Comitant strabismus: Perspectives, present and future

An Update on Dragged-Fovea Diplopia Syndrome

Dragged-fovea diplopia syndrome (DFDS) is a type of binocular double vision caused by a displacement of the fovea in one or both eyes due to retinal disorders including epiretinal membranes or other maculopathies. DFDS induces diplopia through a mismatch between peripheral motor fusion and central (foveal) fusion. It can be diagnosed by utilizing the Lights on - Lights off test. While there is no cure, there are treatments for DFDS including monocular occlusion or blurring (tape, lenses, IOL), Bangerter filter, and Fresnel prisms. While this syndrome has been identified in the literature by multiple names including central-peripheral Rivalry (CPR)-type diplopia, macular diplopia, and foveal displacement syndrome, this article works to summarize the current known characteristics, diagnostic tests, and treatment for this syndrome.

Identification and characterization of differentially expressed circular RNAs in extraocular muscle of oculomotor nerve palsy

BACKGROUND

Oculomotor nerve palsy (ONP) is a neuroparalytic disorder resulting in dysfunction of innervating extraocular muscles (EOMs), of which the pathological characteristics remain underexplored.

METHODS

In this study, medial rectus muscle tissue samples from four ONP patients and four constant exotropia (CXT) patients were collected for RNA sequencing. Differentially expressed circular RNAs (circRNAs) were identified and included in functional enrichment analysis, followed by interaction analysis with microRNAs and mRNAs as well as RNA binding proteins. Furthermore, RT-qPCR was used to validate the expression level of the differentially expressed circRNAs.

RESULTS

A total of 84 differentially expressed circRNAs were identified from 10,504 predicted circRNAs. Functional enrichment analysis indicated that the differentially expressed circRNAs significantly correlated with skeletal muscle contraction. In addition, interaction analyses showed that up-regulated circRNA_03628 was significantly interacted with RNA binding protein AGO2 and EIF4A3 as well as microRNA hsa-miR-188-5p and hsa-miR-4529-5p. The up-regulation of circRNA_03628 was validated by RT-qPCR, followed by further elaboration of the expression, location and clinical significance of circRNA_03628 in EOMs of ONP.

CONCLUSIONS

Our study may shed light on the role of differentially expressed circRNAs, especially circRNA_03628, in the pathological changes of EOMs in ONP.

Altered interhemispheric functional connectivity in patients with comitant exotropia before and after surgery: a resting-state fMRI study

Purpose

To assess the interhemispheric homotopic connectivity alterations in patients with comitant exotropia (CE) before and after surgery, using resting-state functional magnetic resonance imaging (rs-fMRI) with voxel-mirrored homotopic connectivity (VMHC).

Methods

Thirty-four patients with CE and twenty-four well-matched healthy controls (HCs) were enrolled to undergo a preoperative rs-fMRI scan. The rs-fMRI scan was performed again in twenty-four patients 1 month after surgery. The VMHC method was applied to evaluate the group differences of interhemispheric functional connectivity. The correlations between VMHC values and clinical variables were analyzed in the patient group.

Results

Compared with HCs, 34 patients with CE showed significantly increased VMHC values in occipital lobe (cuneus/superior occipital gyrus/middle occipital gyrus/calcarine), cerebellar area 8/cerebellar Crus1 area, and cerebellar Crus1 area. In CE group, VMHC in the cuneus was positively correlated with stereoacuity (r = 0.417, P = 0.014), meanwhile VMHC in the cerebellar Crus1 area was positively correlated with stereoacuity (r = 0.395, P = 0.021). One month after surgery, the 24 CE patients with follow-up showed decreased VMHC values in the cuneus and superior occipital gyrus compared with preoperative collection, meanwhile, non-significant difference compared with HCs.

Conclusion

Our study revealed the interhemispheric homotopic connectivity changes of patients with CE in the occipital lobe and cerebellum before and after surgery. The findings may provide a new perspective for the neurological alterations of CE.

Altered Brain Structure and Spontaneous Functional Activity in Children With Concomitant Strabismus

Strabismus occurs in about 2% of children and may result in amblyopia or lazy eyes and loss of depth perception. However, whether/how long-term strabismus shapes the brain structure and functions in children with concomitant strabismus (CS) is still unclear. In this study, a total of 26 patients with CS and 28 age-, sex-, and education-matched healthy controls (HCs) underwent structural and resting-state functional magnetic resonance imaging examination. The cortical thickness and amplitude of low-frequency fluctuation (ALFF) were calculated to assess the structural and functional plasticity in children with CS. Compared with HCs group, patients with CS showed increased cortical thickness in the precentral gyrus and angular gyrus while decreased cortical thickness in the left intraparietal sulcus, parieto-occipital sulcus, superior and middle temporal gyrus, right ventral premotor cortex, anterior insula, orbitofrontal cortex, and paracentral lobule. Meanwhile, CS patients exhibited increased ALFF in the prefrontal cortex and superior temporal gyrus, and decreased ALFF in the caudate and hippocampus. These results show that children with CS have abnormal structure and function in brain regions subserving eye movement, controls, and high-order cognitive functions. Our findings revealed the structural and functional abnormalities induced by CS and may provide new insight into the underlying neural mechanisms for CS.

Strabismus prevalence and associated factors among pediatric patients in southern Ethiopia: a cross-sectional study

Objective

To assess the strabismus prevalence and associated factors among children aged ≤15 years.

Methods

This hospital-based cross-sectional study was conducted from March 2017 to October 2017 in the Department of Ophthalmology & Optometry, Hawassa University Comprehensive Specialized Hospital. Interviewer-administered questionnaires were used to collect relevant data and clinical examinations were performed for patient diagnosis.

Results

Overall, 582 children participated in the study (response rate, 97%). The prevalence of childhood strabismus was 17.9% [95% confidence interval: 14.6–21.1]. Additionally, 9.6%, 16.7%, and 9.6% of the children had anisometropia, amblyopia, and dense cataract, respectively. Among the 16.7% of children with amblyopia, 56.7% had strabismus; among the 22.5% of children with clinically significant refractive error, 52.7% had strabismus. Moreover, among the 9.6% of children with anisometropia, 58.9% had strabismus. The presence of amblyopia (adjusted odds ratio [95% confidence interval]: 3.9, 1.7–8.6), age <5 years (13.5 [5.0–36.1]), age 5 to 10 years (6.1 [2.3–16.3]), and clinically significant refractive error (13.3 [5.8–30.6]) were significantly associated with childhood strabismus.

Conclusions

The prevalence of strabismus was relatively high among patients in this study. Early screening for childhood strabismus is essential. A well-controlled community-based study is needed to confirm strabismus prevalence and predictors.

Altered Brain Network Centrality in Patients with Adult Strabismus with Amblyopia: A Resting-State Functional Magnetic Resonance Imaging (fMRI) Study

Background

The aim of this study was to explore potential changes in brain function network activity in patients with adult strabismus with amblyopia (SA) using the voxel-wise degree centrality (DC) method.

Material/Methods

We enrolled 15 patients with SA (6 males, 9 females) and 15 sex-matched healthy controls (HCs). All subjects completed resting functional magnetic resonance imaging scans. Independent-sample t tests and receiver operating characteristic (ROC) curves were used to assess DC value differences between groups, and Pearson correlation analysis was performed to evaluate correlations between DC-changed brain regions and clinical data of patients with SA.

Results

Compared with the HC group, DC values that were lower in patients with SA included the left middle frontal gyrus and bilateral angular gyri. Increases were observed in the left fusiform gyrus, right lingual gyrus, right middle occipital gyrus, right postcentral gyrus, and left paracentral lobule. However, DC values were not correlated with clinical manifestations. ROC curve analysis showed high accuracy.

Conclusions

We found abnormal neural activity in specific brain regions in patients with SA. Specifically, we observed significant changes in DC values compared to HCs. These changes may be useful to identify the specific mechanisms involved in brain dysfunction in SA.

A study of consanguineous marriage as a risk factor for developing comitant strabismus

Inheritance has an important role in the etiology of comitant strabismus. Consanguineous marriage is a leading factor in birth defects in which inheritance has a role. The aim of this study is to reveal if consanguineous marriage increases the risk of developing comitant strabismus. We included 461 patients who underwent primary surgery for comitant strabismus in Shiraz University Khalili Hospital (Fars province, southern Iran) between years 2003 and 2013 in our study. All the patients were living in Shiraz, Iran. Patients were categorized into the following 4 groups: (1) intermittent or constant exotropia, (2) infantile esotropia, (3) non-accommodative acquired esotropia, and (4) accommodative acquired esotropia. A total of 421 healthy children who were born in Shiraz, at the same period of time, were also studied as a control group. Presence and type of the consanguineous marriages were evaluated in the parents of the patients and control group by a questionnaire. Mean of inbreeding coefficient (α) was calculated in each group of patients and was compared with those of control group. The proportion of parental first cousin marriage was 37.7 and 23.5 % among patient and control groups. The mean of inbreeding coefficients (α) were 0.0236, 0.0283, 0.0288, and 0.0236 in four groups of the patients, respectively. The mean of inbreeding coefficient was 0.0263 in total patients, which was significantly higher than 0.0164 of control group (T = 5.27, df = 880, P < 0.001). Patients with non-accommodative acquired esotropia had the highest mean of inbreeding coefficient (α) (0.0288). It seems that recessive form of inheritance plays an important role in the etiology of comitant strabismus. Modified screening programs may be needed for earlier detection of strabismus in the offspring of consanguineous couples.