Irregular Astigmatism.. Starbursts Rgp Torics, And So On?
November 10, 2009 by admin
Filed under FAQ on advance for astigmatism
This is my first question on Yahoo answers, so hello to all from Portugal.
I have always had a perfect vision, until one year ago due to an accident. Now I have an irregular astigmatism (doctors say there are no signs of Keratoconus). My cornea thickness is ok (did several Orbscans and Pentacams).
With spectacles I can achieve 20/20 vision, but there are some issues though:
During the day, or in a well lit room everything is perfect, but during the night, there are some starbursts. For example, if I look at night to a street lamp, there is some kind of bleeding, it looks like the bulb is extending to the itself. With car headlights the same thing, the same bleeding. For example, I have problems with white text on a black background, neons and so on. The farther the distance, the greater the bleeding is.
I can see perfectly, but the “bleeding” kind of annoys me… Of course I’ve told it to my doctor(s), they say it’s normal, bla bla bla, and they said that perhaps RGP would fix the bleeding.
I’ve tried some RGP’s with good results, they definitely reduced the amount of “bleeding” (they didn’t completely eliminate the problem, but at least they did something), but due to the fact that I’ve an irregular cornea, it’s too difficult to center the lens properly. I feel the lens (like a little scratch) whenever I to any direction, but even with that I can completely tolerate the lens (I’ve used one pair for a week 19 hours at a time).
Now, aren’t RGP’s lenses supposedly correct the “bleeding” completely? Why In my case they are only reducing the amount of “bleeding” (is that because they are not centering well in the cornea?)
If they don’t manage to correct it, are Toric RGP’s a solution for my problem, how do they work, do they have a ballast like a soft toric?
My Astigmatism prescription:
Right Eye CIL–> DIO 1.75 AXIS 25
Left Eye: CIL–> DIO 2.00 AXIS 165
Sorry for my English.
Kind Regards.
The RGP will correct the corneal irregular astigmatism providing a well-centred fit and an adequate size of lens is possible.
The outer zone of an RGP lens is necessarily blended for comfort not optical precision and if part of that is over your pupil, due to riding in a decentered position, that will produce its own visual distortions – akin to irregular astigmatism!
A larger lens my be possible, or perhaps the Synergeyes lens, a RGP with a soft skirt (it’s not available in every country as yet: you or your practitioner would need to check)
A back-surface toric RGP might improve stability but they often need a compensating and different front-surface toricity added to eliminate residual astigmatism.
The aim would be to avoid a prism ballast , which does nothing for lens comfort. That’s more commonly needed in *front*surface toric RGP lenses for lenticular astigmatism which are rarely used these days since the progress with soft toric lenes.
Bi-toric RGP’s are about the most complex lens to calculate and manufacture.
Dificult, expensive. Great when they solve a problem that can’t be tackled any other way.
I’ve done a few, a good many years back, but It’s a long way from lens of first choice.