The role of eye movement driven attention in functional strabismic amblyopia

Cortical Deficits are Correlated with Impaired Stereopsis in Patients with Strabismus

In this study, we explored the neural mechanism underlying impaired stereopsis and possible functional plasticity after strabismus surgery. We enrolled 18 stereo-deficient patients with intermittent exotropia before and after surgery, along with 18 healthy controls. Functional magnetic resonance imaging data were collected when participants viewed three-dimensional stimuli. Compared with controls, preoperative patients showed hypoactivation in higher-level dorsal (visual and parietal) areas and ventral visual areas. Pre- and postoperative activation did not significantly differ in patients overall; patients with improved stereopsis showed stronger postoperative activation than preoperative activation in the right V3A and left intraparietal sulcus. Worse stereopsis and fusional control were correlated with preoperative hypoactivation, suggesting that cortical deficits along the two streams might reflect impaired stereopsis in intermittent exotropia. The correlation between improved stereopsis and activation in the right V3A after surgery indicates that functional plasticity may underlie the improvement of stereopsis. Thus, additional postoperative strategies are needed to promote functional plasticity and enhance the recovery of stereopsis.

Functional Deficits and Structural Changes Associated With the Visual Attention Network During Resting State in Adult Strabismic and Anisometropic Amblyopes

Our previous study has shown impaired blood oxygen level-dependent (BOLD)/functional magnetic resonance imaging (fMRI) activation of the visual attention network in strabismic amblyopia (SA). However, there has been no comparison of resting state fMRI activation and functional connectivity (FC) in brain regions of interest (ROIs) along the visual attention network including visual cortex (V1), intraparietal sulcus (IPS), and frontal eye fields (FEFs) during closed eye resting across the SA (n = 20, 13LE), or anisometropic amblyopes (AA) (n = 20, 13LE) groups. Hence, we compared, gray matter volume (GMV), amplitude of low frequency fluctuations (ALFFs), regional homogeneity (ReHo), and FC in the left and right hemisphere ROIs of the visual attention network in SA, AA, and healthy controls (HCs) (n = 21). Correlation analyses of corrected visual acuity (cVA) of amblyopic eye and MRI results were also performed and showed that the LogMAR cVA of the amblyopic eye positively correlated with right zALFF and zReHo FEF of SA and right IPS of AA only. GMV of both left and right hemisphere V1 areas was significantly greater but ALFF was significantly lower for SA compared to AA and HC groups. zALFF and zReHo analyses in the AA and SA groups indicated significantly higher activation than that in the HC group in the right FEF and IPS but lower than that in the HC group in the left FEF, and only the SA group showed lower activation in both V1 areas than the HC group. FC values of the right FEF–left V1, right FEF–right V1, and right FEF–right IPS pathways in the SA and AA groups were also significantly higher than those in the HC group whereas all other FC values were non-significant. Thus, this study indicates that even during resting-state the visual attention network function is impaired in SA and AA participants with only right hemisphere FEF showing significant activation in SA and IPS in AA suggesting that the slower saccade activation times characteristic of amblyopic eyes lead to the dominant eye controlling activation of the visual attention network.

Psychomotor, Psychosocial and Reading Skills in Children with Amblyopia and the Effect of Different Treatments

Amblyopia influences psychomotor and psychosocial skills, although not all studies are unanimous. Different treatments coexist, but the effect on those variables is not clear. This study aims to probe whether children with amblyopia have impairments in these areas and if different optometric treatments reduce them effectively. 50 children, diagnosed with amblyopia, and 33 without amblyopia participated in this study. Eye-hand coordination, psychosocial skills and reading abilities, were measured before and after three months of different treatments (patch, patch and near vision activities and perceptual learning). Results revealed lower scores in eye-hand coordination and some reading issues in children with amblyopia, without differences in psychosocial skills in regard to the control group. Moreover, optometric treatments improved eye-hand coordination.

Impaired Activation of Visual Attention Network for Motion Salience Is Accompanied by Reduced Functional Connectivity between Frontal Eye Fields and Visual Cortex in Strabismic Amblyopia

Strabismic amblyopia is now acknowledged to be more than a simple loss of acuity and to involve alterations in visually driven attention, though whether this applies to both stimulus-driven and goal-directed attention has not been explored. Hence we investigated monocular threshold performance during a motion salience-driven attention task involving detection of a coherent dot motion target in one of four quadrants in adult controls and those with strabismic amblyopia. Psychophysical motion thresholds were impaired for the strabismic amblyopic eye, requiring longer inspection time and consequently slower target speed for detection compared to the fellow eye or control eyes. We compared fMRI activation and functional connectivity between four ROIs of the occipital-parieto-frontal visual attention network [primary visual cortex (V1), motion sensitive area V5, intraparietal sulcus (IPS) and frontal eye fields (FEF)], during a suprathreshold version of the motion-driven attention task, and also a simple goal-directed task, requiring voluntary saccades to targets randomly appearing along a horizontal line. Activation was compared when viewed monocularly by controls and the amblyopic and its fellow eye in strabismics. BOLD activation was weaker in IPS, FEF and V5 for both tasks when viewing through the amblyopic eye compared to viewing through the fellow eye or control participants' non-dominant eye. No difference in V1 activation was seen between the amblyopic and fellow eye, nor between the two eyes of control participants during the motion salience task, though V1 activation was significantly less through the amblyopic eye than through the fellow eye and control group non-dominant eye viewing during the voluntary saccade task. Functional correlations of ROIs within the attention network were impaired through the amblyopic eye during the motion salience task, whereas this was not the case during the voluntary saccade task. Specifically, FEF showed reduced functional connectivity with visual cortical nodes during the motion salience task through the amblyopic eye, despite suprathreshold detection performance. This suggests that the reduced ability of the amblyopic eye to activate the frontal components of the attention networks may help explain the aberrant control of visual attention and eye movements in amblyopes.

Importance of visual inputs quality for postural stability in strabismic children

OBJECTIVE

The first goal of the present study is to analyze the postural control in strabismic children in four different visual conditions (eyes open, eyes closed and monocular viewing with squint eye and non-squint eye). Secondly, we wish to explore the effect of strabismus surgery in postural control.

METHOD

Postural stability was recorded with a platform (TechnoConcept) in 23 strabismic children aged from 4.4 to 14.8 years old (mean age: 8.4 years); 12 of these children were also examined at least two months after strabismus surgery. We analyzed the surface, the length, and the mean speed of the Center of Pressure displacement (CdP), and we calculated the Romberg's Quotient (that is for each postural parameter the ratio between eyes closed relative to eyes open).

RESULTS

Strabismic children are significantly more stable when they can use their visual information to control their posture. Also, postural stability was better when the non-squint eye was viewing. For the first time, we observed the important role of vision (by calculating Romberg's Quotient) in strabismic children with binocular vision in comparison of strabismic children without binocular vision. Finally, we found that eye surgery improves postural stability.

CONCLUSION

Strabismic children use visual inputs to control their posture. Moreover, binocular vision plays an important role in postural control. Strabismus surgery improves postural stability.

SIGNIFICANCE

Visual inputs from the non-squint eye and binocular vision are important to control stability.

Altered functional connectivity density in high myopia

Abnormal visual experience can affect the brain structure and function. Visual functional performances of high myopia (HM) individuals were observed to be abnormal in contrast to emmetropics, even with a corrected visual acuity. Attention deficits and brain morphological changes have been revealed in the HM, but it is unknown whether there are functional connectivity (FC) alterations. The current study combined the resting-state functional connectivity density (FCD) mapping and seed-based correlation analysis to investigate FC alterations in the brain of HM. In our results, the HM exhibited decreased short- and long-range FCD in the posterior cingulate cortex/precuneus and decreased long-range FCD in the inferior temporal gyrus, supramarginal gyrus and rostrolateral prefrontal cortex. Specially, long-range FCD in the rostrolateral prefrontal cortex showed a significant positive correlation with the uncorrected visual acuity in the HM. Moreover, the HM showed significantly decreased FC not only between the supramarginal gyrus and rostrolateral prefrontal cortex, but also between networks they belong to, the ventral attention and frontoparietal control networks. These results provide evidence for the FC changes in the HM and may help to understand the attention deficits in myopes.

Visual Outcomes at 12 Months in Patients Following Implantation of a Diffractive Multifocal Intraocular Lens

Introduction

The aim of this study was to assess distance, intermediate, and near visual acuity, contrast sensitivity, and patient satisfaction outcomes of a multifocal intraocular lens (IOL).

Methods

This multicenter, prospective clinical study was conducted at seven study sites in Turkey. Patients who underwent bilateral cataract removal and implantation of a diffractive, acrylic, hydrophobic, multifocal IOL (Acriva UD Reviol MFB 625; VSY Biotechnology, Istanbul, Turkey) were included. The uncorrected and best corrected distance visual acuities (UCDVA and BCDVA), uncorrected and best corrected intermediate visual acuities (UCIVA and BCIVA), and uncorrected and best corrected near visual acuities (UCNVA and BCNVA) were measured preoperatively and at postoperative 1, 6, and 12 months. Distance and near visual acuity scores (VAS) contrast sensitivities were measured at these time points. Quality of life was evaluated by visual function-14 (VF-14) questionnaire.

Results

Two hundred eyes of 100 patients were included. Monocular and binocular visual acuities at all distances showed improvement at postoperative 12 months compared to preoperative measurements (P < 0.001). Monocular and binocular UCIVA and binocular BCIVA at postoperative 12 months were significantly improved compared to measurements at 1 month (P < 0.001). Binocular contrast sensitivity at distance showed significant improvement from postoperative 1 month to postoperative 12 months, except for 3 cycles per degree (cpd; without glare) and 18 cpd (with glare). VAS improved from 75.96 at postoperative 1 month to 76.85 at postoperative 12 months. VF-14 score was 98.2 ± 4.6.

Conclusion

The Acriva UD Reviol MFB 625 appears to provide a good level of distance and near visual acuity, quality of life, and patient satisfaction. Further studies with longer follow-up will provide valuable insight into the long-term stability of these visual outcomes.

Electronic supplementary material

The online version of this article (doi:10.1007/s40123-015-0032-4) contains supplementary material, which is available to authorized users.