Final answer:
Under FMCSA regulations, the Medical Examiner evaluates pupil reactivity and iris symmetry during an eye examination, which are crucial for safe vehicle operation. The corneal thickness isn't typically assessed, but the corneal reflex might be tested to check protective responses.
Step-by-step explanation:
According to FMCSA regulations, when examining a driver's eyes, the Medical Examiner (ME) evaluates various aspects of the visual system to ensure a driver's ability to safely operate a commercial vehicle. Notably, the ME must evaluate pupil reactivity, which includes assessing the pupillary light reflex that involves sensory input through the optic nerve and a motor response through the oculomotor nerve. This reflex tests how well the pupils constrict to limit the amount of light entering the eye in response to bright lighting conditions.
The iris, which adjusts the amount of light coming into the eye, is also assessed for any issues such as iris symmetry, ensuring both eyes respond equally to light and there is no abnormality in their appearance. While not specifically mentioned in standard FMCSA guidelines, conjunctiva injection (redness of the eye) might be observed as a sign of possible eye disease or condition. D). The corneal thickness is not typically evaluated by the ME during standard examinations as per FMCSA regulations; however, the corneal reflex, a protective response, may be tested to ensure the integrity of the sensory and motor pathways involved in blinking.