Westphal-Piltz Phenomenon: Function, Tasks, Role & Diseases

Westphal-Piltz phenomenon is a lid closure reaction in which the pupils of the eyes contract. It occurs together with Bell’s phenomenon and is used for differential diagnosis in pupillary motor disorders.

What is Westphal-Piltz phenomenon?

Westphal-Piltz phenomenon is a lid closure reaction in which the pupils of the eyes decrease in size. Westphal-Piltz phenomenon characterizes the reduction in pupil size during eyelid closure. Each time the eyelids reflexively close, the size of the pupils also decreases. Thus, this phenomenon is directly related to the so-called eyelid closure reflex. The eyelid closure reflex represents a reflexive protective mechanism of the eyes. It is a so-called foreign reflex, which is not triggered in the organ where the stimulus takes place. Mechanical action on the cornea and the immediate surroundings of the eye causes rapid closure of the eyelids. This reflex is intended to protect the eyes from foreign bodies, from dehydration and from damage to the eyeball. The eyelids are also involuntarily closed when exposed to strong light, acoustic stimuli or shock. As a foreign reflex, a habituation effect sets in after some time. Thus, contact lens wearers can switch off the reflex by habituation and touch the cornea. The tactile, visual, and auditory 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 and task

Two phenomena occur in parallel with eyelid closure. These are Bell’s phenomenon and the Westphal-Piltz phenomenon. The Westphal-Piltz phenomenon, as mentioned earlier, characterizes the miosis (reduction) of the pupils during eyelid closure. At the same time, in Bell’s phenomenon, the eyeball is rolled upward to protect the delicate cornea. In facial paralysis, Bell’s phenomenon has been found to occur despite the failure of eyelid closure. Like the eyelid closure reflex, the pupillary reflex is triggered by the same pathway. Both are consensual reflexes. That is, even if only one eye is stimulated, the reflexes occur in both eyes. Also independent of eyelid closure, dilations and constrictions of the pupils take place. Thus, the pupils react to light exposure with constriction (miosis) and to dim light conditions with pupillary dilation (mydriasis). The sphincter pupillae muscle is responsible for pupil constriction and the dilatator pupillae muscle for pupil dilation. 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 eyelid closure (Westphal-Piltz phenomenon) must have other causes than their contraction during light irradiation. This assumes a co-movement of the pupils when the eyelids are closed. Thus, in certain diseases, although no reactions of the pupil to light irradiation are registered, they are registered to the eyelid closure reflex. Certain eye diseases associated with paralysis can therefore be diagnosed by examining the Westphal-Piltz phenomenon. However, this is not unproblematic, because in addition to the Westphal-Piltz phenomenon, Bell’s phenomenon also occurs. The pupil is often no longer visible due to the rolling up of the eyes.

Diseases and complaints

With the help of the Westphal-Piltz phenomenon, indications of the cause of the disease can be found in disorders of pupillary motor function. First, it should be reemphasized that pupillary constriction and dilation are realized via two different pathways. While pupil dilation is regulated by sympathetic efferents, parasympathetic efferents are responsible for 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. In strong light the pupils are nevertheless dilated due to pupillotonia. In darkened rooms, however, they become smaller than in healthy persons under comparable conditions. In close-up situations, the pupils become constricted. Pupillotonia almost always begins unilaterally. Sometimes paralysis of the sphincter pupillae muscle also leads to absolute pupillary rigidity.Causes for this paralysis can be aneurysms, hematomas or brain tumors. In this case, the pupil is dilated and does not react to light or to a close-up view. The so-called Horner syndrome is again a weakness of the musculus dilatator pupillae. As a consequence, the pupils hardly dilate in the dark, resulting in visual difficulties in the dark. However, since the musculus dilatator pupillae and the musculus sphincter pupillae work independently of each other, pupil contraction works perfectly when exposed to light and when the eyelids close. More rarely, the so-called reflex pupillary rigidity occurs. Here, both eyes are immediately affected. Only the optical reflexes are disturbed. The pupils do not react to the light stimulus. However, the motor reflexes (close focus and convergence response) are intact. This symptom is referred to as the Argyll-Robertson sign. In reflex pupillary rigidity, there is damage to the midbrain, which often occurs in inflammation and tumors, but is also common in syphilis.