Westphal-Piltz phenomenon

The Westphal-Piltz phenomenon is an eyelid closing reaction in which the pupils of the eyes shrink. It occurs together with Bell's phenomenon and is used for the differential diagnosis of disorders of the pupillary motor skills.

What is the Westphal-Piltz phenomenon?

The Westphal-Piltz phenomenon characterizes the reduction in size of the pupils when the eyelid closes. Every time the eyelids reflexively close, the size of the pupils also decreases.

This phenomenon is therefore directly related to the so-called eyelid closing reflex. The eyelid closing reflex is a reflective protective mechanism of the eyes. It is a so-called external reflex which is not triggered in the organ where the stimulus occurs. Mechanical action on the cornea and the immediate area around the eyes causes the eyelids to close quickly. This reflex is supposed to protect the eyes from foreign bodies, from drying out and from damage to the eyeball.

Even when exposed to strong light, acoustic stimuli or shock, the eyelids are involuntarily closed. After some time, a habitual effect sets in as a foreign reflex. Contact lens wearers can switch off the reflex and touch the cornea by getting used to it. The tactile, optical and acoustic stimuli are conducted via the affective limb of the reflex arc to the reflex center of the brain and from there trigger the contraction of the orbicularis oculi muscle via the efferent limb through the facial nerve.

Function & task

Two phenomena occur parallel to the eyelid closure. These are the Bell phenomenon and the Westphal-Piltz phenomenon. As already mentioned, the Westphal-Piltz phenomenon characterizes the miosis (reduction in size) of the pupils when the eyelids are closed. At the same time, as part of Bell's phenomenon, the eyeball is rolled up to protect the sensitive cornea.

In facial paralysis, it was found that Bell's phenomenon occurs despite the failure of the eyelid to close. Like the blink reflex, the pupil reflex is triggered in the same way. Both are consensual reflexes. That is, even if only one eye is irritated, the reflexes appear in both eyes.

Widening and narrowing of the pupils also take place independently of the eyelid closure. When exposed to light, the pupils react with constriction (miosis) and with weak light conditions with pupil dilation (mydriasis). The sphincter pupillae muscle is responsible for the constriction of the pupils and the dilatator pupillae muscle is responsible for the widening of the pupils.

The sphincter pupillae muscle is supplied by the parasympathetic nervous system and the dilatator pupillae muscle by the sympathetic nervous system.

It was found that the contraction of the pupils after closing the eyelids (Westphal-Piltz phenomenon) must have other causes than their contraction when exposed to light. It is assumed that the pupils also move when the eyelids are closed. With certain diseases, for example, the pupil does not react to light radiation, but it does register the blink reflex. Certain eye disorders associated with paralysis can therefore be diagnosed by examining the Westphal-Piltz phenomenon. However, this does not turn out to be unproblematic, since in addition to the Westphal-Piltz phenomenon, the Bell phenomenon also occurs. The pupil can often no longer be seen as the eyes roll up.

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Illnesses & ailments

With the help of the Westphal-Piltz phenomenon, indications of the cause of the disease can be found in disorders of the pupillary motor skills. First of all, it should be emphasized once again that pupil constriction and dilatation are realized in two different ways. While the dilation of the pupils is regulated by sympathetic efferents, parasympathetic efferents are responsible for the pupil constriction.

Most motor disorders are caused by paralysis of the sphincter pupillae muscle. Pupillotonia is present, which in the majority of cases has harmless causes. With strong incidence of light, the pupils are still dilated due to the pupillotonia. In darkened rooms, however, they become smaller than in healthy people under comparable conditions. When focusing closely, the pupils constrict. Pupillotonia almost always begins unilaterally.

Sometimes paralysis of the sphincter pupillae muscle also leads to absolute pupillary rigidity. The causes of this paralysis can be aneurysms, hematomas or brain tumors. The pupil is wide and shows no reactions to the influence of light or to a close focus.

The so-called Horner syndrome is again a weakness of the dilatator pupillae muscle. As a result, the pupils hardly dilate in the dark, which results in visual difficulties in the dark. However, since the dilator pupillae muscle and the sphincter pupillae muscle work independently of each other, the pupil contraction works perfectly when exposed to light and when the eyelids are closed.

The so-called reflex pupillary rigidity occurs less frequently. Both eyes are affected immediately. Only the optical reflections are disturbed. The pupils do not respond to the light stimulus. However, the motor reflexes (close focus and convergence reaction) are intact. This symptom is known as the Argyll-Robertson sign. In the case of reflex pupillary rigidity, there is damage to the midbrain, which often arises from inflammation and tumors, but often also from syphilis.