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October 30, 2005

Iseikonic Lenses and Aniseikonia

by @ 9:41 pm. Filed under Optician's Friend Blog

Not too long ago in the field of opticianry, iseikonic lenses were a common topic. I asked some seasoned opticians and an optometrist to find out why iseikonic lenses have decreased in popularity.

For those of you who don’t know, iseikonic lenses are lenses in which the magnification has been balanced. Each lens produces a certain amount of magnification or minification (small-ification if you will). Differing magnifications become a problem if there is a significant disparity between the two lenses. Orthodoxy holds that a difference of 5% magnification or more is enough to break fusion in most individuals. The difference in image size produced by the difference in magnification is called aniseikonia. Fusion is the process in which the two eyes combine their respective images into one. When fusion breaks, people complain of diplopia, or double vision. Some people who do not break fusion, but still have magnification differences of over 1%, may complain of headaches and nausea when wearing glasses that do not correct for the magnification difference. Some people with a high astigmatism that significantly supercedes any astigmatism in the other eye will also experience similar problems. People in this category have meridional aniseikonia.

Getting back to the original topic, why has this aspect of opticianry tapered off? In my case, it may be the setting. I work in an optical chain that is geared more for retail. Where I work, we do not usually make iseikonic lenses for people, but I have done them and it is a real battle with the lab. Another reason as mentioned by the optometrist I work with, contact lenses have a high success rate in correcting the magnification imbalance. I would imagine that surgery would also be a factor. Another offered that many opticians simply do not know how to make iseikonic lenses and either refers it out or simply has the patient get used to it. This is not to say there are times that a patient who has had a change in their prescription needs time to adjust to their new Rx. Vision is a brain thing as much as it is an eye thing. I feel that in these cases, although somewhat rare, aniseikonia is a real problem for some since either they can’t wear (or don’t want to wear) contacts or there are other issues that surgery can not correct. This situation provides an opportunity for the optician to make a huge impact on someone’s life. Binocular vision is not overrated! Many people who do not have binocular vision may lose out on opportunities that require it. Making iseikonic lenses are a hassle, I know, but I actually provide some reprieve. On this site there is an Iseikonic Lens Calculator that should help out with the math. I originally made it as part of a project when I went to Raritan Valley Community College. It has been a lifesaver in terms of time. The only thing I would ask is that once you are done, double check the answer manually and let me know how it turns out (bear in mind things may be rounded). I want to make my programs as reliable and robust as possible. Email (at the bottom of the page) me if you want to know how to use the meridional aspect of the calculator.

Remember, what we do as opticians, in my opinion, is noble work and it is important to not lose sight of that.

9 Responses to “Iseikonic Lenses and Aniseikonia”

  1. Steve Tronnes Says:

    Is there a way to estimate the aniseikonia produced by a particular prescription without knowing base curves, thickess etc.

  2. Peter J Shaw OD Says:

    SHAW lens are lenses that correct aniseikonia and anisophoria, software that calculates image difference and rotational magnification may be downloaded

  3. Carol Sidofsky Says:

    Thank you very much! By “googling”, I just figured out that I have aniseikonia (smaller images seen in left eye, compared with right eye). I just had cataract surgery a few days ago, so now that I have sharp, clear vision in left eye, the size difference is very apparent. I will speak with my eye surgeon and optometrist, to plan ahead for a left iseikonic lens, if needed, after I get my right cataract removed. Your info is appreciated,just in case they should need it.

  4. Carol Sidofsky Says:

    Slightly off topic, but here goes: I wish IOL manufacturers would show photos of what a scene with a blue sky, white house, and green grass and green trees, plus something red and something yellow, would look like after getting various IOL’s implanted. This way, patients could get an idea BEFORE getting their IOL’s, about color shifts brought about by various IOL’s. For instance, my Abbott ZCB00 is wonderful for sharpness, but seems a tad skewed towards blue & purple (gray looks purplish, brown looks purplish, and greens look dark & bluish).

    I counter this by wearing Jonathan Paul (borrowed my hubby’s pair) of “fitover” (in my case, Navigators), with Polarvue amber lenses.

    In bright sunshine, these fantastic sunglasses bring back warmth to grass, trees, etc., without unduly muting vivid blue skies!

    Do you or your readers know of clip-on, flip-ups, that are a bit lighter, but still “amber”, that I could use indoors, when I want to see the warm yellow glow of incandescent lightbulbs, instead of seeing harsh, cool blue looking lightbulbs (due to the blue color shift of the ZCB00’s)?

  5. Michael Walach Says:

    Hi Alvaro,
    I just visited your page; some good stuff!
    Pertaining to your magnification calculations, they are fine, but I wonder why you do not consider cornea-pupil distance? I sure does make a difference.
    Also, I would like to see how you are dealing with the meridional anisekonia. I just did a challenging pair; the patient had an eye surgery which resulted in meridional anisekonia without eyeglasses. On top of it, his corrective eyeglasses had significant difference in sphere power, cyl. power and both cylinders had oblique axes in different meridian; it was quite a challenge. You have mentioned that in your experience it was quite a hassle to work with the lab. Next time when you get a challenging Rx and don’t get from your lab what you need try Quest Vision Care Specialty Lab in Largo, FL. We do nothing but specialty work and would be happy to work with you any time you get some fun prescriptions. Great to see opticians like you!

    My cell is 727-25l-3l29. Use it at any time time I can be of help.

    Best regards,

    Michael Walach

  6. EDRIC Says:

    Hi Cardova,

    Do you know where can i obtained an iseikonic lens? Im from Malaysia and i have found it no where in these region. Looking forward to hearing from you. Thank you.

    Regards,
    Edric

  7. david Says:

    I have aniseikonia after lasik surgery years ago and is now getting to be bothersome after cataract surgery — — my L eye image is smaller
    than my R eye. Should I consult an optometrist or ophthalmologist ? Where can I obtain anisekonia lenses or contact lens in southern
    California ? I also have amblyopia or lazy eye from that requiring prism of 5 ; 5. Would this complicate getting the right aniseikonic lens ?
    Many thanks,

    David Low

  8. Alvaro Cordova Says:

    Aniseikonia is a tough correction using spectacles especially if there is cylinder/astigmatism involved.
    -Consult with anyone willing and able to help you. I wish I could say definitively that Ophthalmologists or optometrists, in general, would help, but I can’t make that statement at this time.
    -Depending on the amount, the Rx itself may need to sacrifice some clarity for depth. As to where to obtain them? You really have to look for independent opticians. Corporate does not want to touch this issue since it involves trial and error and that can be a problem because, as you already mentioned, access to such services seem limited.
    -Aniseikonic lenses are meant to correct depth perception, so you will not have “1” aniseikonic lens. Both lenses are calculated to minimize the difference in magnification/minification between them. This is a very specific solution to a very specific problem.
    -sorry for the almost 2 year response. Blame it on the spam since for every message I get I have to sift through about 1000+ messages that are bots.

  9. Alvaro Cordova Says:

    Unfortunately, you have to ask around and find an optician who will help you. Some opticians refuse to offer this service because there is an element of trial and error involved and generally trial and error mean higher costs on the part of the optician. That said, avoid chains and find an independent guy. They generally have access to better labs that can do these sometimes difficult corrections.

    I truly apologize for the long duration it took to respond. I have to deal with over 1000+ spam messages for each message I receive that isn’t a bot.

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Optician n. One who is extensively trained in the interpreting of ophthalmic prescriptions and applies that knowledge to obtain the optimum visual and safety performance for the patient in a pair of spectacles or contact lenses.

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