Human TUBB3 mutations perturb microtubule dynamics, kinesin interactions, and axon guidance.

We report that eight heterozygous missense mutations in TUBB3, encoding the neuron-specific beta-tubulin isotype III, result in a spectrum of human nervous system disorders that we now call the TUBB3 syndromes. Each mutation causes the ocular motility disorder CFEOM3, whereas some also result in intellectual and behavioral impairments, facial paralysis, and/or later-onset axonal sensorimotor polyneuropathy. Neuroimaging reveals a spectrum of abnormalities including hypoplasia of oculomotor nerves and dysgenesis of the corpus callosum, anterior commissure, and corticospinal tracts. A knock-in disease mouse model reveals axon guidance defects without evidence of cortical cell migration abnormalities. We show that the disease-associated mutations can impair tubulin heterodimer formation in vitro, although folded mutant heterodimers can still polymerize into microtubules. Modeling each mutation in yeast tubulin demonstrates that all alter dynamic instability whereas a subset disrupts the interaction of microtubules with kinesin motors. These findings demonstrate that normal TUBB3 is required for axon guidance and maintenance in mammals.

In vivo quasi-elastic light scattering detects molecular changes in the lenses of adolescents with Down syndrome.

Down syndrome (DS) is the most common chromosomal disorder in humans. DS is associated with increased prevalence of several ocular sequelae, including characteristic blue-dot cerulean cataract. DS is accompanied by age-dependent accumulation of Alzheimer's disease (AD) amyloid-ß (Aß) peptides and amyloid pathology in the brain and comorbid early-onset Aß amyloidopathy and colocalizing cataracts in the lens. Quasi-elastic light scattering (QLS) is an established optical technique that noninvasively measures changes in protein size distributions in the human lens in vivo. In this cross-sectional study, lenticular QLS correlation time was decreased in adolescent subjects with DS compared to age-matched control subjects. Clinical QLS was consistent with alterations in relative particle hydrodynamic radius in lenses of adolescents with DS. These correlative results suggest that noninvasive QLS can be used to evaluate molecular changes in the lenses of individuals with DS.

The Incidence of Strabismus After Upper and Lower Blepharoplasty in the United States.

PURPOSE: To compare the incidence of strabismus after upper and lower blepharoplasty in the United States. METHODS: Retrospective cohort study of adults (age ≥18 years) in the IRIS Registry (Intelligent Research in Sight) who underwent blepharoplasty between January 1, 2013 and December 31, 2020. The primary outcome was the Kaplan-Meier estimated cumulative incidence of strabismus diagnosis and surgery within 3 years of blepharoplasty. Multivariable Cox regression was used to determine the association of blepharoplasty type with strabismus diagnosis and surgery, adjusting for patient age, sex, and geographic region. RESULTS: Blepharoplasty was performed in 368,623 patients (median [interquartile range] age, 69 [63-75] years, and 69% female). Compared with those undergoing upper eyelid blepharoplasty, patients treated with lower eyelid blepharoplasty were slightly younger (median age, 66 vs. 69 years; p < 0.001) and more likely to be female (71% vs. 69%; p < 0.001). There was a greater 3-year incidence of strabismus diagnosis (2.0% vs. 1.5%; p < 0.001) and a greater 3-year incidence of strabismus surgery (0.15% vs. 0.06%; p = 0.003) for individuals undergoing lower vs. upper blepharoplasty. After adjusting for age, sex, and geographic region, lower blepharoplasty was associated with a higher 3-year risk of strabismus diagnosis (HR, 1.49; 95% CI, 1.23-1.81; p < 0.001) and surgery (HR, 2.53; 95% CI, 1.27-5.03; p = 0.008). CONCLUSIONS: This registry-based analysis found that individuals undergoing lower eyelid blepharoplasty were at higher risk of strabismus compared with those undergoing upper eyelid blepharoplasty. Using large databases to understand the incidence of complications of frequently performed procedures may improve ophthalmologists' ability to provide data-driven counseling on surgical risks prior to intervention.

Detection of visuomotor dysfunction in mild traumatic brain injury using binocular retinal polarization scanning.

OBJECTIVE: The head and intraocular trauma tool (HITT) is a portable, binocular retinal polarization scanner (RPS) that detects ocular fixation with high precision to assess visuomotor function. We conducted a pilot evaluation of a prototype binocular RPS device to evaluate alterations in fixation stability, binocularity (convergence), and saccadic latency after mild traumatic brain injury (mTBI). METHODS: Two groups were studied prospectively: (1) single observation study of mTBI patients in a hospital ER (n = 7) and age-matched controls (n = 43); (2) high-school athletes preseason (n = 28), after sports-related mTBI (n = 3), and at season end (n = 5). Subjects were asked to fixate on an internal target and track randomly presented peripheral and central targets as fixation was assessed using binocular RPS. RESULTS: There were clinically and statistically significant alterations in the hospital ER group after mTBI, including a decrease in fixation stability (54.6% in patents vs 90.2% in controls, p = 0.014) and binocularity (28.7% in patients vs 86.6% in controls; p = 0.004). Similar trends, not statistically significant, were observed in saccadic latency in the hospital ER group as well as in the injured high school athletes. CONCLUSION: The HITT device shows promise as an objective, noninvasive method for assessment of the impact of mTBI on visuomotor function. Additional studies with larger patient populations are required to evaluate efficacy for clinical use.

Recessive variants in COL25A1 gene as novel cause of arthrogryposis multiplex congenita with ocular congenital cranial dysinnervation disorder.

A proper interaction between muscle-derived collagen XXV and its motor neuron-derived receptors protein tyrosine phosphatases σ and δ (PTP σ/δ) is indispensable for intramuscular motor innervation. Despite this, thus far, pathogenic recessive variants in the COL25A1 gene had only been detected in a few patients with isolated ocular congenital cranial dysinnervation disorders. Here we describe five patients from three unrelated families with recessive missense and splice site COL25A1 variants presenting with a recognizable phenotype characterized by arthrogryposis multiplex congenita with or without an ocular congenital cranial dysinnervation disorder phenotype. The clinical features of the older patients remained stable over time, without central nervous system involvement. This study extends the phenotypic and genotypic spectrum of COL25A1 related conditions, and further adds to our knowledge of the complex process of intramuscular motor innervation. Our observations indicate a role for collagen XXV in regulating the appropriate innervation not only of extraocular muscles, but also of bulbar, axial, and limb muscles in the human.

Adjustable Suture Technique Is Associated with Fewer Strabismus Reoperations in the Intelligent Research in Sight Registry.

PURPOSE: To compare the reoperation rates after strabismus surgery with and without the adjustable suture technique. DESIGN: Retrospective cohort study. PARTICIPANTS: Patients 18 years of age or older in the Intelligent Research in Sight (IRIS®) Registry who underwent strabismus surgery between January 1, 2013, and December 31, 2018. METHODS: Data were collected from the electronic health records of practices participating in the IRIS Registry. The primary exposure of interest was use of the adjustable suture technique, identified by Current Procedural Terminology coding. MAIN OUTCOME MEASURES: The primary outcome was repeat strabismus surgery within 1 year of initial strabismus surgery. Odds ratios (ORs) were derived from a multivariable logistic regression model evaluating the association between the use of adjustable sutures and reoperation rate, adjusting for patient demographics and surgical factors. RESULTS: A total of 34 872 patients who underwent strabismus surgery during the study interval were identified: 72% underwent horizontal muscle surgery, 17% underwent vertical muscle surgery, and 11% underwent combined horizontal and vertical muscle surgery. Adjustable sutures were used in 18% of patients. The overall reoperation rate within 1 year of strabismus surgery was 7.7%. The 1-year reoperation rate was 6.0% for patients treated with adjustable sutures and 8.1% for patients treated without adjustable sutures (P < 0.001). The multivariable regression model revealed a statistically significant 30% decrease in the odds of reoperation within 1 year of surgery when adjustable sutures were used (OR, 0.70; 95% confidence interval [CI], 0.62-0.78), a 40% increase in those with a history of prior strabismus surgery (OR, 1.40; 95% CI, 1.28-1.53), and a 9% increase per decade of age at surgery (OR, 1.09; 95% CI, 1.06-1.11). CONCLUSIONS: In adults cared for in practices participating in the IRIS Registry, the adjustable suture technique was associated with a significantly lower reoperation rate within 1 year of undergoing horizontal or combined horizontal and vertical strabismus surgery. Adjustable suture use in vertical strabismus surgery alone did not reduce the 1-year reoperation rate significantly. A history of prior strabismus surgery was associated with increased odds of reoperation.

Randomized Controlled Trial of a Dichoptic Digital Therapeutic for Amblyopia.

PURPOSE: Digital therapeutics are a new class of interventions that are software driven and are intended to treat various conditions. We developed and evaluated a dichoptic digital therapeutic for amblyopia, a neurodevelopmental disorder for which current treatments may be limited by poor adherence and residual vision deficits. DESIGN: Randomized controlled trial. PARTICIPANTS: One hundred five children 4 to 7 years of age with amblyopia were enrolled at 21 academic and community sites in the United States. Participants were randomized 1:1 to the treatment or comparison group, stratified by site. METHODS: We conducted a phase 3 randomized controlled trial to evaluate the safety and efficacy of a dichoptic digital therapeutic for amblyopia. Participants in the treatment group used the therapeutic at home for 1 hour per day, 6 days per week and wore glasses full-time. Participants in the comparison group continued wearing glasses full-time alone. MAIN OUTCOME MEASURES: The primary efficacy outcome was change in amblyopic eye visual acuity (VA) from baseline at 12 weeks, and VA was measured by masked examiners. Safety was evaluated using the frequency and severity of study-related adverse events. Primary analyses were conducted using the intention-to-treat population. RESULTS: Between January 16, 2019, and January 15, 2020, 105 participants were enrolled; 51 were randomized to the treatment group and 54 were randomized to the comparison group. At 12 weeks, amblyopic eye VA improved by 1.8 lines (95% confidence interval [CI], 1.4-2.3 lines; n = 45) in the treatment group and by 0.8 lines (95% CI, 0.4-1.3 lines; n = 45) in the comparison group. At the planned interim analysis (adjusted α = 0.0193), the difference between groups was significant (1.0 lines; P = 0.0011; 96.14% CI, 0.33-1.63 lines) and the study was stopped early for success, according to the protocol. No serious adverse events were reported. CONCLUSIONS: Our findings support the value of the therapeutic in clinical practice as an effective treatment. Future studies should evaluate the therapeutic compared with other methods and in additional patient populations.

TUBB3 Arg262His causes a recognizable syndrome including CFEOM3, facial palsy, joint contractures, and early-onset peripheral neuropathy.

Microtubules are formed from heterodimers of alpha- and beta-tubulin, each of which has multiple isoforms encoded by separate genes. Pathogenic missense variants in multiple different tubulin isoforms cause brain malformations. Missense mutations in TUBB3, which encodes the neuron-specific beta-tubulin isotype, can cause congenital fibrosis of the extraocular muscles type 3 (CFEOM3) and/or malformations of cortical development, with distinct genotype-phenotype correlations. Here, we report fourteen individuals from thirteen unrelated families, each of whom harbors the identical NM_006086.4 (TUBB3):c.785G>A (p.Arg262His) variant resulting in a phenotype we refer to as the TUBB3 R262H syndrome. The affected individuals present at birth with ptosis, ophthalmoplegia, exotropia, facial weakness, facial dysmorphisms, and, in most cases, distal congenital joint contractures, and subsequently develop intellectual disabilities, gait disorders with proximal joint contractures, Kallmann syndrome (hypogonadotropic hypogonadism and anosmia), and a progressive peripheral neuropathy during the first decade of life. Subsets may also have vocal cord paralysis, auditory dysfunction, cyclic vomiting, and/or tachycardia at rest. All fourteen subjects share a recognizable set of brain malformations, including hypoplasia of the corpus callosum and anterior commissure, basal ganglia malformations, absent olfactory bulbs and sulci, and subtle cerebellar malformations. While similar, individuals with the TUBB3 R262H syndrome can be distinguished from individuals with the TUBB3 E410K syndrome by the presence of congenital and acquired joint contractures, an earlier onset peripheral neuropathy, impaired gait, and basal ganglia malformations.

Use of Botulinum Toxin in Ophthalmology.

Botulinum toxin is an important treatment for many conditions in ophthalmology, including strabismus, nystagmus, blepharospasm, hemifacial spasm, spastic and congenital entropion, corneal exposure, and persistent epithelial defects. The mechanism of action of botulinum toxin for both strabismus and nystagmus is the neuromuscular blockade and transient paralysis of extraocular muscles, but when botulinum toxin is used for some forms of strabismus, a single injection can convey indefinite benefits. There are two unique mechanisms of action that account for the long-term effect on ocular alignment: (1) the disruption of a balanced system of agonist-antagonist extraocular muscles and (2) the reestablishment of central control of alignment by the binocular visual system. For other ocular conditions, botulinum toxin acts through transient paralysis of periocular muscles. Botulinum toxin is a powerful tool in ophthalmology, achieving its therapeutic effects by direct neuromuscular blockade of extraocular and periocular muscles and by unique mechanisms related to the underlying structure and function of the visual system.

Virtual Visits in Ophthalmology: Timely Advice for Implementation During the COVID-19 Public Health Crisis.

Virtual visits (VVs) are necessitated due to the public health crisis and social distancing mandates due to COVID-19. However, these have been rare in ophthalmology. Over 3.5 years of conducting >350 ophthalmological VVs, our group has gained numerous insights into best practices. This communication shares these experiences with the medical community to support patient care during this difficult time and beyond. We highlight that mastering the technological platform of choice, optimizing lighting, camera positioning, and "eye contact," being thoughtful and creative with the virtual eye examination, and ensuring good documenting and billing will make a successful and efficient VV. Moreover, we think these ideas will stimulate further VV creativity and expertise to be developed in ophthalmology and across medicine. This approach, holds promise for increasing its adoption after the crisis has passed.

Loss of MAFB Function in Humans and Mice Causes Duane Syndrome, Aberrant Extraocular Muscle Innervation, and Inner-Ear Defects.

Duane retraction syndrome (DRS) is a congenital eye-movement disorder defined by limited outward gaze and retraction of the eye on attempted inward gaze. Here, we report on three heterozygous loss-of-function MAFB mutations causing DRS and a dominant-negative MAFB mutation causing DRS and deafness. Using genotype-phenotype correlations in humans and Mafb-knockout mice, we propose a threshold model for variable loss of MAFB function. Postmortem studies of DRS have reported abducens nerve hypoplasia and aberrant innervation of the lateral rectus muscle by the oculomotor nerve. Our studies in mice now confirm this human DRS pathology. Moreover, we demonstrate that selectively disrupting abducens nerve development is sufficient to cause secondary innervation of the lateral rectus muscle by aberrant oculomotor nerve branches, which form at developmental decision regions close to target extraocular muscles. Thus, we present evidence that the primary cause of DRS is failure of the abducens nerve to fully innervate the lateral rectus muscle in early development.

Bifocals Fail to Improve Stereopsis Outcomes in High AC/A Accommodative Esotropia.

PURPOSE: To assess whether stereopsis outcomes of patients with accommodative esotropia with high accommodative convergence/accommodation relationship (AC/A) were improved after treatment with bifocal glasses compared with single-vision lenses. DESIGN: Retrospective cohort study. PARTICIPANTS: Patients with high AC/A accommodative esotropia; evidence of stereopsis, binocularity (on Worth 4-dot testing), or improvement in near angle with +3.00 D lenses; and at least 4 years of records available for review, who were seen in the Department of Ophthalmology at Boston Children's Hospital between 2006 and 2014. METHODS: Use of bifocal or single-vision glasses. Charts were reviewed retrospectively. Stereopsis was log transformed for statistical analysis. Linear (for stereopsis) or logistic (for surgery) regression was used to control for confounders. MAIN OUTCOME MEASURES: Stereopsis at final follow-up, difference in stereopsis between final and initial visits, and progression to strabismus surgery. Secondary outcomes included final near and distance deviations. RESULTS: Of the 180 patients who met inclusion criteria, 77 used bifocals and 103 used single-vision lenses. Bifocals did not improve stereopsis outcomes compared with single-vision lenses. In both groups, stereopsis was similar at the initial and final visits, with similar improvement in both groups. Children in the bifocal group had a 3.6-fold higher rate of strabismus surgery than children in the single-lens group (P = 0.04.) Additionally, children in the bifocal group had near deviations 4 PD larger than those with single lenses at final follow-up, even after controlling for age and initial deviation (P = 0.02). These results did not change if surgical patients were eliminated or in the subgroup with initial distance deviation of 0 PD in full hyperopic correction. CONCLUSIONS: Despite their widespread use, there is no evidence that bifocals improve outcomes in children with accommodative esotropia with high AC/A. In our retrospective review, children with bifocals had higher surgical rates and a smaller improvement in near deviation over time. Although our results suggest that eliminating bifocals could reduce the cost and complexity of care while potentially improving quality, prospective, randomized controlled trials are needed to determine whether a change in practice is warranted.

Two unique TUBB3 mutations cause both CFEOM3 and malformations of cortical development.

One set of missense mutations in the neuron specific beta tubulin isotype 3 (TUBB3) has been reported to cause malformations of cortical development (MCD), while a second set has been reported to cause isolated or syndromic Congenital Fibrosis of the Extraocular Muscles type 3 (CFEOM3). Because TUBB3 mutations reported to cause CFEOM had not been associated with cortical malformations, while mutations reported to cause MCD had not been associated with CFEOM or other forms of paralytic strabismus, it was hypothesized that each set of mutations might alter microtubule function differently. Here, however, we report two novel de novo heterozygous TUBB3 amino acid substitutions, G71R and G98S, in four patients with both MCD and syndromic CFEOM3. These patients present with moderately severe CFEOM3, nystagmus, torticollis, and developmental delay, and have intellectual and social disabilities. Neuroimaging reveals defective cortical gyration, as well as hypoplasia or agenesis of the corpus callosum and anterior commissure, malformations of hippocampi, thalami, basal ganglia and cerebella, and brainstem and cranial nerve hypoplasia. These new TUBB3 substitutions meld the two previously distinct TUBB3-associated phenotypes, and implicate similar microtubule dysfunction underlying both.

HOXB1 founder mutation in humans recapitulates the phenotype of Hoxb1-/- mice.

Members of the highly conserved homeobox (HOX) gene family encode transcription factors that confer cellular and tissue identities along the antero-posterior axis of mice and humans. We have identified a founder homozygous missense mutation in HOXB1 in two families from a conservative German American population. The resulting phenotype includes bilateral facial palsy, hearing loss, and strabismus and correlates extensively with the previously reported Hoxb1(-/-) mouse phenotype. The missense variant is predicted to result in the substitution of a cysteine for an arginine at amino acid residue 207 (Arg207Cys), which corresponds to the highly conserved Arg5 of the homeodomain. Arg5 interacts with thymine in the minor groove of DNA through hydrogen bonding and electrostatic attraction. Molecular modeling and an in vitro DNA-protein binding assay predict that the mutation would disrupt these interactions, destabilize the HOXB1:PBX1:DNA complex, and alter HOXB1 transcriptional activity.