Snellen Equivalent for the Bailey-Lovie Acuity Chart

Abstract

To the Editor. —Many researchers have used the Bailey-Lovie acuity chart¹ in multicenter clinical investigations, such as the Early Treatment Retinopathy Study and the Prospective Evaluation of Radial Keratotomy, because testing with this chart eliminates many of the inherent problems associated with the standard Snellen acuity chart.² Thus far, to our knowledge, no one has reported a method for directly converting the number of letters read correctly from the Bailey-Lovie chart to the denominator of the Snellen fraction for 2 ft. Since the Bailey-Lovie chart is designed to have an equal logarithmic change between lines and there is an equal number of letters per line, a simple exponential equation can be derived to relate these two factors to Snellen acuity as follows: Snellen acuity = 20×10^{[(55 - x)/50].} where X is the number of letters read correctly from the Bailey-Lovie chart. For example, if all Bailey-Lovie letters (X = 70) are correctly identified, the score