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Dr. Rick
Dr. Rick, Board Certified MD
Category: Eye
Satisfied Customers: 11002
Experience:  Ophthalmology since 1994 with Retina sub-specialty interest
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Hi, Ive been prescibed contact lenses. Both eyes are myopic

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I've been prescibed contact lenses. Both eyes are myopic but my left is slightly astigmatic as well.

My prescription for glasses is -3.25 Left (with astigmatism details), -3.5 Right.

I was prescribed non-toric lenses of -4.25 Left and -3.75 Right.

When I asked why the left eye was so different I was told this was because it needed additional power to compensate for the astigmatism, but that I could trial Toric lenses if I wanted.

The Toric lenses I was prescribed were -3.5, Cyl -0.75 Axis 180. (Right eye just -3.75 as above).

My right eye sees absolutely brilliantly but my left eye is not quite as good as it is with glasses using the -4.25 non-toric lens.

Using the toric left eye lens, it is not so bad but still not perfect.

Amazingly though, as an experiment I tried putting my right eye's lens into my left eye and it actaully saw better than with the toric lens or the -4.25 lens.

I was hoping you could clear up for me:

1. Is there any way the non-toric prescription for the left eye can be correct given how different it is from the eyeglass prescription.

2. Have you ever heard of using additional power to compensate for astigmatism or is this nonsense?

3. Why do you speculate my optician might have given me a toric and a non-toric prescription if my left eye is astigmatic.

Thanks very much, just hoping for a second opinion really.


Dr. Rick :

Hi. I'm online and happy to answer your question today.

Dr. Rick :

Hi. Lets deal with your questions in turn:

Dr. Rick :

1. Yes, it is correct. It is just a different way of doing the same skinning a cat -- lots of different ways to get the same result.

Dr. Rick :

2. yes, that is how it is done. It is a math thing. A spherical equivalent is the sphere power plus half of the cylinder power added works out, so what you were given is correct.

Dr. Rick :

3. The toric lens corrects both the sphere and the cylinder, but it has to sit just so on your eye. This can be a problem, for instance, if you lay on your side and try to read as the lens shifts and things get blurry. The "non-toric", or spherical equivalent lens, uses the above math, and other things to do with a lens formed by your tear film etc (more then you want to know :o), to take care of the majority, if not all, of your astigmatism with a "spherical equivalent" lens

Dr. Rick :

So, try not to focus on the numbers......yes, they are different numbers, but they are all "equivalent" lens powers per established mathmatics. What your optician is doing is correct.

Dr. Rick :

Does this answer your question?

Dr. Rick :

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