the ethical and research committee of al noor association for the blind approved this study . as case records
were reviewed without disclosing the identity of the participants , we did not obtain written consent of parents .
field investigators were optometrists and ophthalmologists trained in vision assessment and working for the school health department .
findings in cover - uncover test , ocular movements in nine cardinal positions of gaze , saccades , and nystagmus were recorded .
if reflection of light corneal reflex was not center while the child was looking straight at far distance , it was considered as strabismus present . if it was turned inward , strabismus was of ecotype esotropia , and if it was deviated outward , strabismus was of exo type exotropia . if the deviation of eye was in vertical direction , the strabismus was of hyper or hypo type hypotropia .
if eyes were moving rapidly involuntarily , nystagmus was present . while tracking an object , the movements of eyes of the child were observed . to test for saccades ,
the examiner sat in front of the child at 1 m distance and held two toys of > 10 cm in size .
the child was asked to see from one toy to another and his / her eye movements were observed . to grade the saccades
we noted the ability to complete round trips in following two objects , ability of the child to accurately and consistently fixate objects and presence of head and body movements during saccade testing .
we referred age and sex of the child and minimum score for testing saccadic eye movements to define normal and defective saccades .
the anterior segment of the eyeball was examined with a flashlight to detect abnormalities of eyelid , conjunctiva , cornea and lens and pupillary reaction to the light was recorded .
homatropine 2% was used for cycloplegic refraction using a direct retinoscope ( heine , germany ) .
children who needed new spectacles were assessed for their visual functions on the subsequent visit scheduled after 1 week .
myopia was defined as mild ( 0.75d<2d ) , moderate ( 25d ) , and severe ( > 5d ) .
hypermetropia was graded for spectacle prescription if it was more than + 0.75d without esotropia . the value of astigmatism of < 2d was transposed into spherical equivalent . while prescribing re corrections ( distance and near ) , we considered child 's age , systemic condition , and accommodation values .
myopia of > 1.00d , hyperopia of > 1.00d , and astigmatism of > + 1.00d were registered and corrected if relevant within the child 's visual and cognitive sphere .
weak accommodation was supported with appropriate near vision correction to allow age appropriate near vision tasks . visual acuity for near
was recorded with the help of lea symbols near vision test card ( good - lite , usa ) .
the card was held at the standard 40 cm distance from the eyes . if the child preferred to keep the card at other than the 40 cm distance , the distance used was noted for calculation of visual acuity values . if a child was unable to respond to the lea symbols card , responses to lea gratings paddles were recorded in a preferential looking situation at distances from 50 to 100 cm . to assess for distance visual acuity
if the child could not recognize any symbol in the top line of the chart , the test was repeated at 1.5 m distance and even closer .
log value ( 0.02 ) of each optotype of a line was considered while determining distance visual acuity of each eye .
low contrast visual acuity was assessed with the lea symbols low contrast test with symbols of 10 m size .
this test was performed only for children who responded to the distance vision using full contrast lea symbols chart . for children who responded to lea gratings , the hiding heidi low contrast face test was used for assessment of communication distances . if there was more than three line difference in distant vision reading between 100% and 2.5% contrast chart , we considered the contrast test as defective .
the child was first shown the pilot colored disc and then explained how to match with the other one disc that has nearly matching color .
the test was repeated to complete all 16 disc color identification . on completion of the task
the disc was reversed , and numbers on the back of color discs were recorded .
the confusion between color shades was revealed by an altered sequence of the numbers even after repeating the test .
if there was a consistent jump of more than two serial numbers , we considered color vision of the child as defective . motion perception was observed using the figure - in - motion pepi test on the computer screen .
to attract child 's attention , red and white moving strips were shown in the center of the screen . then the figure - in - motion pepi target was displayed .
children 's eye movements were observed during the test : quick saccades to the corners of the screen where the figure appears and slow following movements diagonally across the screen , after which they were asked to name the moving object ( any animal with four legs was recorded as a correct description ) and to show the directions of movement . for children with communication problems , eye movements following the moving target were used as the correct answer .
the test was repeated for those children who were either totally inattentive or failed to follow the moving target although they fixated the central target .
inability to track the moving dog on computer screen in any one of four directions was labeled as defective motion perception .
early visual processing functions ( in occipital cortex ) were tested using three tests : ( 1 ) mailbox test ( good - lite ) was used to evaluate the visual recognition of direction of lines and objects for eye - hand coordination .
( 2 ) rectangles test ( good - lite ) was used to evaluate child 's ability to perceive differences in size and to use that information for eye - hand - coordination .
one set of the rectangles was placed in front of the child and he / she was asked to place a rectangle from the other set on a rectangle of similar size on the table or , if unable to use hand movements , was asked to point to the similar rectangle with gaze .
( 3 ) heidi expressions testwas used to test children 's ability to perceive and match pictures with different facial expressions at different contrast levels . for details of visual functions testing
, we referred to the relevant chapters of book for low vision testing and the detailed instructions of the tests .
if the child was unable to correctly perform any of the above - mentioned tests , we considered that child 's higher visual functions were defective .
we used epidata ( data management and basic statistical analysis system , odense , denmark ) to enter the data .
the univariate data analysis using parametric method was carried out using software called statistical package for social science ( spss 23 , ibm , new york , usa ) .
teachers and parents were advised to adjust the environment of the child to meet each child 's needs .
the outcomes of this study were discussed with the institutions in charge of the care and education of children , and timely follow - up was recommended .
children were referred to the low vision unit of the eye health care program , ministry of health in muscat by the school or the day care centers for further evaluation .
the cohort was of 321 children that were referred from 32 centers for disabled children .
the age range of children was 38 years and the mean age 8.7 years ( standard deviation 4.39 years ) .
based on the principal clinical diagnosis by the child 's pediatrician , the participants were grouped into ( 1 ) children with down syndrome ( ds )  61 ( 19% ) , ( 2 ) children with intellectual disability ( i d ) but without ds  72 ( 22.4% ) , ( 3 ) children with impaired hearing  67 ( 20.9% ) , and ( 4 ) children with other conditions ( other )  121 ( 37.7% ) . the group 4 included 8 children with aphakia , 31 with retinal conditions , 13 with microcephaly and cerebral palsy , 11 autistic children , 16 spastic children , 28 children with delayed general development , and 9 children with a syndrome affecting eyes .
strabismus was in higher proportion ( 26 out of 121 ) in children with ocular morbidities ( group :  other  ) resulting in strabismic amblyopia in 1 eye in 121 children .
although ocular movements were affected in 12 children with low vision disabilities in this cohort , there was no specific pattern by the groups .
problems in ocular motor functions of children with other disabilities twenty - five ( 41% ) children with ds were using spectacles ; in two cases , the spectacles were changed as the lenses had significant scratch marks .
twenty children were myopic ( 15 of them with 5d9d myopia ; 5 with moderate myopia [ 2d5d ] and 6 were hyperopic [ 1d2d ] ) .
visual functioning in different groups is displayed in table 2 . in nine children with ds , values of distance vision were lower than values of near vision with full correction .
low accuracy of measurements of the field of vision using the arc perimeter was found especially among children with low intelligence quotient ( iq ) .
problems in visual functions of children with other disabilities a large number 69% ( 77/111 ) of children in low vision group due to other causes , had problems in their visual functions .
spectacles were the most often prescribed low vision device ( lvd ) in the group of children with  other causes ;  seven children were tested for and then provided filter lenses . nearly , one - fourth of children in this group with a single disability affecting eyes ( other group ) , were prescribed telescopes to explore distant objects .
this is a large series of visual functions and low vision care of the children with special needs .
the largest group of vision - impaired infants and children with the need of early intervention and special assessments and support is to be found among children with other more visible disorders among the children with special needs .
although each child is an individual for providing low vision care , an attempt was made in this study to categorize the outcomes based on other morbidities the child had .
our study has clearly demonstrated the need for and the value of assessing comprehensive visual functions of the children with special needs .
however , it was evident that it may not be possible to assess all visual functions in all children .
the provision of low vision care improved the visual functions of many ( 58/321 ) children .
therefore , findings of our study are likely to be accurate and less affected by measurement bias
res ( 26 ) , especially high myopia ( > 5d in 15 children ) , were the single most common finding in children with ds ( 51 ) .
adio reported that 76.2% of 42 ds children had re higher than 5d in nigeria .
in contrast , mohd - ali et al . in malaysia reported that only 30% of 73 children with ds had re higher than 5d .
strabismus and nystagmus among children with ds in our study were lower than that reported by karlica et al . and ljubic et al .
lower proportion of hyperopia and already using spectacles in a large number of children with ds perhaps could explain less cases of strabismus in our study .
accommodative insufficiency is often found in children with ds . in this study , we found 23% of children with ds having accommodation lag .
undercorrection of myopia and provision of the addition of near vision correction were , therefore , important for these children . with increasing age , many children with ds show changes in accommodation power .
the children with low iq but without ds were difficult to assess as their attention span is short and test is often time - consuming . interpreting the assessment outcomes and intervention , therefore ,
the importance of assessing visual functions in children with hearing impairment is stressed in the literature .
only children with hearing impairment and multiple disabilities who did not attend the school were assessed .
it is worth to note that we did not find a significant deficiency in visual functioning in children with hearing impairment in the present study .
contrast sensitivity which is usually affected in ushers syndrome was noted in 13% of children with hearing impairment only in our study .
normal interpretation of facial expressions was not present in more than one - third of children with hearing impairment . in 15% ( 5/34 )
correction of res ( 42/67 ) and providing more illumination to 10/67 children with hearing impairment compensated poor contrast sensitivity .
the group with  other causes  of visual disabilities mainly included pathologies like retinitis pigmentosa , autism , developmental delay , cerebral palsy , and spastic children .
poor distance and near vision were present in more than half of children in this group .
use of telescope , filter , and magnification were useful for some children of this group .
the visual functioning of children with other disabilities show great variation and thus are difficult to group .
information from teachers , parents , and caregivers at day care institution is important for assessing visual functions .
while performing an assessment , clues could be noticed for suggestions that might be helpful in early intervention and education .
 background : we assessed the visual functioning of the children with special needs in oman between 2009 and 2012 . 
 we present the methods of assessing different visual functions , outcomes , and interventions carried out to improve their functioning.methods:optometrists assessed visual functions of children of  day care centres  in oman . 
 experts further assessed them and provided low vision care . 
 ocular movements , refractive corrections , near , distance , contrast color , motion , field of vision , and cognitive visual function test results were noted . 
 feedback to caregivers was given to improve visual functioning of these children.results:we grouped 321 participants , ( 196 [ 61.1% ] boys , age range of 318 years ) into 61 ; down syndrome ( ds ) , 72 with intellectual disabilities ( ids ) , 67 ; hearing impaired and 121 with other conditions . 
 refractive error and lag of accommodation were 26 ( 42.6% ) and 14 ( 22.6% ) among children with ds . 
 contrast sensitivity was impaired in 8 ( 12.7% ) among hearing impaired children . 
 defective distant and near vision was in 162 ( 70% ) and 104 ( 42% ) of our cohort . 
 children with i d were most difficult to assess . 
 children in a group of other disabilities had a higher proportion of impaired visual functioning . 
 they were given low vision aids ( telescopes [ 22 ] , filters [ 7 ] , and magnifiers [ 3 ] ) in large numbers compared to those in other groups.conclusions:visual functioning of children with other disabilities show great variation and difficult to group . 
 the care , therefore , should be at individual level . 
 all visual functions can not be assessed at one time . 
Methods
Results
Discussion
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