Refractions are not included in the general ophthalmological service codes (i.e. 92002, 92012, 92004, 92014) or the evaluation and management series codes (i.e. 99xxx), thus it is proper to add 92015 to the claim each time one is performed. Beyond being the proper thing to do from a coding perspective, it is a good thing to do from a revenue perspective. It is a non-covered service for most non-vision plan third parties, meaning that it is one of the few services you can provide that will not be whittled down by insurance allowable charges. In other words, what you charge for this procedure is what the patient pays. Even at $25 per refraction, you can see how this amount would add up over the course of 100, 500, or even 1000 patients.
Of course, the primary motivation for performing any procedure and coding for it is not based on money. However, you determined a refraction to be necessary to evaluate and treat the patient and you deserve to be compensated for your expertise. So do not be shy about coding appropriately for the services you render.