Question on overcorrected cyl

**yeongee** · 08-19-2010, 01:42 AM

Just wondering whether an overcorrected cyl of -0.50DC will cause any significant problem to the patient if he continue to use the overcorrected spectacle?

Here's the scenario:
The patient's actual refractive power is -2.00/-1.25 x 180 but the spectacle he using is -2.00/-1.75 x 180

Does this mean the patient will suffer a blur of about -0.25DS (which is 1 line loss on Snellen chart)?
If the patient refuse to change the lens, will there be any problems after the patient wear the overcorrected spectacle for long time?

Thanks!

**RIMLESS** · 08-19-2010, 05:25 PM

That's -.50 D over corrected on the cylinder component. The sphere equivalent is -.25 as you sumised.
A -.25 over correction will not blur him to the extent you are thinking, unless maybe he's presbyopic. Too much minus gives the pt the illusion of smaller, darker and clearer (sometimes). Bottom line.....sometimes change is not easy, but I don't think it will kill the pt. if he wears the old script :)

**Yeap** · 08-20-2010, 02:55 AM

hi welcome to optiboard.
i second rimless opinion.. somehow the patient may complain to you that the old glasses seem to be better as he/she may have adapted to the over Rx. we does see some who has over corrected by -1.00DC when we get him to the actual rx he find the everything seem to be weird and bright.

**yeongee** · 08-20-2010, 03:25 AM

Thanks guys!!

**eyeguy21** · 08-25-2010, 12:05 PM

You all seem to have the "spherical equivolency" thing down, so I'll just add that in answer to the question "will there be any problems after the patient wears the overcorrected spectacle for long time?" That answer is no it will not harm him/her to wear the overcorrected lenses for a long period of time. In reality they would be fine wearing my Rx for a long time as far as the health of the eye is concerned. They just won't see very well and they'd probably get a massive headache.

**yeongee** · 08-27-2010, 11:58 PM

thanks again!!

**rdcoach5** · 08-28-2010, 07:10 AM

We just had a pt in our office with 2 pair of supposably identical Rx glasses purchased elsewhere. One pair was just not as comfortable so our dr had me check to see if different progressive, mis-aligned, etc. Turns out one pair, this was a pretty high Rx, cyl was too strong by 1/2 diop o.u. Years ago I learned to never over-correct the astigmatism.

**Barry Santini** · 08-31-2010, 09:59 AM

Nor should one overcorrect. The most insidious situation is were the client requires a small (0.50) cyl, but is told they don't require it, cause they don't have astigmatism.

Progressive nightmares!

B

**uncut** · 09-03-2010, 08:19 PM

An interesting observation that I have that may be relevant to this thread. I have been corneal mapping/topographing corneas for a long time, and have noted that a lot of astigmatism is not axially true, nor is the cylinder the same value above versus below mid-point, especially at vertical. Therefore, a slight over correction may not effect acuity as much as one might think.

+$0.02