You can do it for people 40+ as long as their expectations are reasonable. If you target distance vision for both eyes, there is a good chance they will need reading glasses by their mid-40s. LASIK doesn’t change that because it’s a problem with the lens inside the eye not focusing up close. That gets worse throughout your 40s and 50s, hence, reading glasses or bifocals. Or you can set the non-dominant eye a little bit nearsighted to delay the need for reading glasses. That’s monovision (one distance eye, one near eye), which is typically only a good thing to do if you have a successful trial period of monovision using a contact lens, prior to surgery. Once people get into their late 50s, it’s usually better to do lens replacement surgery, because they are getting into cataract territory. If someone gets LASIK at age 60 but needs cataract surgery 5 years later, they didn’t get much mileage out of LASIK. I’ve done LASIK on people in their 70s who had already had cataract surgery and weren’t happy with their refractive result afterwards. Cataract surgery was fine other than the person still needed prescription glasses due to astigmatism or whatever, and they didn’t want glasses. It’s not common but it happens occasionally, and there are rare situations when LASIK (or PRK) might be a good option for people in that age group. I actually had one guy in his mid-80s who turned out great. Which reminds me, as a medical student I rotated with a plastic surgeon for a bit. We had a 90 year old lady schedule a consult for a boob job because her husband had passed and she wanted to date again. The surgeon rightfully turned her down. I still get a little chuckle out of that one.