Snellen original stimuli sizes are reported in Snellen fractions (distance from which the participant perceives the letter in meters in the numerator and the distance from which a normally sighted ind
aIncludes the patients too young to receive the visual acuity examination and those with presenting symptoms too serious to apply to the visual acuity examination. bIncludes the patients too young to
For luminance and contrast, values represent the mean of the nine values measured across the chart for black letters and for adjacent white areas. Chart parameters which do not meet the BS 4274 requir
