No juror shall be impaneled when it appears that the juror is subject to the second, third or fourth grounds of challenge for cause set forth above, although both parties may consent. All other grounds for challenge may be waived by the party or parties in whose favor such grounds of challenge exist.
In this subsection "legally blind" shall mean having not more than 20/200 of visual acuity in the better eye with correcting lenses, or visual acuity greater than 20/200 but with a limitation in the field of vision such that the widest diameter of the visual field subtends an angle no greater than 20 degrees.
Tex. Code Crim. Proc. § 35.16