Astigmatism

Last reviewed: December 2018

Last updated: November 2017

Summary

Astigmatism is a refractive error characterised by a variation in the dioptric power of the eye from one meridian to another.

The most common symptom is diminished visual acuity.

The aetiology is still unknown, but it is probably influenced by both genetic and environmental factors.

Among the common risk factors are a family history of astigmatism; myopia; Native American, East Asian, Hispanic, or Brazilian ethnic origin; eye trauma or surgery; and certain genetic and eyelid pathologies.

In most cases, the diagnosis is clinical and further diagnostic tests are usually not necessary.

Screening in the paediatric population is essential, primarily to decrease the risk of amblyopia.

Definition

Astigmatism is a refractive error characterised by a variation in the dioptric power of the eye from one meridian to another. Instead of having a spherical cross-section, the cornea and/or lens is cylindrical, with different focal power depending on the plane in which the light travels (the meridian). The meridians that have the greatest and the least dioptric power are known as the principal meridians. Astigmatism is termed regular when the principal meridians are at 90° to each other; otherwise, it is termed irregular. When astigmatism is present, the optical system is incapable of generating a clear image. [1]

History and exam

Key diagnostic factors

presence of risk factors
blurred vision

Full details

Other diagnostic factors

asthenopia (eye strain)
distorted retinal reflex
Munson's sign

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Risk factors

positive family history
presence of myopia
East Asian, Hispanic, Native American, or indigenous Brazilian ethnicity
eye trauma or surgery
genetic syndromes
eyelid pathology

Full details

Diagnostic investigations

1st investigations to order

retinoscopy

Full details

Investigations to consider

keratometry
corneal topography

Full details

Emerging tests

wavefront analysis technology
anterior-segment optical coherence tomography (AS-OCT)

Full details

Treatment algorithm

ACUTE

Contributors

Authors VIEW ALL 

Erez Bakshi, MD

Department of Ophthalmology

Assaf Harofeh Medical Center

Tel Aviv University

Israel

Disclosures

EB declares that he has no competing interests.

David Zadok, MD

Principal Investigator

Department of Ophthalmology

Assaf Harofeh Medical Center

Tel Aviv University

Israel

Disclosures

DZ declares that he has no competing interests.

Peer reviewers VIEW ALL 

Michael P. Ehrenhaus, MD

Assistant Professor of Ophthalmology

Cornea External Disease and Refractive Surgery Local Director

Long Island College Hospital Eye Center

Brooklyn

Disclosures

MPE declares that he has no competing interests.

Gus Gazzard, MA, MBBChir, MD, FRCOphth

Consultant Ophthalmic Surgeon

King's College Hospital

Honorary Research Fellow

Institute of Ophthalmology

London

Disclosures

GG declares that he has no competing interests.

Richard Davidson, MD

Assistant Professor

Department of Ophthalmology

Rocky Mountain Lions Eye Institute

University of Colorado Denver School of Medicine

Denver

Disclosures

RD serves on the speakers bureaux for Alcan Inc and Allergan Inc. The work for these companies does not conflict with the review or nature of this monograph.

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Astigmatism

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic investigations

1st investigations to order

Investigations to consider

Emerging tests

Treatment algorithm

regular astigmatism

borderline astigmatism in patients ≥1 year old (age-dependent dioptre cutoffs)

irregular astigmatism

Contributors

Authors VIEW ALL 

Erez Bakshi, MD

Disclosures

David Zadok, MD

Disclosures

Peer reviewers VIEW ALL 

Michael P. Ehrenhaus, MD

Disclosures

Gus Gazzard, MA, MBBChir, MD, FRCOphth

Disclosures

Richard Davidson, MD

Disclosures

Differentials

Guidelines

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