Why are Toric contact lenses bigger?

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Vuchko - 27 Jan 2005 20:32 GMT

Hello!

I was just wondering:
Why are Toric contact lenses bigger? ~14.4, 14.5 DIA and normal sph
lenses ~ 14.0, 14.2 DIA

What is the appropriate equivalent of a 14.5 toric lense for a normal
sph lense?

(For example: I was measured half a cylinder astigmatism and no
dioptry in the right eye and since the lowest value of a toric lense
is -0.75 cyl i would like to try with a normal spheric soft contact
lense with -0.25 sph power.. because with a toric -0.75 i see blurry..
and would like to try the half of cyl rule for sph lense and don't
know wheather to get a 14.0 or 14.2 DIA? 14.5 toric was comfortable)

Thanks!

Have a nice day :)

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Mike Tyner - 27 Jan 2005 20:39 GMT

> I was just wondering:
> Why are Toric contact lenses bigger? ~14.4, 14.5 DIA and normal sph
> lenses ~ 14.0, 14.2 DIA

If the average toric is larger than the average sphere, it may be for
stability. Torics have to sit still and not rotate around.

Not all torics are 14.5, and many non-torics are that large.

Diameter is not really a factor in the optical correction.

Since your only problem is astigmatism, I wouldn't expect much success using
the spherical equivalent contact lens.

You'd see blurry with a -0.25 spherical contact too, plus soft contacts add
their own blur as they get dirty or dry during the day. Not worth it.

-MT

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