Final answer:
The abbreviation for the right eye in medical terms is OD (Oculus Dexter). It's used by eye care professionals for prescriptions and medical notes, and should not be confused with abbreviations for the ear (a.d., a.s.) or the unrelated Os.
Step-by-step explanation:
The abbreviation for the right eye in medical terminology is OD (Oculus Dexter). This term is commonly used by eye care professionals, such as optometrists and ophthalmologists, when noting prescriptions for corrective lenses or documenting medical examinations of the eyes. The options given are abbreviations where 'a.d.' could mean auris dextra, which is for the right ear, 'a.s.' is auris sinistra, for the left ear, and 'Os' stands for os, common in prescriptions to signify orally (by mouth) or it could stand for Oculus Sinister which is the left eye. However, when referring to the right eye, OD is the correct abbreviation. Meanwhile, 'a.d.' and 'a.s.' are related to ears and 'Os' is unrelated in this context.