Causes of aniseikonia

Every pair of lenses causes aniseikonia to some degree. The question is how much can the individual patient tolerate and would reducing it result in more comfort or better adaptation? Traditionally aniseikonia has been thought to be problematic only in extreme anisometropia. But that is only considering static aniseikonia (image size) that’s created by the glasses.

Dynamic aniseikonia is much more uncomfortable and that can occur even when the refraction is equal. Dynamic aniseikonia describes the unequal demand on the movement of the eyes as they move left and right and up and down that is caused by the eye glasses.

Aniseikonia can also be treated with the SHAW™ lens in the following cases:

  1. Spectacle-induced aniseikonia
  2. Congenital anisometropia, which can lead to lazy eye
  3. Axial length changes due to retinal detachment surgery
  4. Refractive induced aniseikonia from cataracts
  5. Cataract refractive surgery
  6. Maculopathy

The SHAW lens is an effective tool in the treatment of all of these cases. When used by your optometrist along with other treatment options, the iseikonic nature of the SHAW lens design means that it is the best practice for the toughest cases.

Even a small amount of aniseikonia can be problematic.

In clinical practice Dr. Shaw has found some remarkable evidence that even a small amount of aniseikonia among moderate myopes can be problematic.

One patient described her experience with her current glasses as annoying. She complained that in the upper and lower areas of her gaze the image made her feel dizzy. She was Minus 1 OD and Minus 1.5 OS, -.25, 180 in the other. Here’s the interesting thing. When the Motor Fusion limits were tested it revealed that she had very little tolerance for vertical distortion. In fact, she was base in .5, base out .5. So this made sense that she wasn’t very happy with traditional lenses.
When we model the traditional lens, we find that in her low tolerance to vertical dymanic aniseikonia was exceeded by traditional lenses by well over 100%. In effect, even though this amount was technically very small to her it made a huge difference.

And she is not alone. Our recommendation is that the SHAW lens will make a noticeable difference to patients who don’t need to wear their glasses for distance but like to so they can read. The new-to-glasses or infrequent glasses wearers can be the least adaptable to glasses. And their tolerance can be measured using simple loose prisms and the sophisticated SHAW lens design software.

With these tools, the optometrist can assess how well traditional lenses serve the patient or design a lens that meets the patient’s tolerance to dynamic aniseikonia using the SHAW lens technology.