Blink reflex

Feldman RG, Chirico-Post J, Proctor SP. 1988. Blink reflex latency after exposure to trichloroethylene in well water. Arch Environ Health 43 143-147. 

Feldman RG, Niles C, Proctor SP, et al. 1992. Blink reflex measurement of effects of trichloroethylene exposure on the trigeminal nerve. Muscle Nerve 15 490-495. 

Conditions that increase the evaporative loss of tears also worsen dry eye. In addition to environmental causes (Table 60-9) an abnormal blink reflex is a common cause of increased evaporative loss.30... 

Perocular Route. The administration of drugs or accidental exposure of chemicals to the eyes is not commonly a concern in systemic toxicity due to the small surface area exposed and the efficiency of the protective mechanisms (i.e., blink reflex and tears). As long as the epithelium of the eyes remains intact, it is impermeable to many molecules, but, if the toxicant has a suitable polar-nonpolar balance, penetration may occur (Kondrizer et al., 1959 Swan and White, 1972). 

Topical anesthesia will increase the bioavailability of ophthalmic agents by decreasing the blink reflex and the production and turnover of tears. 

When the instillation of eye drops is difficult (eg, pediatric patients, adults with particularly strong blink reflex), the close-eye method may be used. This involves lying down, placing the prescribed number of drops on the eyelid in the inner corner of the eye, then opening eye so that drops will fall into the eye by gravity. 

Briellmann RS, Rosier KM, Hess CW (1996). Blink reflex excitability is abnormal in patients with periodic leg movements in sleep. Mov Disord 11 710—714... 

Taiminen T, Jaaskelainen S, Ilonen T, Meyer H, Karlsson H, et al. 2000. Habituation of the blink reflex in first-episode schizophrenia, psychotic depression and non-psychotic depression. Schizophr Res 44 69-79. 

Rabbit (NS) 3.7-36.2 min 45000 (narcosis, tremors, excitement, chewing, loss of pupillary blink reflex pupillary contraction involuntary blinking) Carpenter et al. 1944... 

With the patient s head inclined backward so that the optical axis is as nearly vertical as possible, the lower lid is retracted and the upper lid stabilized.The patient should be instructed to elevate the globe to move the cornea away from the instillation site to minimize the blink reflex. The solution is instilled, and the dropper tip is kept at least 2 cm from the globe to avoid contact contamination (Figure 3-3). After the lids are gently closed, the patient should be cautioned to avoid lid... 

One or two drops of 0.5% proparacaine are sufficient for most ophthalmic diagnostic procedures requiring topical anesthesia. Most often, procedures are performed bilaterally, and it is most efficient if the anesthetic is instilled in both eyes before beginning the procedure. Because the duration of action is 10 to 20 minutes, it is not necessary to reapply anesthetic before beginning the procedure on the second eye. If a procedure is to be performed on one eye only, it is still recommended that anesthetic be instilled in both eyes to inhibit the blink reflex in the fellow eye. Examples of diagnostic procedures that require topical anesthesia on all or some occasions are listed in Box 19-1. 

Under normal conditions the various components of the tear film are continually produced in sufficient quantity, not only to cover the ocular surfece but also to supply a reservoir of tears that is stored at the margin of the upper and lower eyelids. The movement of the upper eyelid distributes this reservoir, called the tear river or tear meniscus, during blinking or voluntary lid closure. As the tear film thins and breaks up, the blink reflex is stimulated. The down-phase of each blink compresses the superficial lipid layer, and the up-phase redistributes the lipid layer, which remains in a fairly dynamic state well after the completion of the blink. Each time the eyelid reopens, a new tear film layer is spread across the ocular surfece. The blink itself may also augment meibomian gland expression. 

The seventh cranial nerve is responsible for eyelid closure during the blink reflex. Partial or complete disturbance of cranial nerve VII can interrupt these impulses, resulting in incomplete lid closure. Loss of muscular tone can also lead to ectropion, disruption of the lacrimal pump, and ultimately impaired tear drainage. 

Of the several effective techniques available for removal of a corneal foreign body, the one chosen often depends on the depth of the foreign body, the cooperation of the patient, and personal preference of the clinician (Figure 26-18). Instillation of a topical anesthetic precedes removal of the foreign body. Instillation of anesthetic drops in both eyes helps to control the patient s blink reflex during removal. 

Transient central blindness has followed an intravenous injection of atropine 0.8 mg in the course of spinal anesthesia blink reflex and pupillary response to light and accommodation were lost vision returned slowly after some hours after the instillation of pilocarpine (6). 

Topical anesthetics Topical anesthetics are used to anesthetize the eye for eye examination and removal of foreign bodies from the eye. Onset is 1 minute and duration is 15 minutes. The blink reflex is temporarily lost and the comeal epithelium temporarily dries. Use a protective eye patch until the... 

The blink reflex is temporarily lost and the comeal epithelium temporarily dries. 

The differences in physiology and sensitivity to tested chemicals between rabbit and human eyes. Indeed, the eyes of rabbits appear to present several anatomical and physiological differences when compared to the human eye such as lower tear production, lower blink reflex, thinner cornea, larger corneal surface area, lack of Bowman s layer, larger conjunctival sac, different tear constituents and the presence of nictitating... 

Other major physiological barrier mechanisms are due to tear production and the blink reflex. The conjunctival and corneal surfaces of the eye are continuously lubricated by a film of fluid secreted by the conjunctival and lachrymal glands. The lachrymal glands secrete a watery fluid called tears, and the sebaceous glands on the margins of the eyelids secrete an oily fluid which spreads over the tear film. The latter reduces the rate of evaporation of the tear film from the exposed surface of the eyes. Blinking assists to evenly spread the tear film over the surface of the eye and to drain the tears via the nasolachrymal duct into the nose, and ultimately down the back of the throat into the gastro-intestinal (GI) tract. 

A variety of novel ophthalmic liquid pack design features are in development or have been developed recently. For example, the Optidyne system being developed by Scherer DDS is an atomised spray which delivers a tiny volume (about 5 p.L) directly to the front of the eyeball so fast that it beats the blink reflex. The volume is similar to the capacity of the precorneal volume in the eye. Unlike the traditional eye-drops, the spray product can be directed more easily and should reduce the wastage associated with conventional eye-drops, which have a typical volume of 40 pX. 

This appendix described four types of tests that have been used to assess the neurotoxicity potential of jet-propulsion fuel 8 and related fuels in humans clinical neurological examinations, posturograms, nerve conduction studies, vibration sensation studies, and blink reflex classical conditioning studies. For each test, a critical analysis ofits use in assessing neurotoxicity from exposure to jet fuels is presented. Limitations of these tests are also presented. 

The use of blink reflex classical conditioning to investigate motor learning in subjects exposed to neurotoxicants has been suggested. Bekkedal et al. (2001) reported that the blink reflex conditioning response may be affected by exposure to JP-8. It has been shown that the cerebellum is involved in the... 

Glocker, FX2,M. Lauk, D. Foil, B. Koster,B. Guschlbauer, J. Timmer, G. Deuschl, and C.H. Lucking. 1999. Classical conditioning of the electrically elicited blink reflex in humans A new method of data analysis. J. Neurosci. Methods 89(2) 133-140. 

Typical ocular symptoms associated with exposure to OC aerosol exposure include lacrimation, conjunctival inflammation, redness, severe burning pain, swelling, and blepharospasm. The application of capsaicin to the eye causes neurogenic inflammation and unresponsiveness to chemical and mechanical stimuli. Topical application of capsaicin eliminates the blink reflex for up to 5 days following dosing. Systemic administration of capsaicin is associated with trigeminal nerve fiber degeneration in the cornea. In humans, exposure to OC can cause loss of the blink reflex. 

Reflexes such as the flexion reflex and the eye blink reflex are affected by psychological factors such as fear and arousal (Koh and Drummond 2006), and it is reasonable to assume that cough may also be influenced by these types of psychological factors. 

Koh CW, Drummond PD (2006) Dissociation between pain and the nociceptive blink reflex during psychological arousal. Clin Neurophysiol 117 851-854 KoUarik M, Undem BJ (2006) Sensory transduction in cough-associated nerves. Am Rev Respir Dis 152 243-254... 

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