fMRI evidence of improved visual function in patients with progressive retinitis pigmentosa by eye-movement training

Importance of two-dimensional gaze analyses in the assessment of reading performance in patients with retinitis pigmentosa

The causes of reading difficulties in people with peripheral visual field loss are not fully understood. We conducted a two-dimensional gaze analysis on eye movements during reading in patients with retinitis pigmentosa to investigate the causes of reading difficulties in relation to the central visual field using a binocular eye mark recorder (EMR-9). Twenty-seven patients with retinitis pigmentosa whose central visual field narrowed to ≤ 20° using Goldmann kinetic perimetry (I/4 target) and this present study included eight healthy participants. The participants' visual acuities were corrected to better than +0.4 logMAR. Correlations and multivariate regression analyses were investigated between the number of letters read correctly, the I/4 central visual field, V/4 perifoveal and peripheral visual field, and visual acuity. Multivariate regression analysis revealed that all these parameters played almost equal roles in the number of letters read correctly. In the two-dimensional gaze analysis, the task performance time of patients during reading increased as the I/4 central visual field narrowed. The task performance time was more clearly correlated with the rotation saccade (r = 0.428, p <0.05) and the distance of the vertical direction (ΣY) of eye movements (r = 0.624, p < 0.01), but not with regressive saccade and the distance of the horizontal direction (ΣX). Visual acuity was correlated with the task performance time (-0.436, <0.05) but not with eye movement directionality. Reading difficulties in patients with retinitis pigmentosa result from impaired eye movement directionality. Understanding eye measurements for people with tunnel vision required a two-dimensional gaze analysis. The two-dimensional gaze analysis also showed that the involvement of the perifoveal and peripheral visual fields, visual acuity, and I/4 central visual field was important for reading in people with tunnel vision.

Altered brain network centrality in patients with retinal vein occlusion: a resting-state fMRI study

AIM

To explore the intrinsic brain activity variations in retinal vein occlusion (RVO) subjects by using the voxel-wise degree centrality (DC) technique.

METHODS

Twenty-one subjects with RVO and twenty-one healthy controls (HCs) were enlisted and underwent the resting-state functional magnetic resonance imaging (rs-fMRI) examination. The spontaneous cerebrum activity variations were inspected using the DC technology. The receiver operating characteristic (ROC) curve was implemented to distinguish the DC values of RVOs from HCs. The relationships between DC signal of definite regions of interest and the clinical characteristics in RVO group were evaluated by Pearson's correlation analysis.

RESULTS

RVOs showed notably higher DC signals in right superior parietal lobule, middle frontal gyrus and left precuneus, but decreased DC signals in left middle temporal gyrus and bilateral anterior cingulated (BAC) when comparing with HCs. The mean DC value of RVOs in the BAC were negatively correlated with the anxiety and depression scale.

CONCLUSION

RVO is associated aberrant intrinsic brain activity patterns in several brain areas including pain-related as well as visual-related regions, which might assist to reveal the latent neural mechanisms.

Oculomotor Training for Poor Saccades Improves Functional Vision Scores and Neurobehavioral Symptoms

OBJECTIVES

To determine if participants with saccadic dysfunction improved after participating in a standardized oculomotor training program. A secondary objective was to accurately quantify change in saccades after training using eye tracking technology. A third objective was to examine patients' neurobehavioral symptoms before and after oculomotor training using the Neurobehavioral Symptom Inventory (NSI).

DESIGN

A prospective study involving treatment and control group pre-post intervention design.

SETTING

Data were collected in eye clinics with a standardized eye tracking equipment setup.

PARTICIPANTS

Participants in the bottom 25th percentile for saccadic eye movements (N=92; intervention=46, control=46) who were currently asymptomatic of specific disorder.

INTERVENTIONS

Participants were randomly assigned to the control or intervention group. The intervention group engaged in 10 minutes of oculomotor training daily for 5 days.

MAIN OUTCOME MEASURES

The ratio of the peak saccadic velocity over its average velocity (the Q ratio), saccadic targeting, and NSI.

RESULTS

Results revealed significant interactions between control and intervention groups (P=.013). The control group increased 7% from pre to post; however, the intervention group exhibited a 6% decreased from pre to post. Participants in the intervention group demonstrated a 25% improvement in targeting saccade accuracy (P=.021). Additionally, there was a significant reduction in all neurobehavioral factors on the NSI in the intervention group, specifically the affective and cognitive factors relating to poor saccades.

CONCLUSIONS

For this population, oculomotor training (Q ratio and saccade accuracy) resulted improved saccadic metrics and a significant reduction in overall symptoms as shown on the NSI. Future participants reported improved symptoms pre- and postintervention. Further research is needed to understand saccadic performance and gaze stability during specific tasks (such as reading).

Quantitative assessment of visual pathway function in blind retinitis pigmentosa patients

OBJECTIVE

The current methods used to assess visual function in blind retinitis pigmentosa (RP) patients are mostly subjective. We aimed to identify effective, objective methods.

METHODS

We enrolled patients diagnosed with blindness associated with RP; we finally selected 26 patients (51 eyes) with a visual field radius less than 10 degrees and divided them into the following 4 groups by best-corrected visual acuity (BCVA): group 1, no light perception (NLP, 4 eyes); group 2, light perception (LP, 12 eyes); group 3, hand movement or finger counting (faint form perception, FFP, 22 eyes); and group 4, BCVA from 0.1 to 0.8 (form perception, FP, 13 eyes). All patients underwent optometry, optical coherence tomography (OCT), color fundus photography, fundus autofluorescence (FAF), full field electroretinography (ffERG), pattern electroretinography (PERG), multifocal electroretinography (mf-ERG), pattern visual evoked potential (PVEP), flash visual evoked potential (FVEP), and pupillary light response (PLR) assessments. Five patients in groups 1, 2, and 3 (1, 2, and 2 subjects, respectively) underwent functional magnetic resonance imaging (fMRI) scans and were compared with five healthy subjects.

RESULTS

The outer plexiform layer was thinner in group 1, and the outer nuclear layer was thinner in groups 1 and 2. The ffERG, PERG, and mf-ERG findings were unrecordable in all four groups. The P2 amplitude of the FVEP was significantly lower in groups 1 and 2, while the P100 amplitude of the PVEP was higher in groups 2, 3 and 4 than in group 1. After white- and blue-light stimuli, the PLR thresholds in the patients without form perception were significantly higher. The threshold of the PLR stimulated by blue and white light was negatively correlated with the amplitudes of P2 and P100. Moreover, the fMRI findings showed that some RP patients have significant visual cortex activation in response to certain types of stimulation. However, statistical analysis was not performed because of the small number of cases.

CONCLUSIONS

OCT, VEP, PLR and fMRI assessments can evaluate residual visual pathway function in blind RP patients.

SIGNIFICANCE

Our study may have clinical significance for the potential prediction of RP patient prognoses and the effects after clinical trials.

Altered intrinsic functional connectivity of the primary visual cortex in patients with retinal vein occlusion: a resting-state fMRI study

Background

To investigate the differences of spontaneous functional connectivity (FC) of the primary visual cortex (V1) between patients with retinal vein occlusion (RVO) and healthy controls (HCs) using resting-state functional magnetic resonance imaging (rs-fMRI) data.

Methods

Twenty-one patients with RVO in total (11 males, 10 females) and 21 HCs similarly analogue in age and sex background were enrolled and inspected with rs-fMRI. The difference in FC of V1 between two groups were compared using two-sample t-test. We used the receiver operating characteristic (ROC) curve to distinguish average FC values of RVO subjects from HCs. The interrelationships between FC signals of specific cerebrum regions and clinical features in RVOs were assessed with the Pearson's correlation analysis.

Results

Compared with HCs, FC in left V1 and right middle frontal gyrus increased significantly in RVO group, while FC in left V1 and right cuneus decreased significantly. Meanwhile, patients with RVO presented increased FC between the right V1 and right middle frontal gyrus, right superior frontal gyrus, but declining FC between right V1 and right cuneus. The mean FC value between the right cuneus and the right V1 as well as the left V1 were negative correlated with the foveal thickness of RVO patients. ROC curve analysis of each brain regions showed the accuracy of AUC was excellent.

Conclusions

RVO involves aberrant FC in V1 in different brain areas including visual-related and cognitive-related region, which might assist to unveil the underlying neural mechanisms of impaired visual function in RVO.

Altered Intrinsic Functional Connectivity of the Primary Visual Cortex in Patients with Corneal Ulcer: A Resting-State fMRI Study

PURPOSE

To investigate differences in the functional connectivity (FC) of the primary visual cortex between patients with corneal ulcer (CU) and healthy controls (HCs) using resting-state functional magnetic resonance imaging.

PATIENTS AND METHODS

A total of 30 patients with CU and 30 HCs were closely matched in terms of sex, age, and level of education. Two-sample t-test, receiver operating characteristic curve, and Pearson's correlation coefficient analyses were used to determine the differences in FC between the two groups, the mean FC value of patients with CU and HCs, and the correlation between FC signal values and clinical manifestations in different brain regions of patients.

RESULTS

The CU group showed significantly elevated FC in the left and right middle frontal gyri and lower FC with the right cuneus compared with the HC group. In addition, the FC of the right cingulate and left superior frontal gyri also increased in the CU group. The receiver operating characteristic curve revealed high diagnostic value in those brain regions.

CONCLUSION

CU involves aberrant FC of the primary visual cortex in different brain areas, including visual-related and cognitive-related regions. This finding may unveil the underlying neural mechanisms of impaired visual function in CU.

An EZ-Diffusion Model Analysis of Attentional Ability in Patients With Retinal Pigmentosa

Retinitis pigmentosa (RP) is characterized by visual acuity decrease and visual field loss. However, the impact of visual field loss on the cognitive performance of RP patients remains unknown. In the present study, in order to understand whether and how RP affects spatial processing and attentional function, one spatial processing task and three attentional tasks were conducted on RP patients and healthy controls. In addition, an EZ-diffusion model was performed for further data analysis with four parameters, mean decision time, non-decision time, drift rate, and boundary separation. It was found that in the spatial processing task, compared with the control group, the RP group exhibited a slower response speed in large and medium visual eccentricities, and slower drift rate for the large stimulus, which is strongly verified by the significant linear correlation between the visual field eccentricity with both reaction time (p = 0.047) and non-decision time (p = 0.043) in RP patients. In the attentional orienting task and the attentional switching task, RP exerted a reduction of speed and an increase of non-decision time on every condition, with a decrease of drift rate in the orienting task and boundary separation in the switching task. In addition, the switching cost for large stimulus was observed in the control group but not in the RP group. The stop-signal task demonstrated similar inhibition function between the two groups. These findings implied that RP exerted the impairment of spatial cognition correlated with the visual field eccentricity, mainly in the peripheral visual field. Moreover, specific to the peripheral visual field, RP patients had deficits in the attentional orienting and flexibility but not in the attentional inhibition.