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difference in the refractive power of the two eyes

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2012/09/02 22:32:28」(JST)

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Anisometropia ( /ænˌaɪsəmɨˈtroʊpiə/ US dict: an·ī′·sə·mə·trō′·pē·ə) is the condition in which the two eyes have unequal refractive power; that is, are in different states of myopia (nearsightedness), hyperopia (farsightedness) or in the extreme, antimetropia (wherein one eye is myopic and the other is hyperopic), the unequal refractive states cause unequal rotations thus leading to diplopia and asthenopia.

Anisometropia can adversely affect the development of binocular vision in infants and children if there is a large difference in clarity between the two eyes. The brain will often suppress the vision of the blurrier eye in a condition called amblyopia, or lazy eye.

The name is from four Greek components: an- "not," iso- "same," metr- "measure," ops "eye."

One study estimated that 6% of those between the ages of 6 and 18 have anisometropia.^[1]

Spectacle correction

For those with large degrees of anisometropia, spectacle correction may cause the person to experience a difference in image magnification between the two eyes which could also prevent the development of good binocular vision.

The solution for spectacle wearers to the problem that spectacle correction may cause the person to experience a difference in image magnification between the two eyes is spectacles incorporating iseikonic lenses. Iseikonic lenses present adjusted image sizes to the eye compared to standard lenses. The formula for iseikonic lenses (without cylinder) is:

where: t = center thickness (in meters) n = refractive index P = front base curve h = vertex distance (in meters) F = back vertex power (essentially, the prescription for the lens)

(see Practical Optical Dispensing by David Wilson)

If the difference between the eyes is up to 3 diopter spheres iseikonic lenses can compensate. At a difference of 3 diopter spheres the lenses would however be very visibly different - one lens would need to be at least 3mm thicker and have a base curve increased by 7.5 spheres.

Contact lens correction

The usual recommendation for those needing iseikonic correction is to wear contact lenses in their normal prescription since the effect of vertex distance is removed and the effect of center thickness is also almost removed, meaning there is minimal and likely unnoticeable image size difference when wearing contacts. This is a good solution for those who can tolerate contact lenses and for whom the contact lenses create sufficient acuity.

References

^ Czepita D, Goslawski W, Mojsa A. "[Occurrence of anisometropia among students ranging from 6 to 18 years of age.]" Klin Oczna. 2005;107(4-6):297-9. Polish. PMID 16118943.

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1. 小児における屈折異常 refractive errors in children
2. Amblyopia in children: Management and outcome
3. Amblyopia in children: Classification, screening, and evaluation
4. 振子様眼振 pendular nystagmus
5. 原発性乳児緑内障 primary infantile glaucoma

English Journal

Results of Descemet Stripping Automated Endothelial Keratoplasty for the Treatment of Late Corneal Decompensation Secondary to Obstetrical Forceps Trauma.

Scorcia V1, Pietropaolo R, Carnevali A, De Luca V, Lucisano A, Busin M.
Cornea.Cornea.2016 Mar;35(3):305-7. doi: 10.1097/ICO.0000000000000715.
PURPOSE: To describe the clinical outcomes of Descemet stripping automated endothelial keratoplasty (DSAEK) in a series of patients affected by progressive endothelial cell loss leading to corneal decompensation with Descemet membrane (DM) breaks caused by obstetrical forceps trauma.METHODS: Seven a
PMID 26655486

Distinct patterns of spontaneous brain activity between children and adults with anisometropic amblyopia: a resting-state fMRI study.

Liang M1, Xie B1, Yang H2, Yu L1,3, Yin X1, Wei L1, Wang J4.
Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv für klinische und experimentelle Ophthalmologie.Graefes Arch Clin Exp Ophthalmol.2016 Mar;254(3):569-76. doi: 10.1007/s00417-015-3117-9. Epub 2015 Aug 6.
PURPOSE: To detect the altered spontaneous brain activity patterns in children and adults with anisometropic amblyopia using resting-state functional magnetic resonance imaging (rs-fMRI) technique combined with the amplitude of low-frequency fluctuation (ALFF) method.METHODS: Thirty-two monocular an
PMID 26245338

Saccadic latency in amblyopia.

McKee SP, Levi DM, Schor CM, Movshon JA.
Journal of vision.J Vis.2016 Mar 1;16(5):3. doi: 10.1167/16.5.3.
We measured saccadic latencies in a large sample (total n = 459) of individuals with amblyopia or risk factors for amblyopia, e.g., strabismus or anisometropia, and normal control subjects. We presented an easily visible target randomly to the left or right, 3.5° from fixation. The interocular diff
PMID 26943348

Japanese Journal

上眼瞼血管腫の増大により片眼視野が完全遮蔽された1例

関亜希子,坂内優子,平野嘉子 [他],伊藤進,舟塚真,篠崎和美,林伸和,大久保麗,大澤眞木子,SEKI Akiko,SAKAUCHI Masako,HIRANO Yoshiko,ITO Susumu,FUNATSUKA Makoto,SHINOZAKI Kazumi,HAYASHI Nobukazu,OKUBO Rei,OSAWA Makiko
東京女子医科大学雑誌 83(E1), E353-E357, 2013-01-31
乳児血管腫は小児期で最も高頻度の良性腫瘍であり、30%の症例で出生時に認められ、その多くは出生後の数週間以内に出現し生後6〜12カ月までは病変は少しずつ増大し(増殖期)、その後、増大は停止する。増大の程度は病変により様々だがその後数年間で病変は縮小傾向を示す(消退期)。最終的に消退するのは5~12歳頃である。男女比は1:3、未熟児にやや多いとされる。苺状血管腫は自然消退が期待できる為、苺状血管腫と …
NAID 110009559409

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須藤史子,Fabricio W MEDEIROS,Steven E WILSON,堀貞夫
東京女子医科大学雑誌 82(E1), E90-E95, 2012-01-31
【目的】モノビジョンとは、優位眼を遠方視に、非優位眼を近方視に用いる老視矯正法である.古くからコンタクトレンズによるモノビジョン法は普及していたが、近年LASIK (laser in situ keratomileusis )においても、老視患者に対してモノビジョンLASIKが行われるようになっている.モノビジョンLASIKの術後成績から、患者満足度の高いモノビジョンLASIKの要因を知ること., …
NAID 110008767958

第54回日本コンタクトレンズ学会弱視と診断され放置されていた初期老視遠視眼の3症例

入道香澄,山崎愛,有賀義之 [他]
日本コンタクトレンズ学会誌 54(4), 274-277, 2012
NAID 40019704628

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