Unless the patient is not a good candidate for contacts, this is one of the first choices for treatment. Contact lenses collapse that distance to nothing. One of the simplest variables to control is the amount of distance between the eye and the lens as that distance increases, the more different the perceived image size. There are several possible treatment options, and each patient will require an individual treatment plan to provide the best solution. A 5% size lens in front of one eye, or a combination of 2.5% larger/smaller as appropriate for each eye should provide both practitioner and patient a sense of how much aniseikonic correction might be needed. Size lenses provide no optical power but make images larger or smaller this can be very helpful in determining the amount of compensation needed to relieve symptoms of aniseikonia. The threshold for symptoms in most cases is about 3.5%, although some people can tolerate much more, and others cannot tolerate even very small amounts of disparity. Patients with aniseikonia can usually adapt to and tolerate small amounts of size difference. As stated earlier, aniseikonia is expressed as a percentage of size difference from the right to the left eye an individual with %5 aniseikonia will require a lens prescription that will provide 5% magnification for the left eye, or a 5% minifying lens for the right. The results of testing will give the eyecare practitioner information about the amount of disparity and the direction. There are several tests to measure aniseikonia. Accidents or other trauma can also result in aniseikonia. ![]() Individually testing each eye makes it easier to find the best lens prescription for each eye, but it says nothing about how the eyes fuse those two images into one or how they work together as a team.Īniseikonia can also be caused by ocular surgery, such as that for cataract removal in one eye, surgery to repair a torn or partially detached retina, swelling in the macular area, or even just an anatomical difference between the size of each eye. Meridional aniseikonia can also be induced by a difference in amounts of astigmatism.Īnother complicating factor is that the eyes are almost always tested individually, with minimal testing binocularly. Sometimes, aniseikonia may exist only in certain meridians for instance, an eye that is set lower in the face than the other may cause a disparity in how large an image appears, but only in the vertical meridian. The perceived size difference from one eye to the other can be made worse by a frame that is not appropriate for the prescription, how the frame sits on the face, the amount of tilt the frame front has and how much it wraps around the face, as well as how the lenses are mounted into it. Shaw believes that most eyeglasses induce aniseikonia even if the lenses are only slightly different. Peter Shaw, OD, a leading expert in this area, notes that sometimes even small differences in lens power can cause the eyes to see different sized images, especially when the eyes are moving. If left untreated, aniseikonia may cause the brain to adapt, sometimes by suppressing the image in one eye and allowing only the dominant eye to see clearly, in motion or in static gaze.Īniseikonia may be optically induced, usually when the two eyes have significant differences in refractive error (nearsightedness, farsightedness or astigmatism), a condition known as anisometropia. Fusing the two images into one and keeping them there is very important, because when that fusion breaks down, we see double. Magnifying an image in one eye is equivalent to making it smaller in the other.ĭynamic aniseikonia is a little trickier, but one way to understand it is to consider that each eye usually needs a slightly different lens prescription for sharp, clear vision when the individual scans a page of printing, the eyes might need to move at slightly different speeds or to rotate slightly more with one eye than with the other. ![]() His aniseikonia may be treated by either magnifying the image in the left eye by 5%, making the one the right eye sees smaller by 5%, or a combination of the two. For example, if Brian sees an image with his right eye that appears to him to be 5% larger than the one he sees with his left, he is said to be experiencing 5% aniseikonia. Static aniseikonia means that when an individual looks at an object with one eye at a time, he or she will perceive a difference in size between them, usually expressed as a percentage. ![]() Aniseikonia is generally thought of as being either static or dynamic.
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