Texas Transportation Code - TRANSP § 647.007. Operator Physical Requirements

(1) is missing a foot, leg, hand, or arm;

(2) has a mental, nervous, organic, or functional disorder that is likely to interfere with the person's ability to safely operate the motor vehicle;

(3) is missing fingers, has impaired use of a foot, leg, finger, hand, or arm, or has another structural defect or limitation likely to interfere with the person's ability to safely operate the motor vehicle;

(4) has a visual acuity of less than 20/40 (Snellen) in each eye either without glasses or with corrective lenses;

(5) has a form field of vision in the horizontal median of less than a total of 140 degrees;

(6) cannot distinguish the colors red, green, and yellow;

(7) has hearing ability of less than 10/20 in the better ear for conversational tones without the use of a hearing aid;  or

(8) is addicted to alcohol, narcotics, or habit-forming drugs.