Question
Are the numbers associated with a distance Rx (e.g., -6.50) and a reading Rx (e.g., +1.50) mathematically combinable? In other words, should one expect a pair of +1.50 readers to reduce the effect of wearing -6.50 contacts by +1.50 (net -5.00), thus improving near vision at the "expense" of denigrating distance vision? Or do these metrics represent "apples and oranges"?
I ask this because I recently discovered (while I temporarily interrupted wearing multifocal lenses to wear an alternative pair of non-multifocal lenses) that my visual acuity improved for ALL distances, near and far, if I sported a pair of weak (+1.50) OTC readers over my -6.50 lenses. While I need stronger magnifiers (+2.50) to read the very finest print, the +1.50 readers distinctly improved my depth of field starting within 18" and continuously to at least 150' (though the amount of improvement tapered off toward infinity). At no distance was my vision denigrated by wearing the low-power readers. I was amazed. Does this suggest that my distance Rx may be too strong? I am 63 years old with minimal astigmatism, and I have eye exams annually.
Answer
To your first question, yes, the numbers from the distance Rx and the near "add" are added algebraically to get the near Rx, in your case -5.00 at near.
And yes, to your second question. If you can place +1.50 over your distance glasses or contact lenses without experiencing significant blur at 20 feet away, your distance Rx is too strong. Sounds like you need a new eye exam.
