Dr. Neha Chandak, C17537, Dr. Shreya Jaiswal, Dr. Sachin Daigavane, Dr. Shashank Banait
Introduction:
Vision plays a fundamental role in the acquisition of skills such as language, interpreting facial expressions, and skills requiring hand–eye coordination.[1]Uncorrected vision affects the emotional, social and cognitive development of a child and also adds to the socio‑economic burden on the family members.[2-4]
Many studies have assessed ocular and visual disorders in mentally retarded adults. However, assessment of ocular disorders in children is challenging, requires great deal of patience, and a broader range of instruments. In a study in Mangalore, India, the prevalence of mental retardation in children was identified as 3 per 1000 in rural area and 5 per 1000 in urban area.[5]Despite the magnitude of the problem,the parents of these children are unaware about the disorders and many of these children never have a visual examination.
The presence of more than one disability in an individual can have a multiplicative rather than an additive effect on their life experience.[6]A stormy perinatal period contributes to many medical disorders in children, which may include ocular disorders.[7-9]Therefore, this study was carried out with the aim to identify the ocular disorders in children with mental retardation attending special schools in a district in central India and to study their relationship with degree of retardation.
Methods:
This prospective, interventional study was carried out inall children <16 years inspecial education schools for children with mental retardation in a district in Central India. The study was approved by the ethical committee of the hospital. The principals were sent a letterproposing the ocular examination of all children. Parentswere informed in advance and were requested to be present on the day of examination with all the previous medical records.Consent was signed by the parents or guardians for the examination ofthe child. Children whose parents did not give consent, deaf/mute children and those children who did not undergointelligence quotient(IQ) testing, were excluded from the study.
Ophthalmologists (senior and resident), 2 optometrists, and a social worker are included in the team.Examination process was explained to the teachers. Teachers and parents were asked to notify the team if they had noticed any of the following: child holding his/her work very close or sits close to the blackboard; squint; drooping eyelids;red eyes; habitual eye rubbing or poking; white spots in the eyes; history of night blindness; had spectacles that had been prescribed previously or any other eye health problem.
The diagnosis of mental retardation was based on Diagnostic and Statistical Manual of Mental Disorders (DSM)‑4 diagnostic criteria and the IQ was assessed using Binet‑Kamat method at the government medical college, which was the official certifying authority.[10]Prior to the examination in school, child’s name, age, sex, address, antenatal and perinatal (details of birth, delivery, major medical events at the time of birth) history, family history,known systemic disorders (cerebral palsy, epilepsy, Down’s syndrome, speech disorders), ocularcomplaints, previous refractive error and Intelligence Quotient (IQ) were noted.
External ocular examination was carried out in diffuse illumination with a torch light. Head posture, facial anomalies,and ocular motility were noted. Orthoptic examination wasperformed using Hirschberg’s reflex and if this was abnormal,
cover/uncover tests were performed. Visual acuity for distance was tested
monocularlyon Snellen’s chart in the language (English, Hindi)which the child was comfortable with. Landolt’s “C”chart was used in children who could not read. Kay picture chart was used for more disabled children.
Cycloplegic refraction was done in children whose visual acuity was less than 6/9 in either eyeusing 1% cyclopentolate or 1% Tropicamide eye drops (only in children with no history of seizures), with Automated Refractometer and Heine’s streak retinoscopy. Subjective refraction was done in all children who were co-operative and responsive. If subjective refraction was not possible, the prescription was given based on retinoscopy findings. Uncooperative children needing special examination were referred to the hospital for detailed examination. Refractive correction was prescribed for all children who required a myopic correction of ≥ −1.0 diopter (D), hypermetropic correction of ≥+3.0 D, and/or astigmatism of ≥0.5 D cylinder (C). Dilated ophthalmoscopy was performed in children with visual acuity <6/12 in either eye with adirect ophthalmoscope.Children whose visual acuity did not improve to 6/18 were termed visually impaired and those whose vision did not improve to 6/60 in thebetter eye were classified as severely visually impaired. Children with signs of vitamin A deficiency, ocular surfaceinfections, and hordeolae were treated medically. The need for low-vision devices and importance of environmental modification, especially in relationto contrast and colour, was explained to the parents.
The data were entered in an excel sheet [Statistical Package for Social Sciences (SPSS) software, 17.0) and was subjected to statistical analysis. The ocular problems were categorized according to IQ. Fisher’s exact was used to study the strength of association between ocular problems and mental retardation. An association between the common ocular problems encountered in the study and the severity of mental retardation was studied by Chi‑square test for the linear trend. A pvalue less than 0.005 was considered significant.
Results:
Of the 186 mentally retarded children in special education schools, 87 children (46.7%) had ocular problems.
52 children had mild mental retardation and 16 children (30.7%) had ocular problems.102 children had moderate mental retardation with ocular problems seen in 49 children (48%). Students having severe mental retardation had more ocular problems [19 out of 28 (67.8%)]. Table 1 depicts the distribution of IQ scores along with the number of children having ocular problems. For finding the association between severity of mental retardation and ocular morbidity, children with profound mental retardation were included in the severe mental retardation group for analysis as their number was small (3/4). Significant statistical association was
found between the severity of mental disability and ocular morbidities (p value= 0.00172). The risk of getting ocular morbidities among the severe and profound mentally retarded children was 3.76 times higher as compared to mild mental retardation group. However, no association was seen between the level of mental retardation refractive error (p value=0.63) and the strabismus (p value=0.33).
A history of perinatal insult was seen in 46 (52.8%) children.
Table 1: Association between severity of mental retardation and ocular disorders
| Intelligence Quotient | Total number of children | Children with ocular problems (%) | p value | Odds Ratio |
| Mild (50-69) | 52 | 16 (30.7) |
0.00172 |
1.03 |
| Moderate (35-49) | 102 | 49 (48) | 1.82 | |
| Severe (20-34) | 28 | 19 (67.8) | 3.76 | |
| Profound (<19) | 4 | 3 (75) | ||
| Total | 186 | 87 (46.7) |
The distribution of IQ scores along with the number of children having ocular problems is presented in Table 2. Refractive error (41.3%) and strabismus (19.5%) were the most common ocular problems seen in these children. We came across 3 profoundly mentally retarded children with ocular problems, of which 1 child had optic atrophy,another 1 had anophthalmos and 1 had ptosis.Myopia was a common refractive error seen in 20 children (55%), followed by hypermetropia in 9 children (25%), andastigmatism in 13 children (36%).Only 2 children were found to be wearing spectacles at the time of examination.
Table 2: Distribution of ocular disorders
| Grade of mental retardation | ||||
| Ocular problem | Mild | Moderate | Severe | Profound |
| Refractive error | 7 | 21 | 8 | – |
| Strabismus | 3 | 10 | 4 | – |
| Nystagmus | 1 | 3 | 2 | – |
| Cataract | 1 | 4 | 1 | – |
| Optic atrophy | 1 | 2 | 1 | 1 |
| Congenital anomalies | 1 | 2 | 1 | 1 |
| Corneal dystrophy | – | 1 | – | – |
| Retinal dystrophy | – | 1 | – | – |
| Ptosis | 1 | 2 | – | 1 |
| Vitamin A deficiency | 1 | 1 | 1 | – |
| Dacryocystitis | 0 | 1 | 1 | – |
| Hordeolum | 0 | 1 | – | – |
| Total | 16 | 49 | 19 | 3 |
Systemic conditions seen in these children are reported in Table 3- Epilepsy in 28 children, cerebral palsy in 15 children, Down’s syndrome in 11 children, and speech disorders in 6 children. Children with Down’s syndromehad highest proportion of visual impairment, 5 of 11 children (45%).
Table 3:Ocular conditions in mentally retarded children with systemic conditions
| Ocular problem | Epilepsy | Cerebral Palsy | Down’s Syndrome | Speech disorders |
| Uncorrected VA < 6/60 | 4 | 2 | 5 | 1 |
| Refractive error | 9 | 6 | 2 | 2 |
| Strabismus | 6 | 3 | 1 | – |
| Nystagmus | 2 | 2 | 1 | 1 |
| Cataract | 1 | 1 | 1 | – |
| Optic atrophy | 4 | 1 | – | – |
| Dacryocystitis | – | – | – | 1 |
| Others | 2 | – | 1 | – |
| Total | 28 | 15 | 11 | 6 |
Discussion:
Children with mental retardation have emerged as a group with a need for ophthalmologic assessment. Nearly half the children (46.7%) in this study had
ocular disorders and only 2 of 36 students with refractive errors were found to be
using spectacles.
Measurement of visual acuity in these special children was a challenge and required patient observation of their eyes, visual attention and fixation. The key was to use intellectual age appropriate visual acuity measurement tests. The evaluation of visual correction in children with moderate and severe learning disability was a big challenge.[11,12]
This study shows a high prevalence of ocular disorders (refractive errors, strabismus and nystagmus) among these children which is in concordance with several other studies.[12-16]Myopia was the common refractive error followed by astigmatism and hypermetropia respectively. A study from Pune showed that 45.3% children had ocular disorders, 27.3% had uncorrected refractive errors followed by strabismus in 15.8%, nystagmus in 6.8%, optic atrophy in 6.5%.[12] Another study from Nagpur demonstrated that out of 241 children examined, 124 children (51.5%) had ocular problems. Out of that refractive error contributed to 49.3%, strabismus 24.1%, and nystagmus 6.9%. Myopia was the commonest refractive error followed by hyperopia and astigmatism.[16]In a study done in Nepal, refractive errors were found in 34.4%, the most common type being hypermetropia.[15]A significant number of children with learning disabilities had visual impairment only because they had not had a formal eye assessment.
The foreground of the study was the significant correlation between severity of mental retardation and ocular morbidity suggesting high risk of getting ocular problems in severely mentally retarded children. However, no correlation was seen between the level of mental retardation, refractive error and strabismus.
In our study, 52.8% children with a known history of perinatal insult had some ocular disorder. Thus,children with abnormal perinatal history were more likely to have ocular and visualissues even in mentally retarded ones.
Children with epilepsy had a high prevalence of refractiveerrors and strabismus, as did those with cerebral palsy and Down’s syndrome, similar to the results in a study from Pune.[12]
The cooperation of school staff and parents establishing a good rapport between the child and the examiner was the keystone of the assessment. Sufficient time was devoted for the examination of all children, more so in children in the grade of moderate and severe mental retardation. The study alsogave us a platform for raising awareness levels in the specialeducators and parents.
The drawback of the study is that, only children admitted to the special school for mental retardation were examined.Long-term follow-up of these children is necessary to note the visual improvement after refractive correction. Near vision and accommodative reserve could not be measured. There could be a recall bias in recollecting the perinatal insult, butthe chances seem minimal as the data wascollected at the time of admission of the child to the special education school and based on the medical records which were well-preserved by the parents.
Conclusion:
Children with mental retardationare often given insufficient ophthalmic careand the irony is that many of these children never even have an ophthalmic examination. Therefore, they should be assessed as soon as the child is admitted to the school and then an annual ophthalmic examination should be performed.Earlier assessment andcorrection of visual problems could prevent unnecessary visual impairment and providemaximum potential for the development of the child.
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