A-scan results and eye axial length

[myopic74]

Dear sir,

I am 34 years old, and highly myopic -18D. Recently I underwent a A-scan to measure my eye axial length. It was done using a machine that is quite similar to one measuring diopters. You just look your eye into the machine, there is an orange light inside, and after looking at it for one or two minutes, it's done.

The readings taken were 30.7mm (Left) and 31.09mm (Right).

However, about ten months before, I also underwent another A-Scan at another hospital, but they used something different. Not a machine, but a manual probe that they have to touch into your eyeball a few times in order to get the measurements.

The readings were 30.6mm (Left) and 30.8mm (Right).

My question is, given the big difference of almost 0.3mm (for the right eye), is it acceptable for there to be such a high margin of difference between the two methods used? If not, is it likely the eye axial length can increase by so much in such a short time span of 10 months, given my age?

Thank you very much!!



      

  

[JodieJ]

If you're taking bets, I'll put my money on the first measurements using the machine (IOL Master).  It's supposed to be more accurate than the second measurements (A-Scan).  (No, I don't think your axial length increased; the difference is measurement error.)

[Winterpeg]

Jodie is correct. I am very myopic as well and am scheduled for cataract surgery in July on my right eye which was -15.0 before my multiple Lasik surgeries, macular tear and then Vitrectomy to repair tear which resulted in the formation of a cataract. My Dr used both instruments to measure my axial length. The IOL MAster gave him a more accurate reading that the regular "scan". The variance was about the same as yours.
Your Dr will go with IOL Master.

[John C Hagan III, MD, FACS]

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[myopic74]

Thanks for the advises!

I feel better if it's just an measurement error :)

Anyway, I will be going for the test again in six months' time using the machine, so I hope the results will remain the same.

Do you think the using the machine will also produce significantly different measurements each and every time since it has to depend on somebody to operate it?

  
Best Regards


  

[Winterpeg]

When the technician did my IOL Master test, she said that she would do at least 2 tests on my eye to ensure consistency of the results. She did 2 only as the second test was exactly what the first test recorded. Hope this helps;

[John C Hagan III, MD, FACS]

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[myopic74]

Thanks for the information! It certainly helps :-)

[John C Hagan III, MD, FACS]

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