If you want to make your patients happy with your service, then make sure you refer them the best place to buy the eyeglasses. Most of the clinics would usually have a pharmacy attached with the clinic so that all the medicines that is prescribed is easily obtained by them. While the doctor could enjoy the commission on each prescription that is bought from the pharmacy attached to the clinic, the reference to the online store may not yield you any commission, but the mouth spread of your service would add more value than money.
Also, since the cheap glasses online store would make the patients happy about addressing their vision problem at a simple cost than having to undergo with an operation it would be definitely give them a lot of relief. So, you should probably gain this trust of your patients so that they become loyal to you and would revisit when another concern pertaining to vision troubles them. Since the patients could get easy delivery of the eyeglasses you have prescribed then the problem will get cured if it is likely to reduce the problem.
It is also a known fact that the vision problem once diagnosed will not get rid of completely, at least your patients would avoid unwanted complications like exchanging the similar items like women using salt and sugar in place of one another, men taking right or left turn on the roads which is more dangerous. So, with the proper diagnoses and with reference to the online store that lets your patients find the best frames with multiple styles and colours that would make them look pretty. With the pretty frames it is possible that none would be able to guess that the individual is suffering with some vision problem, they would rather think of it as a symbol of fashion like many people are doing these days.