The E optotype on the chart had 3 limbs of equal length.A regular geometric progression of optotype sizes and distribution was employed to arrange 14 lines with 4 optotypes on each line.

• 采用三划等长的E形视标，视标大小及排列采用均匀的几何增率，每行视标数为4个，共14行，每两行视标变化进率为拶而。