Abstract
Purpose:
The present study was a population-based study to determine the prevalence and causes of low vision in children less than 16 years in North India.
Methods:
This cross-sectional study was conducted in 40 clusters of urban Delhi. Children aged less than 16 years underwent visual acuity screening using age-appropriate visual acuity charts. All children with visual acuity of <6/12 in any eye in the age group between 3 and 15 years and inability to follow the light in age less than 3 years were referred for detailed ophthalmic examination in a centrally based clinic. Cycloplegic examination and best-corrected visual acuity (BCVA) were assessed. They were examined by an ophthalmologist to determine the prevalence and causes of functional low vision (FLV). The prevalence of FLV was compared with other population-based studies across India and other parts of the world.
Results:
Amongst 20,955 children examined for visual acuity, 789 children were referred to the central clinic for detailed ophthalmic examination. The overall prevalence of low vision was 0.62 per 1,000 children (95% confidence interval [CI] 0.12–1.90). The main anatomical cause of low vision was retinal abnormalities.
Conclusion:
Although the prevalence of children with low vision decreased as compared to previous population-based studies. There is an important need to create awareness among parents on appropriate and timely usage of low-vision devices (LVDs) at an affordable cost to improve the visual quality in children with low vision.
Keywords: Children, low vision, prevalence
Childhood blindness (CHB) has an immense psychosocial impact, not only on the affected child, but also on the family, community, and society to a large extent. Globally, around 1.4 million blind children less than 16 years of age are blind, of this approximately 75% of them belong to developing countries. The prevalence of blindness in children varies from 0.3 per thousand children in developed countries to 1.5 per thousand in developing countries.[1-4] There are numerous studies on the prevalence of CHB but only a very few population-based studies have been conducted in India on the prevalence and causes of functional low vision (FLV).[5-9]
The prevalence of low vision using functional definition is 1.05%, which extrapolates to around 13 million low-vision people across the country. A survey conducted globally amongst seven South East Asian countries, including India, reported that low vision services were provided only to approximately 10% of individuals diagnosed with low vision. Also, the same survey revealed that low-vision services should also include a component of rehabilitation that includes education, social welfare services, mobility, and activities of daily living besides being clinically oriented, that is, monodisciplinary to provide optical visual aids in the form of distance and near magnifiers.[5] The control of blindness is one of the priority areas for the World Health Organization (WHO) “Vision 2020”- the right-to-sight program.[10] This is a global initiative, that was launched by WHO in 1999 to eliminate avoidable blindness worldwide by the year 2020. The main diseases on prioritization for control in the first phase were cataracts, onchocerciasis, trachoma, refractive errors, and low vision, as not only blindness but even suboptimal vision in the form of low vision also interferes with the complete well-being of the child. This has not been extended to 2030 IN SIGHT[11] with more emphasis on cataract surgical coverage and refractive error coverage. This quality of vision is an important component of quality of life. Low vision leads to difficulties with everyday living, hampering activities previously taken for granted, such as dressing, eating, writing, traveling from place to place, and simple communication, or interacting with others. This study aims to determine the causes of low vision among children in a cross-sectional-based childhood visual impairment.
Methods
This population-based cross-sectional study was conducted from January 2015 to August 2018 in the East Delhi district of North India. The study was initiated after taking due permission from the District Blindness Control Program officer of East Delhi District and approval by the Ethics Committee of AIIMS. All children aged < 16 years at the time of the visit and stay in the East Delhi district for 6 months or more were included in the study. The sample size was calculated to be 20,000 based on an estimated 3.34 per thousand prevalence of visual impairment (presenting visual acuity < 6/18 in the better eye).[12] Cluster random sampling (CRS) methods were used to select 40 clusters in the district with a target sample size of 500 children in each cluster and 90% coverage. The team included field workers, social workers, and optometrists who were trained in study methods before the initiation of the study after providing them 1 week of training on visual acuity examination and filling out an enumeration form. There were two phases in the study, the enumeration phase and the detailed ophthalmic examination phase.
Enumeration and screening
A detailed house-to-house visual acuity examination was conducted by the study team. Parents of all children were informed about the nature of the study after taking informed written consent. Demographic details about the parents and eligible children in visited households were recorded. Besides this, socioeconomic status was elicited using modified Kuppuswamy criteria that included occupation, education of the head of household, and family income per month.[13] The children who could not communicate and parents of children refusing to give consent were excluded from the study. A history of common ocular symptoms was elicited for each eligible child. Unaided visual acuity of enumerated children aged over 2 years was assessed by using the Lea symbols chart in the 3–5 years age group and logMAR tumbling E charts for the 6–15 years age group. For children aged 0–2 years, fixation and following torchlight were assessed. All children with unaided visual acuity < 6/12 in any eye, children wearing glasses, and children who did not fix and follow were referred to a centrally located clinic for a detailed ophthalmic examination. At the clinic, all referred children underwent detailed visual acuity examination using Cardiff acuity cards for children < 3 years, Lea charts for 3–5 years ages, and logMAR E chart for the 6–15 years age group.
Clinical examination
All children with unaided visual acuity less than 6/12 in any eye were referred for clinical examination in a centrally based clinic. There, an ophthalmologist and optometrist conducted a detailed ophthalmic examination including a repeat assessment of visual acuity using retro-illuminated logMAR E charts, dry, and cycloplegic refraction, anterior segment examination, and a dilated posterior segment evaluation. Detailed anterior segment examination included the Hirschberg test and slit-lamp biomicroscopic examination. Pupils were dilated using 2% homatropine or 0.5% tropicamide in case the child was > 10 years with no strabismus. Refraction was performed after a minimum of 45 min of instillation of cycloplegic drops (homatropine 2%) and achieving adequate pupillary dilatation. Lensometry was done to check the power of the glasses already worn by children. To ensure uniformity between refraction, an inter-observer variation assessment was conducted between the four optometrists with one of the ophthalmologists as a gold standard. The kappa for this was 0.74 signifying adequate agreement.
An ophthalmologist examined the posterior segment using direct and indirect ophthalmoscopes. The causes of VI were classified according to the WHO PBL form, which divides the form into anatomical and etiological categories.[3] The anatomical section comprised eye-wise sections related to abnormalities in ocular structures such as the whole globe, cornea, lens, uvea, retina, and optic nerve, along with the subsections related to each category to define the further abnormalities in them. Etiological sections comprised six major sections of hereditary, intrauterine, perinatal, and postnatal, which cannot determine the further subsections to be filled for categorization. With two or more anatomical sites involved for VI, the major site was selected or if two sites contributed equally, the most treatable condition was selected. We followed the standard classification of visual impairment and blindness as per the International classification of disease (ICD 10)[14] and the children less than 3 years that were unable to fix and follow the light were considered blind. Here along with a detailed ophthalmic examination by an ophthalmologist, the detailed cycloplegic examination was conducted to determine the best corrected visual acuity (BCVA), the children who had impairment of visual functioning even after treatment and/or standard refractive correction and BCVA of less than 6/18 to light perception or a visual field of fewer than 20 degrees from the point of fixation, but who uses, or can potentially use, vision for planning and/or execution of a task were defined as functional low vision (FLV).[5]
Children with major eye problems such as pediatric cataracts, strabismus, congenital nasolacrimal duct abnormality, and retinal degeneration were referred to the base hospital and the study team facilitated their treatment. Those referred children who did not visit the central clinic even after repeated requests were visited at home by the clinical team to minimize attrition.
Finally, children with low vision were provided training on the use of low-vision devices (LVDs) and rehabilitation to make the best possible use of their remaining vision.
Statistical analysis
The analysis was done after data entry in a specifically designed database in Epi data. The entered data were exported and final data analysis was done using Stata 14. The distribution of participants with respect to age, gender, residence type, education status, and income was tabulated. A P value of < 0.05 was considered statistically significant. Categories of visual impairment and blindness were as per ICD-10 that categorized the visual impairment using the criteria of presenting visual acuity in the better eye as mild, moderate, and severe visual impairment and blindness.[14]
Results
Overall, 21,532 children were enumerated from 40 different clusters that covered a total of 9,859 households. Of these enumerated children, 20,955 (97.3%) underwent screening for visual acuity. A total of 20,166 (96.2%) children had unaided visual acuity either normal or >6/12 in both eyes or were able to fix and follow (<3 years). The remaining 789 (3.8%) children aged 0–15 years having unaided visual acuity less than 6/12 in any eye were referred by optometrists for detailed ophthalmic examination to the central clinic.
Amongst these 789 children referred, 453 (57.4%) were aged between 11 and 15 years, followed by 286 (36.3%) children in the age group of 6–10 years and 46 (5.8%) children between 3 and 5 years and the remaining 4 (0.5%) children were less than 3 years. There were 384 (48.7%) female and 405 (51.3%) male children. A total of 629 (79.7%) children underwent examination at the clinic and the remaining 93 (20.3%) underwent detailed ocular examination at home [Table 1].
Table 1.
Distribution of children examined and referred for clinical examination according to socio-demographic characteristics
| Characteristics | Screened in house-to-house visit (n=20,955) | Referred (%) (n=789) | Referral rate (%) |
|---|---|---|---|
| Age (yrs.) | |||
| <3 | 3376 (16.1) | 4 (0.5) | 0.1 |
| 3-5 | 3946 (18.8) | 46 (5.8) | 1.2 |
| 6-10 | 7085 (33.8) | 286 (36.3) | 4 |
| 11-15 | 6548 (31.2) | 453 (57.4) | 6.9 |
| Gender | |||
| Male | 11032 (32.6) | 405 (51.3) | 3.7 |
| Female | 9923 (47.4) | 384 (48.7) | 3.9 |
| Education of child | |||
| Preschool | 7663 (36.6) | 68 (8.6) | 0.9 |
| Primary school | 7500 (35.8) | 295 (37.4) | 3.9 |
| Middle school | 4054 (19.3) | 278 (35.2) | 6.9 |
| ≥9th standard | 1738 (8.3) | 148 (18.8) | 8.5 |
| Child wearing glasses | |||
| No | 20088 (95.9) | 368 (46.6) | 1.8 |
| Yes | 867 (4.1) | 421 (53.4) | 48.6 |
| Education of father | |||
| Illiterate and primary school | 3968 (19.0) | 97 (12.3) | 2.4 |
| Middle school | 3717 (17.7) | 122 (15.5) | 3.3 |
| High school | 6394 (30.5) | 237 (30.0) | 3.7 |
| Intermediate | 4273 (20.4) | 190 (24.1) | 4.5 |
| Graduate and above | 2603 (12.4) | 143 (18.1) | 5.5 |
| Father wearing glasses | |||
| No | 19422 (92.7) | 687 (88.3) | 3.5 |
| Yes | 1201 (5.7) | 91 (11.7) | 7.6 |
| Education of mother | |||
| Illiterate and primary school | 7400 (35.3) | 214 (27.1) | 2.9 |
| Middle school | 4191 (20.4) | 161 (20.4) | 3.8 |
| High school | 5127 (24.5) | 225 (28.5) | 4.4 |
| Intermediate | 2621 | 108 (13.7) | 4.1 |
| Graduate and above | 1616 (7.7) | 81 (10.3) | 5 |
| Mother wearing glasses | |||
| No | 19843 (94.7) | 697 (89.0) | 3.5 |
| Yes | 1018 (4.8) | 86 (11.0) | 8.5 |
| Socioeconomic status | |||
| Upper middle (II) | 2526 (12.1) | 119 (15.1) | 4.7 |
| Lower middle (III) | 6959 (33.2) | 323 (40.9) | 4.6 |
| Upper lower (IV)/lower (V) | 11470 (54.7) | 347 (44.0) | 3 |
Source: Wadhwani M, Vashist P, Senjam SS, Gupta V, Saxena R, Tandon R. A population-based study on the prevalence and causes of childhood blindness and visual impairment in North India. Indian J Ophthalmol. 2021;69 (6):1381-1387
Using the above-defined criteria, 13 children fitted the criteria for FLV (BCVA < 6/18 to PL positive) in the age group of 3 to15 years. Amongst these 13 children, 8 (61.5%) were males and 5 (38.5%) were females. A total of 6 of these 13 children with low vision were wearing glasses. Parents of these children were not wearing glasses and all belonged to upper lower or lower socio-economic groups [Tables 2 and 3].
Table 2.
Distribution of demographic features among children diagnosed with low vision
| Low vision (%) | No low vision (%) | Total (%) | |
|---|---|---|---|
| Age (yrs.) | |||
| 3-5 | 4 (30.8) | 36 (5.1) | 40 (5.57) |
| 6-10 | 5 (38.5) | 256 (36.3) | 261 (36.35) |
| 11-15 | 4 (30.8) | 413 (58.6) | 417 (58.08) |
| Total | 13 (100.0) | 705 (100.0) | 718 (100.0) |
| Gender | |||
| Male | 8 (61.5) | 362 (51.4) | 370 (51.53) |
| Female | 5 (38.5) | 343 (48.7) | 348 (48.47) |
| Total | 13 (100.0) | 705 (100.0) | 718 (100.0) |
| Children wearing glasses | |||
| No | 7 (53.8) | 360 (51.1) | 367 (51.11) |
| Yes | 6 (46.2) | 345 (48.9) | 351 (48.89) |
| Total | 13 (100.0) | 705 (100.0) | 718 (100.0) |
| Education of father | |||
| Primary school | 3 (23.1) | 87 (12.3) | 90 (12.53) |
| Middle | 2 (15.4) | 109 (15.5) | 111 (15.46) |
| High School | 6 (46.2) | 213 (30.2) | 219 (30.5) |
| Intermediate | 1 (7.7) | 176 (25) | 177 (24.65) |
| Graduate and above | 1 (7.7) | 120 (17) | 121 (16.85) |
| Total | 13 (100.0) | 705 (100.0) | 718 (100.0) |
| Father wearing glasses | |||
| No | 13 (100.0) | 610 (87.6) | 623 (87.87) |
| Yes | 0 (0.0) | 86 (12.4) | 86 (12.13) |
| Total | 13 (100.0) | 705 (100.0) | 718 (100.0) |
| Education of mother | |||
| Primary school | 4 (30.8) | 195 (27.7) | 199 (27.72) |
| Middle | 5 (38.5) | 143 (20.3) | 148 (20.61) |
| High School | 3 (23.1) | 196 (27.8) | 199 (27.72) |
| Intermediate | 1 (7.7) | 100 (14.2) | 101 (14.07) |
| Graduate and above | 0 (0.0) | 71 (10.1) | 71 (9.89) |
| Total | 13 (100.0) | 705 (100.0) | 718 (100.0) |
| Mother wearing glasses | |||
| No | 13 (100.0) | 622 (88.9) | 635 (89.06) |
| Yes | 0 (0.0) | 78 (11.1) | 78 (10.94) |
| Total | 13 (100.0) | 705 (100.0) | 718 (100.0) |
| Socioeconomic | |||
| Upper Middle (II) | 1 (7.7) | 102 (14.5) | 103 (14.35) |
| Lower Middle (III) | 4 (30.8) | 289 (41) | 293 (40.81) |
| Upper Lower (IV) | 8 (61.5) | 314 (44.5) | 322 (44.85) |
| Total | 13 (100.0) | 705 (100.0) | 718 (100.0) |
*We have not included six children with no perception of light, as the definition of low vision includes BCVA<PL positive to 6/18
Table 3.
Distribution of anatomical and etiological causes of low vision according to demographic details
| Anatomical causes | Age | |||||
|---|---|---|---|---|---|---|
|
| ||||||
| 3-5 yrs | 6-10 yrs | 11-15 yrs | Male | Female | Total | |
| Cornea | 1 | |||||
| Scar | 0 | 1 | 0 | 1 | ||
| Lens | 1 | |||||
| Aphakia | 0 | 0 | 1 | 1 | 0 | `1 |
| Retina (other) | 7 | |||||
| Cone deficiency | 1 | 0 | 0 | 1 | 0 | 1 |
| Foveal hypoplasia | 0 | 0 | 1 | 1 | 0 | 1 |
| Fundus coloboma, grade IV involving disc and macula | 2 | 0 | 0 | 1 | 1 | 2 |
| High myopia, chorio retinal degeneration | 0 | 1 | 1 | 0 | 2 | 2 |
| Rod cone deficiency | 0 | 1 | 0 | 1 | 0 | 1 |
| Etiological causes Amblyopia | 1 | 2 | 1 | 2 | 2 | 4 |
| Total | 4 | 5 | 4 | 8 | 5 | 13 |
Causes
Amongst these 13 children with low vision, 7 had retinal abnormalities, 1 each had corneal or lenticular, 4 had no identifiable anatomical abnormality, and other etiological abnormalities in the form of amblyopia [Table 4].
Table 4.
Prevalence of anatomical causes in low-vision children
| Anatomical causes | n (%) | Prevalence (95% CI) per 1000 |
|---|---|---|
| Cornea | ||
| Scar | 1 (7.7) | 0.056 (0.052-0.594) |
| Lens | ||
| Aphakia | 1 (7.7) | 0.056 (0.052-0.594) |
| Retina | 7 (53.9) | 0.398 (0.390-0.405) |
| Cone deficiency | 1 | |
| Foveal hypoplasia | 1 | |
| Fundus coloboma grade IV involving disc and macula | 2 | |
| High myopia, chorioretinal degeneration | 2 | |
| Rod cone deficiency | 1 | |
| Etiological cause (amblyopia) | 4 (30.7) | 0.227 (0.220-0.233) |
| Total | 13 (100.0) | 0.739 (0.723-0.745) |
Prevalence
The prevalence of low vision in the current study was 0.62 per thousand. Of these 13 children with low vision, only 9 reached the RP center for low vision rehabilitation and counseling even after repeated home visits as 3 had shifted and 1 refused due to the inability of the relative or caretaker. Hence, a team from our institute constituting of medical social workers, low-vision counselors, and an ophthalmologist visited their houses to provide them with training related to rehabilitation and knowledge of centers related to the vocational courses and education near their residence.
This team also visited the home of children that were having a vision as PL negative and educated their parents regarding visual rehabilitation and the presence of a school for the blind in their nearby area. One child was provided training on Braille, two underwent laser delimitation and vitreoretinal surgery in one of the eyes, one was provided with dark gray and tinted glass and one was provided admission to the school for the blind [Table 5]. A rehabilitation counselor guided all these children regarding the use of braille and the type of activities they can do to make their life easier, they were also told the benefits of using yellow-tinted glasses, and other optical devices. They were taught about the use of optical LVDs in the form of magnifying lenses. One child was referred to a nearby low vision rehabilitation center for providing him training on braille use to continue his study and was asked telephonically after 6 months, the child reported happily that now his studies have become easier and more interesting for him.
Table 5.
Distribution of low-vision children according to service provided at the base hospital
| Low vision and rehabilitation counseling | n |
|---|---|
| Braille | 1 |
| Surgery and magnifying lenses in post-operative period | 2 |
| Dark grey glasses | 1 |
| Tinted-yellow glass | 1 |
| Admission to school for blind | 1 |
| Laser delimitation | 2 |
| Refraction | 8 |
Discussion
Children with low vision have to deal with an inverse relationship between the extent of visual impairment and functional independence. These children face many challenges in school, with orientation and mobility, and with social interactions.[15] Impairment of visual function makes them physically inactive due to a lack of functional independence and appropriate programming by schools. Low vision can lead to social isolation, which can eventually lead to depression and diminished self-esteem.
On comparing the prevalence of the current study with other population-based studies in children done across the world, it was found that the prevalence of low vision has decreased over a period of time [Table 6].[16]A more detailed evaluation of these parameters including psychological assessment can aid in planning special education for visually impaired children. Changes in the environment that do not cost much, should be an integral part of the low-vision care of these children. Depending on the educational need to use Braille or the ability to use print as an educational medium, additional wings of low vision care need to be set up within available rehabilitation services in schools for the blind. Some of these children with low vision, studying in a school for the blind, after being trained once, can possibly be integrated into regular schools and thus the school for the blind can be reclassified as a school for the visually impaired.[5-9]
Table 6.
Comparison of prevalence and causes of functional low vision across various countries in South East Asia[16]
| Study Site | Rural | Urban | Malaysia[20] | South Africa[21] | China[22] | Current study (India) | ||
|---|---|---|---|---|---|---|---|---|
|
|
|
|||||||
| India[17] | Nepal[18] | India[4] | Chile[19] | |||||
| Visual acuity examination | 3997 | 4802 | 5949 | 5265 | 4622 | 4679 | 5882 | 20955 |
| Low vision (n) | 11 | 9 | 14 | 11 | 3 | 4 | 5 | 13 |
| Prevalence (CI) | 2.75 (1.37-4.92) | 1.87 (0.85-3.55) | 2.35 (1.29-3.95) | 2.09 (1.04-3.74) | 0.65 (0.13-1.90) | 0.85 (0.23-2.19) | 0.85 (0.28-1,98) | 0.62 (0.12-1.90) |
| Causes | ||||||||
| Retina | 3 | 5 | 6 | 3 | 0 | 3 | 1 | 7 |
| Cornea | - | 2 | 1 | - | - | 1 | - | 1 |
| cataract | - | - | - | 1 | 1 | - | - | 1 |
| Amblyopia | 1 | 1 | 6 | 2 | 2 | 0 | 4 | 4 |
| Could not be determined | 1 | 1 | - | 4 | - | - | - | - |
In the current study, these children felt satisfied after providing them with visual rehabilitation. This is similar to the study conducted by Wadhwani et al.,[2] in their study on visually impaired children (with presenting visual acuity less than 6/18 in the better eye), a total of 89 children out of 118 reported a significant improvement (P < 0.005) in functional vision after providing them with services in the form of spectacles and surgery if needed. Gogate et al.[23] conducted a study to evaluate visual acuity and vision function before and after providing spectacles and LVDs in deaf–mute students at schools for deaf-mute in all special schools in the Pune district, these children underwent detailed visual acuity testing (with teachers’ help), refraction, external ocular examination, and fundoscopy. The LV Prasad - Functional Vision Questionnaire consisting of 20 items was administered to each subject before and after providing spectacles, LVDs. Two-hundred fifty students were dispensed spectacles and LVDs. The mean logMAR visual acuity before the introduction of spectacles and LVDs was 0.33 ± 0.36, which improved to 0.058 (P < 0.0001) after the intervention.
In another study conducted by Titiyal et al.[5] in North India in 13 schools for the blind to ascertain the need for spectacles and magnifiers as LVD in children with useful residual vision, attending school for the blind. Of a total of 703 children (less than 16 years of age) examined, 133 (18.91%) with useful residual vision were refracted and analyzed. Further 124 (17.6%) of the children were diagnosed with low vision with a visual acuity of <20/60 to light perception in the better eye. Of these, children with low vision having a useful residual vision, 51 were able to read N 10 unaided or with distance glasses, hence not evaluated on magnifiers. Thirty (22.6%) children improved to N 10 with spectacle magnifiers and were prescribed magnifiers. The main cause of low vision was aphakia in 56%, iridofundal coloboma in 5, optic atrophy in 4, and corneal scar in one child. In comparison with the current study, retinal causes were the main culprit for low vision in 7 out of 13 children with low vision., 8 children showed improvement due to the useful residual vision on using LVD in the form of spectacle magnifiers and yellow-green glasses. Even, other studies conducted on low vision globally[6-9] reported that LVDs are easily adaptive and give satisfying results in children with low vision. Hence, low-vision services enable people who are visually impaired to use adaptive devices and techniques to independently perform daily activities. Studies measuring the direct effect of low-vision intervention frequently concentrate on measures of task performance such as visual acuity change, magnification prescribed, or reading speed obtained as part of the process of evaluating, training, and prescribing for individual patients are required to help many children with low vision studying in blind schools to be shifted to integrated schools.
Conclusion
There is an important need to create awareness among parents on appropriate and timely usage of LVDs at an affordable cost to improve the visual quality in children with low vision through various non-government organizations (NGOs) and government policies. Also, we should give more insight to elevate and integrate low vision as an important part of the healthcare system by activating the knowledge of caretakers and healthcare providers for a better quality of vision in these children.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
- 1.Wadhwani M, Vashist P, Singh SS, Gupta V, Gupta N, Saxena R. Prevalence and causes of childhood blindness in India:A systematic review. Indian J Ophthalmol. 2020;68:311–5. doi: 10.4103/ijo.IJO_2076_18. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Wadhwani M, Vashist P, Senjam SS, Gupta V, Saxena R, Tandon R. A population-based study on the prevalence and causes of childhood blindness and visual impairment in North India. Indian J Ophthalmol. 2021;69:1381–7. doi: 10.4103/ijo.IJO_2408_20. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Gilbert C, Foster A, Negrel D, Thylefors B. Childhood blindness:A new form for recording causes of visual loss in children. Bull World Health Organ. 1993;71:485–9. [PMC free article] [PubMed] [Google Scholar]
- 4.Murthy GVS, Sanjeev K, Leon B, Sergio R, Gopal P, Lalit S, et al. Refractive error in children inan urban population in New Delhi. InvestigOphthalmolVis Sci. 2002;43:623–31. [PubMed] [Google Scholar]
- 5.Titiyal JS, Pal N, Murthy GV, Gupta SK, Tandon R, Vajpayee RB. Causes and temporal trends of blindness and severe visual impairment in children in schools for the blind in North India. Br J Ophthalmol. 2003;87:941–5. doi: 10.1136/bjo.87.8.941. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Faye EE, Padula WV, Padula JB. 2nd ed. Little, Brown and Co; Boston, USA: 1984. The Low Vision Child Clinical Low Vision; pp. 437–75. [Google Scholar]
- 7.Hornby S, Adolph S, Gothwal VK, Gilbert CE, Dandona L, Foster A. Evaluation of children in six blind schools of Andhra Pradesh. Indian J Ophthalmol. 2000;48:195–200. [PubMed] [Google Scholar]
- 8.Dandona L, Williams JD, Williams BC, Rao GN. Population based assessment of childhood blindness in Southern India. Arch Ophthalmol. 1998;116:545–6. [PubMed] [Google Scholar]
- 9.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. doi: 10.1136/bjo.79.9.814. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Gilbert C, Foster A. Childhood blindness in the context of VISION 2020 –The right to sight. Bull World Health Organ. 2001;79:227–32. [PMC free article] [PubMed] [Google Scholar]
- 11. [Last accessed on 2022 Sep 28]. Available from:www.globalvisiondata.org/InSight 2030 .
- 12.Dorairaj SK, Bandrakalli P, Shetty C, Vathsala R, Misquith D, Ritch R. Childhood blindness in a Rural Population of Southern India:Prevalence andetiology. Ophthalmic Epidemiol. 2008;15:176–82. doi: 10.1080/09286580801977668. [DOI] [PubMed] [Google Scholar]
- 13.Wani, Rabbanie Tariq. Socioeconomic status scales-modified Kuppuswamy and UdaiPareekh's scale updated for 2019. J Family Med Prim Care. 2019;8:1846–9. doi: 10.4103/jfmpc.jfmpc_288_19. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.World Health Organization. Cumulative official updates to ICD –Feb 2009. [Last accessed on 2021 Jul]. Available from:http://www. Who.int/clasification/icd/Official updates Combined 1996-2008 VOLUME1.pdf .
- 15.Wadhwani M, Vashist P, Singh SS, Gupta V, Saxena R, Tandon R, et al. Development of age appropriate vision function questionnaire for children with visual impairment (CHVI-VFQ) Indian J Ophthalmol. 2022;70:930–8. doi: 10.4103/ijo.IJO_1177_21. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Gilbert CE, Ellwein LB The Refractive Error Study in Children Study Group. Prevalence and causes of functional low vision in school age children. Results from standardized population surveys in Asia, Africa and Latin America. InvestOphthalmol Vis Sci. 2008;49:877–81. doi: 10.1167/iovs.07-0973. [DOI] [PubMed] [Google Scholar]
- 17.Dandona R, Dandona L, Srinivas M, Sahare P. Refractive error inchildren inan rural population in India. InvestOphthalmolVis Sci. 2002;43:615–22. [PubMed] [Google Scholar]
- 18.Pokharel GP, Negrel AD, Munoz SR, Ellwein LB. Refractive error study in children:Results from Mechi Zone, Nepal. Am J Ophthalmol. 2000;129:436–44. doi: 10.1016/s0002-9394(99)00453-5. [DOI] [PubMed] [Google Scholar]
- 19.Maul E, Barroso S, Munoz SR, Sperduto RD, Ellwein LB. Refractive error study in children:Results from La Florida, Chile. Am J Ophthalmol. 2000;129:445–54. doi: 10.1016/s0002-9394(99)00454-7. [DOI] [PubMed] [Google Scholar]
- 20.Goh PP, Abqariyah Y, Pokharel GP, Ellwein LB. Refractive error and visual impairment in school-age children in Gombak District, Malaysia. Ophthalmology. 2005;112:678–85. doi: 10.1016/j.ophtha.2004.10.048. [DOI] [PubMed] [Google Scholar]
- 21.Naidoo KS, Raghunandan A, Mashige KP, Govender P, Holden BA, Pokharel GP, et al. Refractive error and visual impairment in African children in South Africa. Invest Ophthalmol Vis Sci. 2003;44:3764–70. doi: 10.1167/iovs.03-0283. [DOI] [PubMed] [Google Scholar]
- 22.Zhao J, Pan X, Sui R, Munoz SR, Sperduto RD, Ellwein LB. Refractive error study in children:Results from Shunyi District, China. Am J Ophthalmol. 2000;129:427–35. doi: 10.1016/s0002-9394(99)00452-3. [DOI] [PubMed] [Google Scholar]
- 23.Gogate P, Deshpande M, Sudrik S, Taras S, Kishore H, Gilbert C. Changing patterns of childhood blindness in Maharashtra, India. Br J Ophthalmol. 2007;91:8–12. doi: 10.1136/bjo.2006.094433. [DOI] [PMC free article] [PubMed] [Google Scholar]