Optonet Vision Unit Documentation
Please note that this User Guide is being currently updated; new sections will be added shortly.
4.5.5.E of Snellen
This optotype uses the Snellen “E” drawn on a 5×5 matrix. The E can be oriented in one of the 4 positions (left, right, up and down).
Snellen “Es” have traditionally been used in children, although many children cannot correctly identify these four orientations. In addition, Snellen’s “E’s” are similar to grating acuity, which appear to be less sensitive for identifying amblyopia than recognition acuity.