Let’s start off by assuming your new prescription is accurate, and your glasses were made with high quality designs and materials, and were properly fitted. If you’re NOT sure they were, and you wear progressive lenses, read “Trouble with New Progressives”.
So what’s going on? Why the swimming, pulling, or headaches? Here’s the interesting part. Your eyes do only about 10% of your seeing – the rest is done by your visual system interpreting the signals your eyes are sending to your brain. Dr. Cheryl Murphy has a great article explaining this part of your vision. So, the light that is focused on your retina is converted into electro-chemical impulses that travel up each eyes optic nerve, joins at the optic chiasm, and then goes to the brain. Normally your brain is so used to interpreting the visual signals sent by the eye that it uses very little of its “processing power” to make sense of what you are looking at.
Then you get a new eyeglass prescription. Due to the changed nature of the visual signals, the brain now has to “think” about making sense of information instead of relying on previously programmed “visual memory.” It will send a message to the rest of your body, letting it know it’s not happy having to do this work, and that message is perceived as swimming, headaches, or pulling. To get out of the hard work of adjusting to the new Rx, it whispers “The old glasses were better.”
It’s as if you had to cross a field to get to work, and over the weeks, months and years, you have worn a comfortable path through the field, an easy passage through otherwise waist-high grasses and weeds. One day you find that someone has blocked the passage along your path, and you must take an alternate route, tramping down the overgrown vegetation to get to the other side. It’s hard, sweaty work, and doesn’t happen quickly. Over time, however, the path is established, and the walking becomes easy again.
Habituating your brains “vision module” to a new prescription is especially noticeable if you have had any type of a change in correction for astigmatism, if there has been a major change in the Rx for one eye only, or if a new element (such as the first correction for presbyopia) has been introduced.
The easy answer for an eyecare professional is to tell you – without any investigation - to “wear them for two weeks.” In my experience, 94.37% of the time, three days is all the time it takes to adapt to the new Rx. Understanding what is going on “behind blue eyes” will help you get past the initial reaction of “Why am I having trouble adapting to my new glasses?” Good luck, and hang in there!