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Message: <blockquote data-quote="imhotep" data-source="post: 30391108" data-attributes="member: 562115">Visit an Optometrist. Simple conversion tables aren't exactly right and can only be used as guidance. Contacts rests on the eye surface and the curvature of the cornea affects it.Also the distance between the lens and eye matters. This is called the vertex distance which is the distance from the back of the lens to the front surface of the cornea. Depending on how far a lens sits from your eye, your brain perceives it as stronger or weaker.The simple conversion rule isPerceived Power = Actual Lens power / { 1 - (vertex distance * actual lens power)}There are free conversion charts available on the Net for contacts.  But my advice is just visit an optometrist. Don't try to re-invent the wheel.</blockquote>

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