Contact Lens Question (Prescription)?
August 12th, 2010 | See the Top Answers to this Question Below
I just went to the eye doctor and got my one lens changed from an aspheric lens to a toric lens. The spherical power (sph) of the old aspheric contact was -4.75. Now, with the new toric one, The spherical power (sph) has gone down to -4.00 with a cyl of -0.75. I feel like my vision is somewhat foggy now and i have been getting a bit blurry vision. Also I feel like I cannot see as clearly looking at things from far away. Is the toric lens the right spherical power? Should it have gone down by -0.75 (4.75 to 4.00) in the change to a toric lens?
Thanks for the response! The only thing I don’t understand is why the power dropped when he switched me from a regular contact to a toric one. Shouldn’t the sph have stayed the same?
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There are many things that go into a toric prescription. Your blurry vision now could be from the lens not sitting on your eye at the correct axis. All lenses sit on peoples eyes differently. You were probably given the spherical equivalent in your original prescription, but if the doctor put you in a toric now, there is most likely a reason. I would give it a chance.
Typically, the power changes when we switch from a toric to a sphere or vice-versa. See, when we do the sphere, we don’t just cut off the cyl, we actually try to incorporate it by doing something called "equivalent sphere". Basically, we take half the cyl and add it to the sphere to get the best possible sphere-only prescription for you — so that would be (-4.00) + (-0.75)/2 = -4.37D. (Contacts don’t, and glasses usually don’t come in that specific of a power, so we’d round down to a -4.25D). The above poster was right though — although the sphere being off by a bit could affect your vision, it’s more likely that the lens is rotating off-axis, giving you some blurry vision, especially if you find the blurring comes and goes. Is this a trial lens that you can go back in a week and get it fine-tuned?