Posts Tagged Homonymous
[ARTICLE] Use of NeuroEyeCoach™ to Improve Eye Movement Efficacy in Patients with Homonymous Visual Field Loss – Full Text
Visual field deficits are common in patients with damaged retinogeniculostriate pathways. The patient’s eye movements are often affected leading to inefficient visual search. Systematic eye movement training also called compensatory therapy is needed to allow patients to develop effective coping strategies. There is a lack of evidence-based, clinical gold-standard registered medical device accessible to patients at home or in clinical settings and NeuroEyeCoach (NEC) is developed to address this need. In three experiments, we report on performance of patients on NEC compared to the data obtained previously on the earlier versions of the search task (); we assessed whether the self-administered computerised tasks can be used to monitor the progress () and compared the findings in a subgroup of patients to a healthy control group. Performance on cancellation tasks, simple visual search, and self-reported responses on activities of daily living was compared, before and after training. Patients performed similarly well on NEC as on previous versions of the therapy; the inbuilt functionality for pre- and postevaluation functions was sensitive to allowing assessment of improvements; and improvements in patients were significantly greater than those in a group of healthy adults. In conclusion, NeuroEyeCoach can be used as an effective rehabilitation tool to develop compensatory strategies in patients with visual field deficits after brain injury.
We explore our surrounding environment by moving our eyes on average three times per second. The eye movement episodes are punctuated by brief periods (100–300 ms) of fixations. This pattern of activity ensures detailed image processing by the high density cone-receptor region of our central vision . The resultant continuous perception of the stable world relies on amalgamation of lower resolution peripheral vision with high resolution central information in a spatiotopic frame of reference . This dynamic process encompasses the suppression of noise or distractors and selective enhancement of target objects . The selection of candidate targets for subsequent eye movements (saccades) is achieved through a combination of stimulus driven bottom-up and goal driven top-down mechanisms .
Visual field deficits often accompany lesions of the visual pathways which in turn disrupt the selection of targets falling within the impaired visual fields . Abnormal patterns of eye movement are reported in approximately 60% of such cases . One method for quantifying disturbances of visual processing is to make use of a visual search paradigm where the patient is required to report the presence or absence of a target amongst distractor items, often but not exclusively, presented on a computer screen . The reaction times are then compared to those for target detection in the sighted field in the same individual or in a group of healthy individuals. The inverse of the slope for a linearly fitted plot of reaction times as a function of the number of distractor items reflects “search efficiency” . In general, for healthy adults when targets and distractors are easily discriminable (pop-out search), the slope is shallow (high efficiency), but steeper slopes are expected when targets and distractors share features (complex or conjunction search).
Eye movement recordings of patients with visual field deficits following brain injury reveal a number of characteristics . These include smaller saccade amplitudes, and, hence, a larger number of fixations; limited exploration of the contralesioned visual field; and more between-hemifield saccades often summarised as disorganised eye movements leading to slower reaction times for targets in contralesioned hemifields. Disturbances of eye movement dynamics are also reported in the sighted (ipsilesioned) hemifield [6, 10].
In clinical practice, the rehabilitation of patients with visual field deficits is often conducted by occupational therapists or low-vision experts. The aim of any intervention is to improve the patient’s interactions with their immediate surrounding and increasing their confidence in tasks such as shopping or commuting. The use of computerised visual search tasks as a rehabilitation tool to improve eye movements after brain injury was first reported in a group of 30 patients . Patients were given systematic practice with large saccadic eye movements to search for targets presented at unpredictable positions in both the affected hemifield and the entire field of gaze. This class of treatment was later extended by use of a visual search paradigm to improve scanning strategy. Simultaneous recording of eye movements in a group of 60 patients provided further evidence for spatially disorganised pattern of eye movements in 60% of cases , with improved visual scanning in all 13 cases that underwent visual search training. With better use of the remaining sight as well as efficient search strategy, patients were able to compensate for their partial blindness; hence, the technique has been termed compensatory. This technique with various modifications has been used in 14 studies to date, with a total of 593 patients with homonymous visual field loss and persistent visual disabilities (see Table 1). Indeed a recent systematic review  has identified eye movement training as the most promising approach to visual rehabilitation in stroke patients.
What is Homonymous Hemianopia?
The ability to see is a complex process involving the eyes and the brain. Both parts must be working for us to see. A Homonymous Hemianopia is caused by damage to the visual pathway in the brain, usually in the occipital lobe on one side.
People often think that they have lost the vision in one eye. In actual fact they have lost half the vision in both eyes. Damage to the right occipital lobe will affect the left visual field and conversely damage to the left will result in a right visual field loss.
[POSTER] Visual Field Expanding Peripheral Prisms Improve Detection of Roadside Pedestrians in Patients with Hemianopia
…For hemianopia, peripheral prisms (p-prisms) expand the visual field up to 40° on standard perimetry (Jung and Peli, 2014). In prior studies, p-prisms improved self-reported mobility scores over a sham in a randomized controlled clinical trial (Bowers, 2013) and improved responses to hazards in a pilot on-road study. However, gaze was not tracked in either of these studies and there was no control over when or where hazards appeared. We therefore conducted a study to objectively measure detection and gaze behavior with the p-prisms in the controlled environment of a driving simulator…