Get checked for keratosis? Prescription lenses make certain assumption about the shape of your eye. Keratosis means your eye is a slightly wonky shape and doesn't fit the "spherical with cylindrical astigmatism" model, so a lens won't correct your vision properly.
Does the problem persist with contact lenses? Soft contact lenses can do a better job of correcting vision for someone with keratosis, as they conform to the wonky surface of the cornea.
Edit: Just realised you're probably doing market research rather than asking for yourself. Either way, people with keratosis, who don't fit into the box, might be something to consider.
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