Eyelid movements in health and disease. The supranuclear impairment of the palpebral motility

Selective α1A-Adrenoceptor Stimulation Induces Mueller’s Smooth Muscle Contraction in an Isolated Canine Upper Eyelid Preparation

“…4 The levator palpebrae superioris muscle is one of the extraocular muscles. The fibers are made up with fast-twich and slow-twich muscles.…”

Distribution of spontaneous inter-blink interval in repeated measurements with and without topical ocular anesthesia

“…The neural control of blinking involves a complex set of supranuclear mesencephalic structures (superior colliculus, periaqueductal gray matter, substantia nigra, pyramidal tract, and medial longitudinal fasciculus) that control the orbicular musculature activation, as well as the concomitant inhibition of the upper eyelid levator muscle tonus (4) . The inter-blink time intervals temporarily reflect the joint action of these inhibitory (levator muscle) and activating (orbicular muscle) processes.…”

“…These patterns may be the expression of an intrinsic feature of each individual determined by mesencephalic dopaminergic activity. Although the hypothesis of blinking rate central regulation is well accepted in neuropsychology (4)(5)(6)(7)(8)(9) , there are several lines of ophthalmologic evidence showing that the condition of the ocular surface modulates the blink rate (1,(10)(11) . A classical example is the reduced blink rate that occurs after topical ocular anesthesia (12) .…”

Spontaneous eye blinks are entrained by finger tapping

“…The physiological basis of blinking is simple: two antagonistic muscles, the levator palpebrae superioris and orbicularis oculi, participate in eyelid movements during blinking (Evinger, Manning, & Sibony, 1991;Esteban, Traba, & Prieto, 2004); turning off the otherwise tonically active levator palpebrae superioris together with bursts of activity of the orbicularis oculi causes a rapid lowering of the upper eyelid. The opposite process elevates the eyelid back to the upper position (Evinger, 1995).…”