The diagnosis code should match the service and in the case of 92015, it is far more common to use a refractive Dx code. In rare cases, possibly with corneal disease, maybe incipient cataracts, possibly systemic diabetes, the refraction might be a tool to assist in diagnosis and management, but in the vast majority of cases it is done purely to determine refractive error.
The other issue is that a refraction is not considered a covered service by most payers, including Medicare, of course, and is billed to the patient or the patient’s vision plan. In those cases, using a medical diagnosis code might actually cause the claim to be rejected by the vision plan. In general, unless it is a very unusual case, a refraction will be reported in combination with a refractive code.