Abstract
Purpose:
Refractive error is major cause of visual impairment in school children. We intend to determine the accuracy of visual acuity and infrared photorefraction testing in school, by comparing it to visual acuity and cycloplegic autorefraction done in the hospital.
Methods:
Retrospective data was collected from 4 schools with 1241 children (5 to 18 years) screened with visual acuity and infrared photorefraction using the Plusoptix Autorefractor A09 (Plusoptix GmbH, Nuremberg, Germany). Children referred for further examination met at least one of these criteria: 1. Vision worse than 6/12; 2. Refractive spherical equivalent lesser than -0.5D (myopia) or greater than +3.0D (hypermetropia); 3. Cylindrical error greater than 2.5D; 4.Any complaint or obvious eye pathology. Of the children who were referred for further examination, the following was done in clinic:1. Visual acuity; 2. Cycloplegic autorefraction.
Results:
Of the 1241 children listed in the schools 133 were absent. Visual acuity was recorded in 2071 eyes of which 92 eyes were worse than 6/12. Visual acuity was rechecked in clinic for 73 eyes and 28 were found to have vision of 6/12 or better .Of the 1108 children screened, 17 children were referred for vision complaints. Of the 2216 eyes screened, refraction was recorded using the photorefractor in 1892 eyes. The device was not able to get readings in 197 eyes. Myopia worse than -0.50D was seen in 100 eyes, hypermetropia worse than +3.00D was seen in 22 eyes and a cylindrical refractive error greater than 2.5D was seen in 46 eyes. Sensitivity and specificity data was calculated using the limits of our screening criteria. Visual acuity measurements alone in school screening were 42% sensitive and 93% specific. The photo refractor prediction of myopia worse than -0.5D was 62% sensitive and 84% specific, that for hypermetropia worse than +3.0D was 100% sensitive and 95% specific, and that for cylinder worse than 2.5D was 100% sensitive and 93% specific.
Conclusions:
During school screening, visual acuity measurement alone may not be sensitive enough to detect poor vision. Photorefraction can help detect significant refractive errors with reasonable accuracy. However, careful selection of screening criteria is important to be most sensitive and specific for the population screened.