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The corneal reflex, also known as the blink reflex or eyelid reflex, [1] is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), though it could result from any peripheral stimulus. Stimulation should elicit both a direct and consensual response (response of the opposite eye).
Cervico-spinal reflex; Churchill–Cope reflex; Corneal reflex — blinking of both eyes when the cornea of either eye is touched. Coronary reflex; Cough reflex — a rapid expulsion of air from the lungs after sudden opening of the glottis, and usually following irritation of the trachea.
In the fields of optometry and ophthalmology, the Hirschberg test, also Hirschberg corneal reflex test, is a screening test that can be used to assess whether a person has strabismus (ocular misalignment). A photographic version of the Hirschberg test is used to quantify strabismus. [1]
The cornea has unmyelinated nerve endings sensitive to touch, temperature and chemicals; a touch of the cornea causes an involuntary reflex to close the eyelid.Because transparency is of prime importance, the healthy cornea does not have or need blood vessels within it.
A reflex blink is not necessarily a conscious blink either; however it does happen faster than a spontaneous blink. [1] Reflex blink may occur in response to tactile stimuli (e.g., corneal, eyelash, skin of eyelid, contact with eyebrow), optical stimuli (e.g. dazzle reflex, [20] or menace reflex) or auditory stimuli (e.g., menace reflex).
During the accommodation reflex, the pupil constricts to increase the depth of focus of the eye by blocking the light scattered by the periphery of the cornea. The lens then increases its curvature to become more biconvex, thus increasing refractive power. The ciliary muscles are responsible for the lens accommodation response. [4]
The blink reflex [ edit ] When a US is delivered to the cornea of the eye, sensory information is carried to the trigeminal nucleus and relayed both directly and indirectly (via reticular formation ) to the accessory abducens and abducens motor nuclei (see Cranial nerve nucleus ).
At least four Purkinje images are usually visible in the normal eye. The first Purkinje image (P1) is the reflection from the outer surface of the cornea. The second Purkinje image (P2) is the reflection from the inner surface of the cornea. The third Purkinje image (P3) is the reflection from the outer (anterior) surface of the lens. The ...