Eyes becoming heavy and blurry could be due to a refractive error. Since, your last visit was 6 months back you should see an ophthalmologist/optometrist again for a check-up. You could be having developing cataract causing this change in prescription glasses. You may be required to wear glasses for distance as well. Dryness in eyes is another possibility for which you may require lubricating drops like Refresh Tears or Systane. Thanks and best wishes.
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