If you take or have ever taken hydroxy, you need to see a retinal specialist for a complete retina exam. That is how you tell. I had a baseline before I started and a check a year later. While most people get checked every few years, I will get a check every year. That said, on proper doses hydroxy is extremely safe and only rarely causes retina issues (retina specialist told me this as well as my rheumy). Yes, it can cause retina issues, so you must get checked.

Depending on your age and the kinds of changes you've had in your vision, it could be cataracts. Whoever did your eye exam should have been able to tell you if you have developing cataracts. They can take years before they are ripe enough to need surgery, but they will start causing vision issues before then. How old are you? Do you have a history of taking steroids?