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Endocrine Disease
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Lid lag is present in any form of hyperthyroidism. The levator palpebrae superioris (LPS), partly sympathetically innervated, is affected by increased catecholamine sensitivity. Spasm of the LPS causes upper eyelid retraction and a typical ‘stare’. Blinking is frequent with eye grittiness. The sclera is visible above the cornea. Less severe lid retraction is elicited by demonstrating lid lag.
Specific Diseases and Procedures
Published in Michele Barletta, Jane Quandt, Rachel Reed, Equine Anesthesia and Pain Management, 2023
General anesthesia must provide immobility of the eyelids or globe, avoid increased intraocular pressure (IOP), for some procedures ensure that the globe is in a central position within the orbit, and analgesia. Note that TIVA with an alpha-2 agonist sedative and ketamine, with or without guaifenesin, is accompanied by varying degrees of nystagmus that may interfere with the surgical procedure.The presence of rapid globe movement during TIVA is a common reason for choosing inhalation anesthesia for ophthalmologic procedures. Nystagmus will be absent, but the eye may slowly rotate during a light-moderate plane of inhalation anesthesia.Blinking can be prevented by an auriculopalpebral nerve block, but this block provides no analgesia.
Anatomy of the Forehead and Periocular Region
Published in Neil S. Sadick, Illustrated Manual of Injectable Fillers, 2020
Marcelo B. Antunes, Stephen A. Goldstein
The orbicularis oculi muscle arises medially from the frontal process of the maxilla, lacrimal bone, medial palpebral ligament, and nasal process of the frontal bone. It then extends laterally to insert into the subcutaneous tissue at the lateral part of the orbit (Figure 4.2). The orbicularis oculi is a sphincter of muscle responsible for eye closure. It is divided into three portions: orbital, palpebral, and tarsal. The orbital portion is the thickest, most peripheral portion. The palpebral portion travels from the medial canthal tendon to the lateral canthal tendon immediately underneath the skin of the superior and inferior eyelids. The tarsal portion arises from the posterior lacrimal crest, behind the lacrimal sac, and travels laterally, superficial to the tarsal plate, to insert into the lateral canthal tendon. The palpebral and tarsal portions act involuntarily. They are responsible for the involuntary closure of the eyelids such as during blinking. They also form a significant part of the lacrimal pump system. The orbital portion of the orbicularis is a voluntary muscle. Its contraction results in tight closure of the eyelids, drawing the eyebrows inferiorly and creating rhytides over the lateral portion of the orbit, often called crow’s feet. The action of the orbicularis oculi contributes significantly to facial expression and may be the most important source of nonverbal communication: as we all know, “the eyes are the window to the soul.” Through movement of the eyelids, one can express many emotions, such as pain, anger, fear, and surprise.
Ocular surface predisposing factors for digital display-induced dry eye
Published in Clinical and Experimental Optometry, 2023
Cristian Talens-Estarelles, José Vicente García-Marqués, Alejandro Cerviño, Santiago García-Lázaro
Furthermore, in the present study tear volume significantly increased with computer use. Conversely, some authors reported significantly lower tear meniscus height and Schirmer test results in long-term office workers while others obtained no difference.7,11,31 Blinking keeps the eye surface humid and hydrated by favouring the secretion of tears and spreading them through the ocular surface.32,33 Nielsen et al.34 reported a compensatory burst of blinks right after cessation of an active digital display task. Authors attributed this phenomenon to compensation for the oppression of blinking during the digital display task and therefore as a wetting process secondary to ocular surface disturbance, which could be behind the greater post-task tear volume obtained in the present study.
Evaluation of corneal sublayers thickness and corneal parameters in patients with Parkinson’s disease
Published in International Journal of Neuroscience, 2021
Ersin Kasım Ulusoy, Döndü Melek Ulusoy
Blinking and tears function are the protective mechanism of the eye. A regular precorneal tear film is sourced by the blinking which not only smoothes out irregularities of corneal surface but a symmetric tear-cornea optical interface is also maintained [18]. Many studies indicate that patients with PD have a reduced BR and it is also regarded as a symptom that leads to the diagnosis of PD [7,8,19,20]. Low dopaminergic activity develops hypokinesia which leads to reduced BR in patients with PD [7]. Patients with PD as observed by Karson et al. were found to have reduced BRs whereas patients with minor disability had relatively normal BRs [20]. A study analyzed various situations for BR in patients with PD (while reading a book, watching a video and being interviewed), notably in all circumstances low BR was found in the patient group as compared to the control group. Nevertheless, the disease severity and BR were found to have no association [21]. BR in patients with PD and the H-Y scores are reported to have a negative correlation in other studies [20–22]. As already explained, we have analyzed in our study that significantly reduced BR is found in the patients with PD in contrast to the healthy controls as well as disease severity and the BR having negative correlation notably [7,21].
The Hawthorne Effect in Eye-blinking: Awareness that One’s Blinks are Being Counted Alters Blink Behavior
Published in Current Eye Research, 2020
Nina Shaafi Kabiri, Chris Brooks, Tom Comery, Michael Erb Kelley, Pete Fried, Jaspreet Bhangu, Kevin Thomas
In order to best leverage blink behavior as a biomarker or clinical outcome, it is essential to understand how its functions may be altered by environmental, cognitive, or pathological factors. Anatomically, blinking is crucial to maintaining corneal integrity through spreading tear film across the eyeball, removing irritants, and blocking dangerous stimuli (e.g., light, dust, etc.).14 Behaviorally, the rate of blinking is affected by internal emotional states15, cognitive processes such as attention and arousal16, and may be involved in non-verbal communication.17 Neurologically, blinks are widely believed to be partially dependent on dopamine transmission.1 Although recent fluorodopa positron emission topography (FDOPA-PET) evidence has challenged this assertion18, numerous diseases that modify dopaminergic concentration and transmission also alter one’s spontaneous eye-blink rate (SEBR) – Hypodopaminergic conditions such as Parkinson’s disease experience decreased SEBR19, where-as SEBR is increased in hyperdopaminergic conditions like schizophrenia20 and Huntington’s disease.21