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An Argument Against Axial Length–Disc Area Ratio as the Causeof Esotropic Amblyopia

An Argument Against Axial Length–Disc Area Ratio as the Causeof Esotropic Amblyopia I read with interest the article by Dr Lempert1 inthe June 2003 issue of the ARCHIVES. The author reports axiallength and disc areas for hyperopic patients with and without esotropia andamblyopia. In this article, he states that “reductions in disc areaare consistently found in eyes with esotropia with and without amblyopia.”In addition, he comments that in patients with amblyopia the eyes with poorervision have a greater relative reduction in disc area. As a result of thesefindings, he states that “a paucity of nerve fibers may be a factorin the explanation for decreased visual acuity in amblyopic eyes.” I feel that there may be a flaw in this line of reasoning. In this study,patients are grouped into 4 categories: hyperopes with no amblyopia or strabismus,hyperopes with strabismus, the nonamblyopic eye of hyperopic esotropes, andthe amblyopic eye of esotropes. When one evaluates the table comparing these4 groups, it is readily apparent that there is a significant difference inthe spherical equivalent of their refractive error. As a result of this, thegroups that were more hyperopic tended to have the shorter axial length, aswould be expected. These groups also had the smaller disc areas and the largestratio of axial length to disc area. The relationship between axial lengthand disc area may not be a linear one, especially at higher levels of hyperopia.The results of this study would be more valid if the patients placed intoeach group had more comparable levels of hyperopia. For example, it wouldbe more applicable to take a group of amblyopes with 5 diopters (D) of hyperopiaand compare them with a group of patients who are not amblyopic with a similardegree of refractive error. Until this comparison is performed, all this study shows is that therelationship between axial length and disc area may not be a linear one, especiallyat higher levels of hyperopia. Certainly, it is not appropriate to state thatthe paucity of nerve fibers may be a factor in the explanation of decreasedvisual acuity in amblyopic eyes when we know that the patient’s strabismusand in many cases anisometropia are clearly amblyogenic factors. Correspondence: Dr Bacal, Eye Physiciansand Surgeons, PC, 202 Cherry St, Milford, CT 06460. References 1. Lempert P Axial length–disc area ratio in esotropic amblyopia. Arch Ophthalmol 2003;121821- 824PubMedGoogle ScholarCrossref http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Ophthalmology American Medical Association

An Argument Against Axial Length–Disc Area Ratio as the Causeof Esotropic Amblyopia

Archives of Ophthalmology , Volume 122 (11) – Nov 1, 2004

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References (1)

Publisher
American Medical Association
Copyright
Copyright © 2004 American Medical Association. All Rights Reserved.
ISSN
0003-9950
eISSN
1538-3687
DOI
10.1001/archopht.122.11.1732-a
Publisher site
See Article on Publisher Site

Abstract

I read with interest the article by Dr Lempert1 inthe June 2003 issue of the ARCHIVES. The author reports axiallength and disc areas for hyperopic patients with and without esotropia andamblyopia. In this article, he states that “reductions in disc areaare consistently found in eyes with esotropia with and without amblyopia.”In addition, he comments that in patients with amblyopia the eyes with poorervision have a greater relative reduction in disc area. As a result of thesefindings, he states that “a paucity of nerve fibers may be a factorin the explanation for decreased visual acuity in amblyopic eyes.” I feel that there may be a flaw in this line of reasoning. In this study,patients are grouped into 4 categories: hyperopes with no amblyopia or strabismus,hyperopes with strabismus, the nonamblyopic eye of hyperopic esotropes, andthe amblyopic eye of esotropes. When one evaluates the table comparing these4 groups, it is readily apparent that there is a significant difference inthe spherical equivalent of their refractive error. As a result of this, thegroups that were more hyperopic tended to have the shorter axial length, aswould be expected. These groups also had the smaller disc areas and the largestratio of axial length to disc area. The relationship between axial lengthand disc area may not be a linear one, especially at higher levels of hyperopia.The results of this study would be more valid if the patients placed intoeach group had more comparable levels of hyperopia. For example, it wouldbe more applicable to take a group of amblyopes with 5 diopters (D) of hyperopiaand compare them with a group of patients who are not amblyopic with a similardegree of refractive error. Until this comparison is performed, all this study shows is that therelationship between axial length and disc area may not be a linear one, especiallyat higher levels of hyperopia. Certainly, it is not appropriate to state thatthe paucity of nerve fibers may be a factor in the explanation of decreasedvisual acuity in amblyopic eyes when we know that the patient’s strabismusand in many cases anisometropia are clearly amblyogenic factors. Correspondence: Dr Bacal, Eye Physiciansand Surgeons, PC, 202 Cherry St, Milford, CT 06460. References 1. Lempert P Axial length–disc area ratio in esotropic amblyopia. Arch Ophthalmol 2003;121821- 824PubMedGoogle ScholarCrossref

Journal

Archives of OphthalmologyAmerican Medical Association

Published: Nov 1, 2004

Keywords: amblyopia

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