Reading performance in school going children with visual function anomalies

Introduction

Reading is one of the most visually demanding tasks we do daily,1 including various psychological tasks as well as quick movements of both eyes in the same direction (saccades) from one word to the next or, on occasion, backward to previously read the literature.2, 3 Binocular coordination ensures that a steady, unified percept of the text is maintained across eye movements during reading and other visually demanding tasks, helping visual processing to occur without interruptions produced by diplopia.4, 5, 6, 7

Furthermore, reading is a visuo-cognitive mechanism, and single-vision perception is essential for this process to occur and function appropriately in today's world.7 Reading involves coordinating several visual functions that provide coordinated information to the visual cortex, including refraction, accommodation, visual acuity, saccades, convergence, and fusion.8 When children start school, their most crucial education element is learning through reading. Many myths about reading issues come from the importance of the eyes in reading.9 Low levels of academic performance and educational outcomes can be linked to health (dyslexia, lower intellectual ability, binocular vision anomalies, and speech sound disorders) 10, 11, 12 as well as the familial, social, physical, and economic environment in which children and teenagers live. 11

Reading includes both accommodative and vergence mechanisms. An imbalance between the sensory-motor integrated functions leads to non-strabismic accommodative and/or binocular vision anomalies. As a result, any abnormalities in the visual system will impact children's cognitive and educational performance.13 Poor reading performance and binocular vision abnormalities have been linked in the literature. These problems include poor pursuits, abnormal convergence, 14 insufficient amplitude of accommodation, 15 accommodative infacility, 14, 15, 16 weak fusional vergence reserves, and abnormal fixation disparity.17

In India, the reported prevalence of specific learning difficulties among 8–11 years-old children are 15.17%.18 Carla Costa et al.19 reported that 16.4% of all school-age children in Portugal showed poor academic performance due to visual function anomalies. Accommodation and vergence anomalies affect approximately 80% of the children with learning disabilities, including convergence insufficiency(CI), the reduced amplitude of accommodation(AOA), accommodative and vergence facility, fusional ranges and low accommodative convergence/accommodation(AC/A) ratio.20, 21 In addition, children with reading and writing difficulties have impairments in accommodation and vergence parameters compared to age-matched controls who do not have reading and writing problems.15, 22, 23, 24 Several studies have found that children with reading and learning problems have a higher incidence of hypermetropia and non-strabismic binocular vision problems than normal readers.17, 25, 26, 27, 28, 29 Appropriate spectacles prescription and vision therapy are important in relieving symptoms in these children.30, 31, 32

From an optometrist’s perspective, a decrease in reading ability may be associated with Visual function anomalies. To the best of our knowledge, there are no prevalence data in the Bangladeshi literature for binocular vision anomalies. Therefore, we attempt to determine the correlation of reading performance (error, accuracy, and reading speed) in children with and without visual function anomalies.

Materials and Methods

This observational cross-sectional study was carried out at the Vision Therapy Clinic of a multispecialty eye hospital in Dhaka, Bangladesh, from May 2021 to April 2022. The study subjects (6 -15 years) with asthenopia symptoms (Reading impairment) were selected by simple random sampling. All patients had 6/6 BCVA in each eye.

A written questionnaire (CISS-score) was used to identify the asthenopia complaints along with reading difficulties while having a normal vision and normal retinal function only selected for recruitment. We excluded from the study who were not willing to participate, subjects previously diagnosed with VFA, Neurocognitive disability, Dyslexia, Speech sound disorder, any ocular surface disorder, systemic illness, previous history of any intraocular surgery, strabismus, or previous surgery to correct strabismus, amblyopia, and nystagmus.

All participants had undergone complete ophthalmic and binocular vision examination, including visual acuity, dry and wet retinoscopy, pupillary reaction examination, Stereopsis, ocular alignment, extraocular motility, Cover and alternate cover test, AC/A-ratio, NPC (Push into-double), amplitude of accommodation (push-into-blur), MEM dynamic retinoscopy, NRA, PRA, NFV, PFV, accommodative facility, vergence facility. Reading error, accuracy and reading speed were assessed with an N-notation chart with an N6 target size. The time taken to complete the task was recorded with a stopwatch.

Results

In this study, we evaluated 200 children with complaining asthenopia symptoms with reading; the mean age of participants was 12.04 (±2.44) years, ranging from 6-15 years. Most of them study in secondary school (12-15 years) than primary school (6-11 years). Of all, boys were 46.5% (N=94) and girls were 53.5% (N=106). Among the study subjects, the most frequent range of uncorrected visual acuity (UCVA) in the Right eye and Left eye had 0.00LogMAR (Snellen's 6/6) and the percentage was 80.5% in the right eye and 81.50% in the left eye, which was strongly statistically significant (p=0.001). The Mean, Median and standard deviation of UCVA in the right eye and left eye in Table 1 are shown:

All subjects acquired had the best corrected visual acuity (BCVA) in both eyes, 0.00 Log MAR (Snellen's6/6). About 99.5% of subjects were able to read N6 letters comfortably. Only 0.5% of subjects were able to read N8 letters. On sensory evaluation, all subjects presented with BSV at both near and distant. About 85.5% had normal 40-60 seconds of arc and 14.5% had reduced 120 seconds of arc in the stereopsis evaluation. Orthophoria was noted as 30.5% on motor evaluation at the near cover test and 71.5% at the distance cover test, respectively. About 66% were exophoric at the near cover test and 28.5% at distance cover test, respectively. Only 3.5% were esophoria at the near-cover test. By prism cover test, Orthophoria was 31% and 73% at near and distance, respectively.

We also found that 48.5% and 15% of study samples had (2-6PD) Exophoria at near and distant. 9% and 1% were (8-12PD) Exophoric at near and distance, respectively. About 8% and 11% were (14-20PD) Exophoria near and distant, respectively. 3.5% were (2-6PD) Esophoria at near cover test.

AC/A-ratio was normal at 70.5%, high at 11.5% and low at 18%. Out of 200 subjects, NPC was normal in 58.50%, reduced in 21.50% and defective in 20% of subjects. The Mean NPC subjective and objective values are shown in Table 2.

Among all subjects, MEM retinoscopy findings were normal in 49.5%, Low in 43% and High in 7.5%, ranging from (-1.00 to+1.50DS). In relative accommodation, NRA was normal at 26%, Low at 66.50% and high at 7.5%. Also, PRA was normal among 32%, Low 19.50% and high among 48.50% of subjects.

The amplitude of accommodation was normal in 95.5% and reduced in 4.5% of subjects. The mean amplitude of accommodation was 11.77±1.9D in the right eye, 11.78±1.9D in the left eye and 11.77±1.89D in both eyes, with ranged from (4-16.5) D. The vergence facility was normal (10-12cpm) among 24% and low (<8cpm) among 76% subjects. The mean AF was 8.42±3.19cpm in the right eye and 8.46±3.34cpm in the left eye, while in binocularly 7.06±3.31cpm respectively. The mean NFV BI to break/recovery at near was 11.35/7.95PD (SD=3.24/2.57), while at a distance was 7.40/5.05PD (SD=1.96/1.86), respectively. Similarly, the mean PFV BO to break/recovery at near was 15.79/11.96PD (SD=5.68/5.26), while at a distance, mean values were 9.49/6.53PD (SD=3.07/2.63) respectively. The results of the distribution of reading performance per NVF and AVF are mentioned in Table 3.

Of all 200 subjects, 15.5% (n=31) was NVF and 84.5% (n=169) was AVF. Among all AVF, convergence insufficiency was 31% (n=62), followed by Convergence excess (3%), fusional vergence dysfunctions (25%), accommodative insufficiency (4.5%), accommodative excess (3.5%), accommodative infacility (6.5%), divergence excess (10%) and basic exophoria (1%). Children with AVF had higher reading errors (AVF=7.833±5.08; NVF= 6.55±3.67; p=0.001). Children in first to fifth school grades presented a higher risk of having reading impairment when compared with 6^th to 10^th grades. Among them, the Mean ± SD reading speed of the 10^thgrade was 112 ± 20.69 wpm which was higher than the 6th to 9^th grade (Table 4).

Out of 200 subjects, 81% (n=162) were emmetropes and 19% (n=38) had refractive error only. Among the students with refractive error, 3% (n=6) had simple myopia, 2.5% simple hyperopia, 3.5% simple myopic astigmatism, 2.5% simple hyperopic astigmatism, 6% compound myopic astigmatism, 0.5% compound hyperopic astigmatism and 1% mixed astigmatism. Reading performance was worst in compound hyperopic astigmatism and simple hyperopic astigmatism compared to others. Among all participants, only 16.5% students did not need any management; 3% were treated with only spectacles; 35.5% with only convergence exercise; 20% only fusional exercise; 9% only accommodative exercise; 9% with spectacles along with convergence exercise, 5% with spectacles along with fusional exercise; and 2% with spectacles along with accommodative exercise.

Discussion

This study compared the reading performance in children with normal and abnormal visual functions. Children with visual function anomalies have poor reading performance (higher number of errors, similar accuracy, and lower reading speed). Our results are supported by earlier research showing that children with visual function anomalies may suffer with reading, writing, and academic performance.1, 15, 19, 20, 21, 22, 23, 24, 33, 34, 35, 36 Our study found that children with the reading problem have a higher frequency of AVF (84.50%) and normal visual function 15.5%, which was strongly statistically significant (p=0.001). Also, a significant association between reading and non-strabismic anomalies of binocular vision has been reported in the literature.1, 15 Poor reading comprehension was more common in the group of adolescents with vision anomalies (n=109, 31.2%) than in those without vision anomalies (n=80, 18.8%; p=0.05).37 A cross-sectional study by Ragnarsdottir et al.38 showed that no correlation was found between reading speed and binocular accommodative amplitude, binocular accommodative facility, positive and negative relative accommodation, MEM retinoscopy and cross card. A prospective study by Stifter et al.39 found significant differences in binocular maximum reading speed (MRS) between children with micro strabismic amblyopia and normal controls (p=0.03). There were no significant differences between the two groups in terms of binocular log MAR visual acuity and reading acuity (p=0.05). Another cross-sectional study found that poor readers had nearly two prism diopter lower mean distance base-in break and base-in recovery values (p<0.01) than the control group.(1)Muriel Dysli et al.40 found that acute changes in horizontal and vertical vergence tone did not affectreading performance or reading-related eye movements. Prisms have little effect on reading performance on healthy people. This finding contradicts the role of phoria in dyslexia. Their result contradicts the suggestion for correcting small angle heterophorias in dyslexic children.

Studies reported a high frequency of AVF (63% - 69.9%) in children with reading problems in India and Norway. 13, 37, 41 Our results are very high (84.5%). Hussaindeen JR et al. 41 showed that NSBV anomalies in urban and rural areas were 31.5% and 29.6%, respectively, which was lower than our study. It could be because of the participants' age and study areas.

In our study, Convergence insufficiency was highly prevalent 31%, followed by fusional vergence dysfunctions 25% in school-going children. Almost similarly, Magdalene et al. 13 reported Convergence insufficiency at 37.10%. However, a study from India 41 showed that accommodative infacility was highly prevalent (67%), followed by convergence insufficiency (25%) which is different from our study. A similar trend has been reported in other populations (20–22 years) wherein the prevalence of AIF ranged between 26 and 31.7% and CI between 14 and 38%.

In this study, children with AVF had a higher reading error (7.833±5.08). A study from Portugal showed a higher number of reading errors (3.00 errors), but our results were very high. 19 We also found lower reading accuracy (AVF=86.11±14; NVF=86.43±13.12) and reading speed (AVF=79.47±39.20 wpm; NVF=84.51±36.84 wpm). Similar trends were reported on reading accuracy (AVF=91.18%; NVF=97.06%) and reading speed (AVF=24.71 wpm; NVF=27.39 wpm). 19 Our findings also demonstrate that Reading speed was so much lower in basic exophoria (42.0±45.25), followed by accommodative insufficiency (74.44±44.69), but Lanca CC et al, 19 found lower reading speed in convergence insufficiency (29.30±0.99) that is opposite in our results. At the same time, Husssiandeen and colleagues 42 and Maples and colleagues 43 have correlated AI and CI as factors affecting the academic performance of school-age children. Simons et al. 44 reviewed 34 studies of vision anomalies and reading skill and showed that hyperopia, exophoria at near, vertical phoria, anisometropia, and aniseikonia are associated with below average reading performance. Several studies have indicated that children with reading and learning problems show a higher incidence of hypermetropia 22, 23, 24, 25, 43 and non-strabismic binocular vision disorders than normal readers. 14, 41, 44 Myopia and esophoria and esophoria at far are associated with average and above-average reading performance.45 In the present study, we also found similar results. A retrospective study by Christian et al. 46 identified no significant refractive error in 81% of children and our present study. We also found the same result. Previous research on refractive status and reading performance suggested that myopic children are better readers than hyperopic children, 44, 47 we also have the same results. However, other studies 24, 29 do not find any association between refractive error and reading in children and have no relation between ocular function and academic performance. 45, 48, 49 The association between visual skill level and reading outcomes is controversial because of a perceived lack of scientifically rigorous evidence. 1

We also compared the three measurements of reading performance by children's grade (1^stto 10^th). Children in first to fifth grades presented a higher risk of reading impairment than sixth to tenth grades. In the first to fifth grades^, first and second grades presented a higher risk of having low reading performance. Another study compared the three measurements of reading performance by children’s only grade (first to fourth), and they showed that second, third, and fourth grade presented a lower risk of having a low reading performance when compared with the first grade.19 David Grisham et al. 20 found that high numbers of poor readers in high school may be at high risk of visual skills dysfunction, which is also opposite to our study.

The tenth grade has a higher reading speed of 112 ± 20.69 wpm than the sixth to ninth grade. So, we assume that as one gets older, the reading problems of a younger age due to visual anomalies appear to be overcome or somehow compensated by other strategies. In our study, 3% of subjects were treated with only spectacles; 35.5% with only convergence exercise; 20% with only fusional exercise; 9% with only accommodative exercise; 9% with spectacles along with convergence exercise, 5% with spectacles along with fusional exercise; and 2% with spectacles along with accommodative exercise.

The limitations of this study include limited sample size, not including all children, only hospital attended school going children included in study, and preschool children were excluded from the study. This study recommended a comprehensive eye examination for school-aged children with a reading problem to ensure proper diagnosis and management.

Conclusion

Poor reading performance is strongly significant to abnormal visual function in school-aged children. Abnormal visual functions can decrease children's quality of life and impact school performance and near activities. As a result, this study concludes that accurate binocular vision evaluation, early detection, and treatment are essential for addressing reading problems and providing the best opportunity for academic success in the school-age group.

Ethics Approval and Consent to Participate

The study received ethical clearance from the Institutional Ethical Review Committee of Ispahani Islamia Eye Institute and Hospital, Dhaka-1215, Bangladesh. Informed written consent was obtained from all patients or patient’s guardians. All methods were performed in accordance with the relevant guidelines and regulations adhered to the tenets of the Declaration of Helsinki as amended in 2008.

Consent for publication

Not applicable

Availability of data and materials

The data sets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Author's Contributions

NA, MK and GKB designed the study, procured the samples, and performed the experiments; NA, SS and MM designed and performed the statistical analyses; NA, SS, and SMK provided critical input NA and GKB interpreted the results; MM, SMK, RPM and SC conducted the critical appraisal of the manuscript; NA, and SMK edited final manuscript; all authors reviewed and approved the final version of the manuscript prior to submission.

Abbreviations

NPC=Near Point of Convergence, NPA=Near point of Accommodation, NRA=Negative Relative Accommodation, PRA=Positive Relative Accommodation, NFV=Negative Fusional Vergence, PFV=Positive Fusional Vergence, AC/A-ratio=Accommodative Convergence by Accommodative ratio, MEM-Retinoscopy=Monocular Estimation Method Retinoscopy, BSV=Binocular Single Vision, LogMAR=Log unit of Minimum Angle of Resolution, NVF=Normal Visual Function, AVF=Abnormal Visual Function, WPM=Word Per Minute, SD=Standard Deviation, SPSS=Statistical Package for Social Science, CISS=Convergence Insufficiency Symptoms Survey, NA=Nilufa Akter, MK=Mastura Khatun, GKB=Gaurav Kumar Bhardwaj, MM=Mohammad Masihuzzaman, SMK=Syeed Mehbub Ul Kadir, SC=Sayantan Chakraborty, SS= Sunanda Sarkhel, RPM=Rajendra Prakash Maurya.

Conflict of Interests

None of the authors has proprietary interests or any potential conflicts of interest.

Source of Funding

There was no financial support in terms of grants orfunds for this study from any source.

Acknowledgement

The authors would like to express gratitude and thanks to the management of Ispahani Islamia Eye Institute and Hospital, for their help in collecting the data. We are also grateful to our patients for their willing participation in this study.