Talk:Hemianopsia

External links

This article is breaching the external link guidelines by including ext links in its sections. 218.248.65.140 (talk) 07:59, 3 October 2011 (UTC)

NovaVision

Why is the section for NovaVision included? There are no sources and the British Journal of Ophthalmology has an article claiming it is of limited use, if any. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1772467/ — Preceding unsigned comment added by Vesped (talk • contribs) 22:27, 5 February 2014 (UTC)

It looks like the company NovaVision may have contributed to the article. I see reference now, although I haven't looked at them and it seems like it might be biased. I think this needs attention. I hope to look into it. --JonathanWilliford (talk) 15:06, 4 April 2016 (UTC)

Koons et al, 2010 Citation

This article references Koons et al, 2010 multiple times (see: Treatment) but does not list the study in the references. If you know where this study can be found, please add it to the references. — Preceding unsigned comment added by 67.253.226.96 (talk) 18:54, 10 August 2015 (UTC)

https://www.dovepress.com/scanning-training-in-neurological-vision-loss-case-studies-peer-reviewed-article-EB I am not sure if this is a high quality study suitable for use as a reference. I cannot find it in PubMed nor have I ever heard of the Journal "Eye and Brain" or publisher DovePress. It does not have a DOI. Hombre de Vitruvio (talk) 06:15, 24 January 2017 (UTC)

Turns out that Dove Medical Press has a less than stellar history. I don't think we should be using it as a source. This article needs some serious re-work. Hombre de Vitruvio (talk) 06:20, 24 January 2017 (UTC)

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Treatment

Many different types of treatments are available to patients with hemianopsia, depending on patient preference, age, type of hemianopsia, and how long they have been diagnosed. Some of these treatments include Audiovisual Stimulation Training, Explorative Saccade Training, Optical Visual Span Expanders, and Visual Restoration Therapy. None of these treatments will cure hemianopsia, but they will allow patients to have better perception of the world around them. Most doctors recommend the uses of a combination of these treatments, after a complete vision examination (Koons et al., 2010). Research is still being done on which of these treatments is most effective, and which patients will benefit the most from different combinations of treatments. The Department of Veteran Affairs medical center currently uses Explorative Saccade Training as their ‘go to’ form of treatment for patients with hemianopsia (Koons et al., 2010). Also, a treatment outcome model has been developed for Visual Restoration Therapy in order to better understand which patients this specific therapy will help (Guenther et al., 2009). More studies need to be done in order to develop a similar model for more of the hemianopsia treatments and different combinations of them. Currently, advantages and disadvantages are known for most treatments, which is discussed below along with descriptions of each treatment.

Audiovisual Stimulation Training

Audiovisual stimulation training has been developed as an effective treatment for patients suffering from Homonymous hemianopsia which uses multi-sensory stimulation to improve vision. Patients can go through an intensive program of up to 4 hours a day for 2 weeks, in which areas of their visual field, both intact and affected, are stimulated using sound and light.

How it works

A semicircular structure should be set up with marks at azimuths of 8°, 24°, 40°, and 56° on both right and left of the central fixation point (Passamonti et al., 2009). At each point a light and a sound speaker should be fixed. For one round of training, a light will be illuminated along with a shout sound, and the patient is asked to move their gaze toward the stimulus which just has occurred. As trials continue, the sound and the visual cue will randomly alternate between being located at the same azimuth, or different azimuths. The stimulation should be most focused on the patients’ blind hemi-field.

Results

Many patients have seen lasting results from Audio-visual Stimulation Training, allowing them some recovery. This training affects different parts of the patients’ saccades, including spatial and temporal aspects (Passamonti et al., 2009). Patients with Right hemianopsia tend to show fewer progressive and regressive saccades, larger amplitude of these saccades, and reduced duration of fixation time (Passamonti et al., 2009). They also show improved accuracy on reading performance tasks. However, performance is still impaired (Passamonti et al., 2009). Left hemianopsia patients show even greater improvements, showing a significantly smaller number of saccades, and following reading tasks their ocular responses are comparable to ‘normal’ vision patients (Passamonti et al.,2009).. There are also some negative aspects of Audio-visual stimulation Therapy, being that the field of vision is not improved (Windsor et al., n.d.). Studies have shown that sensitivity of perception showed no significant difference when the patient was told to keep their eye stationary, from the original treatment which allowed the patient to move their eye while adjusting their gaze (Passamonti et al.,2009). If visual field had been increased, the sensitivity should have increased when the eye was held in one position.

Explorative Saccade Training

Explorative Saccade Training was developed to train patients to make exploratory saccades without head movement in the area of the visual field which has been lost, and sometimes may be referred to as Scanning Therapy (Koons et al., 2010). Many methods have been developed for performing this type of therapy, most of which are performed by an occupational therapists, and the individual patient. These patients learn to apply these search strategies to everyday tasks.

How it works

Explorative Saccade Training begins with the development of large saccades, followed by the development of smaller saccades. The patient should start to try to improve the speed of these saccades in order to develop a natural flow to their visual perception. Once this has been accomplished, the patient should try and attempt to integrate this system into everyday life. Some activities which may help develop large saccades include head and eye shifts, descriptive walking, different search strategies, large table cars, and even games such as WII Tennis (Roth et al., 2009). Small saccades can be improved upon by pen and paper search, last letter cancellation for Right hemianopsia, computerized trainers, and even puzzles (Roth et al., 2009).

Results

Explorative Saccade Training improves exploratory behavior, and enhances performance of digit search tasks (Roth et al., 2009). Lasting effects are shown for improvement of natural search performance on the patients’ blind side after only about six weeks of training (Windsor et al., n.d); with scanning improvements of up to 35° into the affected side of vision (Koons et al., 2010). An advantage Explorative Saccade Training is that it has been shown to be affective for patients who have been living with hemianopsia for many years and have had the time to come up with their own adaptive strategies to deal with their vision (Roth et al., 2009). Even with the benefits to patients who have had hemianopsia for a long time, Explorative Saccade Training is most effective with younger patients who have been recently diagnosed (Roth et al., 2009). A downside to this therapy is that reading speed is not improved (Roth et al., 2009). Also, since Explorative Saccade Training uses activation eye-movement exploration, asymmetry has been seen in patients on their blind side (Roth et al., 2009). Overall patients should experience significant improvements in performing activities of daily life.

Optical Visual Span Expanders

Optical Visual Span Expanders are yet another option for patients with hemianopsia. The main idea behind this treatment is that the patients’ glasses have a special prism mounted on them to help increase the visual field (Windsor et al., n.d.). The patient must combine the image from the prism with the image they receive from the rest of the visual field in order to perceive a larger visual field (Windsor et al., n.d.).

Operation

There are three main varieties of expanders, which have all been derived from Fresnel prisms: the Gottlieb Visual Field Awareness System, the Chadwick hemianopsia lens, and the EP horizontal lens.

Gottlieb Visual Field Awareness System

The Gottlieb System (Figure 1) uses a circular prism mounted on the lens of the affected eye with the base pointing in the direction of the affected visual field. Ideally, small wedge prisms are used at 18.5 prism diopters (Gottlieb, 1988). This allows for improved optics without severe spatial distortion or reduced resolution (Gottlieb, 1988). The prisms can be coated to suit the prescribed power of the patients’ glasses.

Chadwick hemianopsia lens

Chadwick hemianopsia lens (Figure 2) was developed by Michael Onufryuk of Rochester, New York (Windsor et al., n.d.). Along with the Gottlieb system, this is a monocular system. The prism used is mounted on the periphery of the affected side, taking up the entire outer twenty percent (roughly) of the glasses lens (Windsor et al., n.d.). The glasses used to mount these lenses should have relatively small frames, in order to control the thickness of the glasses (Windsor et al., n.d.). The larger the frame, the thicker the Chadwick lens must be in order to achieve the same effect.

EP horizontal lens

The EP (Peli) horizontal lens (Figure 3) was developed by Eli Peli, a professor at Harvard in 1999 (Windsor et al., n.d.). These lenses are mounted in the center of one lens of the patients’ glasses, either the left or right lens to coincide with the side of vision which is affected. The patient may be prescribed with one or two EP lenses at 57 diopters ("Chadwick optical Inc.," 2011), mounting one above the line of sight or one below the line of sight, 12 mm apart from one another (Bowers et al., 2008). Due to placement, the eye can freely scan the horizontal. The EP segments shift the image into the patient's unimpaired side of the visual field, and the brain fills in the rest of the perception (Bowers et al., 2008).

Results

All three lenses have shown improvement of the perception of the visual field. Overall, experience has shown that younger patients tend to adapt to the expanders better than older patients (Windsor et al., n.d). Not all patients will benefit from Optical Visual Span expanders, as some patients are so well adapted to their visual field loss that the expanders are not necessary for them to be high functioning (Windsor et al., n.d).. The Gottlieb Visual Field Awareness System and the Chadwick hemianopsia Lens have significantly higher contrast and brightness than the EP lens (Windsor et al., n.d). The Gottlieb Visual Field Awareness System may not be ideal for patients with severe cognitive impairments, since the patient must alternate viewing between the prism and the rest of the lens. Also, due to the alternation between the prism and the rest of the lens, perception can be quite jumpy (Windsor et al., n.d). The innovation of EP Horizontal Lens has taken away this problem, and allows the patient to no longer have to scan to the edge of the visual field to jump between the two perceptions (Bowers et al., 2008). However, as stated above, the EP lens does sacrifice contrast so that the images from the expander and visual field can be integrated better together (Windsor et al., n.d). EP lenses also use a higher power, giving the patient about 30° of visual expansion, more than the other types of expanders (Figure 4.) ("Chadwick optical inc.," 2011).

-- Jytdog (talk) 06:13, 1 October 2017 (UTC)