Advantages and disadvantages of snellens chart

Advantages:
The chart is familiar
Inexpensive, quick and easy to use and interpret
Disadvantages:
Snellen chart has only one 6/60 letter and an increasing number of letters increase as we go down the lines.
Patients with poor acuity are required to read less number of letters than those with good visual acuity .
The letters are lower lines are more crowded than those on the top on the chart.
There is no standard relationships between the width or height of the letters and spacing between each letters.