Soft Contacts and astigmatism

What is the maximum range of astigmatism that can be masked by a soft lens
before a toric is needed?

In general do certain spherical soft lenses provide better vision for people
with astigmatism than others? Is a stiffer lens better, or a thinner/softer
lens that draps better? I guess at the end of the day the best lens is what
provides the best fit.

Is the way a lens drapes the cornea the reason why different powers are
needed between lens designs. i.e using the Ciba calculator different
strength are required between Ciba Dallies and Ciba N&D etc.

In article <fIa9d.9243$(E-Mail Removed)>,
"Stuart Rose" <(E-Mail Removed)> wrote:

> What is the maximum range of astigmatism that can be masked by a soft lens
> before a toric is needed?

Objectively, about .5D for the thicker or more rigid plastics, zero for
the most. Subjectively, using aspheric optics, about 1D horiz, .75D
vert.
>
> In general do certain spherical soft lenses provide better vision for people
> with astigmatism than others? Is a stiffer lens better, or a thinner/softer
> lens that draps better?

See above.

> I guess at the end of the day the best lens is what
> provides the best fit.
Yes. If the lens gets coated with debris or dehydrates or decenters,
the vision, and comfort, suffer.
>
> Is the way a lens drapes the cornea the reason why different powers are
> needed between lens designs. i.e using the Ciba calculator different
> strength are required between Ciba Dallies and Ciba N&D etc.

Exactly. And using a "lens predictor" is only a starting point. It's
best to measure the effective lens power on the eye, especially when
dealing with a little astigmatism and with higher powers.

--LB

--
Dr. Larry Bickford, O.D.
Family Practice Eye Health & Vision Care

The Eyecare Connection
http://www.eyecarecontacts.com
larrydoc at eye-care-contacts dot com (remove -)

>> What is the maximum range of astigmatism that can be masked by a soft
>> lens
>> before a toric is needed?
>
> Objectively, about .5D for the thicker or more rigid plastics, zero for
> the most. Subjectively, using aspheric optics, about 1D horiz, .75D
> vert.

In terms of monthly replacement or extended wear what lenses tend to offer a
better performace for masking astigmatism? (i.e Proclear, Acuvue, Surevue
etc). Is there a list of which lenses are aspheric anywhere?