Packing Include: an eye chart, hoodwink board, and baton.

Acuity charts are used during many kinds of vision examinations, such as "refracting" the eye to determine the best eyeglass prescription.
The largest letter on an eye chart often represents an acuity of 6/60 (20/200), the value that is considered "legally blind" in the US.
Many individuals with high myopia cannot read the large E without glasses but can read the 6/6 (20/20) line or 6/4.5 (20/15) line with glasses.
By contrast, legally blind individuals have a visual acuity of 6/60 (20/200) or less when using the best corrective lens.

The American Academy of Pediatrics Standards for Visual Acuity:

A child should be able to see the 20/40 line by age 3 or 4 and the 20/30 line by age 5.
Older kids or adults should be reading the 20/20 line.

You should arrange for a medical eye examination by an ophthalmologist if there are abnormal results.
In addition to their visual acuity, how a child's two eyes compare to each other is also important.