled one if the corresponding behaviour had occurred before the study.
Multiple logistic regression was conducted to ascertain the relationship between TPC and vision care–seeking behaviour, including refraction examination history and spectacle ownership. In all regression analyses, the same covariates were controlled. Variables included standardised maths score, grade (grade 5=1), sex (male=1), boarding status (boarding at school=1), logMAR (continuous scale of visual acuity), whether parents are the main caregivers (yes=1), parental education for both mother and father (completed >=12 years of education=1), siblings (at least one sibling=1), whether any family members wear spectacles (yes=1), whether parents think spectacles are useful (yes=1), family wealth, and distance from school to the county seat. A P value of <0.05 was regarded as a statistically significant difference. All analyses were performed using Stata 14.1 (Stata Corp, College Station [TX], United States).
Among 19 934 students in 252 schools, 4839 (24.3%) students failed the vision screening. In total, 3177 (65.7%) students in 250 schools were eligible for spectacles to improve visual acuity (two schools were excluded because no students at either school met the inclusion criteria). After the exclusion of students with missing information, the remaining 2922 students were divided into four subgroups. In our study, 42.3% (n=1235) of parents were not informed by either their children or their children’s teachers. Teacher-to-parent communication enabled 35.9% (n=1050) of parents to learn about vision problems in their children. In total, 20.2% (n=590) parents were informed only by teachers and 15.7% (n=460) were informed by both teachers and students, respectively (Fig).
The mean (± standard deviation) age of all students with vision problems was 10.51 ± 1.10 years (range, 8-15). Among all respondents, 1418 (48.5%) were boys and 1504 (51.5%) were girls. Most students’ main caregivers were their parents (86.4%). Other participants’ characteristics are shown in Table 1, including the comparison of characteristics among the four groups.
Table 1. Characteristics of children with correctable refractive error, stratified according to subgroup* (n=2922 included in subgroup analyses)
The rate of vision care–seeking behaviour among all students was very low. The number of students who received vision care services decreased gradually at each step. In all, 57.7% (n=1687) of parents were informed about vision problems in their children; only 32.7% (n=954) of all parents took their children for refraction examinations. Finally, only 19.2% (n=560) of students owned spectacles before the study (Table 2). The rates of vision care–seeking behaviour significantly differed among the four groups. When comparing the rates of refraction examination history and spectacle ownership among three types of informed groups with the uninformed group, we found significant differences (P<0.001) in all comparisons (Table 2). In the uninformed group, comparatively few parents took their children to receive a refraction examination and/or obtained spectacles for their children. In the group where parents were informed only by students, more children had undergone refraction examinations and/or owned spectacles than in the group where parents were informed only by teachers. When both teachers and students informed parents, the rates of refraction examinations and spectacles ownership were highest among the four groups.
Table 2. Vision care-seeking behaviours among subgroups of children with correctable refractive error (n=2922)
In the multiple logistic regression analyses of potential predictors of refraction examination, we found that information sharing (including TPC) was significantly associated with refraction examination history (Table 3). Compared with the uninformed group, the odds of students having a refraction examination was higher in each of the other three groups. When only teachers informed parents, the odds ratio (OR) was 1.499, which was lower than in the group where only students informed parents (OR=2.839). When both students and teachers informed parents, the odds of students having a refraction examination was highest (OR=5.565). Additionally, the following characteristics were significantly positively associated with refraction examination history: receiving a better maths score (P=0.031), being male (P=0.015), having a worse visual ability (P<0.001), having at least one other family member who wears spectacles (P<0.001), being in the top wealth tercile (P<0.018), and having parents who think that spectacles are useful (P<0.001) [Table 3].
Table 3. Multiple logistic regression analyses of potential predictors of refraction examination (n=2922)
Multiple logistic regression analyses were used to estimate the relationship between TPC and spectacles ownership (Table 4). Teacher-to-parent communication was significantly positively associated with spectacles ownership, regardless of whether students informed parents about their vision problems. The odds of students having spectacles ownership in the group where parents were informed by both teachers and students (OR=7.935) was almost 1.8 times that in the group where parents were informed only by students (OR=4.413). The odds of students having spectacles ownership in the group where parents were informed by students only was twice that in the group where parents were informed only by teachers (OR=1.755). Furthermore, the following characteristics were significantly positively associated with spectacles ownership: having worse visual acuity (P<0.001), having parents as the main caregivers (P<0.017), having at least one other family member who wears spectacles (P<0.001), and having parents who think spectacles are useful (P<0.001). Notably, students with at least one sibling (P=0.003) were more unlikely to purchase spectacles (Table 4).
Table 4. Multiple logistic regression analyses of potential predictors of spectacles ownership (n=2922)
Factors affecting vision care–seeking behaviour
In this study, we found that the rate of vision care–seeking behaviour was very low in our sample area, similar to previous results.16 17 There are two possible reasons for the low vision care–seeking behaviour rate. First, parents may not know that their children cannot see the blackboard clearly; thus, they will not actively seek vision care services. Second, the number of students receiving vision care services has been decreasing throughout the process of three stages: parental knowledge that their children have vision problems, parental action to ensure their children undergo refraction examinations, and parental acquisition of spectacles for their children. Furthermore, despite sufficient information, many parents do not seek vision care services because of misinformation or misunderstanding.18 19
Knowledge of vision problems is the initial aspect of the vision care–seeking process for students. The rates of refraction examination history (18.1%) and spectacles ownership (6.6%) were the lowest in the uninformed group, which comprised more than 40% of parents in this study. When parents were informed by students and/or teachers, the rate of vision care–seeking behaviour was much higher. Teacher-to-parent communication provides an important method for parents to learn about vision problems in their children. In this study, 20.2% of parents learned about their children’s vision problems only from teachers.
Effects of teacher-to-parent communication on vision care–seeking behaviour
Although a considerable proportion of students did not receive vision care in the care-seeking process, TPC can reduce this to some extent. When both teachers and students informed parents, the rate of spectacles ownership was the highest. In the group that parents were informed by both teachers and students, 46% of students finally received spectacles, which is 7-times more students than in the group in which parents were not informed. Furthermore, the odds of students having refraction examination and spectacles ownership were higher in the group where parents were informed only by students than in the group where parents were informed only by teachers. These additional opportunities may increase the likelihood that parents act to correct those vision problems.
There are two possible explanations for the positive association between TPC and vision care–seeking behaviours among students in this study. Teacher-to-parent communication provides an important channel for parents to learn about the vision problems in their children, which is a starting point and key aspect of vision care for students. Second, TPC reinforces the effects of students informing their parents. Compared with the group where parents were informed only by students, the rates of refraction examinations and spectacles ownership were nearly twofold greater in the group where parents were informed by both students and teachers. This was presumably because parents learned about vision problems in their children from two sources; the information from the students was reinforced by the information from the teacher.20
Implications of promoting teacher-to-parent communication
Small efforts by teachers may have great benefits in terms of vision care for students. Compared with intervention programmes to increase the correction rate,7 21 the results of present study indicate that TPC is both easy and cost-effective. Teachers should inform parents that their children cannot see the blackboard clearly. Studies of free spectacles distribution programmes have also shown that teachers can improve spectacles usage rates among students who have received spectacles.13 22 Moreover, wearing spectacles can improve academic performance,7 21 implying that TPC may both increase the correction rate and have a positive role in academic performance. Therefore, policymakers should carefully consider the role of teachers in protecting vision among students. Indeed, the Chinese Government has noted that multilateral cooperation (involving teachers, schools, parents, and society in general) should be encouraged to protect vision among students, in an effort to improve health status among young people by 2020.23
Unfortunately, the TPC ratio is very low. A recent study in China noted that approximately half of the parents and teachers communicate, in any form, during the course of an entire school year.24 In our study, the proportion of parents who were informed by teachers was only approximately 36%, including parents informed only by teachers (20%) and parents informed by both teachers and students (16%). This is presumably because teachers do not know a particular student’s vision status because it is not a vital consideration for most education work. Vision screening is the best method to detect vision problems.25 The education bureau and the health bureau should conduct routine vision screenings and encourage teachers to engage in vision protection (eg, communicate with parents about vision problems in students).5 25 If those stakeholders began to take action, more parents will learn about vision problems in their children and seek vision care services.
Effects of students’ informing on vision care–seeking behaviour
In the present study, the effects of students informing parents were greater than the effects of teachers informing parents when only one party informs the parents of vision problems. This finding implies that parents were more likely to act when they received information from students. However, students are often unaware of vision problems. Thus, teachers have an important effect; a previous survey reported that teachers were most likely to perceive visual impairment in children (70.6%), followed by the children’s parents (18.9%) and by the children themselves (7.9%).26 Therefore, careful attention is needed concerning the role of teachers in identifying vision problems, encouraging communication between students and their parents about such problems.
There were three important limitations in this study. First, the study could not investigate any causal link between TPC and vision care–seeking behaviour because of the cross-sectional design. However, the findings provide a foundation for follow-up analyses of causality. Second, this study only focused on whether teachers informed parents about vision problems in their children; it did not collect information concerning how parents were informed. Teacher-to-parent communication may happen in many ways, particularly in the internet era (eg, teachers communicate with parents via instant messenger). Additional research is needed to determine the types of TPC that are most effective in vision care for students. Third, the participants in this study were recruited from two provinces in rural north-western China, which limits the external validity of the findings. Despite this limitation, in the context of widespread uncorrected vision impairment among students,27 our study still has important implications for improving the uptake rate of vision care services.
Teacher-to-parent communication can significantly enhance the rates of refractive examinations and spectacles uptake through direct and indirect ways. Not only teacher informing provides a new channel for parents to learn about their students’ vision problems, but also reinforce the information told by students. Teacher-to-parent communication is an easy and cost-effective way to improve the rate of vision care–seeking behaviour. Policymakers should encourage teachers to be more involved in students’ vision protection, such as motivating teachers to communicate timely with parents about the students’ vision status.
Concept or design: K Du, J Huang.
Acquisition of data: H Guan, Y Shi.
Analysis or interpretation of data: All authors.
Drafting of the manuscript: K Du.
Critical revision of the manuscript for important intellectual content: All authors.
Acquisition of data: H Guan, Y Shi.
Analysis or interpretation of data: All authors.
Drafting of the manuscript: K Du.
Critical revision of the manuscript for important intellectual content: All authors.
All authors had full access to the data, contributed to the study, approved the final version for publication, and take responsibility for its accuracy and integrity.
Conflicts of interest
All authors have no conflicts of interest to disclose.
This research was supported by the 111 Project (Ref: B16031). H Guan has received funding from the National Natural Science Foundation of China (Ref: 71803107). The funders had no role in the design of the study, the acquisition or interpretation of results, or the decision to submit the manuscript for publication.
This study was approved by Stanford University (No. ISRCTN03252665). Permission was received from local boards of education in each region and the principals of all schools. The presented data are anonymised, and the risk of identification is low. The principles of the Declaration of Helsinki were followed throughout.
1. Jonas JB, Xu L, Wei WB, et al. Myopia in China: a population-based cross-sectional, histological, and experimental study. The Lancet 2016;388:S20. Crossref
2. Smith TS, Frick KD, Holden BA, Fricke TR, Naidoo KS. Potential lost productivity resulting from the global burden of uncorrected refractive error. Bull World Health Organ 2009;87:431-7. Crossref
3. Yi H, Zhang L, Ma X, et al. Poor vision among China’s rural primary school students: Prevalence, correlates and consequences. China Econ Rev 2015;33:247-62. Crossref
4. Chadha RK, Subramanian A. The effect of visual impairment on quality of life of children aged 3-16 years. Br J Ophthalmol 2011;95:642-5. Crossref
5. World Health Organization. Sight test and glasses could dramatically improve the lives of 150 million people with poor vision. 2006; Available from: http://www.who.int/mediacentre/news/releases/2006/pr55/en/. Accessed 9 Jan 2018.
6. He M, Xu J, Yin Q, Ellwein LB. Need and challenges of refractive correction in urban Chinese school children. Optom Vis Sci 2005;82:229-34. Crossref
7. Ma X, Zhou Z, Yi H, et al. Effect of providing free glasses on children’s educational outcomes in China: cluster randomized controlled trial. BMJ 2014;349:g5740. Crossref
8. Resnikoff S, Pasolini D, Mariotti SP, Pokharel GP. Global magnitude of visual impairment caused by uncorrected refractive errors in 2004. Bull World Health Organ 2008;86:63-70. Crossref
9. Adams KS, Christenson SL. Trust and the family–school relationship examination of parent–teacher differences in elementary and secondary grades. J Sch Psychol 2000;38:477-97. Crossref
10. Franklin CG, Kim JS, Ryan TN, Kelly MS, Montgomery KL. Teacher involvement in school mental health interventions: A systematic review. Child Youth Serv Rev 2012;34:973-82. Crossref
11. Kraft M, Dougherty SM. The effect of teacher-family communication on student engagement: evidence from a randomized field experiment. J Res Educ Eff 2013;6:199-222. Crossref
12. Sharma A, Li L, Song Y, et al. Strategies to improve the accuracy of vision measurement by teachers in rural Chinese secondary schoolchildren: Xichang pediatric refractive error study (X-PRES) report no. 6. Arch Ophthalmol 2008;126:1434-40. Crossref
13. Yi H, Zhang H, Ma X, et al. Impact of free glasses and a teacher incentive on children’s use of eyeglasses: a cluster-randomized controlled trial. Am J Ophthalmol 2015;160:889-96.e1. Crossref
14. China National Bureau of Statistics. China Statistical Yearbook. Beijing, China: China State Statistical Press; 2013.
15. Camparini M, Cassinari P, Ferrigno L, Macaluso C. ETDRS-Fast: implementing psychophysical adaptive methods to standardized visual acuity measurement with ETDRS charts. Invest Ophthalmol Vis Sci 2001;42:1226-31.
16. Qian DJ, Zhong H, Nie Q, Li J, Yuan Y, Pan CW. Spectacles need and ownership among multiethnic students in rural China. Public Health 2018;157:86-93. Crossref
17. Zhao J, Guan H, Du K, et al. Visual impairment and spectacles ownership among upper secondary school students in northwestern China. Hong Kong Med J 2020;26:35-43. Crossref
18. Dudovitz RN, Izadpanah N, Chung PJ, Slusser W. Parent, teacher, and student perspectives on how corrective lenses improve child wellbeing and school function. Matern Child Health J 2016;20:974-83. Crossref
19. Senthilkumar D, Balasubramaniam SM, Kumaran SE, Ramani KK. Parents’ awareness and perception of children’s eye diseases in Chennai, India. Optom Vis Sci 2013;90:1462-6. Crossref
20. Verhulst FC, Dekker MC, van der Ende J. Parent, teacher and self-reports as predictors of signs of disturbance in adolescents: whose information carries the most weight? Acta Psychiatr Scand 1997;96:75-81. Crossref
21. Ma Y, Congdon N, Shi Y, et al. Effect of a local vision care center on eyeglasses use and school performance in rural China: a cluster randomized clinical trial. JAMA Ophthalmol 2018;136:731-7. Crossref
22. Wang X, Ma Y, Hu M, et al. Teachers’ influence on purchase and wear of children’s glasses in rural China: The PRICE study. Clin Exp Ophthalmol 2019;47:179-86. Crossref
23. Ministry of Education, PRC Government. Ministry of education on implement plan for comprehensive prevention and control of myopia among children and adolescents. Available from: http://www.moe.gov.cn/srcsite/A17/moe_943/s3285/201808/t20180830_346672.html. Accessed 9 Jan 2020.
24. Li G, Lin M, Liu C, Johnson A, Li Y, Loyalka P. The prevalence of parent-teacher interaction in developing countries and its effect on student outcomes. Teach Teach Educ 2019;86:102878. Crossref
25. Glewwe P, Park A, Meng Z. A better vision for development: eyeglasses and academic performance in rural primary schools in China. J Dev Econ 2016;122:170-82. Crossref
26. Alves MR, Temporini ER, Kara-José N. Ophthalmological evaluation of schoolchildren of the public educational system of the city of São Paulo, Brazil: medical and social aspects [in Portuguese]. Arq Bras Oftalmol 2000;63:359-63. Crossref
27. Ma Y, Zhang X, He F, et al. Visual impairment in rural and migrant Chinese school-going children: prevalence, severity, correction and associations. Br J Ophthal 2022;106:275-80. Crossref