We thank Drs Bullimore and Zadnik for their interest and appreciatetheir theoretical explanation and interesting results, but we are not completelyconvinced that visual acuity scores measured at shorter distances are morereliable. Several factors in their simulation may have influenced the results.
1. Drs Bullimore and Zadnik pointed out that a steeper slope β,associated with subjects with good visual acuity, decreased the differencesin visual acuity scores between test distances. This seems to suggest thatthe phenomenon would be minimal among subjects with good vision. However,there are reports1,2 showingit was not minimal even when print sizes were available at all distances.
Dong LM, Hawkins BS, Marsh MJ. Consistency Between Visual Acuity Scores Obtained at Different TestDistances—Reply. Arch Ophthalmol. 2004;122(11):1731-1732. doi:10.1001/archopht.122.11.1731