Eyestríng. n.s. [eye and string.] The string of the eye; the tendon by which the eye is moved.

I would have broke mine eyestrings; crackt them, but
To look upon him. Shakespeare's Cymbeline.

To know whether the sheep are sound or not, see that their gums be red, the brisket-skin red, and the eyestrings ruddy. Mortimer's Husbandry.