Aniseikonia GudangMovies21 Rebahinxxi LK21

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.




Symptoms and signs


Up to 7% difference in image size is well tolerated. If magnification difference becomes excessive the effect can cause diplopia, suppression, disorientation, eyestrain, headache, and dizziness and balance disorders. Asthenopic symptoms alone may occur even if image size difference is less than 7%.




Causes


Retinal image size is determined by many factors. The size and position of the object being viewed affects the characteristics of the light entering the system. Corrective lenses affect these characteristics and are used commonly to correct refractive error. The optics of the eye including its refractive power and axial length also play a major role in retinal image size.
Aniseikonia can occur naturally or be induced by the correction of a refractive error, usually anisometropia (having significantly different refractive errors between each eye) or antimetropia (being myopic (nearsighted) in one eye and hyperopic (farsighted) in the other.) Meridional aniseikonia occurs when these refractive differences only occur in one meridian (see astigmatism).
One cause of significant anisometropia and subsequent aniseikonia has been aphakia. Aphakic patients do not have a crystalline lens. The crystalline lens is often removed because of opacities called cataracts. The absence of this lens left the patient highly hyperopic (farsighted) in that eye. For some patients the removal was only performed on one eye, resulting in the anisometropia / aniseikonia. Today, this is rarely a problem because when the lens is removed in cataract surgery, an intraocular lens, or IOL is left in its place.
Retinal aniseikonia occur due to forward displacement, stretching or edema of retina.




Diagnosis


A way to demonstrate aniseikonia is to hold a near target (e.g., a pen or a finger) approximately 6 inches directly in front of one eye. The person then closes one eye, and then the other. The person should notice that the target appears larger to the eye that it is directly in front of. When this object is viewed with both eyes, it is seen with a small amount of aniseikonia. The principles behind this demonstration are relative distance magnification (closer objects appear larger) and asymmetrical convergence (the target is not an equal distance from each eye).




Treatment


Optical aniseikonia due to anisometropia can be corrected by spectacles, contact lenses or refractive corneal surgeries.
Spectacle correction is done by changing the optical magnification properties of the auxiliary optics (corrective lenses). The optical magnification properties of spectacle lenses can be adjusted by changing parameters like the base curve, vertex distance, and center thickness. Magnification size matched lenses that are used to correct aniseikonia are known as iseikonic lenses.
Contact lenses may also provide less difference in retinal image size. Wider and better field of vision is another benefit of contact lens use. The difference in magnification can also be eliminated by a combination of contact lenses and glasses (creating a weak telescope system). The optimum design solution will depend on different parameters like cost, cosmetic implications, and if the patient can tolerate wearing a contact lens.
For reducing aniseikonia, similar to contact lens correction, optical image size difference will be reduced in refractive surgeries also.
Aniseikonia due to uniocular aphakia is best corrected surgically by intraocular lens implantation. Similarly retinal aniseikonia is corrected by treating causative retinal disease.
Note however that before the optics can be designed, first the aniseikonia should be measured. When the image disparity is astigmatic (cylindrical) and not uniform, images can appear wider, taller, or diagonally different. When the disparity appears to vary across the visual field (field-dependent aniseikonia), as may be the case with an epiretinal membrane or retinal detachment, the aniseikonia cannot fully be corrected with traditional optical techniques like standard corrective lenses. However, partial correction often improves the patient's vision comfort significantly.




Etymology


The word "aniseikonia" is derived from the following Greek morphemes:

"an" = "not" (as in "anæmia");
"is(o)" = "equal" (as in "isobar");
"eikōn" = "image" (as in "icon").




See also


Adelbert Ames, Jr. (Dartmouth Eye Institute, research in the 1930s and 1940s on aniseikonia)
Anisometropia
Macropsia
Micropsia




References






Further reading


Bannon, Robert E.; Neumueller, Julius; Boeder, Paul; Burian, Hermann M. (June 1970), "Aniseikonia and space perception: After 50 years", American Journal of Optometry & Archives of American Academy of Optometry, 47 (6): 423–441, doi:10.1097/00006324-197006000-00001, PMID 4912937, S2CID 37288776
Bisno, David C. (1994), Eyes in the Storm—President Hopkins' Dilemma: The Dartmouth Eye Institute, Norwich, Vermont: Norwich Book Press, p. 288




External links


Aniseikonia Calculator, Chadwick Optical (U.S.A.) — a magnification calculator for iseikonic prescriptions or aniseikonia.

Kata Kunci Pencarian:

• Penyakit mata
• Retinitis sitomegalovirus
• Retinopati
• Retinitis
• Hifema
• Retinopati diabetik
• Retinopati hipertensi
• Aniseikonia
• Macropsia
• Epiretinal membrane
• Anisometropia
• Contact lens
• Adelbert Ames Jr.
• Diplopia
• Amblyopia
• Suppression (eye)
• Refractive error

Aniseikonia - YouTube

Aniseikonia - YouTube

Aniseikonia - YouTube

aniseikonia PRONUNCIATION - YouTube

How to pronounce aniseikonia - YouTube

Aniseikonia - How to pronounce Aniseikonia - YouTube

Aniseikonia _ 01 | Ocular, Two by two, Meridian

bva_aniseikonia

Aniseikonia

Aniseikonia

Aniseikonia

Aniseikonia

aniseikonia

Daftar Isi

• Aniseikonia - Wikipedia
• Aniseikonia: What It Is, Symptoms & Causes - Cleveland Clinic
• Aniseikonia - EyeWiki
• Aniseikonia - StatPearls - NCBI Bookshelf
• Aniseikonia: Causes, Symptoms, and Treatment - DoveMed
• Aniseikonia: What It’s All About - nao.org
• Aniseikonia - Understanding the Visual Condition and Its ...

Aniseikonia - Wikipedia

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. [1] If the ocular image size in both eyes are equal, the condition is …

Aniseikonia: What It Is, Symptoms & Causes - Cleveland Clinic

Dec 10, 2024 · There are two main types of aniseikonia: Optical aniseikonia. This kind of aniseikonia happens because of differences in how light enters and passes through each of your eyes. Retinal aniseikonia. This kind of aniseikonia happens because of differences between the retinas at the backs of your eyes. What are the symptoms of aniseikonia?

Aniseikonia - EyeWiki

Aniseikonia is the difference in image size perceived between the eyes from unequal magnification. The two most common causes are anisometropia and retinal pathology. Symptoms of aniseikonia include diplopia, headache, dizziness, disorientation, and excessive eye strain.

Aniseikonia - StatPearls - NCBI Bookshelf

Aug 8, 2023 · Aniseikonia occurs when there is a difference in perceived image size or shape. It is usually caused by anisometropia, called optical aniseikonia, or by changes in the macula, such as edema or distortion, called retinal aniseikonia. Aniseikonia at a young age can result in amblyopia.

Aniseikonia: Causes, Symptoms, and Treatment - DoveMed

Jul 11, 2023 · Aniseikonia is a condition in which the two eyes perceive images of different sizes, causing a distorted or uneven perception of visual space. While it can be a frustrating and uncomfortable condition, treatment options are available to help …

Aniseikonia: What It’s All About - nao.org

Derived from the Greek, meaning, “without/not equal images”,1 aniseikonia is defined as, “A relative difference in size and/or shape of the ocular images formed by the two eyes.”2, 3 When aniseikonia results from anatomic conditions, such as an unequal distribution of rods and cones between both eyes, or differences in cortical image

Aniseikonia - Understanding the Visual Condition and Its ...

Aniseikonia is a visual condition that affects the perception of image size and shape between the eyes. Early diagnosis and appropriate management, including prescription eyewear and vision therapy, can help alleviate symptoms and improve visual comfort, enhancing the quality of life for individuals living with aniseikonia.