They are defined as routine ophthalmological examination, including refraction. They are HCPCS codes, not CPT codes, all of which makes them less than ideal. Also, it is not proper to consider them to be ‘private pay’ codes or ‘no insurance codes.’ Offices that are using them have to be careful to use them every time the patient has no medical reason for the visit, whether the patient has insurance or not, and use the CPT office visit codes (992xx series or 920xx series) for all visits that do have a medical reason/complaint/presenting problem. This causes some problems with vision plans, of course, most of which do not accept the S codes and require the use of the 920xx codes for non-medical visits, with or without refraction, depending on the payer.