Ocular movements

The eyes are normally parallel in all positions of gaze except convergence. When they are not. a squint is present. Squints may be associated with paresis of one of the extraocular muscles (paralytic or inconcomitant squint) or with defective binocular vision (non-paralytic or concomitant squints).

Acquired paralytic squints cause diplopia, the images being maximally separated and squint greatest in the direction of action of the paretic muscle. Congenital and long-standing paralytic squints often result in abnormal head postures with the head turned or tilted to minimise the diplopia.

Concomitant squints are the same in all positions of gaze. They usually become manifest in childhood (Fig. 7.8) when they arc not associated with diplopia, as this symptom is suppressed centrally in young children. Central suppression causes amblyopia (lazy eye). Eye movements should be examined by:

• Testing movements in all positions of gaze (pp. 201-2). Both eyes should move symmetrically with no diplopia. If diplopia is present, the most peripheral double image is the one from the paretic eye (Fig. 7.9).

• The cover test. The cover/uncover tesi is particularly helpful in detecting small concomitant squints in children.

Examination sequence

□ Ask the patient to look at a distant object.

TAB LE 7.2 Pupil abnormal ¡ties

Cause

Appearance

Reaction

Retinal/optic nerve disease

Abnormal s normal side

Afferent pupil defect

Poor direct light reaction, normal consensual reaction and normal accommodative

reaction on affected side

Reduced consensual reaction on normal side

Neurosyphilis causing pretectal lesion

Small, irregular, unequal

Argyll Robertson pupils

No reaction lo light

Normal reaction to accommodation

III nerve palsy

Abnormal > normal side

Efferent pupil defect

Parasympathetic bfocking drops

No reaction to light or accommodation Normal side reacts consensually

Ciliary ganglion lesion

Abnormal > normal side

Holmes-Adie (myotonic) pupil No reaction lo light

Slow, sustained reaction to accommodation

Sympathetic lesion

Abnormal < normal side

Horner's

Reacts to light/accommodation Does not dilate with cocaine drops

Inflammation of iris

Abnormal < normal side Festooned

Poor/absent reaction to light/accommodation Other pupil reacts consensually

Iris Ischaemla in acute glaucoma

Abnormal > normal side

No reaction lo light/accommodation Other pupil may not react consensually

Images Concomitant Squint
Fig. 7.8 Concomitant right convergent squint in a child.

□ Closely observe the uncovered eye for any movements.

If it moves to take up fixation, that eye was squinting. _1 Repeat the sequence for the other eye.

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