Asymmetry of Blinking

PURPOSE. Too investigate asymmetry in eyelid movements with blinking, the stability of the asymmetry, and its modifiability in normal humans. METHODS. Differences in the start time and amplitude between the two eyelids were assessed for voluntary blinks and reflex blinks evoked by supraorbital trigeminal nerve stimulation. These variables were also measured before and up to 18 months after 2 hours of unilateral upper lid restraint. RESULTS. With voluntary blinks, one eyelid consistently began to close earlier and made a larger eyelid movement than the other eyelid. Stimulation of the supraorbital branch of the trigeminal nerve evoked relatively larger amplitude blinks in one eyelid that correlated with the asymmetries of voluntary blinks. There was a continuum of eyelid asymmetry across all subjects that was stable and independent of other biological asymmetries, such as handedness. Briefly reducing eyelid mobility created a long-lasting change in eyelid asymmetry with blinking. CONCLUSIONS. Eyelid asymmetry results from differences in the excitability of motoneurons in the left and right facial motor nuclei and does not appear to involve asymmetries in cortical inputs to the brain stem. Because adaptive processes modify the motoneuron excitability that creates eyelid asymmetry, these processes may underlie changes in blinking associated with facial palsy and may play a role in the development of disorders that affect one side of the face, such as hemifacial spasm. (Invest Ophthalmol Vis Sci. 2006;47:195-201) DOI: 10.1167/iovs.04-1279 H umans exhibit several motor, sensory, and functional asymmetries in which one side of the body is dominant or more responsive than the other. The most evident motor asymmetry is handedness, with people typically being either right or left handed. In addition to this well-known asymmetry, human facial expressions of happiness and sadness produce larger movements of the left than the right side of the face. 1,2 The accepted explanation of this facial motor asymmetry is specialization of the right cerebral hemisphere for emotional expression. Clinical studies suggest that differences in excitability between motoneurons in the left and right facial motor nuclei may create asymmetries for reflex blinking. Facial palsy patients exhibit increased motoneuron excitability in the facial nucleus on the affected relative to the unaffected side of the face. 4 -6 One explanation for this increased excitability in Bell's palsy is changes in the motoneuron membrane properties caused by axotomy. It is also possible that the increased excitability involves an adaptive increase in excitatory presynaptic drive to facial motoneurons, 7 to compensate for muscle weakness. Consistent with this explanation, mimicking facial palsy with unilateral eyelid restraint in normal humans appears to increase motoneuron excitability in the restrained eyelid in the absence of axotomy. 8 Our study determined whether eyelid asymmetry exists in normal individuals and investigated whether eyelid asymmetries result from cortical or brain stem mechanisms. Assessing the timing and amplitude of left and right eyelid movement with cortically controlled voluntary blinks and brain stemgenerated trigeminal reflex blinks demonstrates the presence of functional eyelid asymmetry. Comparison of the eyelid asymmetry present in voluntary and reflex blinks showed that a difference in motoneuron excitability is the primary source of eyelid asymmetry in both voluntary and reflex blinks. We also showed that eyelid asymmetry is a modifiable property of the eyelid motor system. METHODS Subjects All experiments adhered to the tenets of the Declaration of Helsinki. Informed consent from the participants and prior institutional review board approval were obtained. The 18 subjects, 10 men and 8 women, ranging from 22 to 59 (mean, 29 Ϯ 10) years of age, did not have any history of medications or neurologic, eye, or eyelid disorders that would affect blinking. Procedures Upper eyelid position was monitored bilaterally with the magnetic search coil technique using a 30-turn, 2-mm diameter coil attached to the middle of the upper eyelid as close as possible to its margin. 9 Unilateral electrical stimulation of the supraorbital branch of the trigeminal nerve (SO) evoked bilateral trigeminal reflex blinks. To elicit these reflex blinks, a pair of 9-mm diameter gold-plated electrodes (Grass-Telefactor, West Warwick, RI) was placed over both the left and right SO. One electrode of the pair was placed directly over the supraorbital notch and the second approximately 2.5 cm above the first. The SO stimulus was a 170-s constant current delivered at twice the threshold current (2T) necessary to evoke a blink consistently when stimuli occurred with at least a 20-second interstimulus interval. Across all subjects, 2T current intensity ranged from 2.8 to 8 mA. In four of the eighteen subjects, the effect of changing SO stimulus intensity on eyelid asymmetry was also tested. For these subjects, the perception threshold (PT), the lowest SO stimulus intensity at which the subject consistently reported perceiving SO stimulation, was determined. The subjects then received SO stimuli ranging from twice to six times perception threshold (2PT-6PT). Four times perception threshold is roughly equivalent to the twice blink threshold stimulus intensity used for all the other subjects

A Case Report of Ablepharon-Macrostomia Syndrome with Amniotic Membrane Grafting

We describe a rare case of an infant who was born with multiple congenital anomalies, including the absence of eyelids. This patient had many dysmorphic features consistent with a severe phenotype of ablepharon-macrostomia syndrome (AMS) including a fish-like appearance of the mouth, rudimentary ears, absence of body hair, thin skin, absent nipples, abdominal distension, and genital abnormalities. Upon presentation, there was severe exposure keratopathy causing large bilateral sterile ulcers culminating in corneal melting of both eyes. An amniotic membrane graft was used to attempt to maintain the corneal surface integrity. However, because of the late presentation, the corneas could not be salvaged. Extensive surgical reconstruction of both eyelids and bilateral penetrating keratoplasty was ultimately performed successfully to protect the ocular surfaces while trying to maximize the visual potential. Early amniotic membrane grafting may be done at the bedside and may help preserve the ocular in patients with severe eyelid deformities until more definitive treatment is performed

Exotropia in children with high hyperopia

PURPOSE: To describe the clinical characteristics, treatment, and subsequent clinical course of children with exotropia and high hyperopia. METHODS: The medical records of 26 patients seen between 1990 and 2009 who had an exotropia and ≥4.00 D of hyperopia were retrospectively reviewed. We analyzed the clinical characteristics, treatments and subsequent alignment outcomes. RESULTS: A total of 26 patients between the ages of 2.5 months and 9 years were included. Of these, 15 had associated medical conditions or developmental delay. Of 22 patients with measured visual acuities, 19 had amblyopia (10 unilateral, 9 bilateral). None of the patients demonstrated fine stereoacuity. Twenty-three exotropic children were treated with spectacles; 15 were fully corrected, 10 of whose exotropia improved; 8 received partial correction of their hyperopia, 3 of whose exotropia improved. Six patients who presented with large, poorly controlled exotropia and did not improve with spectacle correction required strabismus surgery. CONCLUSIONS: Children with high hyperopia and exotropia are likely to have developmental delay or other systemic diseases, amblyopia, and poor stereopsis. Treatment of high hyperopia in exotropic children with their full cycloplegic refraction can result in excellent alignment

Association between myopia progression and quantity of laser treatment for retinopathy of prematurity.

BackgroundPrevious studies found that infants with retinopathy of prematurity (ROP) who were treated for more posterior disease with a greater number of laser spots developed higher myopia. These studies included multiple physicians with variations in laser density. In treatments by a single physician, laser spot count is a better surrogate for area of avascular retina and anterior-posterior location of disease, so that the relationship with myopia can be better assessed.MethodsOur retrospective study included infants treated with laser for ROP by a single surgeon at a single center. Exclusion criteria were irregularities during laser and additional treatment for ROP. We assessed correlation between laser spot count and change in refractive error over time using a linear mixed effects model.ResultsWe studied 153 eyes from 78 subjects treated with laser for ROP. The average gestational age at birth was 25.3±1.8 weeks, birth weight 737±248 grams, laser spot count 1793±728, and post-treatment follow up 37±29 months. Between corrected ages 0-1 years, the mean spherical equivalent was +0.4±2.3 diopters; between ages 1-2, it was -1.3±3.2D; and ages 2-3 was -0.8±3.1D. Eyes that received more laser spots had significantly greater change in refractive error over time (0.30D more myopia per year per 1000 spots). None of the eyes with hyperopia before 18 months developed myopia during the follow-up period.ConclusionsGreater myopia developed over time in infants with ROP treated by laser to a larger area of avascular retina

Decorin Concentrations in Aqueous Humor of Patients with Diabetic Retinopathy

Diabetic retinopathy (DR) is a microvascular complication of diabetes in the retina. Chronic hyperglycemia damages retinal microvasculature embedded into the extracellular matrix (ECM), causing fluid leakage and ischemic retinal neovascularization. Current treatment strategies include intravitreal anti-vascular endothelial growth factor (VEGF) or steroidal injections, laser photocoagulation, or vitrectomy in severe cases. However, treatment may require multiple modalities or repeat treatments due to variable response. Though DR management has achieved great success, improved, long-lasting, and predictable treatments are needed, including new biomarkers and therapeutic approaches. Small-leucine rich proteoglycans, such as decorin, constitute an integral component of retinal endothelial ECM. Therefore, any damage to microvasculature can trigger its antifibrotic and antiangiogenic response against retinal vascular pathologies, including DR. We conducted a cross-sectional study to examine the association between aqueous humor (AH) decorin levels, if any, and severity of DR. A total of 82 subjects (26 control, 56 DR) were recruited. AH was collected and decorin concentrations were measured using an enzyme-linked immunosorbent assay (ELISA). Decorin was significantly increased in the AH of DR subjects compared to controls (p = 0.0034). AH decorin levels were increased in severe DR groups in ETDRS and Gloucestershire classifications. Decorin concentrations also displayed a significant association with visual acuity (LogMAR) measurements. In conclusion, aqueous humor decorin concentrations were found elevated in DR subjects, possibly due to a compensatory response to the retinal microvascular changes during hyperglycemia

Second asymptomatic carotid surgery trial (ACST-2) : a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86-1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91-1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable