Anatomical and Histological Study of the Upper Tarsus in Asian.

OBJECTIVE: The aim of this study was to observe and analyze the anatomical and histological characteristics of the upper tarsus in Asian. METHODS: A total of 15 Asians (14 adults, 1 child) were used. The sagittal sections with thickness of 3 µm in the middle of the upper eyelid were prepared and stained with hematoxylin-eosin, Masson trichrome and anti-smooth muscle actin antibody staining, and then were observed and photographed under light microscopy. RESULTS: On the sagittal section, the upper end of the tarsus was connected with the Müller muscle and the part of the posterior layer of the levator aponeurosis; the lower end was the inflated part of the palpebral margin; the superficial surface was connected with the pretarsal fascia; and the deep surface was connected with Müller muscle aponeurosis and palpebral conjunctiva. Histologically, the tarsus was similar to the structure between dense fibrous connective tissue and cartilage, and its main structures include meibomian glands and its ducts, accessory lacrimal glands, glands of Moll, glands of Zeis, eyelash hair follicles, Riolan muscle, blood vessels, and collagen fibers. Through the observation of the tarsus of a child, compared with the adult specimen, the meibomian gland tissue was more abundant; the collagen fibers density was significantly lower and arranged orderly; the blood vessel density was significantly higher; α-SMA positive smooth muscle cells could be seen in the upper end of the tarsus and its superficial and deep surfaces. CONCLUSIONS: In this study, the internal and adjacent anatomical structures of the upper tarsus in Asians were observed under a microscope, and according to the histological characteristics, the tarsus was divided into 3 parts and 3 types. Through the preliminary analysis, the tarsus was likely to show different histological characteristics in different individuals and age groups of Asians. There was a certain correlation between the degree of meibomian gland atrophy, the degree of collagen fibrosis and the density of blood vessel in the tarsus.

Müller's Muscle as a Sensory Proprioceptive Organ: Histological and Histochemical Analysis.

Purpose: The purpose of this study was to determine whether proprioceptive nerves are present in Müller's muscle. Methods: This was a prospective cohort study in which histologic and immunofluorescence analyses of excised Müller's muscle specimens were performed. Twenty fresh Müller's muscle's specimens from patients undergoing posterior approach ptosis surgery in one center between 2017 and 2018 were evaluated by histologic and immunofluorescent analysis. Axonal types were determined by measuring axon diameter in methylene blue stained plastic sections and by immunofluorescence of frozen sections. Results: We identified large (greater than 10 microns) and small myelinated fibers in the Müller's muscle, with 6.4% of these fibers being large. Immunofluorescent labeling with choline acetyltransferase showed no evidence of skeletal motor axons in the samples, indicating large axons are likely to be sensory and proprioceptive. In addition, we identified C-fibers using double labeling with peripherin and neural cell adhesion molecules. Conclusions: Overall, large myelinated sensory fibers are present in the Müller's muscle, likely serving proprioceptive innervation. This suggests that proprioception signals from Müller's muscle may have a role in eyelid spatial positioning and retracting, in addition to visual deprivation. This finding sheds new light on our understanding of this complex mechanism.

Sensory Innervation of the Upper Eyelid and Its Implication for Upper Eyelid Surgery.

PURPOSE: Sensory alterations of the upper eyelid skin and eyelashes are frequently encountered after upper eyelid surgery. The objective of this study was to provide information on the exact course and distribution of sensory nerve fibers through the anatomic planes in the upper eyelid. METHODS: Ten formalin-fixed hemifaces were dissected. The nerve branches of the ophthalmic nerve in the upper eyelid were traced in an anterograde fashion. RESULTS: A total of 151 nerve fibers were recorded during dissection. The infratrochlear, supratrochlear, supraorbital, and lacrimal nerve contributed each to both the upper eyelid skin innervation and the upper eyelid rim plexus in different distribution patterns. The mean distance from the eyelid margin at which nerve fibers pierced from preseptal into the orbicularis muscle was 14 ± 1.1 mm for nerve fibers targeting the eyelid dermis and 3.7 ± 1.2 mm for nerve fibers targeting the eyelid rim plexus ( p < 0.001). The mean intraorbicular course of nerve fibers was 3 mm (0-17; standard deviation 4.1). The mean distance from the eyelid margin at which nerve fibers pierced from the orbicularis muscle into the preorbicular plane was 10 ± 1 mm for nerve fibers innervating the eyelid dermis and 1.3 ± 0.8 mm for nerve fibers innervating the eyelid rim plexus ( p < 0.001). The mean distance of the preorbicular course of nerve fibers was 2 mm (0-15; standard deviation 3.6). CONCLUSIONS: Based on the findings, a certain degree of postoperative eyelid skin numbness is inevitable while eyelash innervation may be spared in upper blepharoplasty.

Prevalence and Predictors of Hering's Response in Müller's Muscle-conjunctival Resection.

PURPOSE: Determine the prevalence and predictors of Hering's response following Muller's muscle-conjunctival resection (MMCR). METHODS: Seventy-five consecutive patients undergoing unilateral MMCR were recruited in this prospective, multicenter, cohort study. Margin-reflex distance-1 (MRD1) of both eyelids was recorded preoperatively and postoperatively. One hundred forty-three variables were investigated as potential predictors of a late postoperative (≥3 months) Hering's response using regression analyses. Main outcome measures were Hering's response (≥0.5 mm descent of the unoperated eyelid from baseline), and a clinically relevant Hering's response (descent of the unoperated from baseline to a MRD1 ≤ 2.0 mm, or descent from baseline such that the MRD1 of the unoperated eyelid became >1 mm lower than the operated eyelid). RESULTS: Twenty-four (32.0%) patients had a late postoperative Hering's response, but only 6 (8.0%) responses were clinically relevant. A Hering's response at the immediate (OR 16.24, p = 0.02) and 1-week postoperative (OR 8.94, p = 0.04) timepoints predicted a late postoperative response. However, the presence (OR 7.84, p = 0.07) and amplitude (OR 8.13, p = 0.06) of a preoperative phenylephrine Hering's response did not predict a late postoperative response. Of the 10 patients with a clinically relevant phenylephrine Hering's response, only 1 demonstrated a clinically relevant response late postoperatively. CONCLUSION: Unilateral MMCR induces a clinically relevant Hering's response in 8% of patients. A preoperative phenylephrine Hering's response does not predict a late postoperative Hering's response. Therefore, when unilateral phenylephrine testing unmasks contralateral blepharoptosis, only the side with blepharoptosis at baseline should be operated.

Effects of Upper Blepharoplasty Techniques on Headaches, Eyebrow Position, and Electromyographic Outcomes: A Randomized Controlled Trial.

The aim of this study was to assess changes in headaches, eyebrow height, and electromyographic (EMG) outcomes of the frontalis and orbicularis oculi muscles, after an upper blepharoplasty with or without resecting a strip of orbicularis oculi muscle. In a randomized controlled trial, 54 patients received an upper blepharoplasty involving either only removing skin (group A) or removing skin with an additional strip of orbicularis muscle (group B). Preoperative, and 6 and 12 months postoperative headache complaints were assessed using the HIT-6 scores and eyebrow heights were measured on standardised photographs. Surface EMG measurements, i.e., electrical activity and muscle fatigue, were assessed for the frontalis and orbicularis oculi muscles preoperatively and 2, 6, and 12 months postoperatively. Significantly fewer headaches were reported following a blepharoplasty. The eyebrow height had decreased, but did not differ between groups. Regarding the surface EMG measurements, only group A's frontalis muscle electrical activity had decreased significantly during maximal contraction 12 months after surgery (80 vs. 39 mV, p = 0.026). Fatigue of both the frontalis and the orbicularis oculi muscles did not change significantly postoperatively compared to baseline. EMG differences between groups were minor and clinically insignificant. The eyebrow height decreased and patients reported less headaches after upper blepharoplasty irrespective of the used technique.

'Are dynamic procedures superior to static in treating the paralytic eyelid in facial paralysis?'

BACKGROUND: Facial nerve weakness can cause deficient eye closure with reduced corneal protection. Surgical remedies can be static to oppose the levator muscle (lid loading) or dynamic procedures, which act to increase the strength of closure. This retrospective cohort study compares these groups. The hypothesis is that dynamic reconstruction has advantages over static techniques in terms of eye closure, symptomatic improvement, blink restoration, and complication rate. METHODS: Two cohorts were compared: those treated with a gold weight insertion into the upper eyelid and those who had received dynamic reconstruction. These included temporalis transfer; cross face nerve grafting alone (CFNG) and CFNG followed by free tissue transfer. Assessments included standard photography and video; measurement of eyelid excursion including residual gap and if full eye closure was possible. The presence of the blink reflex and symptoms of dry eye was assessed. RESULTS: Overall improvement in eye closure was similar with the gold weight compared to dynamic procedures (5.1 mm vs 5.3 mm). Dynamic procedures however gave improved results in terms of symptom relief and restoration of blink. They also had fewer complications and revision rates overall. CONCLUSION: The study confirms the hypothesis that dynamic reconstructions of the paralysed eyelid confer advantages compared to simple lid loading techniques. Improvements in lid excursion are similar, but symptom improvement and blink restoration are significantly better. A decision regarding eyelid reanimation should be made early in the patient's journey of facial reanimation to allow for accurate planning and placement of nerve grafts at an early stage.

Single access upper blepharoplasty and lower lid lateral fat pad removal: A proven technique with low recurrence rate.

BACKGROUND: The transconjunctival approach is commonly performed in lower lid blepharoplasty so as not to violate the orbicularis oculi muscle integrity and avoid additional scars. This technique does not, however, permit easy access to the lateral fat pad (LFP). As upper and lower blepharoplasty are frequently combined in our clinical practice, the removal of LFP via upper blepharoplasty is a surgical approach that we found most applicable with good outcomes. METHODS: A prospective review of 47 consecutive bilateral combined upper and lower blepharoplasty cases using a single access technique was conducted; patient outcomes and the occurrence of any complications were recorded, in addition to preoperative and postoperative measurements between standardized anatomical landmarks. RESULTS: Forty-seven patients were included in our study. Postoperative measurements showed a decrease of both lateral cantus to inferior orbital border distance and horizontal width of LFP. Good esthetic outcomes and patient satisfaction with surgical results were achieved in the majority of patients. CONCLUSION: The single access upper blepharoplasty and lower lid LFP removal technique can improve esthetic outcomes in lower blepharoplasty. The advantages are many; a low risk of missing the lateral pad, ease of achieving a uniform contour of lower eyelid; short lower transconjunctival incision, minimizing complications associated with an intra-conjunctival scar. This technique, based on cadaveric anatomical studies, has been found to be safe and is of great utility to those patients requiring upper and lower lid blepharoplasties.

Overcoming Facial Paralysis with an Implantable Actuator for Restoration of Blink.

The loss of the ability to blink the eyelid is considered the most severe effect of facial nerve paralysis. The delicate homeostasis of the eye is disrupted, and without frequent intervention, the cornea can become damaged, ultimately resulting in blindness. The psychosocial impact is also significant, with individuals withdrawing from society to hide what they perceive to be a disfigurement. Surgical and engineering interventions have been devised to reanimate blink, however, a solution has yet to be designed which addresses both functional and aesthetic concerns. Here we describe an implantable electromagnetic actuator to restore the capacity to blink. Triggered synchronously with the contralateral eye, and externally modifiable to tailor treatment post-operatively to the individual, this implant restores complete blinking and a natural appearance. Cadaver studies (N=12) have been used to validate the device design, including the form factor and force required to elicit a blink, while a passive in vivo study (N=1) has verified the surgical protocol and recovery.

Driver drowsiness estimation using EEG signals with a dynamical encoder-decoder modeling framework.

Drowsiness is a leading cause of accidents on the road as it negatively affects the driver's ability to safely operate a vehicle. Neural activity recorded by EEG electrodes is a widely used physiological correlate of driver drowsiness. This paper presents a novel dynamical modeling solution to estimate the instantaneous level of the driver drowsiness using EEG signals, where the PERcentage of eyelid CLOSure (PERCLOS) is employed as the ground truth of driver drowsiness. Applying our proposed modeling framework, we find neural features present in EEG data that encode PERCLOS. In the decoding phase, we use a Bayesian filtering solution to estimate the PERCLOS level over time. A data set that comprises 18 driving tests, conducted by 13 drivers, has been used to investigate the performance of the proposed framework. The modeling performance in estimation of PERCLOS provides robust and repeatable results in tests with manual and automated driving modes by an average RMSE of 0.117 (at a PERCLOS range of 0 to 1) and average High Probability Density percentage of 62.5%. We further hypothesized that there are biomarkers that encode the PERCLOS across different driving tests and participants. Using this solution, we identified possible biomarkers such as Theta and Delta powers. Results show that about 73% and 66% of the Theta and Delta powers which are selected as biomarkers are increasing as PERCLOS grows during the driving test. We argue that the proposed method is a robust and reliable solution to estimate drowsiness in real-time which opens the door in utilizing EEG-based measures in driver drowsiness detection systems.

The influence of luminous intensity on the eyelid aperture and measurement of the margin reflex distance.

PURPOSE: To evaluate whether the flashlight feature of smartphones can be used to replace the traditional flashlight for measuring MRD and investigate the relation between increasing light intensities and MRD measurements. METHODS: A prospective clinical study was conducted with 40 individuals from Hospital de Clínicas de Porto Alegre. Outcome measures: MRD1, MRD2, and palpebral fissure height (PFH) were analyzed by photographic record using different intensity light sources. RESULTS: Flashlight (10 lux): MRD1 mean: 3.97 mm ±1.16; PFH mean: 9.87 mm ±1.53; Smartphone (100 lux) MRD1 mean: 4.02 mm ±1.17; and PFH mean: 9.62 mm ± 1.45 (p > .05). Using a dimmable source of light resulted in a mean reduction of the PFH of 0.75 mm with the highest light intensity (1200 lux). There was no statistically significant association between MRD changes and the iris color, age, and gender of the subjects. CONCLUSIONS: There was no statistically significant difference between the MRD measurements using traditional flashlights compared to higher intensity smartphone flashlight. Using a dimmable source of light, there is a statistically significant reduction in palpebral fissure with higher light intensity, which occurs mostly by upper eyelid lowering, probably due to orbicularis oculi muscle contraction. A smartphone with a built-in flashlight can be used to replace the traditional flashlight in clinical practice without prejudice to the evaluation of the MRD.

Facial nerve paralysis: A review on the evolution of implantable prosthesis in restoring dynamic eye closure.

Facial nerve paralysis (FNP) is a debilitating condition that leaves those affected with disfigurement and loss of function. The most important function of the facial nerve is protecting the eye through eye closure and blinking. A series of reanimation techniques have been reported to restore dynamic function in FNP, but the lack of a universally accepted method that is reliable and reproducible with immediate effect has led to the introduction of several implantable devices. Most of these devices have been applied to assist blinking; however, the delicate anatomy and unique mechanics of eye closure are difficult to replicate. Lid loading is the most frequently used implant today, which is a passive device that can aid in volitional eye closure but has a limited effect on blinking. Dynamic action can be achieved with active prostheses but achieving successful long-term function remains elusive. Device action must also be coupled with a real-time feedback mechanism in order to capture the natural variation in facial muscle movements. This review discusses all prostheses used for restoring eye closure and blinking to date and explores their relative merits.

Role of the motor cortex in the generation of classically conditioned eyelid and vibrissae responses.

The eyelid motor system has been used for years as an experimental model for studying the neuronal mechanisms underlying motor and cognitive learning, mainly with classical conditioning procedures. Nonetheless, it is not known yet which brain structures, or neuronal mechanisms, are responsible for the acquisition, storage, and expression of these motor responses. Here, we studied the temporal correlation between unitary activities of identified eyelid and vibrissae motor cortex neurons and the electromyographic activity of the orbicularis oculi and vibrissae muscles and magnetically recorded eyelid positions during classical conditioning of eyelid and vibrissae responses, using both delay and trace conditioning paradigms in behaving mice. We also studied the involvement of motor cortex neurons in reflexively evoked eyelid responses and the kinematics and oscillatory properties of eyelid movements evoked by motor cortex microstimulation. Results show the involvement of the motor cortex in the performance of conditioned responses elicited during the classical conditioning task. However, a timing correlation analysis showed that both electromyographic activities preceded the firing of motor cortex neurons, which must therefore be related more with the reinforcement and/or proper performance of the conditioned responses than with their acquisition and storage.

Epiphora before and after upper eyelid functional blepharoplasty: A retrospective cohort study.

Epiphora and dermatochalasis are common presentations in the ophthalmology clinic. To evaluate the change of epiphora before and after functional blepharoplasty, this retrospective cohort study reviewed 39 medical records of epiphora patients who underwent upper blepharoplasty. Severity of epiphora using MUNK score was collected and compared between before and at 6 months after blepharoplasty. The analysis model was performed to measure tear breakup time (TBUT) and frequency of artificial tears use. Subgroups of subjects before blepharoplasty to short baseline TBUT (≤ 10 seconds) and long TBUT (≥ 10 seconds) were also evaluated for the MUNK score change. From the analysis of 39 patients, the results showed a statistically significant decrease in post blepharoplasty MUNK score compared to the baseline (all P < 0.001). There was no significant difference between baseline and post-operative TBUT (P > 0.05). Twenty patients were in the short TBUT group and 19 in the long TBUT group. The reduction of MUNK score after blepharoplasty in the short TBUT group was not different to the long TBUT group (P = 0.50, 95% CI -0.84 to 0.41). However, in short TBUT group, frequency of artificial tears use after surgery was less than pre-operation. From the study, upper eyelid blepharoplasty might be one technique reducing the bothersome epiphora in dermatochalasis patients.

Macaque monkey trigeminal blink reflex circuits targeting levator palpebrae superioris motoneurons.

For normal viewing, the eyes are held open by the tonic actions of the levator palpebrae superioris (levator) muscle raising the upper eyelid. This activity is interrupted during blinks, when the eyelid sweeps down to spread the tear film or protect the cornea. We examined the circuit connecting the principal trigeminal nucleus to the levator motoneurons by use of both anterograde and retrograde tracers in macaque monkeys. Injections of anterograde tracer were made into the principal trigeminal nucleus using either a stereotaxic approach or localization following physiological characterization of trigeminal second order neurons. Anterogradely labeled axonal arbors were located both within the caudal central subdivision, which contains levator motoneurons, and in the adjacent supraoculomotor area. Labeled boutons made synaptic contacts on retrogradely labeled levator motoneurons indicating a monosynaptic connection. As the eye is also retracted through the actions of the rectus muscles during a blink, we examined whether these trigeminal injections labeled boutons contacting rectus motoneurons within the oculomotor nucleus. These were not found when the injection sites were confined to the principal trigeminal nucleus region. To identify the source of the projection to the levator motoneurons, we injected retrograde tracer into the oculomotor complex. Retrogradely labeled cells were confined to a narrow, dorsoventrally oriented cell population that lined the rostral edge of the principal trigeminal nucleus. Presumably these cells inhibit levator motoneurons, while other parts of the trigeminal sensory complex are activating orbicularis oculi motoneurons, when a blink is initiated by sensory stimuli contacting the face.

Implanted Microsensor Continuous IOP Telemetry Suggests Gaze and Eyelid Closure Effects on IOP-A Preliminary Study.

Purpose: To explore the effect of gaze direction and eyelid closure on intraocular pressure (IOP). Methods: Eleven patients with primary open-angle glaucoma previously implanted with a telemetric IOP sensor were instructed to view eight equally-spaced fixation targets each at three eccentricities (10°, 20°, and 25°). Nine patients also performed eyelid closure. IOP was recorded via an external antenna placed around the study eye. Differences of mean IOP between consecutive gaze positions were calculated. Furthermore, the effect of eyelid closure on gaze-dependent IOP was assessed. Results: The maximum IOP increase was observed at 25° superior gaze (mean ± SD: 4.4 ± 4.9 mm Hg) and maximum decrease at 25° inferonasal gaze (-1.6 ± 0.8 mm Hg). There was a significant interaction between gaze direction and eccentricity (P = 0.003). Post-hoc tests confirmed significant decreases inferonasally for all eccentricities (mean ± SEM: 10°: -0.7 ± 0.2, P = 0.007; 20°: -1.1 ± 0.2, P = 0.006; and 25°: -1.6 ± 0.2, P = 0.006). Eight of 11 eyes showed significant IOP differences between superior and inferonasal gaze at 25°. IOP decreased during eyelid closure, which was significantly lower than downgaze at 25° (mean ± SEM: -2.1 ± 0.3 mm Hg vs. -0.7 ± 0.2 mm Hg, P = 0.014). Conclusions: Our data suggest that IOP varies reproducibly with gaze direction, albeit with patient variability. IOP generally increased in upgaze but decreased in inferonasal gaze and on eyelid closure. Future studies should investigate the patient variability and IOP dynamics.

Lateral Canthal Sling Procedure for Meibomian Gland Dysfunction? Results of a Pilot Study.

Background: Involutional changes of lid structures often induce horizontal lid laxity; this can result in a reduction of Meibomian gland expression, potentially leading to symptoms of dry eye. The aim of this study was to evaluate the effect of tightening the lower eyelid via a lateral canthal sling (LCS) procedure on dry eye parameters.Methods: Patients with Meibomian Gland Dysfunction (MGD), lower lid laxity (positive Snap-back Test and positive Pinch Test) and no previous lid surgery were evaluated before and 3 months after LCS procedure for symptoms by OSDI. The fellow eye without surgery functioned as a control group. MGD parameters included lipid layer thickness (LLT), non-invasive breakup time (NIBUT), tear meniscus height, loss of Meibomian glands, lid margin parallel conjunctival folds (LIPCOFs), Schirmer's test, the number of expressible Meibomian glands as well as quality of Meibum.Results: Fourteen patients (8 men and 6 women; 79.2 ± 4.0 years) were enrolled in this prospective clinical study. After 3 months, the OSDI showed a significant reduction (preop 42.9 ± 24.7; postop 23.8 ± 21.6; p = .002); NIBUT (5.5 ± 2.6 s to 9.9 ± 6.8 s p = .08) and LLT (64.3 ± 30.4 to 74.1 ± 27.8; p = .025) improved, while Schirmer Test (15.3 ± 4.7 mm to 11.9 ± 2.9 mm; p = .03) and tear meniscus height were reduced (0.8 ± 0.3 to 0.6 ± 0.2; p = .05). Meibomian gland loss scored by the meiboscale slightly increased postoperatively (1.2 ± 0.9 to 1.4 ± 0.9; p = .18). The number of expressible Meibomian glands improved (4.4 ± 2.6 to 6.8 ± 2.1, p = .002) as well as the quality of Meibum (0.9 ± 1.0 to 0.5 ± 0.8, p = .04). Snap back test as well the pinch test were negative in all patients postoperatively.Conclusion: Addressing lower lid laxity with an LCS procedure simultaneously enhances tear drainage, reduces tear film volume parameters and increases tear film stability results with an improvement of dry eye symptoms. It is likely that increased lower eyelid tension and thus excretory pressure on the Meibomian glands is responsible for these alterations.

Thermal Imaging of the Ocular Surface in Thyroid Eye Disease: A Comparison between Active, Inactive and Healthy Eyes.

Aim: To report the temperature differences on the ocular surface using infrared thermal imaging (TI) in thyroid eye disease (TED) and healthy eyesMethods: Prospective, consecutive, comparative case series comparing TI parameters between active and inactive TED with healthy controls. The data captured included baseline demography, activity of TED and the TI parameters. Area under the receiver operating characteristic curves (AUROC) were calculated for the temperature values to determine the sensitivity and specificity in distinguishing active from inactive TED. The Youden index and the predictor cut off values were also reported.Results: The study included 11 eyes with active TED, 46 eyes with inactive TED and 40 eyes healthy patients. Temperatures of pre-determined points on the ocular surface in degrees were compared between the three groups. Temperature at the caruncle, medial and lateral conjunctiva was noted to be significantly higher in the active TED group compared to inactive TED and healthy eyes. The most favorable Youden index (0.7) was noted for the caruncle with an AUROC value of 0.91, a sensitivity of 91% and a specificity of 79%. Correlation coefficient for the caruncular temperature with the corresponding CAS (clinical activity score) was 0.65 (95% C.I. 0.45 to 0.78, p < .0001).Conclusion: Thermal imaging in TED is an objective way of documenting surface inflammation by the surrogate marker of temperature change. It supplements CAS in clinically evident cases and could be useful in staging eyes with subtle clinical signs as well as those where signs have reduced following initiation of treatment.

When reflex reactions oppose voluntary commands: The StartReact effect on eye opening.

A startling auditory stimulus (SAS) induces a reflex response involving, among other reactions, a strong contraction of the orbicularis oculi muscle (OOc) and subsequent eye closure. A SAS also induces the StartReact effect, a significant shortening of reaction time in subjects ready for task execution. We examined the obvious conflict appearing when a StartReact paradigm requires participants with eyes closed to open their eyes to look for a visual target. We recorded OOc EMG activity and eyelid movements in healthy volunteers who were instructed to open their eyes at perception of a somatosensory imperative stimulus (IS) and locate the position of a Libet's clock's hand shown on a computer screen at 80 cm distance. In 6 out of 20 trials, we delivered a SAS simultaneously with the IS. The main outcome measures were reaction time at onset of eyelid movement and the time gap (TG) separating subjective assessment of the clock's hand position from real IS issuing. Control experiments included reaction time to eye closing and target location with eyes open to the same IS. Reaction time was significantly faster in SAS than in noSAS trials and slower for eye opening than for eye closing in both conditions. In the eye-opening task, TG was significantly shorter in SAS with respect to noSAS trials, despite the presence of the SAS-related burst in the OOc before EMG cessation. Our results indicate that the StartReact effect speeds up eye opening and location of a target in the visual field despite the startle reaction opposing the task.

The Claustrum is Involved in Cognitive Processes Related to the Classical Conditioning of Eyelid Responses in Behaving Rabbits.

It is assumed that the claustrum (CL) is involved in sensorimotor integration and cognitive processes. We recorded the firing activity of identified CL neurons during classical eyeblink conditioning in rabbits, using a delay paradigm in which a tone was presented as conditioned stimulus (CS), followed by a corneal air puff as unconditioned stimulus (US). Neurons were identified by their activation from motor (MC), cingulate (CC), and medial prefrontal (mPFC) cortices. CL neurons were rarely activated by single stimuli of any modality. In contrast, their firing was significantly modulated during the first sessions of paired CS/US presentations, but not in well-trained animals. Neuron firing rates did not correlate with the kinematics of conditioned responses (CRs). CL local field potentials (LFPs) changed their spectral power across learning and presented well-differentiated CL-mPFC/CL-MC network dynamics, as shown by crossfrequency spectral measurements. CL electrical stimulation did not evoke eyelid responses, even in trained animals. Silencing of synaptic transmission of CL neurons by the vINSIST method delayed the acquisition of CRs but did not affect their presentation rate. The CL plays an important role in the acquisition of associative learning, mostly in relation to the novelty of CS/US association, but not in the expression of CRs.

New insight into the physiologic function of Müller's muscle.

PURPOSE: Müller's muscle is a sympathetically innervated smooth muscle which serves as an accessory upper eyelid retractor. Its physiologic function and purpose have not yet been clearly defined. We hypothesize that sympathetic innervation to Müller's muscle serves to adjust the upper eyelid's position to variations in pupil size in response to changes in light intensity. METHODS: This is a single center cross-sectional study. Healthy volunteers were asked to fixate on a distant non-accommodative target, and a video scan of the anterior segment was performed for each subject's right eye using the Heidelberg Spectralis® optical coherence tomography scanner in infrared mode. The video was taken both in photopic and scotopic conditions, recording the resultant transition of the pupil and eyelids. The pupil diameter (PD), upper eyelid margin-to-reflex distance (MRD1), lower eyelid margin-to-reflex distance (MRD2), and vertical palpebral fissure height (PFH) were measured. RESULTS: Thirty-three healthy volunteers (19 women, 57.6%) with a median age of 40 years (range 30-58) were included. The mean PD under photopic conditions increased significantly under scotopic conditions, from 3483 ± 521 µm to 6135 ± 703 µm, respectively (P < 0.0001). An increase in MRD1 was observed following transition from light to dark, with a mean change of 348 ± 311 µm (P < 0.0001). There was no significant change in MRD2. CONCLUSIONS: Upper eyelid retraction occurs after transition from photopic to scotopic conditions. This movement suggests the existence of an "eyelid-light reflex" involving Müller's muscle that adjusts the position of the eyelids as the pupil dilates under scotopic conditions.