Original Article

International Journal of Audiology 2004; 43:172–176

Double disability: the hearing-impaired

blind in the Sultanate of Oman

Doble discapacidad: hipoacúsicos ciegos en el

Sultanato de Omán

Rajiv Khandekar*Mazin Al Khabori†

*Eye and Ear Health Care Program,†Department of Otolaryngology,Head and Neck Surgery andCommunication Disorders. Al Nahdha Hospital, Ministry of Health, Sultanate of Oman

Key WordsDouble disabilityHearing impairedBlindEpidemiologySurvey

AbstractA survey to estimate the magnitude and causes of blind-ness and hearing loss was undertaken in Oman in1996–97. An analysis correlating blindness with hearingloss is presented. Twenty-eight subjects among 11 400examined had double disability, with a prevalence rate of2.46/1000 (95% CI 1.55–3.36). Females and older agegroups had a higher risk of double disability than didmales (relative risk (RR) 3.95, 95% CI 1.34–8.1) andyounger age groups (RR 9.91, 95% CI 3.9–21.2). Twenty-five per cent of subjects with double disability had cur-able blindness, while 33% had preventable blindness.Only 10% of subjects with double disability had curablecauses of hearing loss. The number of cases with doubledisabilities in Oman might decrease, due to the improvedhealthcare in last two decades. However, the increase inthe aging population necessitates intervention to preventdouble disability. An emphasis on the prevention ofblindness could address the problem more effectively.

SumarioSe realizó una encuesta para conocer la magnitud y lascausas de ceguera e hipoacusia en Omán en 1996–97. Sepresenta un análisis de correlación entre ceguera e hipo-acusia. Veintiocho sujetos de los 11400 examinados pre-sentaban esta doble discapacidad, representando unaprevalencia de 2.46/1000 (95% CI 1.55–3.36). Las mujeresy los grupos de mayor edad tuvieron un riesgo más altopara doble discapacidad que los hombres (riesgo relativo(RR) 3.95, 95% CI 1.34–8.1) y que los jóvenes (RR 9.91,95% CI 3.9–21.1). Veinticinco por ciento de los sujetoscon doble discapacidad tenían una ceguera curable, mien-tras que en el 33% la ceguera era prevenible. Sólo 10% delos sujetos con doble discapacidad tenían una causa cu-rable de hipoacusia. El número de casos con doble dis-capacidad en Omán puede disminuir por la mejoría delos servicios de salud en las últimas dos décadas. Sinembargo el aumento del promedio de edad en la población,hace necesaria una intervención para prevenir la dobledisabilidad. Podría ser más efectivo el énfasis en la pre-vención de la ceguera.

Mazin Al KhaboriENT Department,Al Nahdha Hospital, POB 937, post code 112, Muscat, OmanE-mail: nadiamaz@omantel.net.om

Received:February 1, 2002Accepted:March 7, 2003

Introduction

Eyes and ears are the most important sensory organs. Quality oflife is affected considerably if either of them does not functionoptimally. It is severely affected if both do not work (Downing,1993). These disabilities also cause economic and social depen-dency of the subjects in day-to-day life (Scheffelin, 1981). Theearlier the onset of disability, the worse is the effect on the overalldevelopment of a child (Dumoulin & Bonnard, 1987). In socio-economically developed countries, a decline in communicablediseases and a rise in age-related and non-communicable diseaseshas changed the etiologic profile of visual and hearing disability(Admiraal & Huygen, 2000). Information on the magnitude anddeterminants of dual disability would be of interest to healthplanners. There are few reports in the literature on combinedvisual and hearing disability and increased handicap due to a sec-ond disability.

Oman is a country in the Arabian Peninsula with a popula-tion of 2.3 million (Ministry of Health, 2001). It has 10 healthregions. Muscat (capital), Dhofar (southern state) and Dhahira

(adjoining to the United Arab Emirates) have experienced rapidsocio-economic development. The largely semi-urban populationhas had access to the health services since the 1970s. The remain-ing regions, such as Dhakhiliya, North and South Sharqiya,North and South Batinah, Musundam and Wousta, maderemarkable progress only in the late 1980s and 1990s. The firstthree regions could be classified as low-risk regions for eye andear diseases, while the other regions could be classified as high-risk areas.

The situation changed considerably in Oman in the 1990s.Rapid socio-economic development, particularly in the healthsector, made Oman one of the 10 leading countries in theworld with regard to optimal utilizing of health resources(World Health Organization, 2000). Sustaining these initiativesis vital, and hence health plans for next two decades have beendeveloped. In view of the epidemiologic changes taking place,periodic information is important for such planning. There-fore, a community-based survey was conducted for the firsttime, using the same subjects and field investigators to estimatethe magnitude and causes of both visual and hearing disability in

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173Khandekar/Al KhaboriDouble disability: the hearing-impairedblind in the Sultanate of Oman

1996–97 (Khandekar et al, 2002). The authors analyzed thesedata, correlated the visual and hearing disability, and esti-mated the magnitude and determinants of (bilateral blindnessand hearing loss) double disability.

Methods and materials

This was a cross-sectional descriptive study. We sought to gener-ate a sample representing Omanis of all ages. We estimated that12 437 people were needed in order to measure the prevalence ofhearing loss and blindness in the population. To collect thissample, 116 clusters were randomly selected using the ‘PopulationProportion to the Sample’. This could achieve a 95% confidenceinterval and 90% power of the study with the assumption of1.5% prevalence of disability that could be detected with anacceptable 5% error margin. The sample was further stratifiedinto regional samples. Each cluster comprised a random selec-tion of 12 houses, and all the inhabitants of the houses wereincluded in the survey and examined.

Trained physicians who were experienced in vision and audi-ological testing were the field staff. They visited people in theirhouses. The Optotype ‘E’ chart was used at a distance of 3 m forvision screening. A confrontation test was performed to deter-mine gross constriction of the field of vision. The vision in eacheye was tested in natural daylight. Ophthalmologists examinedthe eyes of all cases with visual disability at ophthalmic unitswith standard diagnostic tools. They confirmed the findings andidentified the principal cause of visual disability in each eye andfor each subject.

Bilateral blindness was defined as vision less than 3/60 in thebetter eye or a corresponding constriction of the field of visionthat was determined in ophthalmic units. A cataract was consid-ered to be a curable cause of visual loss. Corneal opacities, bothtrachomatous and non-trachomatous, diabetic retinopathy, glau-coma, and post-measles and nutritional causes of disorganizedglobe, were considered to be the preventable causes of visual loss.

Hearing screening was performed using portable audiome-ters. Cuffed headphones were used to minimize the ambientnoise. Each ear was tested separately. One ear was randomlysubjected to stimuli of 25, 30 and 40 dB at frequencies of 1, 2and 4 kHz, without the knowledge of the subject.

Bilateral hearing loss was defined as a hearing threshold of26 dB or greater in the better ear at any of the above-mentionedfrequencies on repeated testing. Bilateral disabling hearing losswas defined as a hearing threshold of 41 dB or more in adultsand of 31 dB or more in the better ear of a child less than 10 yearsof age. All cases of hearing loss were re-examined by otolaryn-gologists to confirm the hearing capacity. A standard sound-proof cabin was used for this test, and then the cause of hearingloss was ascertained.

Middle ear diseases such as dry perforation, chronic suppura-tive otitis media and otitis media with effusion were consideredto be temporary or curable causes of hearing loss, while innerear conditions involving sensorineural loss were considered tobe non-curable causes. Presbyacusis was defined as bilateralsymmetric hearing loss of gradual onset with minimal clinicalfindings in a person more than 60 years of age and without anyother cause of hearing loss.

Double disability was defined as the presence of bilateralblindness and bilateral disabling hearing loss. Partial double

disability was defined as bilateral blindness with bilateral hearingloss of all grades. As the survey could not estimate ‘low-vision’cases (vision less than 6/18 but more than 3/60), partial visual dis-ability could not be estimated.

Quality assurance procedures such as a pilot survey, stan-dardization of methods through training, preparing an instruc-tion manual, calibration of equipment, validating the first-levelscreening, monitoring of field activities and statistical validationwere undertaken in this survey.

The data on blindness and hearing loss survey were analyzedusing the Statistical Package for Social Studies (SPSS9).Frequencies, rates per 1000 and relative risk of double disabilitywere calculated. For statistical validation, 95% confidence inter-vals (CIs) of the relative risks of double disabilities among dif-ferent epidemiologic variants were estimated. Four age groupswere formed: less than 20 years; 20–39 years; 40–59 years; and60 years and above.

The health authorities at both regional and national levelssupported this survey. The results of the study were used forimproving the Eye and Ear Health Care Program, and were dis-cussed with regional health authorities. The cases with hearingand visual disabilities were treated free of cost.

Although histories of genetic and childhood infection wereobtained from the subjects and their relatives, recall bias couldhave affected the accuracy of the report, especially among theelderly.

Results

The total sample comprised 12437 subjects. Of these, 11400(91.7%) were examined. Among those examined, 128 subjectshad bilateral blindness and 223 had disabling hearing loss.

The profile of subjects with bilateral blindness and bilateraldisabling hearing loss (double disability) is given in Table 1.Twenty-eight subjects with double disability were found, givinga rate of 2.46/1000 population (95% CI 1.55–3.36). Three thou-sand two hundred subjects were estimated to have double disability in Oman. Females had a significantly higher riskof double disability than males (RR 3.29 (95% CI 1.34–8.1)). Thepopulation 60 years of age and above had a significantly higherrisk of double disability than those between 40 and 59 years ofage (RR 9.02 (95% CI 3.9–21.2)). Regional variation of thedouble disability was significant.

Among the examined sample, 577 subjects had bilateralhearing loss of all grades, and 128 subjects had bilateral blind-ness. They were reviewed to estimate partial double disability.The subjects with bilateral hearing loss include those with disabling hearing loss (Table 2). Partial double disabilitywas found in 40 subjects, giving a rate of 3.51/1000 popula-tion (95% CI 2.42–4.69). Thus, there were about 6400 peoplewith partial double disability in Oman. Gender, age andregional variations of the partial double disability were alsosignificant.

Curable causes of blindness were responsible for double disability in seven (25%) people. Nine people (33%) had pre-ventable causes of blindness (Table 3). In contrast, only three(10%) people had double disability due to curable/preventablecauses of hearing loss. In 19 (67.9%) subjects with double dis-abilities, presbyacusis was the cause of hearing loss. The cause ofhearing loss in six subjects (21.4%) could not be determined.

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Discussion

People with combined hearing and visual disabilities have majorsocial problems (Stoop, 1996). Their quality of life is usuallyworse than that of those with a single disability (Murdoch, 1996).Preventive, curative and rehabilitative interventions can beplanned more effectively if the magnitude and determinants areknown. This survey provided epidemiologically and statistically

sound information regarding visual and hearing disability inOman.

The prevalence of double disability was 2.46/1000 Omanipopulation in our study. Thus, there are nearly 3200 people withdouble disability in Oman. Similar community-based studieshave not been reported in the literature, so this double disabilityrate could not be compared to others. By using the existingnational register for the blind and initiating a registry for the

Table 1. Double disability (bilateral blindness and bilateral disabling hearing loss) in Oman

Double disabilityExamined Relative 95% Confidence

sample No. Per 1000 risk interval

GenderMale 5395 6 1.11 3.29 1.34–8.10Female 6005 22 3.66

RegionHigh-risk regions 7084 26 3.67 7.92 1.88–33.4Low-risk regions 4316 2 0.46

Age groupLess than 20 years 8530 1 0.1220–39 years 1660 0 0.0040–59 years 919 7 7.62 9.02 3.85–21.1260 years and above 291 20 68.73

Total 11 400 28 2.46 1.55–3.36

Table 2. Partial double disability (bilateral blind with bilateral hearing loss) in Oman

Partial double disability

Examined Relative 95% Confidencesample No. Per 1000 risk interval

GenderMale 5395 13 2.41 1.87 0.96–3.6Female 6005 27 4.50

TerrainHigh-risk regions 7084 36 5.08 5.48 1.95–15.4Low-risk regions 4316 4 0.93

Age groupLess than 20 years 8530 1 0.1220–39 years 1660 1 0.60 4.34 2.3–8.240–59 years 919 16 17.4160 years and above 291 22 75.60

Total 11 400 40 3.51 2.42–4.69

Table 3. Causes of double disability

Causes of bilateral Causes of bilateral disabling hearing loss

blindness Presbyacusis CSOMa Dry perforation Glue ear Unknown Total

Phthisis/absent globe 3 0 0 0 0 3Cataract 6 1 0 0 0 7Trachomatous corneal opacity 6 0 1 1 3 11Non-trachomatous corneal opacity 1 0 0 0 0 1Glaucoma 2 0 0 0 3 5Macular degeneration 1 0 0 0 0 1

Total blind 19 1 1 1 6 28aCSOM, chronic suppurative otitis media.

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175Khandekar/Al KhaboriDouble disability: the hearing-impairedblind in the Sultanate of Oman

hearing disabled, these subjects could be identified. The doubledisability could be addressed through offering them correctivemedical/surgical care or rehabilitative/social measures.

In our study, females showed higher rates of double disabilitycompared to males. This is a matter of concern, since the popula-tion proportion of males to females is 51 : 49 (Ministry of Health,2001), and access to the health services, even of a tertiary nature,for either gender is easy and free of cost. Underlying causes—social factors, differential awareness, etc.—should be furtherexplored so that they can be addressed. The large number ofnon-infective causes of hearing loss in females should be furtherinvestigated. Although genetic causes could be responsible forthe double disability, there are no significant gender differencesfor genetic blood disorders in Omani children (Rajab et al, 2000).

The demographic profile in Oman shows that more than50% of the population is below 20 years of age (Ministry ofHealth, 2001). The rate of double disability in this age groupwas as low as 1/10 000, with an estimated 200 Omani subjects inthis age group. Rubella is the leading cause of bilateral dis-abling hearing loss and bilateral blindness in childhood(Lockett & Rudolph, 1980). The last rubella outbreak in Omanwas noted in 1993. Significant organized efforts since then haveresulted in there being fewer than five cases of congenitalrubella syndrome (Cutts et al, 1997). Proper antenatal care anda 95% rate of hospital delivery in Oman have also markedlyreduced the rate of maternal infections that could cause visualand hearing disabilities in neonates (Sulaiman et al, 2001).Thus, a marked reduction in the rate of communicable diseasesin children in the last two decades could be one of the impor-tant factors responsible for the low rates of double disability inthe younger population.

The population of 40 years of age and above comprises14.5% of the total Omani population. The life-expectancy of anaverage Omani is 72 years (Ministry of Health, 2001). The rateof double disability in this age group was high in our study, andwe can expect that the number of people with double disabilityin this age group will increase in the future. The marked reduc-tion in communicable disease, excellent surveillance system andeasy accessibility of health services could slow this rise in thecoming years. It should be noted that the disabled are providedwith around US$100/month as ‘disability allowance’ by the gov-ernment of Oman. The economic burden of rehabilitating themcould be reduced if they are identified and managed in the earlystages.

The risk of double disability was eight times higher in resi-dents of high-risk regions compared to those living in low-riskregions. Differential improvements in socio-economic conditionsand urbanization could have resulted in the double disabilityrate differences. Identification of the causes for the higher rate inhigh-risk region and taking corrective measures would be a chal-lenging but essential measure.

Even though the magnitude of partial double disability ishigh, the risk factors seem to be the same as they are for doubledisability. The gender, age group and regional differences in therates of partial double disability are not as marked as those fordouble disability.

The causes of double disability highlighted some interestingfacts. In 25% of subjects with double disability, blindness wasdue to curable causes. However, in only 10% of the subjects withdouble disability was disabling hearing loss of a conductive

nature and thus considered to be curable or of a temporarynature. Thus, interventions to reduce double disability shouldfocus more on the prevention of blindness initiatives rather thanon preventing hearing loss.

None of the visually or hearing-impaired subjects had classi-cal evidence of congenital rubella syndrome (CRS). This pro-bably indicates the success of the Ministry of Health initiativesto prevent CRS. More than 95% of children aged 15 months to18 years were immunized in Oman during the MR vaccinationcampaign in March to April 1994, and MR vaccine wasincluded in the expanded immunization schedule in the sameyear. Only 8% of pregnant women showed serologic evidenceof susceptibility to rubella infection in a recent study (Ministryof Health, 2000). From 2001, mothers have been immunizedagainst rubella within 40 days of delivery. The surveillance forrubella is proactive in Oman. The findings of our study suggestthat CRS is unlikely to be the cause of double disabilities in thecoming years.

Curable blindness and incurable hearing loss were mostlyfound in the elderly population. Ocular infection, mainly tra-choma, resulted in a large proportion of cases of corneal blind-ness. Tissue-specific infection with trachoma organisms involvingthe eyes and low rates of sequelae of middle ear infection couldbe responsible for this observation.

Presbyacusis, which was responsible for two-thirds of cases ofdisabling hearing loss, was associated with bilateral blindness dueto age-related conditions such as cataract, glaucoma and age-related macular degeneration (ARMD). The national geriatricdiseases control program should involve consideration of doubledisability in the aging population and address it effectively.

Surprisingly, in our study, very few subjects with double dis-ability had genetic diseases responsible. The rates of congenitalanomalies and genetic blood disorders in children are also veryhigh (Sulaiman et al, 2001). In addition, the consanguinity rateis also as high as 55% (Rajab & Patton, 2000) and is a knownrisk factor for congenital diseases in the offspring. A less sensi-tive methodology to detect sensorineural hearing loss in childrenless than 4 years of age and the possibility of recall bias couldhave resulted in the underestimation of hearing loss of a geneticnature in our study.

The immediate goal of reducing double disability by theEye and Ear Health Care Program in Oman should focus onidentification of these subjects and the treatment of blindnessdue to curable causes. Special emphasis on primary ear care andthe introduction of universal hearing screening in 2001 couldhelp in detecting sensorineural hearing loss in early childhood.Even though hearing loss in the majority of cases is not curable,provision of hearing aids and rehabilitative efforts could improvetheir quality of life. Control of double disability should be anintegral part of national health programs. Estimation of doubledisability in the future and comparison of the results with thoseof the present study would enable health planners to assess theimpact of such initiatives.

Acknowledgments

We would like to acknowledge the help given by the Ministryof Health (MOH), Sultanate of Oman. We thank Dr Ali JafferMohammed, Professor Peter Alberti, Dr Subrender Kumar,Dr Susan Lewallence and Ruth Mabry for their support.

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Ministry of Health. 2000. Elimination of rubella & CRS in Oman by2005. Community Health Dis Surveillance Newslett, 9(3), 1–3.

Ministry of Health. 2001. Annual Health Report 2000. Muscat: Al ZahraPrinters, pp. 1–8, 8–41.

Murdoch, H. 1996. Stereotyped behaviors in deaf and hard of hearingchildren. Am Ann Deaf, 141(5), 379–386.

Rajab, A. & Patton, M.A. 2000. A study of consanguinity in the Sultanateof Oman. Ann Hum Biol, 27(3), 321–326.

Rajab, A.G., Patton, M.A. & Modell, B. 2000. Study of hemoglo-binopathies in Oman through a national register. Saudi Med J,21(12), 1168–1172.

Scheffelin, M.A. 1981. Employability of persons who are both deaf andblind. Int J Rehabil Res, 4(1), 92.

Stoop, J.A. 1996. Deafness–blindness in the elderly leading to psychoso-cial problems. Ned Tijdschr Geneeskd, 140(37), 1845–1848.

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