The College of Optometrists

Hey! I did ret on a patient recently and found a -1.75 cyl. They could read 6/6 before subjective (BVS was O.K) When I started cross cyl he wanted -2.50 cyl and still managed 6/6. What should I do in a case like this? Do I prescribe the full cyl or not? On subjective the patient certainly didn't want less. Thanking you, Sara

There is a bril book in the library called Clinical Pearls of REfractive Care - phone the library and borrow it.

What you did is okay. Its best practice to use the minimum cyl you can - 'cos

lenses will be easier to adapt to lenses will be thinner more lenses available px less concerned about 'getting worse'

I like yr ret result. then you do subjective - and it gets higher and higher.

If its getting unexpected - then drop it - and do the other eye. Then blur back the other eye to 6/9 and return to the first eye. By ding a bino refraction - you will find that things don't get carried away. It maybe that he needs a high cyl. But make him prove that he needs it to you.

Check your questions arenot implying stronger is better. I usually ask - 'what does this lens do? ' 'How does this lens change things?'

On XCyl I normally say -"this lens blurs or distorts the picture - doesn't it? - What happens if I turn it over?"

It could also be that the trail frame is not centred properly - make sure they are seeing through the middle!

As a general rule : never change things unless you have too. And aim for comfort - a little less clarity and a lot less eye strain is better than everything pin sharp and strainy.

I wrote other stuff on the site if you do a search.

-hope it helps = steve

Astigmatic patients can often "cope" without their cyls, however they may not be getting their best corrected VA. If they still get 6/6 without their cyl, how low does your chart go, could they have got 6/4 or 6/3 if your chart let them with the cyl?

Having said that I would agree with Stephen, don't fix it unless it is broken is a good rule of thumb.

If you did prescribe a full or partial cylindrical correction you would need to warn the patient of adaptation issues, distortion etc. and the patient might well find that they were uncomfortable following adaptation managing without their spectacles.

I worked with an optometrist a few years ago who had over a two cyl in each eye and didn't wear their spectacles because of the distortion it induced when she did and she didn't want to wear them all the time, so she never fully adapted to them!

...and don't assume the distortion is only due to astigmatic distortion - cyls can also change the binocular field, because each eye will have its own 'distortion' which may stop fusion.

So, you can make up simple rules:

Only increase a cyl - if it makes a worth while difference and when you can't make it better with any more sphere.

Think carefully before increasing an Rx cyl by more than 0.75 or an axis by more than 10 degrees.

Don't forget the other eye a cyl in one and a sphere in the other (for example) - may cause binocular instability. So try to keep things as symetric as you can.

Allow the px to assume their habitual head posture during testing - so the cyl axis will allign with the ocular astigmatism.

=steve

I bet you'd like to know at what power cyl do adaption problems start - For children - you prescribe full amount For adults - you can get into difficulties above 1.50 - less on oblique axes. Problems magnify at onset of presbyopia.

I would really recommend you read the book I suggested - it is a revelation! and will really help.