What does 'OS' refer to in eyeglass prescriptions?

In eyeglass prescriptions, 'OS' stands for Oculus Sinister, which is Latin for "left eye." The prescription uses Latin terms to designate the different eyes, with 'OD' representing Oculus Dexter for the right eye. This terminology is widely accepted in the field of optometry and ophthalmology to standardize eye-related communications.

Using 'OS' helps to clearly differentiate between prescriptions for each eye, ensuring precision in the fitting of eyewear and the delivery of appropriate corrective measures. The use of Latin terms not only maintains historical context but also enhances clarity among professionals in the field, as these terms have been broadly adopted in medical literature and practice.