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IOL measurement error involving an ICL


I had an ICL put in 7 years ago and developed a cataract around year 6 in one eye.  Ten days ago I had the ICL removed (went smoothly!), the cataract broken up, and an IOL implanted.  The goal was to match the distance in my good eye.  I am highly myopic; my ICL power was -11.5.  I figured out quickly that I was undercorrected for distance by 1.5D with the new IOL.  It didn't take me long to dismiss healing time as the reason because I had overheard a conversation in the pre-op area about a delay in my surgery due to some more investigation that needed to be done about my implant.  I know, I know.  Why didn't I force myself to sit up and demand to see the surgeon.  Nevertheless, I am now in the position of making a decision quickly as about IOL transfer, etc.  The surgeon is citing measurement error due to my unusually long eye.  I have not come out and directly asked him if he remembered to tweak the formula or somehow considered that the ICL was in my eye at the time of measurements.  It was some kind of laser device.  No one has given me an answer on what they use.  My question to you is:  would it ever make sense to put in an IOL (Starr nanoflex) of +10.5 if my ICL implant was -11.5.  The fact that I'm off 1.5 (my vision decreased slightly in 7 years) seems fishy.  Possibly it looked fishy to the "lady" double-checking my implant.  They are definitely nervous.  Thank you!
7 Responses
Avatar universal
I appreciate your frustration about your outcome.   Long eyes are definitely more difficult and previous ICL further complicates the matter.  I cannot comment on the the specific IOL power choice.  The more important issue is, what now?  Is it best to correct your "refractive surprise" with corneal surgery or an IOL exchange?  Corneal surgery is less invasive than an IOL exchange.  IOL exchange on a highly myopic eye has a higher risk of retinal tears. Talk to your doctor.  Seek additional opinions as needed. Best wishes.
Avatar universal
A net search shows that an ICL shouldn't impact the measurements taken to do an IOL calculation enough for them to worry about, so that seems unlikely to be the issue, e.g.:

"ICLS do not seem to have much of an effect on biometry for an eventual cataract operation"

I'm assuming by "undercorrected" you mean you are left myopic, which means that the lens power they put in was too high.

IOL powers are determine by formulas that aren't exact, and tend to not work as well for highly myopic people. They are based on taking measurements of lots of eyes for various factors (like axial length, chamber depth, corneal measurements, etc) and seeing the results to determine what the best power would have been for those eyes. Different people have analyzed different data sets and come up with approximate formulas. They usually try a few different formulas to see if they agree, and if they don't they often have some idea of which formulas tend to work best for what kind of eyes (e.g. myopic vs. hyperopic).

There are different theories about why the formulas don't work as well for high myopes. Some speculate there may be   errors in the measurements taken of highly myopic eyes. This gives an illustration that although most eyes are within 1D of the target, some people wind up being the "statistic" that are further off:

"High Myopia and Cataract Surgery [...]

There is also controversy over which formula is the best for calculating IOL power. Traditionally, the SRK/T, a third generation formula, is thought to be an accurate formula for patients with high axial length.[4][3] In a 2012 study, however, the Haigis formula was found to be superior to the SRK/T, SRK II, and Holladay I. 81% of eyes had refractive error within 1.0 D of predicted, and 54% were within 0.5 D of predicted using the Haigis formula. In contrast, 59.5% of eyes were within 1.0 D of predicted, and 29.7% were within 0.5 D of predicted using the SRK/T formula.[5] Still, the third generation (Holladay I, Hoffer Q, SRK/T) and fourth generation (Haigis, Holladay II) formulas may all tend to overminus IOLs in patients with high myopia.[4]"

Here is one page by a prominent doctor that discusses the approaches they use for trying to deal with selecting IOL powers for high myopes:


(he is a consultant for the folks that make the IOL Master device, and consults for other surgeons on difficult lens power cases).

Unfortunately  an IOL power can't be derived from the correction used for contacts, glasses.. or an ICL, which are correcting the refraction error in the natural lens plus the rest of the eye. In this case   the natural lens is of course being removed and they are trying to guess what power it was based on other measurements  since they can't directly measure its power. It depends on the person, but someone without any refractive error usually winds up with an IOL somewhere around 21D or so. Changes in power at the IOL plane are different from changes at the spectacle plane.  I'm guessing if you were left -1.5D myopic that the right lens power might have been closer to a +8.5D for you, but that is just a rough guess.

In my case my left eye was more myopic and was about a -9.5D prescription before the cataract and they used a +10D lens, which left me slightly hyperopic, +0.5 or so, so a 10.5D or 11D might have been closer to the target (or 11.5D to be a bit myopic as I'd have preferred in that eye). The other eye was on target,  plano.  I was around -6D in that eye beforehand and they used a 13.5D lens.
Avatar universal
Thank you for all the detailed information.  I too have come across Dr. Hill, and as it turns out, I could ride a bike to his office.  Hopefully, they will be able to give me a second opinion soon.  I had read an article by him giving his opinion that the formula should account for an ICL implant.  That might have only been using a sonogram however.   It was also dated 2003, so maybe data now proves otherwise.  Did you just leave your hyperopic eye alone?  The surgeon does not like piggybacks, will do an exchange if I really want to but it will have risks, and is going to check into LASIK but I wasn't a candidate for it years ago due to large pupils.  My eye might not tolerate contacts since that was the reason I got ICL seven years ago.  Also, his retinologist did an exam today and everything looks good except I've developed PCO already.  What the heck!  I might just wear glasses and leave well enough alone from now on.
Avatar universal
One question is whether having 1 eye myopic is causing any problems for you, or if you can adapt to what is essentially monovision and benefit from having better near vision in that eye. A -1.5D result for one eye is fairly common in monovision, but not everyone can adapt to it even if most can.   Is it noticeably impacting your binocular distance vision or your depth perception/steropsis due to the difference?

Depending on the reason for your contact lens intolerance, its possible there may be options that could work for you that didn't exist 7 years ago. Contact lens materials have improved quite a bit the last few years and there are now one day disposable lenses. Since it sounds like you have a monofocal   IOL  you might consider trying multifocal contacts.

If you've already got PCO, I suspect that means eventually it'll be bad enough you'll need to get it taken care of. Hopefully you are aware of this, but unfortunately the treatment for PCO makes an IOL exchange more difficult to do, it usually requires the new lens to be placed outside the bag. So you should decide on whether to get a lens exchange before getting the PCO treated.

re: "formula should account for an ICL implant"

A quick search seemed to indicate comments that formulas could in theory be updated to  take an  ICL into account (I think the article I linked to above did mention that), but the impression was that the difference was small enough that most didn't consider it worth worrying about. Even if it does make a difference, it sounded likely to be an order of magnitude less than the error in your eye.

re: "pupil size"

Your pupil size does decrease with age.  I haven't looked into the details of laser enhancement yet, I'd never considered it before getting cataracts, so I hadn't examined the pupil size issue.  A quick check shows some indication it may not be a concern to the degree it was in the past:



However I also don't know how an IOL relates to what laser method should/can be used. There area  number of varied laser treatments out there these days.

Why doesn't the surgeon like piggybacks? Some surgeons have a bad experience with an early version of an approach and that leaves them more conservative about trying it again even if the technology/technique has improved since then. (e.g. some doctors gave up on multifocals after the early ones had trouble and hadn't given the latest ones that are much improved a try).

re: "Did you just leave your hyperopic eye alone?  "

+0.5 is a small error. With the Symfony IOL I have that still leaves my binocular vision almost 20/15 at distance (it may be at 20/15 by now, that was an early preop visit and vision can improve the first few months, I'm just over 6 months postop now), and 20/25 at near due to my other eye.

I suspect I'll just not bother doing anything. It does seem  a shame that I lose a little bit of near with that eye so it is  possible at some point I might consider a lasik touchup to make that eye perhaps -0.5D myopic instead (leaving the other eye on target for distance).  I'd do  a contact lens trial first  and see if it seems worth it.

Avatar universal
Thanks again for all the information.  It has been very helpful.  I have been giving the mni-monovision thing a good try since one of his nurses really encouraged me to after she double-checked to see that distance was in my dominant eye.  I thought it was strange that when the dr came in he seemed very skeptical about it and said to give it three weeks instead of the full three months that the nurse had told me.  The nurse seemed confused too.  On the way home my husband mentioned that he thought the nurse did not do the dominant eye test correctly.  I let that go to the back of my mind I guess.  I just tested it today myself after not being sure if my eyes were making any progress, and he's right.  Distance is in my nondominant and I've been highly myopic for 46 years.  Just when I think I've got a handle on this subject, I feel really stupid.
Avatar universal
Although they generally use the dominant eye for distance, there is some evidence that it isn't required. The issue is mostly whether you are comfortable with it and can adapt to it. Many people don't have a clearly dominant eye or the dominance isn't strong. The test is whether you can see what you need to see well enough, based on your experience and in terms of visual acuity tests for distance to confirm objectively you see well enough to drive.

Some people use monovision most of the time but then do have glasses/contacts to adjust both eyes for distance when they really need good distance vision (or to adjust for near).

e..g. a study presented at a conference last year:

"Pseudophakic monovision: does ocular dominance matter? [...]


We found no significant difference between the conventional and the crossed monovision groups suggesting that not respecting ocular dominance in cataract surgery may not affect patient's visual performance. "

"When targeting monovision, the nondominant eye is usually targeted for near and the dominant eye for distance. However, some patients are able to have the reverse, he said.
  'There are some [patients] who can tolerate, very comfortably, using the opposite from the usual,' Dr. Hovanesian said. 'The usual is to use the dominant eye for distance, but many patients can do the opposite and do just fine with it.'   ...

Most of the time patients like their dominant eye as the distance eye and the nondominant eye as the near eye, but this test helps them understand how tolerable monovision is and also uncovers if they are going to like their dominant eye as their near eye."

"We prefer to set the dominant eye for distance, but sometimes it gets reversed for one reason or another. As long as the difference between the two eyes is slight, most people can adapt to the subtle difference between the two eyes either way."
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