Dispensing opticians core subject 3

The third of the core competency subjects from the GOC as relevant to practising dispensing opticians reads very much like the early curriculum for the optometry course. Refractive management embraces the basics of refraction and correction, binocular status assessment and visual acuity and vision assessment. It is stated as follows:
Competency 3.5 was discussed last week. Much of the area of binocular status assessment and management depends on the accurate taking of history and symptoms. The following summarises some further important points when first ascertaining salient details about such a presentation. Having discussed presentations of diplopia, this week we look at asthenopia and its investigation.

Asthenopia
'Eyestrain' is what patients complain of when they are avoiding blur and diplopia by motor means. They may be over-exerting inadequate accommodation or fusional reserves, or screwing up the eyes and face to supplement them.
Those patients who have early-onset strabismus (usually esotropes) will develop sensory modifications to avoid both diplopia and asthenopia. Patients with acquired muscle palsies may experience asthenopia if the palsy is slight enough or as the spread of concomitance occurs, but, in general, asthenopia of binocular origin is associated with decompensated heterophoria.
The symptoms of asthenopia are similar whether defocus or decompensation causes it and include blur, head and eye ache, lacrimation, nausea and fatigue.
The following questions may enable the practitioner to determine the root cause of the symptoms.

'Does anything in particular seem to set this off?'
Symptoms due to decompensated phoria are usually task-specific (eg reading, using a VDU, prolonged driving).

Do you get the problem every time you read/use the computer and so on?'
Symptoms associated with decompensated phoria are often inconsistent, so the patient may undertake the same task without the symptoms on another day. Most decompensation of phoria is due to compromised fusional reserves rather than to changes in the phoria itself. The fusional capabilities are a high level function of the brain and can be affected by many things, including illness, fatigue and stress, as well as more prosaic things like target characteristics and lighting. Symptoms due to ametropia tend to more consistent, provided the visual task remains constant, whereas patients with decompensated phoria may have good days and bad days.

'Is it worse when looking close up, or in the distance?'
The most common heterophoria problem seen in practice is convergence insufficiency, which will manifest when the patient reads or uses a computer. Divergence excess or 'V' syndromes may be worse with distance tasks.

'Have you changed jobs recently, or are you unusually tired or stressed?'
Most decompensation of phorias is caused by, and probably eventually alleviated by, factors outside optometric control.

'Do you ever see double?'
If the phoria is breaking down, diplopia will be the outcome, except in early-onset deviations where suppression may have developed. For some reason, possibly because the diplopia is transient and intermittent, phoria patients don't like to worry us with this, but may well report it if prompted. An affirmative answer should be followed up as indicated in the section on diplopia (see last week).

optician would like to thank Andy Franklin for his help with this article.

Due to an administrative error, last week's headline should obviously have read 'Refractive management' and not 'Visual function' as it appeared.

BOXTEXT: Summary of possible asthenopia questions
Question Significance
Triggers? Decompensation may be task specific
Consistent or occasional? Distinguish between decompensation and ametropia
Near or distance? Possible convergence insufficiency
Health or lifestyle considerations? Possible ergonomic or systemic health association
Diplopia? Must be ascertained then probed as above