“And suddenly I realized, I couldn’t see anymore!”

In all the years of my clinical training and work as clinical neuropsychologist I heard this or similar statements many, many times. I always followed-up with the question: “And then, what did you do?”

And the majority of my patients answered: “Nothing!”

Well “nothing” was not perfectly correct in most of the cases. But what they wanted to tell me is that after they went to the GP and after that to the ophthalmologist and some even further to the neurologist (or the other way round), they came home with more or less the same conclusion: “You had a stroke, now you are blind on one side and there is nothing we can do about it!” 

Out of desperation some bought new glasses, obviously with no effect. Some discussed with their GP to prescribe new or change some old medication to stabilize their blood pressure, their diabetes or their cholesterol (good idea if you have these risk factors!). Some ended up adding Ginkgo or similar nutrients as food supplements. And a few lucky ones ended up with orthoptists1 and/or in specialized rehabilitation clinics to train with physio-, occupational therapist or neuropsychologists on compensating some of their problems. 

How big is the problem?

Up to 30% of all stroke survivors suffer from some sort of visual deficit. These deficits can vary from slightly blurred vision, blind spots somewhere in the visual field, up to partial, half (commonly know as hemianop(s)ia) or, in very severe cases, complete loss of all vision. 

With the visual deficits, other problems can co-occur like reading problems, insecurity in walking, stumbling or bumping into objects on the street, difficulties recognizing faces, finding objects, and many more. Depending on the size and location of the stroke in the brain, some patients additionally suffer from even more complex neuro-cognitive disorders like visual pseudo-hallucinations2 or visual neglect accompanied by (mostly) short-term memory problems3.

And lastly not to forget the economic and psycho-social implications that visual deficits can have. Unemployment, lack of understanding of the family members of the handicaps, social isolation, frustration, anxieties and depression are unfortunately very common challenges for the patients and the families. 

Is there really nothing we can do about it?

The answer is clearly “Nay”! Our brain has amazing capacities to recover, reconnect, learn and re-learn. And we as individuals and families can always learn to adapt to new situations. But to set your expectations straight: a full recovery is unfortunately nothing anyone can promise you. And life will likely not be the same anymore as it was before. But as time goes by everybody can learn that this is ok. 

Therapeutic strategies

Substitution

If my car breaks, I buy a new one or I take public transportation. That is, in simple terms, substituting one thing by another. As long as I get from point A to point B. With vision loss it’s unfortunately a bit more complicated. However, ask your ophthalmologist for a prescription for glasses with “prism-correction”.

The theory behind is, that specific lenses change the angle of the light falling into your eye therefore projecting the image on a different spot on your retina and so a different part of your brain, not the one damaged by the stroke, can process the visual information. So lets say, you have a vision loss on the right side of your visual field (that includes the right side on both eyes, not only the right eye), the prism would project parts of the right visual field into your left visual field. That sounds super complicated.

Glasses with prisms used for homonymous hemianopia rehabilitation.

But imagine you sit in front of your computer screen and in the left half of the screen you read a newspaper and in the right you watch a youtube video. Now, for some reason the right side of you screen gets damaged. Not cool.

So what can you do? Easy, you take the tab with the youtube video and drag it to the left side. E Voilà. But you see already the disadvantages.

The part of the screen for the newspaper is much smaller, and on top you see the video, which might be disturbing for you because it’s not matching with the content of what you are reading. Bottom line, you can see both but with severe limitations. And that is exactly what many patients report that use prism corrected glasses.

Prism glasses:
Top: Glasses prescribed in the past consist of binocular sector prisms (Fresnel prisms), same on both eyes, placed with a base to the affected side. Visual field plots show schematic of (right side) scotoma in the homonymous hemianopia,

Left: in the left eye, Right: in binocular viewing.

Bottom: Prisms designed by Peli (2000) are worn only on one (affected side) eye. They are restricted to the upper and lower peripheral fields only and extend across the majority of the width of the lens. Visual field plots show visual field changes with a prism,>

Left: in prism-eye-only viewing and Right: in binocular viewing.

This type of one-eye-only prism extends the binocular visual field in HHA. (1)

Compensation

When people suffer from deficits in the visual field, most of the time the peripheral vision is affected. One way of compensating for this narrow visual field is to use fast and targeted eye movements in order to scan a broader area of the visual field. It’s basically like watching a tennis game. If you sit on one side of the court and you keep your eyes and head straight, you will only see the performance of one of the players.

If you want to see the whole action, you need to move your eyes and head. However since in our normal life we don’t have a ball to follow, we teach our patients in therapy with computer programs and other techniques to make quick and targeted eye movements to the impaired side of the visual field. So they can compensate for the deficit and scan a bigger range of the visual field. 

Restoration

This is the holy grail of rehabilitation. And since the discovery of neuroplasticity scientists all around the world try to figure out how to make damaged or new neurons grow, connect or reconnect all over the central and peripheral nervous system. For the visual system, there are unfortunately very few theories based on which treatments were developed. One broadly debated one is the “Residual Vision Activation Theory”. (2)

In short, this theory explains that because of the complexity of our visual system, specifically the part of our brain responsible for seeing, there are not only the two options, “seeing” or “blind”, but there are literally many shades of grey. It is not like in digital camera sensors, which show a black spot on the picture if the pixel (or the light cavity) is broken. The neurons in our brain are not working as single individual sensors but rather integrated into a huge network. Probably it is working much more like a spider web.

Imagine there is a big hole in the spider web and an insect flies right through it. Of course, right in the center of the hole, there is nothing left that could catch the insect, but the surrounding strings are so sensitive, that the wind the insect creates when it passes through the hole is enough to make the strings move a tiny little bit. So in the corner of the web, the spider will still detect that something has happened, not knowing exactly what. Now let’s exchange the spider web with a neural network, the hole with a stroke and the wind with an electrical impulse coming from the visual pathway (eye-retina-optical nerve to the cortex).

We also assume that based on neural plasticity, neurons can grow, re-connect or strengthen their connection when they are trained. So we “fire” as many electrical impulses as possible into the hole to stimulate the surrounding neurons – but of course not in the center of the hole where the impact is the lowest. And also not in the area where the “web” is fully intact. No need for that. Instead, we rather try to target exactly the border zone of the “hole” meaning the neurons at the border of the stroke which are still alive but partially disconnected from the total web. Studies have shown, that the more often we stimulate this area (of residual) vision, the stronger resp. the more sensitive to light they get.

So how do we do that? There are computer programs that present light dots, one after the other, distributed all over a computer screen. When the patient sees one dot, he presses a key. So the program recognizes where the patient can see and where he does not see. After some time we then know exactly the border of the blind area.  Then we have everything to start the training. The program starts giving light dots more frequently in this border zone. And again after many hours of training, in many patients, we can observe the border zone slowly moving into the blind area and therefore the visual field slowly expands. 

When does therapy make sense?

Studies have shown that patients could improve their vision with restoration training even years after the stroke had happened. But from my own experience I can tell that the sooner you start, the better the chances for improvements are. And therapy is not limited to substitution, compensation and restoration. (Neuro)Psychological therapy can help you to adapt to the new life circumstances. This goes way beyond a “glass-half-full attitude”. It’s about learning to accept, and if this is not possible learning how to deal with the frustration, to learn what can improve your quality of life and to find out about what you need in order to be able to go to bed at night and say: “I had a good day”. (1)

Can we expect any developments soon?

There are promising results from newer experiments that try to combine established therapeutic techniques with neuromodulation methods. Neuromodulation means modulating the activity of neurons in different ways, namely with chemical (medicine), electrical or magnetic stimulation. For the visual system transcranial alternating, direct and magnetic stimulation have been and are currently tested for their feasibility and efficiency on the recovery of visual system damage (3,4,5).

But unfortunately there are no clear treatment protocols established yet so only a few specialized clinics and centres are able to provide this still experimental treatment. 

The rewellio team is working hard to integrate all the therapeutic possibilities for visual impairments into our affordable, home training app and the tests of a beta version of our VISION training module are expected to start soon. 

So stay updated by subscribing to our newsletter.

Orthoptists are university-trained, allied health care practitioners, who specialize in disorders of eye movements and diagnostic procedures related to disorders of the eye and visual system.

2 Visual pseudo-hallucinations (also known as Charles-Bonnet Syndrome) are images our brain creates in the blind visual field basically to „auto fill“ the empty space or “auto correct” the reduced information that is processed in the brain. They can be as simple as flickering lights or as complex as whole „scenes“ of people. The main difference to psychotic hallucinations is hat the person does not believe that the images are real. But they are reportedly very disturbing for many patients.

3  The short-term memory problems co-occur in the majority of patients with visual problems, because the part in the brain responsible for vision is very close to the part of the brain responsible for storing new information. Both are supplied with blood from the same artery. Therefore a stroke in this artery can lead to damage in both areas.

Bibliography

    1. Grunda, T., Marsalek, P., & Sykorova, P. (2013)
      . Homonymous hemianopia and related visual defects: Restoration of vision after a stroke. Acta neurobiologiae experimentalis, 73(2), 237-249.
    2. B.A. Sabel, P. Henrich-Noack, A. Fedorov, C. Gall: Vision restoration after brain and retina damage: The “residual vision activation theory”. In: Progress in Brain Research. Band 192, 2011, S. 199–262, doi:10.1016/B978-0-444-53355-5.00013-0.
    3. Plow, E. B., Obretenova, S. N., Halko, M. A., Kenkel, S., Jackson, M. L., Pascual-Leone, A., & Merabet, L. B. (2011). Combining visual rehabilitative training and noninvasive brain stimulation to enhance visual function in patients with hemianopia: a comparative case study. PM&R, 3(9), 825-835. https://doi.org/10.1016/j.pmrj.2011.05.026
    4. Alber, R., Cardoso, A. M. G., & Nafee, T. (2015). Effecs of noninvasive brain stimulation in cerebral stroke related vision loss. Principles and Practice of Clinical Research, 1(2). https://www.researchgate.net/publication/283502692_Effects_of_noninvasive_brain_stimulation_in_cerebral_stroke_related_vision_loss
    5. Alber, R., Moser, H., Gall, C., & Sabel, B. A. (2017). Combined transcranial direct current stimulation and vision restoration training in subacute stroke rehabilitation: a pilot study. PM&R, 9(8), 787-794. https://doi.org/10.1016/j.pmrj.2016.12.003