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Patients suffering from blepharospasm also report sensory symptoms including sensitivity to light, [14] [15] dry eyes, [16] and burning sensation and grittiness in the eyes. [4] Although such symptoms tend to precede the onset of the blepharospasm, they may both be due to a common third factor.
In visual perception, flicker is a human-visible change in luminance of an illuminated surface or light source which can be due to fluctuations of the light source itself, or due to external causes such as due to rapid fluctuations in the voltage of the power supply (power-line flicker) or incompatibility with an external dimmer.
Grammer et al. [5] define an eyebrow flash as a contraction of the inner brow raiser muscle (M. Frontalis, pars medialis) and the outer brow raiser muscle (M. frontalis, pars lateralis) as defined by the Facial Action Coding System. An eyebrow flash is subdivided into three time intervals: the onset (the time during which the eyebrows raise to ...
The requirements of a flicker measurement equipment are defined in the international electro-technical standard IEC 61000-4-15. [2]A flickermeter is composed of several function blocks which simulate a 230 V/60 W or a 120 V/60 W incandescent lamp (reference lamp) and the human perception system (eye-brain model).
Flicker vertigo, sometimes called the Bucha effect, is "an imbalance in brain-cell activity caused by exposure to low-frequency flickering (or flashing) of a relatively bright light." [ 1 ] It is a disorientation -, vertigo -, and nausea -inducing effect of a strobe light flashing at 1 Hz to 20 Hz, approximately the frequency of human brainwaves .
The eyebrows, eyelids, eyelashes, lacrimal gland and drainage apparatus all play a crucial role with regards to globe protection, lubrication, and minimizing the risk of ocular infection. [1] The adnexal structures also help to keep the cornea moist and clean. One source defines "ocular adnexa" as the orbit, conjunctiva, and eyelids. [2]
Blinking is a bodily function; it is a semi-autonomic rapid closing of the eyelid. [1] A single blink is determined by the forceful closing of the eyelid or inactivation of the levator palpebrae superioris and the activation of the palpebral portion of the orbicularis oculi, not the full open and close.
Myerson's sign or glabellar tap sign is a clinical physical examination finding in which a patient is unable to resist blinking when tapped repetitively on the glabella, the area above the nose and between the eyebrows. It is often referred to as the glabellar reflex.