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Welcome to question of the day #289

Eyetools question of the day #289

I am an optometrist. Many of my patients tell me that the glasses I have recommended have made their eyesight worse. What is going on?

This happens to me as well.

In my experience, there are three categories of patients who tell me that the glasses I have recommended have made their eyesight worse.

Firstly, people who are myopic or hyperopic or astigmatic and I have provided their first pair of glasses. When they come back for their next eye examination they tell me that the glasses have made their vision worse. When I ask questions about this they tell me that they now can’t see things without their glasses that they used to be able to see before they had their first pair. When I check their prescription it hasn’t changed. Their problem is with their vision (what they see with glasses or contact lenses) and not their visual acuity (what they see with glasses or contact lenses).

I can think of two possibilities to explain their perceived reduction in vision. One, their ability to recognise blurred things has reduced. Before they had glasses, their world was blurred and they got used to interpreting what things were even though they were blurred. They had good recognition/interpretation of things through blur because that’s the way their visual system made sense of a blurred world and they did it a lot. When wearing my glasses things are very clear and their skill of recognition/interpretation through blur (without glasses) reduces through lack of practice. Two, things are so clear when wearing my glasses that they now can see how blurred things are without them. They have a quick ‘with’ and ‘without’ comparison and this highlights the extent of the blur. Their blur is more obvious.

The second category of patient who tells me that my glasses have made things worse is those that return for their next eye examination and whose prescription has changed. Their visual acuity has reduced because they are no longer wearing the optimum prescription. These patients are often myopic and it is simply a case that their myopia has increased. When I prescribe glasses for the first time to a person who is myopic I do tell them that it is likely that I will need to make their lenses stronger as myopia will naturally increase but I guess they forget this advice. Note, that there is some research to suggest that under or over-correcting people with myopia will drive myopic progression. In my experience myopia progresses for some patients even when an optimum prescription is provided.

The third category of patient who tells me that my glasses have made their sight worse are people who are presbyopic and have had their first pair of glasses for near vision. When they come back for their next eye examination after having had glasses they tell me their eyesight has become worse without their glasses. Blur recognition/interpretation is a factor here, I’m sure, but so is the passage of time. As time passes the ability to accommodate without glasses makes their near vision worse. And of course, as more time passes they will need stronger glasses for reading. I always advise patients of these passage of time-related changes but I think many forget by the time they come back for their next eye examination.

Patients are people and it is easier and psychologically more comfortable for them to blame an innate object (my glasses) on their vision changes rather than changes in their own physiology and/or anatomy or their own mortality.