Quantification of Refractive Error: Comparison of Autorefractor and Focometer

Abstract

This study highlighted the focometer's restricted power range, inaccuracy of astigmatism and axis determination, and dependence on subject understanding and compliance. Therefore, in most clinical settings, the focometer would not be adequate for quantifying refractive error, but the focometer spherical equivalent was within acceptable limits of the autorefractor, and the visual acuity with lenses determined by the focometer indicates its potential usefulness in public health settings, especially where only spherical ready-made spectacles are dispensed. There may be more cost-effective ways to determine refractive error in these circumstances. A potentially important enhancement in focometer methodology that improves its ease of use was identified: use only the third measurement for each eye.

Comparison between focometer and autorefractor in the measurement of refractive error among students in underserved community of sub-Saharan Africa

“…These findings are different from the findings of Du Toit et al 15 in Australia where autorefractor showed that 63% of the study population were myopic, 36% were hypermetropic and 91% had astigmatism while only 32% had astigmatism with the focometer. This variation may be related to differences in the definitions of refractive error used, differences in age group and ethnicity of the study population.…”

“…This was low compared to the findings by Du Toit et al 15 where 99% of the population studied had refractive error using the autorefractor. This may be due to the differences in definitions of the refractive errors used in their study compared with this study.…”

“…Power was set at 80%, significance level of 0.05 was chosen and an estimated prevalence of 84% was the proportion of students with focometer reading (spherical equivalent) within 0.75 DS of that of the autorefractor. 15 …”

“…It has been suggested that there is a need to carry out a field testing in a developing country setting to determine whether the focometer has application as a public health tool in such locality. 15 However, to the best of the author's knowledge there has not been any study conducted to fill this gap in knowledge in Nigeria.…”

“…14 However, there are few published data about the reliability of focometer measurements. 15 A study about its validity conducted by the manufacturer reported that focometer measurements are within 0.50 DS of an autorefractor measurement and 0.10 DS of a subjective refraction. 13 So, as recommended by WHO, the focometer measurements have offered sufficient visual outcomes that can make it to be considered for use in public health programs.…”