Annals of African Medicine, Vol. 10, No. 1, January-March, 2011, pp. 29-33
Ophthalmologic abnormalities among deaf students in Kaduna, Northern Nigeria
ER Abah1, KK Oladigbolu1, E Samaila1, H Merali2, AO Ahmed3, TH Abubakar4
1 Department of Ophthalmology, Ahmadu Bello University Teaching Hospital, Shika-Zaria, Nigeria
Correspondence Address:E R Abah, Department of Ophthalmology, Ahmadu Bello University Teaching Hospital, Shika-Zaria, Nigeria, email@example.com
Code Number: am11006
AbstractBackground : The association between deafness and ocular problems is well established; however the nature and prevalence of these problems are diverse across the globe.
Objective : The aim of this study is to determine the nature and prevalence of ophthalmologic abnormalities in deaf students and offer treatment to those with remediable conditions.
Method : Six hundred and twenty deaf students aged between 5 and 38 years were examined in a school for the deaf.
Results : One hundred and thirty (20.9%) had some form of ophthalmologic abnormality. Some had anterior segment abnormalities such as corneal opacities (0.5%) and allergic conjunctivitis (3.4%) while others had posterior segment abnormalities like optic atrophy (0.3%), Waardenburg syndrome (0.6%) and Ushers syndrome (0.6%). Refractive error was the most common (7.9%).
Conclusion : Since these deaf students use their sight to compensate for the deafness, routine ophthalmologic examination should be carried out on them so that ophthalmologic abnormalities are detected early and treatment offered for remediable diseases.
Keywords: Deafness, ophthalmologic abnormalities, visual screening
A strong link has been established between the functions of the various organs of sensation, particularly between the eyes and ears. This is not uncommon since the retina and the cochlea develop from the same embryonic layers during the 6 th and 7 th week of gestation. Many researchers in the past also presented specific links between these sensory modalities and dysfunctions, particularly between deafness and ophthalmologic problems.
The prevalence of ocular abnormalities among deaf children has been reported to vary from 33 to 60%. ,,,, Globally, these range between 23% (in Nepal);  33% (in Perth),  40.4% (in Turkey),  and 48% (in USA).  In Nigeria, a prevalence of 22.2% was found in a conventional school population in Western Nigeria.  Many researchers have also reported high incidence of ophthalmologic abnormalities among deaf students, compared with hearing population of the same age (44-45% and 17-30%), respectively.  In other related studies, it is established that ocular problems are generally more common in children with hearing problems than in normally hearing  children.  In West Africa, deafness is a common health problem often associated with three major preventable infectious conditions; namely measles, meningitis and rubella. 
Sight is the main sense used to compensate for deafness even though some knowledge is acquired via tactile and olfactory senses.  Therefore, visual screening is very critical for those with irreversible deafness to facilitate early detection and treatment of ocular problems. These are the best assurances for the maximum possible social and professional adjustments for the deaf.  Those with non-correctable and non-treatable visual disorders also require multiple environmental adaptations and appropriate support services.  Routine ophthalmologic screening of the deaf school (as in this study) is necessary to reduce the needless deaf-blind population. This study is therefore undertaken to determine the ophthalmologic abnormalities in deaf students in Kaduna with a view to providing appropriate solutions to treatable abnormalities, and to manage those that are not immediately curable.
Materials and Methods
A cross-sectional study of 620 deaf students of Kaduna State Special Education School ranging from nursery to senior secondary school.
All the deaf students attending the Special School for both deaf and blind  were included in the study. Those students who were absent at the time of the study were excluded.
Clearance to conduct the study was obtained from the Kaduna State Ministry of Education through the school principal and the cooperation of the teachers was sought and some were trained in vision screening. Consent was given by the students. The teachers also helped in explaining the questionnaire to the students.
The study team consisted of three ophthalmologists, one otorhinolaryngologist, a student from College of Medicine, Harvard University USA, and a sign language expert from the Special School.
The students were assessed within the school premises, with their school teachers near them, using a modified screening protocol for visual impairments in children who are Deaf/Hard of Hearing (developed by the Georgia Deaf-Blind Project  USA). They were examined with a teacher nearby and they responded by sign language, which was interpreted by the teachers, or by sign and oral communication in a few.
All the students had systemic examination. The ophthalmic assessment included acuity checks for distance (6 m) and near (33 cm) using the illiterate E-chart, a form of Snellen′s line test for distance, and reduced Snellen′s illiterate chart for near, respectively. Anterior  and posterior segments of the eye were examined by one  of the three ophthalmologists. They had their intraocular pressures measured using a hand-held applanation tonometer (Perkins) where indicated.
Students with poor/subnormal night vision had dark adaptation test. This was conducted by the teacher using sign language in bright illumination and then repeating same after 30 minutes in the dark taking note of misinterpretations.  Those who failed the dark adaptation test and those with abnormalities requiring further examination of the posterior segment all had a dilated fundoscopy. 
Colour vision testing (Using Ishihara Chart) was conducted on all the students.
Refraction was done for those with visual impairment that improve with the use of pinhole.  Difficult refractions especially in the younger age group were referred to a tertiary health facility for further management.
All the children had comprehensive ear examination conducted by an Otorhinolaringologist and drugs were administered to those with treatable eye disease.
A total of 620 deaf students were examined. Their age range was 5-38 years with mean age of 15.7 years + 3.9 (SD). There were 373 males and 235 females, 61.3 and 38.7%, respectively (M : F=1 : 0.6) [Figure - 1].
Those who had no visual impairment for distance in the better eye accounted for 97.8% [Table - 1]; none of the children had impairment of near vision. 
The prevalence of ocular abnormalities in this study population was 20.9%. [Table - 2] shows the ophthalmologic abnormalities. The frequency of refractive errors (7.9%) was higher than other abnormalities.
Hypermetropia was the leading refractive abnormality. Conjunctivitis was also common and predominantly allergic. Some children had color vision deficiency most of which were Blue-Green color defects. Five children had congenital ptosis. Two had optic atrophy secondary to trauma out of which one had exotropia. Five others had squint out of which four were congenital but one due to hypermetropia (convergent squint).
Three students (0.5%) had corneal opacities out of which two followed childhood measles complication while one was due to injury. Four (0.6%) students had iris heterochromia, threebilateral and one unilateral. They also had white forelock hair and together with the deafness were presumed to have Waardenburg syndrome. [Figure - 2],[Figure - 3],[Figure - 4],[Figure - 5]
Similarly, 4 students were part of the 35 (5.6%) of the students that failed the dark adaptation test. They were presumed to have Usher′s syndrome. Twelve children had vertical cupdisc ratio >0.5 out of which 5 had IOP >20 mmHg. These were Glaucoma suspects.
No students  had the typical salt and pepper fundus of congenital rubella. Majority of the students (74.8%) had sensorineural hearing loss. The interventions included the provision of spectacle correction for 18 students out of the 49 that had refractive errors, 30 students were given drugs for both bacterial and allergic conjunctivitis and 32 were referred for tertiary ophthalmic care [Table - 3].
The prevalence of ocular abnormalities in this study population was relatively low  (20.9%) among deaf school students in Northern Nigeria compared to previous studies reported to vary from 33 to 60%. ,,,, The prevalence of ocular abnormalities among deaf children in studies around the globe included the Turkish School for the deaf, 40.4%;  Deaf School, Kathmandu, Nepal, 23%;  Oregon School for the deaf (USA), 48%;  and Princess Margaret Children Hospital Perth, 33%.  This is close to the Kathmandu deaf school study and comparable to what was found in conventional school population of Western Nigeria.  Findings in the developed countries are higher. The relatively high finding in the Western world is most likely attributable to the investigative procedure employed (for example, all the children in the Oregon deaf school study had electroretinogram). This means that even more subtle abnormalities were detected, hence the higher incidence.
The most common ocular abnormality in this study was refractive error (7.9%). Among these, hypermetropia was the commonest (1.9%) while myopia and astigmatism were 1.1 and 0.9%, respectively. In a review of 49% patients with  sensorineural hearing loss in tertiary care, University California, San Francisco, USA, found hypermetropia to be the most common abnormality,  similar to the findings of this study. However, a conventional school screening in India found myopia to be the commonest, followed by hypermetropia.  These eye screenings in both conventional and deaf schools have found refractive error to be a very common cause of ocular morbidity,  which can be readily managed with spectacle correction. The need for routine school eye screening in both conventional and special schools was thus re-emphasized. Moreso  says that the deaf child requires visual compensation for the deafness to prevent a needless deaf-blind  situation.
Sensorineural hearing loss was found to be the commonest in this study and this can be related to the neuro-embryonic origin for both hearing and sight.  It is also for similar reason that ocular auditory syndrome  that have been defined in other reports were also found in this study. They include Usher syndrome type I (congenital deafness, balance difficulties, late walking and retinitis pigmentosa) and Waardenburg syndrome (abnormal pigmentation of skin and hair, dystopia cantorum and ectopic lacrimal punctum).
Although rubella retinopathy was the most common retinal finding in previous reports,  none was detected in this study. This is probably as a result of limited number of students who had dilated fundoscopy, although the incidence of congenital rubella syndrome in Nigeria is remarkably low (54/100,000 live births).  Other ocular abnormalities found were allergic conjunctivitis (3.4%), glaucoma suspect (1.9%), bacterial conjunctivitis (1.5%), Ptosis (0.8%), optic atrophy (0.3%), squint (1.0%) and corneal opacities (0.5%). Similar findings were found elsewhere. ,,,,
Visual abnormalities in deaf students are remarkable in Northern Nigeria (20.9%). Their association with other neurologic/sensory deficits such as deafness appears well established.  The situation in a developing country like Nigeria continues to challenge the country′s socio-economic framework. It calls for an urgent need for improvements in general health services, particularly routine early screening by teachers for the blind who should be trained for continuous screening exercise. This will facilitate early detection of eye/other neurologic diseases. This is to ensure there is none that is needlessly deaf-blind, and to enhance visual compensation for the hearing loss.
Copyright 2011 - Annals of African Medicine
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