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EYE ADVICE: Professional Papers


Part II

Clinical Implications of Meridional Accommodation

by Kon Zagoritis BscOptom FVCO


A precursor of this paper in the form of a handout, accompanied Part I as published in the proceedings of the 11th APOC held in Korea 20th - 24th April 1997. See index for Part I.

It is important to think of the eye as having to accommodate not only for a spherical error, but also for an astigmatic one. A weakness, or overactivity (spasticity), in either one or both types of accommodation will prevent optimal vision.

Parasympathetic meridional accommodation (PMA) can be somewhat fluid in certain cases such as that of Mr G.L. which is described later. Here, temporary contractions are used to correct the astigmatic error similar to spherical ciliary muscle contractions used by hyperopes. At the other extreme are the tonic, rather permanent contractions which, according to Martin, may be relieved only by prolonged cycloplegia. (Quoted by Fletcher 1951).

The fact that atropine and to a lesser extent cyclopentolate, usually give rise to small amounts of with-the-rule (WTR) astigmatism, has long ago been used by Martin and other authors as evidence of meridional accommodation (MA). Although Fletcher (1951) notes that some authors have attributed the WTR change to peripheral zonal aberrations and oblique astigmatism of the lens, Martin found no astigmatic change using mydriasis alone.

The following is an overview of various clinical findings that are relevant to the subject of MA.





Paper 1 - Meridional (Astigmatic) Accommodation  Abstract

Physiology of Meridional Accommodation (A) Ciliary Muscle Action and Innervations
(B) Corneal Changes due to Ciliary Muscle Action
(C) Theory of Initiation of Meridional Accommodation

Clinical Implications of Meridional Accommodation


(A) Astigmatic Changes Related to WTR Corneal Toricity (i) Latent Astigmatism
(ii) Primary Accommodative Astigmatism (PAA)       (B) Reflex or 2°PMA and Induced ATR Astigmatic Changes
(C) Eye Preference and Meridional Accommodation (i) 1° PMA and Eye Preference
(ii) 2° PMA and Eye Preference (D) Proactive Prescribing for Presbyopia (i) Phakic Presbyopes
(ii) Pseudophakes and ATR Corneal Changes (E) Refractive Techniques and MA (i) Balancing Meridional Accommodation
(ii) Binocular Test of Cylinder Power (F) Further Clinical Subject Areas and Meridional Accommodation (i) Preventing Induced Oblique Astigmatism in Children
(ii) Low Vision
(iii) Keratoconus
(iv) Hard Contact Lenses
(v) PRK and PARK (Photorefractive Astigmatic Keratectomy)



Paper 2 - Common Chronic (Infective) Conjunctivitis and Nasal Rinsing

Paper 3 - Primary Open-Angle Glaucoma

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(C) 1997-2011, Kon Zagoritis