Impaired Accommodation - Eye Optics and Refractive Errors

Impaired Accommodation

Accommodation Spasm

Definition

An accommodation spasm is defined as inadequate protracted contraction of the ciliary muscle.

Etiology: 

Accommodation spasms arerare. They may occur asfunctionalimpairment or they may occur iatrogenically when treating young patientswith parasympathomimetic agents (miotic agents). The functional impair-ments are frequently attributable to heightened sensitivity of the accommo-dation center, which especially in children (often girls) can be psychogenic. Rarely the spasm is due to organic causes. In these cases, it is most oftenattributable to irritation in the region of the oculomotor nuclei (from cerebral pressure or cerebral disorders) or to change in the ciliary muscle such as in an ocular contusion.

Symptoms: 

Patients complain of deep eye pain and blurred distance vision(lenticular myopia).

Diagnostic considerations and differential diagnosis: 

The diagnosis ismade on the basis of presenting symptoms and refraction testing, including measurement of the range of accommodation. This is done with an accom-modometer, which determines the difference in refractive power between the near point and far point. A differential diagnosis should exclude latent hyperopia. In children, this will frequently be associated with accommoda-tive esotropia and accommodative pupil narrowing.

Treatment: 

This depends on the underlying disorder. Cycloplegic therapywith agents such as tropicamide or cyclopentolate may be attempted in the presence of recurrent accommodation spasms.

Prognosis: 

Iatrogenic spasms are completely reversible by discontinuing theparasympathomimetic agents. The prognosis is also good for patients with functional causes. Spasms due to organic causes require treatment of the un-derlying disorder but once treatment is initiated the prognosis is usually good.

Accommodation Palsy

Definition

Failure of accommodation due to palsy of the ciliary muscle.

Etiology: 

This rare disorder is primarily to one of the following causes:

❖Iatrogenic drug-induced palsy due to parasympatholytic agents such asatropine, cyclopentolate scopolamine, homatropine, and tropicamide.

❖ Peripheral causes: Oculomotor palsy, lesions of the ciliary ganglion, or theciliary muscle.

❖ Systemic causes: Damage to the accommodation center in diphtheria, dia-betes mellitus, chronic alcoholism, meningitis, cerebral stroke, multiple sclerosis, syphilis, lead or ergotamine poisoning, medications such as isoniazid or piperazine, and tumors.

Symptoms: 

The failure of accommodation leads to blurred near vision andmay be associated with mydriasis where the sphincter pupillae muscle is also involved. The clinical syndromes listed below exhibit a specific constellation of clinical symptoms and therefore warrant further discussion.

❖ Post-diphtheria accommodation palsy: This transitory palsy is a toxicreaction and occurs without pupillary dysfunction approximately four weeks after infection. Sometimes it is associated with palsy of the soft pal-ate and/or impaired motor function in the lower extremities.

❖ Accommodation palsy in botulism: This is also a toxic palsy. Itdoesinvolve the pupil, producing mydriasis, and can be the first symptom of botulism. It is associated with speech, swallowing, and ocular muscle dys-function accompanied by double vision.

❖ Tonic pupillary contraction is associated with tonic accommodation.

❖ Sympathetic ophthalmia is characterized by a decrease in the range ofaccommodation, even in the unaffected eye.

Measurement of the range of accommodation is indicated whenever sympathetic ophthalmia is suspected.

Diagnostic considerations: 

In addition to measuring the range of accommo-dation with an accommodometer, the examiner should inquire about other ocular and general symptoms.

Treatment: 

This depends on the underlying disorder.

Prognosis: 

The clinical course of tonic pupillary contractionis chronic andresults in irreversible loss of accommodation. The toxic accommodation pal-sies are reversible once the underlying disorder is controlled.