Aniseikonia...

[Uncle Fester]

https://www.opticaldiagnostics.com/i...iseikonia.html

Great site explaining aniseikonia

Aniseikonia is an ocular condition where there is a significant difference in the perceived size of images. It can occur as an overall difference between the two eyes, or as a difference in a particular meridian. If the ocular image size in both eyes are equal, the condition is known as iseikonia.


aniseikonia symptoms

Bannon and Triller² reported a list of characteristic aniseikonia symptoms based on a study with 500 patients (see Table 1). Burian³ published a similar list presenting the symptoms the patients most frequently complained about. His main categories were I. Astenopic symptoms, II. Impaired fusion and/or poor stereopsis, and III. Anomalous spatial localization.

Symptom	Percentage of patients
Headaches	67%
Astenopia (fatigue, burning, tearing, ache, pain, pulling, etc)	67%
Photophobia	27%
Reading difficulty	23%
Nausea	15%
Motility (diplopia)	11%
Nervousness	11%
Vertigo and dizziness	7%
General fatigue	7%
Distorted space perception	6%

[Uncle Fester]

At great risk of embarrassing myself (again) how does magnification not involve refraction of some kind?

"The aniseikonia testing discussed above has all been 'objective' testing. However, an eye care provider serious about aniseikonia management should also have a set of size lenses for subjective testing. Size lenses are lenses without refractive power (the image stays sharp), but with an optical magnification. They may provide the patient with a sense of what it would be like to have a certain aniseikonia correction."

Is this achieved through lens thickness?

[drk]

Yes. There is the "power factor" & "shape factor" in the spectacle magnification formula.

With an iseikonic lens design, the "shape factor" is manipulated to offset the unwanted "power factor" magnification, in treatment for aniseikonia.

But the "power factor" could be zero (really, "1"), and all magnification can come from shape factor, if you want, and that would be the "size lens" for demonstration over the patient's current glasses.


Some of the variables in these factors are power, lens thickness, base curve, vertex distance, etc. It's not a hard formula to use.



It looks like you'd have to have the back vertex power of zero so power factor would be a "1".




Hey, those ^^^ look like old aphakic specs!

Good thing for Blue Roll.

[NAICITPO]

Yes. There is the "power factor" & "shape factor" in the spectacle magnification formula.

With an iseikonic lens design, the "shape factor" is manipulated to offset the unwanted "power factor" magnification, in treatment for aniseikonia.

But the "power factor" could be zero (really, "1"), and all magnification can come from shape factor, if you want, and that would be the "size lens" for demonstration over the patient's current glasses.


Some of the variables in these factors are power, lens thickness, base curve, vertex distance, etc. It's not a hard formula to use.



It looks like you'd have to have the back vertex power of zero so power factor would be a "1".




Hey, those ^^^ look like old aphakic specs!

Good thing for Blue Roll.

Solving the world's problems, one blue roll at a time...

[Lelarep]

My only issue with the table of likely symptoms is that the two that are present in the majority of patients are common to a ridiculous number of ocular, and non-ocular, conditions. After the top two, the frequency of presentation drop off dramatically.

[Uncle Fester]

Another step in my long journey to total enlightenment.
Thanks again drk!!!

[Robert Martellaro]

Maybe the only supplier of size lenses in the known universe.

https://chadwickoptical.com/product/...size-lens-kit/

Biconvex/concave trial lenses also work when stacked, but for prescribing, get the kit.

Robert Martellaro

[Barry Santini]

THE most important thing to remember about these 2 formulae is that they described what is happening to the principle planes in relationship to the corrective lenses. I believe this is not widely taught in the schools, and is but one if the failures with the current educational regime.

B