I've never heard of using Lamictal in a PRN way, above a base dose, but if it works for you that's great. No side effects when you take 600 mg in a day? If not, that's great, too. Please be aware that very high doses can cause side effects. Big jumps in dose make people more vulnerable to the Stevens-Johnson Syndrome rash. If that happens, you might want to discuss other options for PRN purposes with your doctor asap. Does your doctor know you sometimes take up to 600 mg in a day? He/she gives you enough that you have so many spare pills? I suppose if he/she is a neurologist, they know what they are doing for you with that medication.

I've never experienced double/blurry vision from Lamictal (only carbamazepine), but someone here did and even went to the ER when they wrote that they accidentally doubled their dose to 400 mg in a day. I know some people are more vulnerable to such side effects than others. Some scare a lot easier when they get them, too.

I'm sorry to read that you've had so many struggles, and still do. Hopefully you will get a break from them soon.