Experimental comparison between the minimum separable and Snellen’s minimum legible

Abstract

Snellen’s optotypes, ordinarily used to determine visual acuity in routine optometric consultation, are also utilized to evaluate results of refractive surgery. Although they are considered adequate for the former purpose, it is possible that they may not be so for the latter, so, it seems convenient to go back to the fundamental basis that originated Snellen’s optotypes, minimum separable and minimum legible and hopefully confirm Snellen’s optotypes as adequate for evaluating the outcomes of refractive surgery. <em><strong>Objective:</strong></em> to establish a comparison between the minimum separable and the minimum legible in a sample from a population with undetermined visual problems. <em><strong>Methods:</strong></em> 24 eyes of people between 7 and 60 years o age with undetermined low or medium refractive anomalies were required to observe two gradually separating minute spots of light (0,3 mm diameter) and report the moment when the spots were well differentiated followed by measurement of Snellen’s visual acuity. <em><strong>Results:</strong></em> statistical analysis was performed over the two samples (paired samples) at a 95% confidence level (alpha 5%). <em><strong>Conclusion:</strong></em> the null hypothesis that established that the mean of visual acuities taken with Snellen’s optotypes was no different from the mean of measurements with the separating minute spots of light stands and cannot be rejected.