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Year : 2021  |  Volume : 10  |  Issue : 1  |  Page : 43-48

Prevalence of undiagnosed, preventable visual impairment in children with intellectual disability in special needs schools in Western Saudi Arab

1 Department of Ophthalmology, King Abdulaziz University, Jeddah, Saudi Arabia
2 Department of Ophthalmology, University of Jeddah, Jeddah, Saudi Arabia
3 Department of Optometry, Faculty of Medical Science, University of Jeddah, Jeddah, Saudi Arabia
4 Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia

Date of Submission22-Oct-2020
Date of Decision04-Feb-2021
Date of Acceptance05-Feb-2021
Date of Web Publication02-Apr-2021

Correspondence Address:
Lina Hassan Raffa
Department of Ophthalmology, King Abdulaziz University Hospital, Prince Majid Road, Al Sulaymaniyah, Jeddah 22252
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sjhs.sjhs_236_20

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Background: Visual disorders have been reported to be higher among children with intellectual disability (ID) than among their peers without special needs; however, prevalence data on visual problems in children in Saudi Arabia are scarce. Aims: The aim of this study is to report the prevalence and causes of undiagnosed, correctable visual impairment in children with ID. Materials and Methods: A cross-sectional study of students enrolled in special educational needs schools in the western region of Saudi Arabia in April 2018. Teller visual acuity (VA) assessment and refractive errors were noted. Participants with mild to profound ID underwent detailed ophthalmologic examinations, including cycloplegic refraction, full orthoptic workup, biomicroscopy, and funduscopy. Results: A total of 61 students participated in this study. Ocular findings in decreasing prevalence were as follows: Subnormal VA (n = 41, 67.2%), refractive errors (n = 31, 51.7%), fundus anomalies (n = 13, 22%), significant strabismus (n = 9, 14.8%), abnormal head posture (n = 8, 13.3%), nystagmus (n = 3, 4.9%), anterior segment abnormality (n = 3, 4.9%), and extraocular motility abnormality (n = 2, 3.3%). Astigmatism was found in 22 cases (36.7%), followed by hyperopia (n = 13, 21.7%), myopia (n = 10, 16.7%), and anisometropia (n = 5, 8.3%). Students with syndromic ID had significantly more moderate-to-severe subnormal VA (P < 0.001) and myopic shift on cycloplegic refraction (P = 0.014 right eyes and P = 0.004 left eyes) than those with nonsyndromic ID. Conclusions: A considerable proportion of ID children have significant visual disorders. This emphasizes the need for adequate diagnostic and therapeutic national eye care services for children with ID.

Keywords: Intellectual disability, prevalence, refractive errors, Saudi Arabia, special needs, visual impairment

How to cite this article:
Raffa LH, Al-Shamrani AZ, Madani FM, AlQarni AS, Allinjawi KF, Fagih AK, Alhibshi N. Prevalence of undiagnosed, preventable visual impairment in children with intellectual disability in special needs schools in Western Saudi Arab. Saudi J Health Sci 2021;10:43-8

How to cite this URL:
Raffa LH, Al-Shamrani AZ, Madani FM, AlQarni AS, Allinjawi KF, Fagih AK, Alhibshi N. Prevalence of undiagnosed, preventable visual impairment in children with intellectual disability in special needs schools in Western Saudi Arab. Saudi J Health Sci [serial online] 2021 [cited 2021 Jul 23];10:43-8. Available from: https://www.saudijhealthsci.org/text.asp?2021/10/1/43/312902

  Introduction Top

Visual disorders are common worldwide, with about 285 million people estimated to live with a visual disability.[1] Approximately 90% of these people live in developing nations, and children represent 3% of this subpopulation. Problems in visual functioning are frequent in children with intellectual disabilities. An intellectual disability is defined (ID) is a disorder, characterized by an individual's inability to learn at an expected level and function in everyday life.[2] According to other investigators, ID involves neurodevelopmental disorders that start in childhood and are characterized by limitations in intellectual functioning and adaptive behavior.[3]

The prevalence and incidence of visual disorders in persons with ID have been more extensively studied in adults,[4],[5],[6],[7] but recently, more research has focused on the epidemiology of visual impairment in children with ID.[5],[8],[9] In pediatric ophthalmology, with or without ID, refractive errors and strabismus are the most common visual disorders, with amblyopia reported as the main risk factor associated with these disorders.[10],[11],[12] In addition, disorders such as refractive errors, strabismus, nystagmus, cataract, and cortical blindness have been reported to be higher among children with ID than among their peers without special needs.[13] A cross-sectional study investigating the prevalence and etiologies of visual impairment in children with ID reported that the prevalence of visual impairment was 10.5%.[5] In another report, the investigators identified strabismus in 26.8% of the children examined – 14.9% of the children had esotropia and 10.3% had exotropia.[9] Other investigators have even claimed to have evidence that all special needs children require visual assessment.[8] However, these children do not get regular screening tests.[7],[14] Consequently, significant refractive errors may not be detected, and if left uncorrected, they can lead to worsening vision, poorer learning acquisition, and permanent visual impairment.

In Saudi Arabia, where ID has been reported in 8.9 per 1000 children with a moderate or severe disability identified in 70.9% of the cases,[15] it is critical to obtain the data on the etiology and prevalence of visual impairment in this subpopulation of children. However, data on the prevalence of visual disorders in children in Saudi Arabia are scarce.[16] This study aims to determine the prevalence of visual impairment in children with ID in the Western Province of Saudi Arabia. This information could help health care policy-makers implement vision screening services and provide low-vision services to this underprivileged group.

  Material and Methods Top

Study population

This study was performed in accordance with the declaration of Helsinki. Approval was granted by the Institutional Ethics Board, and informed consent was obtained from all participating families. Based on two school's requests to assess the children's vision on-site, 46 children attending the first school and 18 attending the second summer school participated in the study. The inclusion criteria included being younger than 18 years, completion of the vision assessment, and residence in the Western Province (Jeddah = 60, Makkah = 1) of Saudi Arabia. Of the 64 children who participated in the study, three were excluded because they were above 18 years of age.

The full medical records of the children were checked for details regarding health status, including details of childbirth, etiology of intellectual disability, and chronic illnesses. Examinations were undertaken on-site to facilitate the acceptance by the students. This assessment was performed by two ophthalmologists and two optometrists. In addition, the participants' caregivers were asked whether their children wore eyeglasses.

Blood pressure, weight, and height were taken within 2 weeks before the commencement of the study for all students. Body mass index (BMI) was calculated, and all anthropometric measurements were plotted on age- and gender-appropriate World Health Organization (WHO) charts.[17]


Syndromic versus Nonsyndromic Intellectual Disability

Syndromic intellectual disability included those children with a defined predisposing cause of intellectual disability, for example, chromosomal disorders, including Down syndrome or gene mutation (achondroplasia or Alazami syndrome). The subsample included nine children. The nonsyndromic group included 52 children with autism, attention-deficit hyperactive disorder, cerebral palsy/perinatal asphyxia, or cerebral malformations.

Vision impairment


  • Visual acuity (VA) between 0.2 and 0.5 Logarithm of the Minimum Angle of Resolution (LogMAR).


  • VA of 0.6–0.9 LogMAR.


  • VA <0.9 LogMAR.

Refractive errors

Myopia is defined as the spherical equivalent (SE) of at least − 0.75 Diopters (D) or more, hyperopia as the SE of ≥+2.0 D, and astigmatism as the cylinder of ≥1.0 Diopters, and anisometropia as the SE difference of at least 1.0 D between the two eyes of the same child.

Ocular abnormality

Ocular abnormality was defined as the presence of one or more of the following on presentation: Subnormal VA (>20/30 in either eye), amblyopia, refractive errors, strabismus, reduced motility, anterior segment anomalies, and/or optic nerve or retinal vessel anomalies.

Ocular examinations

During the examination, each student was accompanied by a school staff member who knew the students well. The Titmus housefly test was attempted in all children to assess binocular function. Teller acuity cards were successfully used to measure the best-corrected VA monocularly in 41 children. An adhesive patch was used to cover the other eye to avoid peeking. Depending on the child's degree of cooperation, strabismus was measured using either the prism cover test (for distant and near fixation) or the Krimsky corneal reflex test. Abnormal head posture was noted at near and distance while the patient was fixating on a near accommodative target and an iPad at a distance. Eye movements were observed while tracking an object. The examiner sat in front of the child at a 1-m distance and held two toys >10 cm in size to test for saccades. Saccades were observed when the child was presented with the first toy and then the second toy was made to appear.

All children underwent manual cycloplegic refraction 40 min after dilation with cyclopentolate 1% and phenylephrine 2.5%, a slit-lamp biomicroscopy, and a detailed dilated fundus examination, including peripheral retinal examination, if possible.

All the participants were fully inspected for any obvious dysmorphic features, and the measurements and observations were recorded on a dysmorphology checklist.[18] A detailed report was given to all caregivers to improve the visual functioning of these children. Spectacles were prescribed to students with uncorrected refractive errors or those whose current spectacles were unsuitable.

Statistical analysis

This study research was analyzed utilizing IBM SPSS version 23 (IBM Corp., Armonk, N.Y., USA). Basic descriptive statistics were utilized to describe and sort out the study variables. The Chi-squared test was used to compare the categorical variables. While looking at two group means and in excess of two group means, an Independent t-test and one-way analysis of variance, with Least Significant Difference (LSD) as a post hoc test, separately was applied. These tests were finished with the presumption of normal distribution. Otherwise, Welch's t-test for two group means and Games Howell for the multiple groups were used as an alternative for the LSD test. Pearson's coefficient was used as a bivariate test to check the linear correlation of variables. In conclusion, a regular P < 0.05 was the criteria to reject the null hypothesis.

  Results Top

Demographic and clinical data

A total of 61 children were included in our analyses (mean [standard deviation] age, 7.4 [2.8] years; range, 3.0–14.8 years). Boys represented more than half of the sample (n = 41, 67%). Nineteen (31%) of the children were born by cesarean section; 55 (91.7%) were full term at delivery. Approximately 28% of the children had chronic illnesses, including epilepsy, heart diseases, asthma, chronic lung diseases, asthma/hyperactive airway disease, renal problems, and/or iron-deficiency anemia. A summary of the etiology of intellectual disability is presented in [Table 1].
Table 1: Summary of diagnoses in the sample

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Characteristics of the children

Fourteen children (23%) had dysmorphic features on examination. Nevertheless, only nine children had been identified with syndromic ID. Median systolic and diastolic blood pressures ranged from 80 to 125 mmHg and 40–90 mmHg, respectively. More than half of the children had normal height and weight according to the WHO growth population chart [Table 2].
Table 2: Summary of anthropometric measurements based on the World Health Organization population charts

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Ophthalmological and orthoptic evaluation

Ophthalmologists detected at least one ocular abnormality in 55 of the children. [Table 3] identifies selected ophthalmological variables comparing them between children with syndromic or non syndromic ID. The Welch's t-test showed that 41 children (67.2%) had a subnormal VA and this did not correlate neither with age nor gender. According to the WHO criteria, seventeen patients (27.8%) were suffering from mild visual impairment. Forty-one percent of the children were found to be functioning with vision at a level classifiable as moderate (n = 22) to severe (n = 3) visual impairment. Normal VA was only found in three of the examined patients (4.9%). The presence of dysmorphic features was significantly correlated with having subnormal VA (P < 0.001), significant refractive errors (P < 0.04 both eyes) and astigmatism (P = 0.036). Amblyopia was found in two children; however, 16 children (26.2%) did not cooperate to be visually assessed for amblyopia. Refractive errors were detected in 51.7% of the children and ranged from + 4.75–−14.25 in SE RE to + 5.625–−13.00 SE LE. High myopia (> −6.00 D) was detected in two patients (3.2%) and moderate myopia (−3.00–−6.00) in two cases (3.2%); testing revealed manifest exotropia in one of these patients. Astigmatism was found in 22 of the patients (36.7%), followed by hyperopia in 13 patients (21.7%), myopia in 10 (16.7%), and anisometropia in 5 (8.3%). Only two children were reported to wear glasses at the time of examination as per the caregivers. Eyeglasses were prescribed, and a follow-up was planned for 30 children (50%).
Table 3: Comparison of selected ophthalmological variables in 61 intellectually disabled children divided into syndromic and nonsyndromic

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According to Welch's t-test, myopia correlated positively with age (P = 0.013). Both VA (LogMAR) and refraction (SE) correlated with height (WHO chart). Lower VA (P = 0.002 RE and P = 0.004 LE) and myopic shift (P = 0.034 RE and P = 0.021 LE) were noted in shorter status individuals. Refraction was not found to correlate with gender.

The anterior segment anomaly noted in three patients included diffuse, bilateral corneal opacity, shallow anterior chamber, and blue sclera. All twenty children with a clear positive response to the stereo test had no misalignment on examination.

  Discussion Top

Uncorrected refractive errors and cataracts are the principal causes of vision impairment worldwide,[19] with up to 80% of all vision impairment considered avoidable.[20] Refractive errors have been identified as the major cause of vision impairment in the pediatric age group.[10],[13],[21] Previous researches[13],[21],[22] also showed that children with ID have a significantly increased risk of visual impairment and refractive errors. Vora et al.[22] evaluated 70 special needs children and 175 otherwise healthy children and reported that 58.5% of children with ID versus 2.9% of healthy children had refractive errors. In another report, 29% of children with ID had refractive errors.[23] We identified refractive errors in 51.7% of the participants, which falls within the range reported in studies conducted among children with ID.[22],[23]

In our study, 40.9% of the children had moderate-to-severe visual impairment based on the WHO criteria. Half of the children had uncorrected refractive errors. The most common disorders included astigmatism (36.7%), hyperopia (21.7%), myopia (16.7%), and anisometropia (8.3%). However, only two children were wearing corrective eyeglasses at the time of the study. Findings from a study of school children in Al Hassa (n = 2002), Saudi Arabia, showed that refractive errors were detected in 13.7% of the children examined myopia and hypermetropia were diagnosed in 9.0% and 1.4% of the students, respectively.[24] Another study that investigated the prevalence of correctable visual disorders in 5176 primary school children in the Eastern Province of Saudi Arabia reported that refractive errors were detected in 16.3% of the students.[25] In a study of 3–10 years old children enrolled in schools across western Saudi Arabia, uncorrected refractive errors were reported in 34.9% of the cases.[26] Astigmatism, anisometropia, hypermetropia, and myopia were diagnosed in 25.3%, 7.4%, 1.5%, and 0.7% of the children, respectively. As expected, the frequency of vision impairment in otherwise healthy children in studies conducted in our region is lower than that reported among children with ID in our study. However, the relatively high frequency of refractive errors in those studies may be due to the lack of national implementation of vision screening programs.

Preferential looking techniques, fixation preference tests, or picture charts are used to estimate VA in young children and disabled persons.[27],[28] These tests are reliable when appropriate diagnostic criteria are applied, as most children with amblyopia are identified.[29] They can therefore be used as an alternative or in conjunction with tests of fixation preference during the assessment of children who cannot complete optotype acuity tests. VA could be reliably assessed in this study due to the children's high level of cooperation. The good degree of cooperation (74%) was possible because examinations were undertaken at schools, thereby facilitating acceptance by the students. Furthermore, during the assessments, a caregiver who knew the child well accompanied each student. These circumstances differ considerably from those in general ophthalmological or optometric practices, where cooperation and success rates are lower in children with learning disabilities.[30] In an unfamiliar setting, children with special needs may become confused or frightened, making ocular examination challenging. The situation is additionally compounded by the children's difficulties in communicating properly. Researchers have also emphasized the importance of the presence of caretakers during the eye examinations of persons with learning difficulties.[31] Besides preparing the patients for the visual assessment, caretakers also provide valuable information regarding each patient's capabilities.

We found that myopia correlated positively with age. In addition, our analyses revealed that both VA and refraction correlated with height. Previous studies conducted among school children also reported a positive correlation between myopia and age,[32],[33],[34] although these studies were not specifically conducted in children with ID. In one report,[32] the incidence of myopia was reported to increase with age children aged 11 years old represented the highest risk group. In another study that assessed the relation between axial ocular dimensions and age, gender, height, and BMI, Roy et al.[34] found that hypermetropic children had a significantly higher BMI than their peers with myopia. However, we found no such correlation between BMI or weight and hypermetropia.

Data on the relationship between VA and stature are scarce, especially in children with ID. In this study, subnormal vision was significantly worse in participants with short stature rather than those with normal stature. Furthermore, myopic shift was significantly greater in participants with normal stature than their peers with short stature.

Studies evaluating visual impairment in persons with visual disability reported that the patient's age, type of ID, and severity of mental disability were associated with an increased risk of visual disorders.[6],[35] Attempts to compare syndromic versus nonsyndromic subgroups have, in most cases, been impossible due to the small sample sizes in these studies, as was the case in our report. The first large-scale study to compare these two subgroups reported that children with syndromic ID were significantly more likely to have a higher incidence of nystagmus and refractive errors.[36] In our analysis, of the nine children who met the definition for syndromic intellectual disability, we identified refractive errors in five with Down syndrome and two with genetic mutation. The prevalence of poor VA and myopic shift was higher in children with syndromic ID. However, our sample size did not permit us to make relevant conclusions.

The main strength of this study is that most of the participants were very co-operative during examinations, and this can be attributed to the fact that vision screening took place in their familiar environment. In addition, we used standardized protocols to decrease inter-examiner discrepancy. To our knowledge, this is the first study that reports full ophthalmologic and orthoptic findings in a group of intellectually disabled children with a detailed medical background. Nevertheless, this study has some limitations that merit discussion. First, our study is a noncomparative, cross-sectional study; therefore, it had all the limitations inherent to these types of study designs. Second, due to the limited number of patients in this study, caution should be exercised when interpreting our results. In addition, because our study is based on a selected and small sample, we cannot apply good statistical evaluation and compare our findings with the general population.

  Conclusions Top

The pediatric population with ID has a high prevalence of preventable visual impairments, refractive errors, and strabismus. Our study has clearly demonstrated the need for and the value of assessing comprehensive visual functions of children with special needs. Nonetheless, a larger study would be required to obtain a more accurate estimate of the prevalence of visual diseases among children with ID in our region. The already available eye services in Saudi Arabia should be utilized to implement mandatory vision assessment, appropriate care management to improve these children's quality of life.


The results were not presented at any meeting. The authors would like to thank all the children and their families for participating in the study. We would also like to thank all the staff at the special needs schools for their invaluable help during the research.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2], [Table 3]


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