Keractometer readings

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Steven Williams
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Keractometer readings

Postby Steven Williams » Tue 17 Oct 2006 12:17 am

Why are contact lenses for KCers not purpose made according to the readings of a digital keractometer rather than fitted by an optomestrist(who may not have perfect vision)on a trial and error basis?

Also on annual check ups to monitor the KC should KCers expect to have readings taken from a keractometer?

At my last consultation I asked if the KC condition had progressed but the optomestrist never gave a response. I know my eyesight has deteriored based on my readings from the snellen charts but was this due to the progression of the KC or the ageing process?

Does anyone have regular annual keractometer readings? In my 23 years of being a KC patient I have had a keratometer reading taken on 4 occasions! Two of them were done upon my insistance.

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Postby jayuk » Tue 17 Oct 2006 7:50 am

Steven

What a good question!!!

And the answer to this is probably, cost or they cant be bothered!

Having a K reading done is, in my opinion, extremely important for KC sufferers as it basically allows us to monitor the progress and changes..before its too late! This is why I always have got a Topography performed every 6 months in the last 2 years, and once a year since Ive had KC.....sadly this was up until 2 years ago at my own cost!!

Anyway, the "how bad is my KC" queston we pose to an optometrist most often gets "accidently on purpose" ignored with a " its moderate, or its got a little worse, or its remained stable......which is ever so irritating!.....with the cost of Topo machines reducing, Ive noticed that more of these machines are becoming available.....so it may just be that you can pop in and have one done?....around 3-4 years back they were £120 a pop! Now I am led to beleive they are as low as £35

HTH

J
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Ali Akay
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Postby Ali Akay » Tue 17 Oct 2006 12:27 pm

That's all very well Jay but there's one little problem. With patients wearing rigid lenses, keratometer readings or topography done when the lenses are removed is influenced by the lenses which, as you know, could alter the shape of the cornea depending on the way the lens is fitting. We often say the lenses leave an "imprint" on the cornea which could take a few days to clear, hence readings would be of limited value and somewhat academic. Clinically, fluorescein pattern underneath the lens is a good indicator of whether the cone has progressed or not as an advancing cone will result in apical bearing (the cone will start pushing the lens up if you like). The other alternative is taking K readings, say 48 hours after lenses have been removed, but this isnt usually feasible for obvious reasons. On top of this there's also time constraints in a busy clinic.

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Postby jayuk » Tue 17 Oct 2006 12:50 pm

Oh definately I agree...and this is a sticking point, but if a person has worn a lenses for say 1 year; for example, and each time they come in, they leave the lens out for say 30 - 60 mins prior to be seen, than surely you can get a good idea, as you have limited the differenciating elements.....?..whilst i would suspect that minor changes in KC may get surpressed, major ones would surely be evident?

Also, the time period given for 48 hours; is that also not questionable? As i swear I read something which states that in the first x minutes the cornea goes back to its pre-lens state?....and the % given was quite high?....

J
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Postby Matthew_ » Tue 17 Oct 2006 1:47 pm

Perhaps its because the surface distortion of the cornea does not explain the whole of the symptoms. There could be problems within the cornea or on the rear surface. It might be difficult to predict the effect of lenses by readings alone!
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brigid downing
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Postby brigid downing » Tue 17 Oct 2006 3:02 pm

I was very hopeful that the computer would be able to create a better fitting lens for me this time - but it didn't work.

I don't know enough really to speculate why, but I guess the technology just isn't quite there yet to completely replace the knowledge and experince of the experts.

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Postby Ali Akay » Tue 17 Oct 2006 6:38 pm

Jay
I agree major changes in corneal shape would be evident, but the point I was making was that careful examination of the fluorescein pattern under magnification would achieve the same goal, and as the practitioner will routinely carry this test out anyway, he wont necessarily learn a lot more by removing the lenses and taking K readings. The actual recovery time of corneal curvature from when lenses are removed would depend on a number of factors eg Oxygen transmission of the lens as a cornea deprived of oxygen will take longer to recover; a very flat lens could flatten the cornea to the extent that it might need several days, sometimes weeks to return to its normal shape. I gave 48 hours as a rough guide.We normally like patients to attend wearing their lenses so that we can asess the fit properly. If lenses are well fitting it's possible to get reliable K readings, but, as I said before it is somewhat academic and perhaps only worth repeating every few years rather than every 6 months unless cone is advancing rapidly.

Re: computer generated lenses based on topography, the idea is very good, and,as you probably know there's a lab in the north west using this technology.We've been waiting for the results of a trial but so far nothing published as far as I know.I think it's the way forward, but I am not sure if current technology is smart enough.Most topography machines have a built-in contact lens design software, but they are usually hopeless with KC

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Postby GarethB » Tue 17 Oct 2006 7:10 pm

Either way, a lens made based on K readings and lens fitted based on the fluoroscene patter still require the expertise of a lens fitter to ensure everything as it should be.

The K reading shows KC to be in one plane and my lens is made according to that measurement however it still sits 20 degress further than the instruments dictate so by no means fool proof.

We tried to compensate for this cahne which just made things worse. For 2 years I have been wearing alens that sits 20 degrees out from the original fitting yet I always achieve at least 6/6, quite often 6/5.

I would always rather have an expet lens fitter determmine what is best rather than a machine :D
Gareth

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Steven Williams
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Postby Steven Williams » Tue 17 Oct 2006 10:55 pm

The last keractometer typography reading and picture I had takem of both eyes was 2-3 years ago by MREH consultant/surgeon Dr Brahma in a private consultation.
It cost me £100 and the optometrists have never referred to it in fact I have yet to see the picture in my file when I visit the optometrist!

I think that Jayuk is probably correct in saying K readings they cant be bothered and eye hospital clinic optometry departments are overloaded with patients. Fitting lenses for KC is time consuming and IMO they cannot allocate the time needed.

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Postby jayuk » Wed 18 Oct 2006 11:07 am

Ali

I think we have been here before on the every 6 month issue...and we'd have to agree to disagree. To me, not having it done every 6-9 months against having it done ever 2 years kinda leaves a big time frame for it to increase.....if for example a KC cornea was left for two years ot ever one year, by the time it progresses and the patient starts feeling the effects, its too late for them to start thinking about tactical and strategic treatment options........again its your experince in practice against my experience as a patient...so I guess there isnt a right or wrong here......

Gareth

Completely agree with you on the technology not up to scractch YET. But moreover, I think the fact that a KC affected cornea' change is soo unpredicatable youd have to have a pretty swift mapping to manufacturer time frame. Granted though that not ALL KC corneas will change at an alarming rate......swings and roundabouts on this one......

Another thing also regarding corneal mapping, the software that is currently used is not intelligent enough to cater for minute surface distortion (which KC corneas have alot of) and thus I would suspect that to fit a KC cornea would be even more challenging!.....but it will still be good to see if this technology and software advances.......
J
KC is about facing the challenges it creates rather than accepting the problems it generates -

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