When You Do Not Get the Whole Picture: Scene Perception After Occipital Cortex Lesions

Background: Occipital cortex lesions (OCLs) typically result in visual field defects (VFDs) contralateral to the damage. VFDs are usually mapped with perimetry involving the detection of point targets. This, however, ignores the important role of integration of visual information across locations in many tasks of everyday life. Here, we ask whether standard perimetry can fully characterize the consequences of OCLs. We compare performance on a rapid scene discrimination task of OCL participants and healthy observers with simulated VFDs. While the healthy observers will only suffer the loss of part of the visual scene, the damage in the OCL participants may further compromise global visual processing.Methods: VFDs were mapped with Humphrey perimetry, and participants performed two rapid scene discrimination tasks. In healthy participants, the VFDs were simulated with hemi- and quadrant occlusions. Additionally, the GIST model, a computational model of scene recognition, was used to make individual predictions based on the VFDs.Results: The GIST model was able to predict the performance of controls regarding the effects of the local occlusion. Using the individual predictions of the GIST model, we can determine that the variability between the OCL participants is much larger than the extent of the VFD could account for. The OCL participants can further be categorized as performing worse, the same, or better as their VFD would predict.Conclusions: While in healthy observers the extent of the simulated occlusion accounts for their performance loss, the OCL participants’ performance is not fully determined by the extent or shape of their VFD as measured with Humphrey perimetry. While some OCL participants are indeed only limited by the local occlusion of the scene, for others, the lesions compromised the visual network in a more global and disruptive way. Yet one outperformed a healthy observer, suggesting a possible adaptation to the VFD. Preliminary analysis of neuroimaging data suggests that damage to the lateral geniculate nucleus and corpus callosum might be associated with the larger disruption of rapid scene discrimination. We believe our approach offers a useful behavioral tool for investigating why similar VFDs can produce widely differing limitations in everyday life.

Novel scotoma detection method using time required for fixation to the random targets

We developed a novel scotoma detection system using time required for fixation to the random targets, or the "eye-guided scotoma detection method". In order to verify the "eye-guided scotoma detection method", we measured 78 eyes of 40 subjects, and examined the measurement results in comparison with the results of measurement by Humphrey perimetry. The results were as follows: (1) Mariotte scotomas were detected in 100\% of the eyes tested; (2) The false-negative rate (the percentage of cases where a scotoma was evaluated as a non-scotoma) was less than 10\%; (3) The positive point distribution in the low-sensitivity eyes was well matched. These findings suggested that the novel scotoma detection method in the current study will pave the way for the realization of mass screening to detect pathological scotoma earlier.

Functional MRI of visual cortex predicts training-induced recovery in stroke patients with homonymous visual field defects

Post-chiasmatic damage to the visual system leads to homonymous visual field defects (HVDs), which can severely interfere with daily life activities. Visual Restitution Training (VRT) can recover parts of the affected visual field in patients with chronic HVDs, but training outcome is variable. An untested hypothesis suggests that training potential may be largest in regions with ‘neural reserve’, where cortical responses to visual stimulation do not lead to visual awareness as assessed by Humphrey perimetry—a standard behavioural visual field test. Here, we tested this hypothesis in a sample of twenty-seven hemianopic stroke patients, who participated in an assiduous 80-hour VRT program. For each patient, we collected Humphrey perimetry and wide-field fMRI-based retinotopic mapping data prior to training. In addition, we used Goal Attainment Scaling to assess whether personal activities in daily living improved. After training, we assessed with a second Humphrey perimetry measurement whether the visual field was improved and evaluated which personal goals were attained. Confirming the hypothesis, we found significantly larger improvements of visual sensitivity at field locations with neural reserve. These visual field improvements implicated both regions in primary visual cortex and higher order visual areas. In addition, improvement in daily life activities correlated with the extent of visual field enlargement but not sensitivity gain. Our findings are an important step toward understanding the mechanisms of visual restitution as well as predicting training efficacy in stroke patients with chronic hemianopia.

Usher Syndrome in Two Siblings, A Case Report

Introduction: Usher Syndrome is a rare genetic disorder involving abnormalities in the retina and hearing, where the patients will experience blindness and hearing loss due to mutations of the gene. Blindness caused by Usher Syndrome has not been prevented until now, but the emphasis is more on focusing early diagnosis, especially patients with Retinitis Pigmentosa. Methods: This Case represent of two siblings with Retinitis Pigmentose (RP) and profound bilateral sensorineural deafness. Diagnosis based on patients decreases of vision since teenagers and worst at night, visual acuity and visual field examination in both patients, Ophthalmoscopic findings, and sensorineural deafness diagnosed by Ear, Nose, and Throat (ENT) department. Electroretinogram (ERG) was not carried out in the two patients because of the limitations of diagnostic facilities. Result: In both eyes of both siblings, ophthalmoscopic evaluation disclosed numerous bone spiculae at peripheral area. Humphrey perimetry showed a tunnel vision. The hearing test also showed a sensorineural hearing loss (SNHL). Conclusion: two affected member of the family were found to exhibit an usher syndrome, this pedigree supports the genetic cotransmission of the traits.

Mapping the Structure-Function Relationship in Glaucoma and Healthy Patients Measured with Spectralis OCT and Humphrey Perimetry

Purpose. To study the structure-function relationship in glaucoma and healthy patients assessed with Spectralis OCT and Humphrey perimetry using new statistical approaches. Materials and Methods. Eighty-five eyes were prospectively selected and divided into 2 groups: glaucoma (44) and healthy patients (41). Three different statistical approaches were carried out: (1) factor analysis of the threshold sensitivities (dB) (automated perimetry) and the macular thickness (μm) (Spectralis OCT), subsequently applying Pearson’s correlation to the obtained regions, (2) nonparametric regression analysis relating the values in each pair of regions that showed significant correlation, and (3) nonparametric spatial regressions using three models designed for the purpose of this study. Results. In the glaucoma group, a map that relates structural and functional damage was drawn. The strongest correlation with visual fields was observed in the peripheral nasal region of both superior and inferior hemigrids (r=0.602 and r=0.458, resp.). The estimated functions obtained with the nonparametric regressions provided the mean sensitivity that corresponds to each given macular thickness. These functions allowed for accurate characterization of the structure-function relationship. Conclusions. Both maps and point-to-point functions obtained linking structure and function damage contribute to a better understanding of this relationship and may help in the future to improve glaucoma diagnosis.

Visual discrimination training improves Humphrey perimetry in chronic cortically induced blindness

Objective:To assess if visual discrimination training improves performance on visual perimetry tests in chronic stroke patients with visual cortex involvement.Methods:24-2 and 10-2 Humphrey visual fields were analyzed for 17 chronic cortically blind stroke patients prior to and following visual discrimination training, as well as in 5 untrained, cortically blind controls. Trained patients practiced direction discrimination, orientation discrimination, or both, at nonoverlapping, blind field locations. All pretraining and posttraining discrimination performance and Humphrey fields were collected with online eye tracking, ensuring gaze-contingent stimulus presentation.Results:Trained patients recovered ∼108 degrees2 of vision on average, while untrained patients spontaneously improved over an area of ∼16 degrees2. Improvement was not affected by patient age, time since lesion, size of initial deficit, or training type, but was proportional to the amount of training performed. Untrained patients counterbalanced their improvements with worsening of sensitivity over ∼9 degrees2 of their visual field. Worsening was minimal in trained patients. Finally, although discrimination performance improved at all trained locations, changes in Humphrey sensitivity occurred both within trained regions and beyond, extending over a larger area along the blind field border.Conclusions:In adults with chronic cortical visual impairment, the blind field border appears to have enhanced plastic potential, which can be recruited by gaze-controlled visual discrimination training to expand the visible field. Our findings underscore a critical need for future studies to measure the effects of vision restoration approaches on perimetry in larger cohorts of patients.