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Managing heterophoria: in this two-part series on heterophoria, optometrist Amar-Kaash Gandecha discusses its management.

WHEN FOCUSING on the management of heterophoria, an optometrist should be aiming to help alleviate symptoms and prevent the heterophoria from breaking down into a strabismus.

A very simple five-step approach can often be enough to alleviate symptoms of a decompensated phoria.

Step one: Remove the cause of decompensation

Apart from more obvious causes of decompensation (for example, low fusional reserves and refractive error), there may be other causes which simply require further questioning of the patient. For example, a student with upcoming exams may have a sudden increase in the amount of close work they do, which potentially induces unnatural stress on the accommodation-convergence relationship, causing their phoria to decompensate. Here, simple advice to improve the patient's visual working environment can potentially restore compensation.

Step two: Refractive correction

Understanding the accommodation-convergence relationship is vital, and in simple terms, the more one accommodates, the more convergence is induced. This is why it is especially important in young patents with significant esophoria to elicit any possible latent hypermetropia by performing a cycloplegic refraction. Bifocals or varifocals, with a reading addition, may help young patients with significant esophoria at near. For exophoric deviations which fail to respond to eye exercises, a 'negative add' may be used to induce accommodative convergence.

As a general rule, the required correction is the smallest which will eliminate a slip on the Mallett Unit and give good cover test recovery. A practitioner should aim to reduce any over correction over time.

Step three: Eye exercises

Here, we are not aiming to strengthen eye muscles, but to instead 're-educate' the visual reflexes in order to re-establish correct muscle and sensory co-ordination. Eye exercises may be considered immediately if refractive correction is not required. These tend to work most successfully with patients aged between 12 and 35 years.

Decompensated exophoria at near is easiest to treat with eye exercise. In this instance, specialist exercises such as the Institute Free-space Stereogram (IFS) can be useful.

In practice, optometrists would most commonly be treating a convergence insufficiency with eye exercises. Although a decompensated exophoria at near and a convergence insufficiency commonly occur together, they are not the same thing. Treatment of a decompensated exophoria would focus on increasing convergent fusional reserves, whereas with convergent insufficiency, focus would! be on improving the near point: of convergence (NPC). Often, both deficiencies would need to be treated together.

If a patient has a symptomatic convergence insufficiency at their working distance, you can treat the patient by educating them to use push-up exercises. Here, a target is slowly brought to the patient's nose while they try to keep it sing le. Jump convergence, where the patient alternates between a near and distance target, may also be a useful way to improve a remote NPC.

Step four: Prism relief

Although possible, hyperphorias are less likely to respond to either refractive correction or eye exercises, and this is where relieving prisms may be appropriate. Practitioner may consider a base-out prism for an esophoria which doesn't respond to refractive correction, or base-in prism for older patients with exophoria at near. The Mallett Unit can determine the appropriate prism to corporate into the prescription. It is important to note that prescribing a prism is not a treatment, but rather a 'relief'.

Step five: Referral

This step should be taken if you suspect a secondary cause for the decompensation, or if the phoria has failed to respond to any of the methods above.
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Title Annotation:PRE-REG FOCUS
Author:Gandecha, Amar-Kaash
Publication:Optometry Today
Geographic Code:4EUUK
Date:Mar 22, 2013
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