Prevalence of visual impairment in dementia patients in india
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Abstract
This study was done to determine the prevalence of visual impairment due to refractive errors and ocular diseases in lower middle class school children of Hyderabad, India. A total of 4,029 children, which included 2,348 males and 1,681 females, in the age range of 3 to 18 years from 9 schools were screened with a detailed ocular examination protocol. Among 3,669 children in whom visual acuity could be recorded, on presentation 115 (3.1%) had visual acuity < 6/18 in the better eye (equivalent to visual impairment), while 41 (1.1%) had visual acuity of 6/60 in the better eye (equivalent to legal blindness) out of which 18 (0.5%) had visual acuity < 6/60 in the better eye (equivalent to economic blindness). Of 115 children who presented with initial visual acuity < 6/18, vision improved to ≥6/18 with refraction in 109 (94.8%). No child was legally or economically blind after refractive correction. Prevalence of hyperopia was 22.6%, myopia 8.6% and astigmatism 10.3%. The prevalence of myopia was significantly higher among children ≥10 years of age (P<0.001). The maximum, mean and median values for myopia were 10.00, 1.35 and 0.75 D in the better eye. For hyperopia these values were 8.50, 0.65 and 0.50 D. The major causes for best corrected visual acuity < 6/9 in the worse eye for 51 (1.4%) children included amblyopia in 40 (1.1%), corneal diseases in 5 (0.1%), cataract in 2 (0.05%) and others in 4 (0.1%). Out of the total, 30 (0.7%) children had strabismus. These data support the assumption that vision screening of school children in developing countries could be useful in detecting correctable causes of decreased vision, especially refractive errors, and in minimising long term permanent visual disability.
Keywords: Visual impairment, refractive errors, ocular diseases, school children, Southern India.
Population based data concerning the prevalence of visual impairment due to uncorrected refractive errors and ocular diseases in children are not readily available for India. Of particular importance are refractive errors, which are common and easily correctable, usually with spectacles. There have been reports on prevalence of refractive errors from other populations,[1][2][3][4][5][6][7][8][9][10][11][12][13][14] but little has been reported from the Indian population.[15] To our knowledge, there is no study available in the literature dealing with prevalence and pattern of refractive errors and eye diseases among children in Southern India. This information is important in planning appropriate eye care programs to reduce the burden of visual impairment among the younger population.
The objective of this study was to determine the prevalence of visual impairment due to refractive errors and ocular diseases among school children from a lower middle income urban population in Southern India.
Objective refraction was performed with streak retinoscope, followed by subjective refraction, till the best corrected visual acuity was achieved. Cycloplegic refraction was performed in hyperopes aged > 4 years and Mohindra retinoscopy was used to test all children aged ≤ 4 years. Mohindra retinoscopy[17],[18] is a non-cycloplegic dynamic retinoscopy performed in a dark room at 50 cm with the eye fixating at the retinoscope light while the other eye is occluded. Subtracting 1.25 dioptres (D) from the power of the neutralising lens gives the refractive correction for distance.
As many children were not cooperative for subjective refraction, retinoscopy values were taken for the analysis of refractive errors. Myopia, hyperopia and astigmatism equal to or more than the absolute value of 0.50D were considered for the analysis.
Anterior segment of the eye was examined with slit lamp biomicroscope. Intraocular pressure was measured with Perkins applanation tonometer. If the child was not cooperative, digital tension was recorded. Retinal examination was performed with the help of direct ophthalmoscope without dilating the pupils.
For all the refractive errors, except myopia >6.00D, glasses were prescribed at the vision screening centre. Children with myopia >6.00D or any other ocular problem apart from refractive error were referred to the L.V. Prasad Eye Institute, Hyderabad for further evaluation and management.
Statistical analysis included estimation of the prevalence of various eye diseases with their 95% confidence intervals. Prevalence of eye disorders was estimated for the worse and better eye. Children were divided into two age groups, < 10 and ≥ 10 years, for comparison of prevalence. Disease prevalence was compared between groups with the test for large samples and Fisher's exact test for small samples.
VST Industries Limited supports the examination centre at which the eye examinations were done.