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Planning low vision services in India
Planning Low Vision Services in India A Population-based Perspective Rakhi Dandona, PhD,1,2,3, Lalit Dandona, MD, MPH,1,3 Marmamula Srinivas, BA,1 Pyda Giridhar, PhD,1 Rishita Nutheti, MSc,1 Gullapalli N. Rao, MD1 Objective: To assess the prevalence and causes of low vision in a population in southern India for planning low vision services. Design: Population-based, cross-sectional study. Participants: A total of 10,293 persons of all ages from 94 clusters representative of the population of the Indian state of Andhra Pradesh. Methods: The participants underwent a detailed eye examination, including measurement of visual acuity with logarithm of the minimum angle of resolution charts, refraction, slit-lamp biomicroscopy, applanation tonometry, gonioscopy, and stereoscopic dilated fundus evaluation. Automated threshold visual fields and slit-lamp and fundus photography were done when indicated using predefined criteria. Main Outcome Measures: Low vision was defined as permanent visual impairment that was not correctable with refractive error correction or surgical intervention. The participants with best-corrected distance visual acuity ⬍6/18 to perception of light or central visual field ⬍10° because of an untreatable cause in both eyes were considered as having low vision. Results: Low vision was present in 144 participants, an age, gender, and urban-rural distribution adjusted prevalence of 1.05% (95% confidence interval, 0.82%–1.28%). The most frequent causes of low vision included retinal diseases (35.2%), amblyopia (25.7%), optic atrophy (14.3%), glaucoma (11.4%), and corneal diseases (8.6%). Multivariate analysis showed that the prevalence of low vision was significantly higher with increasing age, and there was a trend for higher prevalence with decreasing socioeconomic status. Extrapolating these data to the estimated 1014 million population of India in the year 2000, 10.6 (95% confidence interval, 8.4 –12.8) million people would have low vision. Conclusions: These data imply that there is a significant burden of low vision in this population, suggesting the need for low vision services. Ophthalmology 2002;109:1871–1878 © 2002 by the American Academy of Ophthalmology. Low vision has been considered as one of the priorities in the global initiative, VISION 2020 —The Right to Sight, along with cataract, trachoma, onchocerciasis, childhood blindness, and refractive error.1 According to a World Health Organization consultation, a person with low vision is one who has impairment of visual function even after treatment or refractive correction and has visual acuity of
Originally received: July 16, 2001. Accepted: April 9, 2002. Manuscript no. 210489. 1 International Centre for Advancement of Rural Eye Care, L. V. Prasad Eye Institute, Hyderabad, India. 2 Centre for Eye Research Australia, University of Melbourne, Melbourne, Australia. 3 Centre for Social Services, Administrative Staff College of India, Hyderabad, India. Support for the Andhra Pradesh Eye Disease Study was provided by the Hyderabad Eye Research Foundation, Hyderabad, India, and ChristoffelBlindenmission, Bensheim, Germany. Dr. Rakhi Dandona was supported in part by the R. B. McComas and Hugh Noel Puckle scholarships from the University of Melbourne, Melbourne, Australia. Reprint requests to Dr. Rakhi Dandona, Centre for Social Services, Administrative Staff College of India, Bella Vista, Raj Bhavan Road, Hyderabad 500 082, India. © 2002 by the American Academy of Ophthalmology Published by Elsevier Science Inc.
less than 6/18 to perception of light or visual field of less than 10° in the better eye, who uses or is potentially able to use vision for planning or execution of a task.2 Population-based data assessing the prevalence of low vision with this definition are not readily available to plan low vision services. We have previously reported the prevalence of blindness and moderate visual impairment, which included both treatable and untreatable causes, in the population of the Indian state of Andhra Pradesh.3,4 The prevalence of blindness (presenting distance visual acuity ⬍6/60 or central visual field ⬍20° in the better eye) was estimated at 1.84%,3 and moderate visual impairment (presenting distance visual acuity ⬍6/18 to 6/60 or equivalent visual field loss in the better eye) was estimated at 8.09% for this population.4 We now report the prevalence and causes of low vision for this population, data that could assist in planning low vision services.
Material and Methods Study Design Various aspects of the study design of the Andhra Pradesh Eye Disease Study (APEDS) have been described previously.3– 8 A ISSN 0161-6420/02/$–see front matter PII S0161-6420(02)01183-1
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Ophthalmology Volume 109, Number 10, October 2002 brief description of the sampling procedure follows. A multistage sampling procedure was used to select 24 urban clusters and 70 rural clusters from one urban and three rural areas from different parts of the southern Indian state of Andhra Pradesh, with the aim of having a study sample representative of the urban–rural and socioeconomic distribution of the population of this state. These four areas were located in Hyderabad (urban), West Godavari district (well-off rural), and Adilabad and Mahabubnagar districts (poor rural). The sampling strategy for the urban area and for the rural areas of APEDS has been described earlier.3,5,6 The major difference between the urban and rural sampling was that the former was selected from blocks stratified by socioeconomic status and religion, whereas the latter was selected from villages stratified by caste as described previously.3,5,6 A total of 94 clusters were selected for APEDS using stratified random sampling, such that the proportion of each socioeconomic status in the sample would be similar to that in the population of the state.3,5,6 These clusters were mapped, and the number of households and members in each household listed. Every second to fifth household was systematically selected in each cluster to obtain a roughly equal number of households in each cluster. Approximately half the clusters in each of the four areas were randomly assigned to have persons of all ages in the selected households eligible for the study and the other half to have only those 30 years of age or older eligible for the study. This was done to obtain a similar number of participants in the less than and more than 30-year-old age groups.3,5,6 A total of 11,786 persons were sampled in all four areas of APEDS, of which 8832 were in the three rural areas. Eligible persons were interviewed by trained investigators.3– 8 The participants were then invited for a detailed eye examination at a local site. Written informed consent was obtained from participants before examination. For the participants who could not read and write, the consent was read aloud by the receptionist at the examination site in the presence of all the participants on that day. These participants gave their thumb impression after understanding and agreeing with the content of the consent. This study was approved by the Ethics Committee of the L. V. Prasad Eye Institute, Hyderabad, India. APEDS was conducted from October 1996 to February 2000.
Clinical Examination The eye examination conducted in APEDS has been described in detail previously.3– 8 The examinations were done by four ophthalmic technicians and four ophthalmologists who had received special training in the procedures of this study for standardization of the documentation of the clinical findings. The eye examination included measurement of presenting and best-corrected distance and near visual acuities under standardized conditions with logarithm of the minimum angle of resolution charts9; external eye examination; assessment of pupillary reaction; anterior segment examination using the slit-lamp biomicroscope; measurement of intraocular pressure using Goldmann applanation tonometer; gonioscopy; and lens, vitreous, and posterior segment examination (involving examination with the indirect ophthalmoscope using a 20-diopter lens and at the slit lamp using 78-diopter lens) after dilatation unless contraindicated because of the risk of angle closure. Automated visual fields were done with the Humphrey visual field analyzer10 using the threshold central 24-2 strategy in those participants assessed to have any suspicion of glaucoma, any other optic nerve pathology, higher visual pathway lesion, or significant macular pathology according to uniform predefined criteria.3,5,6,8 If the visual field was abnormal or unreliable, it was repeated on another day. Anterior segment pathology was photographed with
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Nikon photo-slit lamp (Nikon Corporation, Tokyo, Japan), and optic disc, macular, or other retinal pathology with a Zeiss fundus camera (Carl Zeiss, Jena, Germany).3,5,6,8 Examination was done at home using portable equipment for the participants who were physically debilitated and were unable to come to the clinic. This examination was essentially similar to the one at the clinic, except that gonioscopy, posterior segment examination using a 78-diopter lens, automated visual fields, and photography were not done.3– 6,8
Definition and Causes of Low Vision Low vision was defined as the permanent visual impairment that was not correctable with refractive error correction or surgical intervention. The participants with best-corrected distance visual acuity ⬍6/18 to perception of light or central visual field ⬍10° because of an untreatable cause in both eyes were considered as having low vision. The subjects with a treatable cause of visual impairment in any eye were not considered as having low vision. The causes considered as treatable were refractive error, cataract, posterior capsular opacification after cataract surgery, and corneal scars that were clinically judged to be treatable by penetrating keratoplasty in the developing country setting (determined by reviewing the clinical findings documented in the medical record and slit-lamp photographic documentation of the corneal scar). All the other causes were considered untreatable. Amblyopia was considered as the cause of low vision when the best-corrected distance visual acuity was ⬍6/18 to perception of light with no apparent organic lesion in the eye and the patient satisfied at least one of these criteria: tropia, nystagmus, bilateral ametropia of spherical equivalent ⫾5.00 diopters or worse, or anisometropia of spherical equivalent ⫾2.00 diopters or worse.
Statistical Analysis Data were entered on self-coded forms by the investigators and the examiners and were then entered into computers by two data entry operators using the Fox Pro program with internal consistency checks.5 Data entered by one data entry operator were checked by the other data entry operator after completion of each cluster. This was done randomly on 10% of all the data entered for each cluster. To determine and verify outliers, monthly range and consistency checks were done using SPSS (Windows). Analyses were done using the SPSS software (SPSS for Windows, Rel.10.0.5. 1999; SPSS Inc., Chicago, IL). The prevalence of low vision was adjusted for the estimated age, gender, and urban–rural distribution of the population of India for the year 200011,12 to obtain composite estimates for the overall prevalence of low vision. The design effect of the sampling strategy was calculated using the low vision prevalence in each cluster,13 and the 95% confidence intervals of the estimates were adjusted accordingly. Poisson distribution14 was assumed for prevalence less than 1% and normal approximation of binomial distribution for prevalence 1% or more. The demographic associations of low vision with age, gender, socioeconomic status, and urban–rural residence were assessed with univariate analysis using the chi-square test followed by multivariate analysis using multiple logistic regression. All variables were introduced in the model simultaneously, and none of the variables were optimized. The effect of each category of a multicategorical risk factor variable was assessed by keeping the first or the last category as the reference. These data on low vision were extrapolated to the population of India for the year 2000.11,12 In addition, the prevalence of low vision was estimated for the years 2010 and 2020 if the current age-specific and gender-specific rates continue, by applying these rates to the estimated age, gender,
Dandona et al 䡠 Low Vision in India
Figure 1. Prevalence of low vision for the four study areas of The Andhra Pradesh Eye Disease Study. The graph shows the prevalence for each of the study areas and of rural study areas adjusted for age and gender distribution of the population of India in 2000, as well as the prevalence for all study areas combined adjusted for age, gender, and urban–rural distribution of the population of India in 2000. PL ⫽ perception of light.
and urban–rural distribution of the population of India in 2010 and 2020.11,12
Results Of the 11,786 eligible subjects, 10,293 (87.3%) participated in the study from the four areas of APEDS. Of these, 7775 (75.3%) were from the three rural areas, 5439 (52.8%) were females, and 122 (1.2%) were examined at home.
Prevalence of Low Vision Of the 10,293 subjects who were clinically examined, 144 (1.4%) had low vision. The prevalence of low vision for the study areas combined, adjusted for age, gender, and urban-rural distribution, was 1.05% (95% confidence interval, 0.82%–1.28%; design effect 1.3). On considering only the three rural study areas of APEDS together, the age-adjusted and gender-adjusted prevalence of low vision was 1.14% (95% confidence interval, 0.87%–1.41%; design effect 1.3). Low vision was subdivided into two groups: (1) visual acuity ⬍6/60 to perception of light or central visual field ⬍10° (⬍6/60 to light perception); and (2) visual acuity ⬍6/18 to 6/60 (⬍6/18 to 6/60). The prevalence of each group is shown in Figure 1. On comparing the prevalence of ⬍6/60 to light perception and ⬍6/18 to 6/60, the former was higher in Hyderabad and was almost similar in Adilabad, but was much lower in West Godavari and Mahabubnagar.
Causes of Low Vision The prevalence of the causes of low vision for all the study areas combined is shown in Table 1. Retinal diseases were responsible
for 35.2% of the low vision followed by amblyopia, which was responsible for 25.7% of the low vision. Figure 2 shows the adjusted prevalence of the causes of low vision for the ⬍6/60 to light perception and ⬍6/18 to 6/60 groups. There was a significant difference in the prevalence of amblyopia, optic atrophy, and glaucoma for ⬍6/60 to light perception and ⬍6/18 to 6/60, but it was not very different for retinal diseases, corneal diseases, and other causes combined (congenital eye anomaly, higher visual pathway lesion, and endophthalmitis). Figure 3 shows gender and urban–rural distribution–adjusted prevalence of the causes of low vision for different age groups for all the study areas combined. The prevalence of low vision increased with increasing age. There was a variation in the causes of Table 1. Distribution of Causes of Low Vision for the Four Study Areas of the Andhra Pradesh Eye Disease Study Combined
Cause of Low Vision
Prevalence in Total Population* (95% Confidence Interval; Design Effect)
Retinal disease Amblyopia Optic atrophy† Glaucoma Corneal disease Higher visual pathway lesion Congenital eye anomaly Endophthalmitis Total
0.37% (0.26–0.51%; 1.00) 0.27% (0.17–0.40%; 1.16) 0.15% (0.08–0.26%; 1.27) 0.12% (0.06–0.21%; 1.00) 0.09% (0.04–0.17%; 1.00) 0.02% (0.004–0.08%; 1.00) 0.02% (0.003–0.07%; 1.00) 0.01% (0.00–0.04%; 1.00) 1.05% (0.82–1.28%; 1.30)
* Adjusted for the estimated age, gender, and urban–rural distribution of the population of India in the year 2000.11,12 † Other than caused by glaucoma.
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Figure 2. Prevalence of causes of low vision for the four study areas combined. The graph shows the prevalence for each cause adjusted for age, gender, and urban–rural distribution of the population of India in 2000. PL ⫽ perception of light.
low vision on the basis of age. Retinal diseases and optic atrophy as causes of low vision increased with increasing age. No case of low vision due to glaucoma was seen in those ⬍40 years of age. Amblyopia accounted for most low vision for those between 40 and 49 years of age. Figure 4 shows the prevalence of different causes of low vision for the two genders for all four study areas combined. The age and urban–rural distribution–adjusted prevalence of low vision for males was 1.06% (95% confidence interval, 0.77%–1.35%) and for females was 1.04% (95% confidence interval, 0.75%–1.33%). Females had a higher prevalence of low vision caused by optic atrophy, whereas males had a higher prevalence of low vision caused by glaucoma and corneal diseases.
Demographic Associations of Low Vision The distribution of those with low vision by age, gender, socioeconomic status, and urban–rural residence is shown in Table 2. On applying multiple logistic regression, the odds of having low vision increased with increasing age and decreasing socioeconomic status (Table 2).
Extrapolations to the Population of India Extrapolating these data from APEDS to the estimated 75 million population of Andhra Pradesh in the year 2000, 787,500 (95%
Figure 3. Gender and urban–rural distribution–adjusted prevalence of causes of low vision for different age categories for the four study areas combined.
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Dandona et al 䡠 Low Vision in India
Figure 4. Age and urban–rural distribution–adjusted prevalence of causes of low vision for both genders for the four study areas combined.
confidence interval, 615,000 –960,000) people would have low vision. Figure 5 shows the prevalence of low vision for the estimated population distribution of India in the years 2010 and 2020 if the current age-specific and gender-specific rates of low vision con-
tinue. If the data are extrapolated to the estimated 1014 million population of India in the year 2000,8 10.6 (95% confidence interval, 8.4 –12.8) million people would have low vision. Similarly, of the estimated 1168 million population of India in 2010,8 13.3 (95% confidence interval, 10.6 –16) million people would
Table 2. Association of Low Vision with Age, Gender, Socioeconomic Status, and Area of Residence
Age (yrs)* 0–15 16–29 30–39 40–49 50–59 60–69 ⱖ70 Gender† Male Female Socioeconomic status‡ Upper Middle Lower Extreme lower Residence§ Hyderabad West Godavari Adilabad Mahabubnagar
Total (n ⴝ 10,293)
No. with Low Vision (%)
Odds Ratio for Having Low Vision with Multiple Logistic Regression (95% Confidence Interval)
2861 1845 1863 1424 1047 900 353
9 (0.3) 7 (0.4) 16 (0.9) 24 (1.7) 31 (3.0) 35 (3.9) 22 (6.2)
1.00 1.28 (0.47–3.44) 2.81 (1.24–6.38) 5.57 (2.56–12.10) 10.15 (4.81–21.44) 12.87 (6.15–26.93) 22.21 (10.10–48.84)
4854 5439
71 (1.5) 73 (1.3)
1.00 0.94 (0.67–1.31)
362 3172 5212 1354
1 (0.3) 37 (1.2) 80 (1.5) 25 (1.8)
1.00 3.67 (0.50–27.0) 5.59 (0.77–40.73) 7.46 (1.00–55.87)
2522 2503 2690 2578
26 (1.0) 48 (1.9) 29 (1.1) 41 (1.6)
1.00 1.54 (0.94–2.51) 0.95 (0.55–1.64) 1.30 (0.78–2.14)
* P ⬍ 0.0001, univariate test for trend. P ⫽ 0.88, univariate chi-square test. P ⫽ 0.011, univariate test for trend; socioeconomic status defined according to monthly per capita income in Indian rupees: upper ⬎2000 (US $45), middle 501–2000, lower 201–500, and extreme lower ⱕ200. Data on socioeconomic status not available for 193 subjects.
† ‡
P ⫽ 0.005, univariate chi-square test; Hyderabad is urban area, West Godavari is relatively well-off rural area, and Adilabad and Mahabubnagar are poor rural areas.
§
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Figure 5. Prevalence of low vision for the four study areas combined of The Andhra Pradesh Eye Disease Study for the years 2000, 2010, and 2020. The graph shows the prevalence for each year adjusted for the estimated age, gender, and urban–rural distribution of the population of India for that year. PL ⫽ perception of light.
have low vision, and of the 1312 million population in 2020,8 16.7 (95% confidence interval, 13.4 –20) million people would have low vision if the current trend continues.
Discussion The APEDS was a cross-sectional population-based study representative of the population of Andhra Pradesh in which the participants underwent a detailed eye examination. This allows us to comment on low vision for the population at large.
Definition and Causes of Low Vision In the commonly used World Health Organization classification of visual impairment, low vision is best-corrected visual acuity ⬍6/18 to 3/60 in the better eye.15 However, this includes treatable causes such as cataract and excludes those individuals who have best-corrected visual acuity ⬍3/60 to perception of light in the better eye who may have useful residual vision and can benefit from low vision services. In this background, modification in the definition of low vision has been suggested by a consultation of the World Health Organization, which defined a person with low vision as one who has impairment of visual function even after treatment or refractive correction and has visual acuity ⬍6/18 to perception of light or central visual field ⬍10°, provided he or she has functional vision for navigation.2 This definition captures those who may benefit from low vision services and hence is preferred. Some data are available on the causes of low vision using the ⬍6/18 to no light perception criterion, mainly from the clinic settings.16,17 In these reports patients with cataract, which is a correctable cause of visual impairment for the most part, have also been included.
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To estimate the prevalence and causes of low vision in an Indian population to form a basis for planning low vision services, in this report we considered people with bestcorrected distance visual acuity ⬍6/18 to perception of light or central visual field ⬍10° because of an untreatable cause in both eyes as having low vision, as suggested by consultation with the World Health Organization.2 To our knowledge, these are the first population-based data on low vision with this definition that can assist in the planning of low vision services. We did not consider cataract, refractive error, posterior capsular opacification after cataract surgery, and corneal scars, which were clinically judged to be treatable by penetrating keratoplasty, as causes of low vision, because these are treatable.
Low Vision in Our Population The prevalence of low vision in our population was estimated to be 1.05%. As expected, the prevalence of low vision in the urban study area was lower compared with the three rural study areas. We have previously reported similar results for blindness in this population.3 These data suggest that 1 of every 100 people in the state of Andhra Pradesh has low vision. The increase in prevalence of low vision with increasing age is not surprising. Retinal diseases and amblyopia accounted for approximately 60% of the low vision. The retinal diseases that accounted for most low vision included age-related maculopathy, macular degeneration caused by myopia, retinitis pigmentosa, and macular scar caused by chorioretinitis. Most of the low vision caused by amblyopia was bilateral ametropia of spherical equivalent ⫾5.00 diopters or worse (79.4%), followed by anisometropia (14.7%), and nystagmus (5.9%). Of the bilateral ametropia, 77.8% was due to myopia, and the rest was due to hyperopia. Amblyopia caused by myopia was associated with spherical equivalent
Dandona et al 䡠 Low Vision in India of ⫺5.00 diopters or worse, including 61.9% with spherical equivalent ⫺10.00 diopters or worse in both eyes. None of the eyes considered as having refractive error–related amblyopia were treatable at this stage. Primary open-angle glaucoma accounted for approximately 70% of low vision caused by glaucoma. Keratitis after fever during childhood, especially exanthematous fever, accounted for most low vision caused by corneal diseases, followed by trauma.
Implications for Low Vision Services Low vision has been considered as one of the priorities in VISION 2020.1 In the background of these data, the following are the implications for low vision services in the context of VISION 2020.
Need for Low Vision Services From these data it is estimated that there were 10.6 million people with low vision in the year 2000 in India. These data also suggest that most low vision was in the elderly population, especially 50 years of age or more. Considering the older age of most of the people with low vision, it is probable that their motivation to use low vision services would be less and that these people are likely to have other age-related disabilities as well. Hence, the actual need for low vision services would probably be less than the number of people with low vision. More research would be needed to determine how many of those having low vision with a certain definition would actually need low vision services.
Priority for Low Vision Services In the same population, we found that the prevalence of blindness (presenting visual acuity ⬍6/60 or central visual field ⬍20° in the better eye) was 1.84% and of moderate visual impairment (presenting visual acuity ⬍6/18 to 6/60 or equivalent visual field loss in the better eye) was 8.09%.3,4 Cataract and refractive error, both of which are easily treatable, were responsible for most blindness and moderate visual impairment. The strategies to reduce low vision in this population should be made in the background of the significant burden of treatable blindness and moderate visual impairment.
Provision of Low Vision Services Provision of low vision services is multidisciplinary. On the basis of the needs of the patient, these services are provided by a team of eye-care personnel, mobility instructors, and school teachers. Eye-care personnel trained in assessment of low vision provide both optical and nonoptical low vision devices. The help of a mobility instructor is sought in cases in which there is difficulty with mobility. Linking with school teachers is important for young patients who attend school. Most low vision service in India is being provided at the tertiary level clinics and hospitals. This is because eye-care personnel trained in low vision services and mobility instructors are available mainly in cities. It is possible that some of the low vision services, such as nonoptical aids and
stand magnifiers, can be made available at the secondary level eye hospitals through trained eye-care personnel. However, the feasibility of extending these services has to be based on the actual need for low vision services in the community. Determination of this actual need will require more research as suggested previously. The other important issues in provision of low vision services are availability and affordability of the low vision devices. Attempts have to be made to reduce the cost of low vision devices to make them affordable for those who have motivation to use these devices. Innovative ways to make simple optical magnifiers at low cost are available.17,18
Strategies to Reduce Low Vision Retinal diseases were the leading cause of low vision. Currently, however, it does not seem feasible to reduce this burden in the developing country setting. The strategies to reduce low vision could include the possibly avoidable causes of low vision such as amblyopia, glaucoma, and corneal diseases. Low vision caused by amblyopia was mainly refractive error related. This calls for effective vision screening programs that can detect the refractive error early and provide refractive services.19 Glaucoma is a silent disease; hence, detection of glaucoma is not easy. However, a significant difference could probably be made if a complete dilated eye examination and a check for intraocular pressure were offered to those who report to the clinics or hospitals for any eye ailment, especially those 40 years of age or older.20,21 This could lead to early diagnosis of glaucoma, perhaps making it possible to stop or delay the progression of vision and visual field loss. Most of the low vision caused by corneal diseases was accounted for by keratitis after fever during childhood. Corneal opacity after exanthematous fever could be due to vitamin A deficiency precipitated by measles. Other cases of corneal opacity could be due to trauma. Both of these causes are preventable and could be reduced through effective health and eye health promotion strategies. The projected burden of low vision in India in 2010 and 2020, calculated for the situation if the current trend continues, would be reduced if effective strategies were put in place to reduce these avoidable causes of low vision. In addition, awareness about low vision services needs to be addressed for the public and the eye-care providers. It is important to make people aware that it is possible to use residual vision to increase the quality of life. In a report from Australia on referral patterns for low vision services among ophthalmologists, most of the ophthalmologists referred the patients with best-corrected visual acuity ⬍6/12 to 6/60 to low vision services and not those with bestcorrected visual acuity ⬍6/60.22 Hence, it is important to make the eye-care personnel aware of the referral criteria for low vision services, so that patients with low vision can use these services. The availability of low vision services is related to the availability of human resources trained in providing these services. An attempt has to be made to increase the number of these trained personnel based on the need for these services. In addition, attempts have to be made to reduce the
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Ophthalmology Volume 109, Number 10, October 2002 cost of low vision devices to make them available and affordable. In conclusion, these data suggest that there is a significant burden of low vision in this population. Therefore, an attempt should be made to make provision of low vision services an integral part of comprehensive eye-care services for the visually disabled. Acknowledgments. The authors acknowledge the guidance of Dr. Catherine A. McCarty and Prof. Hugh R. Taylor in the study design.
References 1. World Health Organization. Global Initiative for the Elimination of Avoidable Blindness. Geneva: World Health Organization, 1997. WHO/PBL/97.61. 2. World Health Organization. The Management of Low Vision in Children. Report of a WHO Consultation: Bangkok, July 1992. Geneva: World Health Organization,1993. WHO/PBL/ 93.27. 3. Dandona L, Dandona R, Srinivas M, et al. Blindness in the Indian state of Andhra Pradesh. Invest Ophthalmol Vis Sci 2001;42:908 –16. 4. Dandona R, Dandona L, Srinivas M, et al. Moderate visual impairment in India: the Andhra Pradesh Eye Disease Study. Br J Ophthalmol 2002;86:373–7. 5. Dandona R, Dandona L, Naduvilath TJ, et al. Design of a population-based study of visual impairment in India: the Andhra Pradesh Eye Disease Study. Indian J Ophthalmol 1997;45:251–7. 6. Dandona L, Dandona R, Naduvilath TJ, et al. Is current eye-care-policy focus almost exclusively on cataract adequate to deal with blindness in India? Lancet 1998;351:1312– 6. 7. Dandona R, Dandona L, Naduvilath TJ, et al. Refractive errors in an urban population in southern India: the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci 1999;40:2810 – 18. 8. Dandona L, Dandona R, Naduvilath TJ, et al. Burden of moderate visual impairment in an urban population in southern India. Ophthalmology 1999;106:497–504.
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9. Ferris FL III, Kassoff A, Bresnick GH, Bailey L. New visual acuity charts for clinical research. Am J Ophthalmol 1982;94: 91– 6. 10. Humphrey Field Analyzer II User’s Guide. San Leandro, CA: Humphrey Instruments Inc, 1994. 11. US Census Bureau. International data base (IDB). Washington, DC: US Census Bureau (accessed [Rev. May 10, 2000, cited December 2000]). Available from URL: http://www. census.gov/cgi-bin/ipc/idbsum?cty⫽IN. 12. World Urbanization Prospects, the 1996 revision. New York: United Nations, 1998. 13. Bennett S, Woods T, Liyanage WM, Smith DL. A simplified general method for cluster-sample surveys of health in developing countries. Stat Q 1991;44:98 –106. 14. Rosner B. Fundamentals of Biostatistics, 2nd ed. Boston: Duxbury Press, 1986;84 –92, 302– 68, 404 – 8. 15. International Statistical Classification of Diseases and Related Health Problems: tenth revision. Geneva: World Health Organization, 1992:456 –7. 16. Elliott DB, Trukolo-Ilic M, Strong JG, et al. Demographic characteristics of the vision-disabled elderly. Invest Ophthalmol Vis Sci 1997;38:2566 –75. 17. Herse P, Gothwal VK. Survey of visual impairment in an Indian tertiary eye hospital. Indian J Ophthalmol 1997;45: 189 –93. 18. Silver J, Gilbert CE, Spoerer P, Foster A. Low vision in east African blind school students: need for optical low vision services. Br J Ophthalmol 1995;79:814 –20. 19. Dandona R, Dandona L. Refractive error blindness. Bull World Health Organ 2001;79:237– 43. 20. Dandona L, Dandona R, Srinivas M, et al. Open-angle glaucoma in an urban population in southern India. The Andhra Pradesh Eye Disease Study. Ophthalmology 2000;107: 1702–9. 21. Dandona L, Dandona R, Mandal P, et al. Angle-closure glaucoma in an urban population in southern India. The Andhra Pradesh Eye Disease Study. Ophthalmology 2000;107: 1710 – 6. 22. Keeffe JE, Lovie-Kitchin JE, Taylor HR. Referral to low vision services by ophthalmologists. Aust N Z J Ophthalmol 1996;24:207–14.
Originally received: July 16, 2001. Accepted: April 9, 2002. Manuscript no. 210489. 1 International Centre for Advancement of Rural Eye Care, L. V. Prasad Eye Institute, Hyderabad, India. 2 Centre for Eye Research Australia, University of Melbourne, Melbourne, Australia. 3 Centre for Social Services, Administrative Staff College of India, Hyderabad, India. Support for the Andhra Pradesh Eye Disease Study was provided by the Hyderabad Eye Research Foundation, Hyderabad, India, and ChristoffelBlindenmission, Bensheim, Germany. Dr. Rakhi Dandona was supported in part by the R. B. McComas and Hugh Noel Puckle scholarships from the University of Melbourne, Melbourne, Australia. Reprint requests to Dr. Rakhi Dandona, Centre for Social Services, Administrative Staff College of India, Bella Vista, Raj Bhavan Road, Hyderabad 500 082, India. © 2002 by the American Academy of Ophthalmology Published by Elsevier Science Inc.
less than 6/18 to perception of light or visual field of less than 10° in the better eye, who uses or is potentially able to use vision for planning or execution of a task.2 Population-based data assessing the prevalence of low vision with this definition are not readily available to plan low vision services. We have previously reported the prevalence of blindness and moderate visual impairment, which included both treatable and untreatable causes, in the population of the Indian state of Andhra Pradesh.3,4 The prevalence of blindness (presenting distance visual acuity ⬍6/60 or central visual field ⬍20° in the better eye) was estimated at 1.84%,3 and moderate visual impairment (presenting distance visual acuity ⬍6/18 to 6/60 or equivalent visual field loss in the better eye) was estimated at 8.09% for this population.4 We now report the prevalence and causes of low vision for this population, data that could assist in planning low vision services.
Material and Methods Study Design Various aspects of the study design of the Andhra Pradesh Eye Disease Study (APEDS) have been described previously.3– 8 A ISSN 0161-6420/02/$–see front matter PII S0161-6420(02)01183-1
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Ophthalmology Volume 109, Number 10, October 2002 brief description of the sampling procedure follows. A multistage sampling procedure was used to select 24 urban clusters and 70 rural clusters from one urban and three rural areas from different parts of the southern Indian state of Andhra Pradesh, with the aim of having a study sample representative of the urban–rural and socioeconomic distribution of the population of this state. These four areas were located in Hyderabad (urban), West Godavari district (well-off rural), and Adilabad and Mahabubnagar districts (poor rural). The sampling strategy for the urban area and for the rural areas of APEDS has been described earlier.3,5,6 The major difference between the urban and rural sampling was that the former was selected from blocks stratified by socioeconomic status and religion, whereas the latter was selected from villages stratified by caste as described previously.3,5,6 A total of 94 clusters were selected for APEDS using stratified random sampling, such that the proportion of each socioeconomic status in the sample would be similar to that in the population of the state.3,5,6 These clusters were mapped, and the number of households and members in each household listed. Every second to fifth household was systematically selected in each cluster to obtain a roughly equal number of households in each cluster. Approximately half the clusters in each of the four areas were randomly assigned to have persons of all ages in the selected households eligible for the study and the other half to have only those 30 years of age or older eligible for the study. This was done to obtain a similar number of participants in the less than and more than 30-year-old age groups.3,5,6 A total of 11,786 persons were sampled in all four areas of APEDS, of which 8832 were in the three rural areas. Eligible persons were interviewed by trained investigators.3– 8 The participants were then invited for a detailed eye examination at a local site. Written informed consent was obtained from participants before examination. For the participants who could not read and write, the consent was read aloud by the receptionist at the examination site in the presence of all the participants on that day. These participants gave their thumb impression after understanding and agreeing with the content of the consent. This study was approved by the Ethics Committee of the L. V. Prasad Eye Institute, Hyderabad, India. APEDS was conducted from October 1996 to February 2000.
Clinical Examination The eye examination conducted in APEDS has been described in detail previously.3– 8 The examinations were done by four ophthalmic technicians and four ophthalmologists who had received special training in the procedures of this study for standardization of the documentation of the clinical findings. The eye examination included measurement of presenting and best-corrected distance and near visual acuities under standardized conditions with logarithm of the minimum angle of resolution charts9; external eye examination; assessment of pupillary reaction; anterior segment examination using the slit-lamp biomicroscope; measurement of intraocular pressure using Goldmann applanation tonometer; gonioscopy; and lens, vitreous, and posterior segment examination (involving examination with the indirect ophthalmoscope using a 20-diopter lens and at the slit lamp using 78-diopter lens) after dilatation unless contraindicated because of the risk of angle closure. Automated visual fields were done with the Humphrey visual field analyzer10 using the threshold central 24-2 strategy in those participants assessed to have any suspicion of glaucoma, any other optic nerve pathology, higher visual pathway lesion, or significant macular pathology according to uniform predefined criteria.3,5,6,8 If the visual field was abnormal or unreliable, it was repeated on another day. Anterior segment pathology was photographed with
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Nikon photo-slit lamp (Nikon Corporation, Tokyo, Japan), and optic disc, macular, or other retinal pathology with a Zeiss fundus camera (Carl Zeiss, Jena, Germany).3,5,6,8 Examination was done at home using portable equipment for the participants who were physically debilitated and were unable to come to the clinic. This examination was essentially similar to the one at the clinic, except that gonioscopy, posterior segment examination using a 78-diopter lens, automated visual fields, and photography were not done.3– 6,8
Definition and Causes of Low Vision Low vision was defined as the permanent visual impairment that was not correctable with refractive error correction or surgical intervention. The participants with best-corrected distance visual acuity ⬍6/18 to perception of light or central visual field ⬍10° because of an untreatable cause in both eyes were considered as having low vision. The subjects with a treatable cause of visual impairment in any eye were not considered as having low vision. The causes considered as treatable were refractive error, cataract, posterior capsular opacification after cataract surgery, and corneal scars that were clinically judged to be treatable by penetrating keratoplasty in the developing country setting (determined by reviewing the clinical findings documented in the medical record and slit-lamp photographic documentation of the corneal scar). All the other causes were considered untreatable. Amblyopia was considered as the cause of low vision when the best-corrected distance visual acuity was ⬍6/18 to perception of light with no apparent organic lesion in the eye and the patient satisfied at least one of these criteria: tropia, nystagmus, bilateral ametropia of spherical equivalent ⫾5.00 diopters or worse, or anisometropia of spherical equivalent ⫾2.00 diopters or worse.
Statistical Analysis Data were entered on self-coded forms by the investigators and the examiners and were then entered into computers by two data entry operators using the Fox Pro program with internal consistency checks.5 Data entered by one data entry operator were checked by the other data entry operator after completion of each cluster. This was done randomly on 10% of all the data entered for each cluster. To determine and verify outliers, monthly range and consistency checks were done using SPSS (Windows). Analyses were done using the SPSS software (SPSS for Windows, Rel.10.0.5. 1999; SPSS Inc., Chicago, IL). The prevalence of low vision was adjusted for the estimated age, gender, and urban–rural distribution of the population of India for the year 200011,12 to obtain composite estimates for the overall prevalence of low vision. The design effect of the sampling strategy was calculated using the low vision prevalence in each cluster,13 and the 95% confidence intervals of the estimates were adjusted accordingly. Poisson distribution14 was assumed for prevalence less than 1% and normal approximation of binomial distribution for prevalence 1% or more. The demographic associations of low vision with age, gender, socioeconomic status, and urban–rural residence were assessed with univariate analysis using the chi-square test followed by multivariate analysis using multiple logistic regression. All variables were introduced in the model simultaneously, and none of the variables were optimized. The effect of each category of a multicategorical risk factor variable was assessed by keeping the first or the last category as the reference. These data on low vision were extrapolated to the population of India for the year 2000.11,12 In addition, the prevalence of low vision was estimated for the years 2010 and 2020 if the current age-specific and gender-specific rates continue, by applying these rates to the estimated age, gender,
Dandona et al 䡠 Low Vision in India
Figure 1. Prevalence of low vision for the four study areas of The Andhra Pradesh Eye Disease Study. The graph shows the prevalence for each of the study areas and of rural study areas adjusted for age and gender distribution of the population of India in 2000, as well as the prevalence for all study areas combined adjusted for age, gender, and urban–rural distribution of the population of India in 2000. PL ⫽ perception of light.
and urban–rural distribution of the population of India in 2010 and 2020.11,12
Results Of the 11,786 eligible subjects, 10,293 (87.3%) participated in the study from the four areas of APEDS. Of these, 7775 (75.3%) were from the three rural areas, 5439 (52.8%) were females, and 122 (1.2%) were examined at home.
Prevalence of Low Vision Of the 10,293 subjects who were clinically examined, 144 (1.4%) had low vision. The prevalence of low vision for the study areas combined, adjusted for age, gender, and urban-rural distribution, was 1.05% (95% confidence interval, 0.82%–1.28%; design effect 1.3). On considering only the three rural study areas of APEDS together, the age-adjusted and gender-adjusted prevalence of low vision was 1.14% (95% confidence interval, 0.87%–1.41%; design effect 1.3). Low vision was subdivided into two groups: (1) visual acuity ⬍6/60 to perception of light or central visual field ⬍10° (⬍6/60 to light perception); and (2) visual acuity ⬍6/18 to 6/60 (⬍6/18 to 6/60). The prevalence of each group is shown in Figure 1. On comparing the prevalence of ⬍6/60 to light perception and ⬍6/18 to 6/60, the former was higher in Hyderabad and was almost similar in Adilabad, but was much lower in West Godavari and Mahabubnagar.
Causes of Low Vision The prevalence of the causes of low vision for all the study areas combined is shown in Table 1. Retinal diseases were responsible
for 35.2% of the low vision followed by amblyopia, which was responsible for 25.7% of the low vision. Figure 2 shows the adjusted prevalence of the causes of low vision for the ⬍6/60 to light perception and ⬍6/18 to 6/60 groups. There was a significant difference in the prevalence of amblyopia, optic atrophy, and glaucoma for ⬍6/60 to light perception and ⬍6/18 to 6/60, but it was not very different for retinal diseases, corneal diseases, and other causes combined (congenital eye anomaly, higher visual pathway lesion, and endophthalmitis). Figure 3 shows gender and urban–rural distribution–adjusted prevalence of the causes of low vision for different age groups for all the study areas combined. The prevalence of low vision increased with increasing age. There was a variation in the causes of Table 1. Distribution of Causes of Low Vision for the Four Study Areas of the Andhra Pradesh Eye Disease Study Combined
Cause of Low Vision
Prevalence in Total Population* (95% Confidence Interval; Design Effect)
Retinal disease Amblyopia Optic atrophy† Glaucoma Corneal disease Higher visual pathway lesion Congenital eye anomaly Endophthalmitis Total
0.37% (0.26–0.51%; 1.00) 0.27% (0.17–0.40%; 1.16) 0.15% (0.08–0.26%; 1.27) 0.12% (0.06–0.21%; 1.00) 0.09% (0.04–0.17%; 1.00) 0.02% (0.004–0.08%; 1.00) 0.02% (0.003–0.07%; 1.00) 0.01% (0.00–0.04%; 1.00) 1.05% (0.82–1.28%; 1.30)
* Adjusted for the estimated age, gender, and urban–rural distribution of the population of India in the year 2000.11,12 † Other than caused by glaucoma.
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Figure 2. Prevalence of causes of low vision for the four study areas combined. The graph shows the prevalence for each cause adjusted for age, gender, and urban–rural distribution of the population of India in 2000. PL ⫽ perception of light.
low vision on the basis of age. Retinal diseases and optic atrophy as causes of low vision increased with increasing age. No case of low vision due to glaucoma was seen in those ⬍40 years of age. Amblyopia accounted for most low vision for those between 40 and 49 years of age. Figure 4 shows the prevalence of different causes of low vision for the two genders for all four study areas combined. The age and urban–rural distribution–adjusted prevalence of low vision for males was 1.06% (95% confidence interval, 0.77%–1.35%) and for females was 1.04% (95% confidence interval, 0.75%–1.33%). Females had a higher prevalence of low vision caused by optic atrophy, whereas males had a higher prevalence of low vision caused by glaucoma and corneal diseases.
Demographic Associations of Low Vision The distribution of those with low vision by age, gender, socioeconomic status, and urban–rural residence is shown in Table 2. On applying multiple logistic regression, the odds of having low vision increased with increasing age and decreasing socioeconomic status (Table 2).
Extrapolations to the Population of India Extrapolating these data from APEDS to the estimated 75 million population of Andhra Pradesh in the year 2000, 787,500 (95%
Figure 3. Gender and urban–rural distribution–adjusted prevalence of causes of low vision for different age categories for the four study areas combined.
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Dandona et al 䡠 Low Vision in India
Figure 4. Age and urban–rural distribution–adjusted prevalence of causes of low vision for both genders for the four study areas combined.
confidence interval, 615,000 –960,000) people would have low vision. Figure 5 shows the prevalence of low vision for the estimated population distribution of India in the years 2010 and 2020 if the current age-specific and gender-specific rates of low vision con-
tinue. If the data are extrapolated to the estimated 1014 million population of India in the year 2000,8 10.6 (95% confidence interval, 8.4 –12.8) million people would have low vision. Similarly, of the estimated 1168 million population of India in 2010,8 13.3 (95% confidence interval, 10.6 –16) million people would
Table 2. Association of Low Vision with Age, Gender, Socioeconomic Status, and Area of Residence
Age (yrs)* 0–15 16–29 30–39 40–49 50–59 60–69 ⱖ70 Gender† Male Female Socioeconomic status‡ Upper Middle Lower Extreme lower Residence§ Hyderabad West Godavari Adilabad Mahabubnagar
Total (n ⴝ 10,293)
No. with Low Vision (%)
Odds Ratio for Having Low Vision with Multiple Logistic Regression (95% Confidence Interval)
2861 1845 1863 1424 1047 900 353
9 (0.3) 7 (0.4) 16 (0.9) 24 (1.7) 31 (3.0) 35 (3.9) 22 (6.2)
1.00 1.28 (0.47–3.44) 2.81 (1.24–6.38) 5.57 (2.56–12.10) 10.15 (4.81–21.44) 12.87 (6.15–26.93) 22.21 (10.10–48.84)
4854 5439
71 (1.5) 73 (1.3)
1.00 0.94 (0.67–1.31)
362 3172 5212 1354
1 (0.3) 37 (1.2) 80 (1.5) 25 (1.8)
1.00 3.67 (0.50–27.0) 5.59 (0.77–40.73) 7.46 (1.00–55.87)
2522 2503 2690 2578
26 (1.0) 48 (1.9) 29 (1.1) 41 (1.6)
1.00 1.54 (0.94–2.51) 0.95 (0.55–1.64) 1.30 (0.78–2.14)
* P ⬍ 0.0001, univariate test for trend. P ⫽ 0.88, univariate chi-square test. P ⫽ 0.011, univariate test for trend; socioeconomic status defined according to monthly per capita income in Indian rupees: upper ⬎2000 (US $45), middle 501–2000, lower 201–500, and extreme lower ⱕ200. Data on socioeconomic status not available for 193 subjects.
† ‡
P ⫽ 0.005, univariate chi-square test; Hyderabad is urban area, West Godavari is relatively well-off rural area, and Adilabad and Mahabubnagar are poor rural areas.
§
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Figure 5. Prevalence of low vision for the four study areas combined of The Andhra Pradesh Eye Disease Study for the years 2000, 2010, and 2020. The graph shows the prevalence for each year adjusted for the estimated age, gender, and urban–rural distribution of the population of India for that year. PL ⫽ perception of light.
have low vision, and of the 1312 million population in 2020,8 16.7 (95% confidence interval, 13.4 –20) million people would have low vision if the current trend continues.
Discussion The APEDS was a cross-sectional population-based study representative of the population of Andhra Pradesh in which the participants underwent a detailed eye examination. This allows us to comment on low vision for the population at large.
Definition and Causes of Low Vision In the commonly used World Health Organization classification of visual impairment, low vision is best-corrected visual acuity ⬍6/18 to 3/60 in the better eye.15 However, this includes treatable causes such as cataract and excludes those individuals who have best-corrected visual acuity ⬍3/60 to perception of light in the better eye who may have useful residual vision and can benefit from low vision services. In this background, modification in the definition of low vision has been suggested by a consultation of the World Health Organization, which defined a person with low vision as one who has impairment of visual function even after treatment or refractive correction and has visual acuity ⬍6/18 to perception of light or central visual field ⬍10°, provided he or she has functional vision for navigation.2 This definition captures those who may benefit from low vision services and hence is preferred. Some data are available on the causes of low vision using the ⬍6/18 to no light perception criterion, mainly from the clinic settings.16,17 In these reports patients with cataract, which is a correctable cause of visual impairment for the most part, have also been included.
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To estimate the prevalence and causes of low vision in an Indian population to form a basis for planning low vision services, in this report we considered people with bestcorrected distance visual acuity ⬍6/18 to perception of light or central visual field ⬍10° because of an untreatable cause in both eyes as having low vision, as suggested by consultation with the World Health Organization.2 To our knowledge, these are the first population-based data on low vision with this definition that can assist in the planning of low vision services. We did not consider cataract, refractive error, posterior capsular opacification after cataract surgery, and corneal scars, which were clinically judged to be treatable by penetrating keratoplasty, as causes of low vision, because these are treatable.
Low Vision in Our Population The prevalence of low vision in our population was estimated to be 1.05%. As expected, the prevalence of low vision in the urban study area was lower compared with the three rural study areas. We have previously reported similar results for blindness in this population.3 These data suggest that 1 of every 100 people in the state of Andhra Pradesh has low vision. The increase in prevalence of low vision with increasing age is not surprising. Retinal diseases and amblyopia accounted for approximately 60% of the low vision. The retinal diseases that accounted for most low vision included age-related maculopathy, macular degeneration caused by myopia, retinitis pigmentosa, and macular scar caused by chorioretinitis. Most of the low vision caused by amblyopia was bilateral ametropia of spherical equivalent ⫾5.00 diopters or worse (79.4%), followed by anisometropia (14.7%), and nystagmus (5.9%). Of the bilateral ametropia, 77.8% was due to myopia, and the rest was due to hyperopia. Amblyopia caused by myopia was associated with spherical equivalent
Dandona et al 䡠 Low Vision in India of ⫺5.00 diopters or worse, including 61.9% with spherical equivalent ⫺10.00 diopters or worse in both eyes. None of the eyes considered as having refractive error–related amblyopia were treatable at this stage. Primary open-angle glaucoma accounted for approximately 70% of low vision caused by glaucoma. Keratitis after fever during childhood, especially exanthematous fever, accounted for most low vision caused by corneal diseases, followed by trauma.
Implications for Low Vision Services Low vision has been considered as one of the priorities in VISION 2020.1 In the background of these data, the following are the implications for low vision services in the context of VISION 2020.
Need for Low Vision Services From these data it is estimated that there were 10.6 million people with low vision in the year 2000 in India. These data also suggest that most low vision was in the elderly population, especially 50 years of age or more. Considering the older age of most of the people with low vision, it is probable that their motivation to use low vision services would be less and that these people are likely to have other age-related disabilities as well. Hence, the actual need for low vision services would probably be less than the number of people with low vision. More research would be needed to determine how many of those having low vision with a certain definition would actually need low vision services.
Priority for Low Vision Services In the same population, we found that the prevalence of blindness (presenting visual acuity ⬍6/60 or central visual field ⬍20° in the better eye) was 1.84% and of moderate visual impairment (presenting visual acuity ⬍6/18 to 6/60 or equivalent visual field loss in the better eye) was 8.09%.3,4 Cataract and refractive error, both of which are easily treatable, were responsible for most blindness and moderate visual impairment. The strategies to reduce low vision in this population should be made in the background of the significant burden of treatable blindness and moderate visual impairment.
Provision of Low Vision Services Provision of low vision services is multidisciplinary. On the basis of the needs of the patient, these services are provided by a team of eye-care personnel, mobility instructors, and school teachers. Eye-care personnel trained in assessment of low vision provide both optical and nonoptical low vision devices. The help of a mobility instructor is sought in cases in which there is difficulty with mobility. Linking with school teachers is important for young patients who attend school. Most low vision service in India is being provided at the tertiary level clinics and hospitals. This is because eye-care personnel trained in low vision services and mobility instructors are available mainly in cities. It is possible that some of the low vision services, such as nonoptical aids and
stand magnifiers, can be made available at the secondary level eye hospitals through trained eye-care personnel. However, the feasibility of extending these services has to be based on the actual need for low vision services in the community. Determination of this actual need will require more research as suggested previously. The other important issues in provision of low vision services are availability and affordability of the low vision devices. Attempts have to be made to reduce the cost of low vision devices to make them affordable for those who have motivation to use these devices. Innovative ways to make simple optical magnifiers at low cost are available.17,18
Strategies to Reduce Low Vision Retinal diseases were the leading cause of low vision. Currently, however, it does not seem feasible to reduce this burden in the developing country setting. The strategies to reduce low vision could include the possibly avoidable causes of low vision such as amblyopia, glaucoma, and corneal diseases. Low vision caused by amblyopia was mainly refractive error related. This calls for effective vision screening programs that can detect the refractive error early and provide refractive services.19 Glaucoma is a silent disease; hence, detection of glaucoma is not easy. However, a significant difference could probably be made if a complete dilated eye examination and a check for intraocular pressure were offered to those who report to the clinics or hospitals for any eye ailment, especially those 40 years of age or older.20,21 This could lead to early diagnosis of glaucoma, perhaps making it possible to stop or delay the progression of vision and visual field loss. Most of the low vision caused by corneal diseases was accounted for by keratitis after fever during childhood. Corneal opacity after exanthematous fever could be due to vitamin A deficiency precipitated by measles. Other cases of corneal opacity could be due to trauma. Both of these causes are preventable and could be reduced through effective health and eye health promotion strategies. The projected burden of low vision in India in 2010 and 2020, calculated for the situation if the current trend continues, would be reduced if effective strategies were put in place to reduce these avoidable causes of low vision. In addition, awareness about low vision services needs to be addressed for the public and the eye-care providers. It is important to make people aware that it is possible to use residual vision to increase the quality of life. In a report from Australia on referral patterns for low vision services among ophthalmologists, most of the ophthalmologists referred the patients with best-corrected visual acuity ⬍6/12 to 6/60 to low vision services and not those with bestcorrected visual acuity ⬍6/60.22 Hence, it is important to make the eye-care personnel aware of the referral criteria for low vision services, so that patients with low vision can use these services. The availability of low vision services is related to the availability of human resources trained in providing these services. An attempt has to be made to increase the number of these trained personnel based on the need for these services. In addition, attempts have to be made to reduce the
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Ophthalmology Volume 109, Number 10, October 2002 cost of low vision devices to make them available and affordable. In conclusion, these data suggest that there is a significant burden of low vision in this population. Therefore, an attempt should be made to make provision of low vision services an integral part of comprehensive eye-care services for the visually disabled. Acknowledgments. The authors acknowledge the guidance of Dr. Catherine A. McCarty and Prof. Hugh R. Taylor in the study design.
References 1. World Health Organization. Global Initiative for the Elimination of Avoidable Blindness. Geneva: World Health Organization, 1997. WHO/PBL/97.61. 2. World Health Organization. The Management of Low Vision in Children. Report of a WHO Consultation: Bangkok, July 1992. Geneva: World Health Organization,1993. WHO/PBL/ 93.27. 3. Dandona L, Dandona R, Srinivas M, et al. Blindness in the Indian state of Andhra Pradesh. Invest Ophthalmol Vis Sci 2001;42:908 –16. 4. Dandona R, Dandona L, Srinivas M, et al. Moderate visual impairment in India: the Andhra Pradesh Eye Disease Study. Br J Ophthalmol 2002;86:373–7. 5. Dandona R, Dandona L, Naduvilath TJ, et al. Design of a population-based study of visual impairment in India: the Andhra Pradesh Eye Disease Study. Indian J Ophthalmol 1997;45:251–7. 6. Dandona L, Dandona R, Naduvilath TJ, et al. Is current eye-care-policy focus almost exclusively on cataract adequate to deal with blindness in India? Lancet 1998;351:1312– 6. 7. Dandona R, Dandona L, Naduvilath TJ, et al. Refractive errors in an urban population in southern India: the Andhra Pradesh Eye Disease Study. Invest Ophthalmol Vis Sci 1999;40:2810 – 18. 8. Dandona L, Dandona R, Naduvilath TJ, et al. Burden of moderate visual impairment in an urban population in southern India. Ophthalmology 1999;106:497–504.
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9. Ferris FL III, Kassoff A, Bresnick GH, Bailey L. New visual acuity charts for clinical research. Am J Ophthalmol 1982;94: 91– 6. 10. Humphrey Field Analyzer II User’s Guide. San Leandro, CA: Humphrey Instruments Inc, 1994. 11. US Census Bureau. International data base (IDB). Washington, DC: US Census Bureau (accessed [Rev. May 10, 2000, cited December 2000]). Available from URL: http://www. census.gov/cgi-bin/ipc/idbsum?cty⫽IN. 12. World Urbanization Prospects, the 1996 revision. New York: United Nations, 1998. 13. Bennett S, Woods T, Liyanage WM, Smith DL. A simplified general method for cluster-sample surveys of health in developing countries. Stat Q 1991;44:98 –106. 14. Rosner B. Fundamentals of Biostatistics, 2nd ed. Boston: Duxbury Press, 1986;84 –92, 302– 68, 404 – 8. 15. International Statistical Classification of Diseases and Related Health Problems: tenth revision. Geneva: World Health Organization, 1992:456 –7. 16. Elliott DB, Trukolo-Ilic M, Strong JG, et al. Demographic characteristics of the vision-disabled elderly. Invest Ophthalmol Vis Sci 1997;38:2566 –75. 17. Herse P, Gothwal VK. Survey of visual impairment in an Indian tertiary eye hospital. Indian J Ophthalmol 1997;45: 189 –93. 18. Silver J, Gilbert CE, Spoerer P, Foster A. Low vision in east African blind school students: need for optical low vision services. Br J Ophthalmol 1995;79:814 –20. 19. Dandona R, Dandona L. Refractive error blindness. Bull World Health Organ 2001;79:237– 43. 20. Dandona L, Dandona R, Srinivas M, et al. Open-angle glaucoma in an urban population in southern India. The Andhra Pradesh Eye Disease Study. Ophthalmology 2000;107: 1702–9. 21. Dandona L, Dandona R, Mandal P, et al. Angle-closure glaucoma in an urban population in southern India. The Andhra Pradesh Eye Disease Study. Ophthalmology 2000;107: 1710 – 6. 22. Keeffe JE, Lovie-Kitchin JE, Taylor HR. Referral to low vision services by ophthalmologists. Aust N Z J Ophthalmol 1996;24:207–14.