Sunday, July 27, 2014

Strabismus, visual field loss and visual-spatial neglect

"Right after I lost vision in my eye, I was so bad at walking that I ran into a girl eating ice cream, and knocked her cone out of her hand. She screamed: ‘Are you blind!?!?’ I turned to her and said: ‘I am blind actually, I’m so sorry, I’ll buy you a new cone.’ And she said: ‘Oh my God! I’m so sorry! Don’t worry! It’s no problem at all! I’ll buy another one.’ So we walked into the ice cream store together, and the clerk said: ‘I heard the whole thing. Ice cream is free.’"

This little charming story by 'Humans of New York' reminded me of the many times I have bumped into people and objects on my left side. For instance, as a kid I was frequently punished for accidently breaking things or 'not behaving'. As a teenager I remember one incident that occurred while I was trying to navigate a busy street. By mistake I bumped into a young woman with my shoulder without bad intentions, immediately apologizing. I quickly left the scene before her Alfa-male boyfriend was ready to punch me. Ha!

On another occasion I quite simply hit the metal detector at the airport with my left side while trying to walk through it. Apparently regulations state that anyone walking onto the detector has to be frisked in any case. Another pleasant left side neglect experience!

Even now, having much less suppression of my left eye, having a wider visual field and being relatively more binocular and bilateral, I frequently bump into objects on my left side. Just yesterday I hit a door post with my shoulder while running into a room. Ouchie.

Fortunately, as it happens, I just read the 'Evaluation and Treatment of Visual Field Loss and Visual-Spatial Neglect' chapter of the book 'Vision Rehabilitation'! Just when I thought I had read all about my life in the Spatial Vision (!) chapter, or at least about what has been missing from it, those vision nerd authors pulled me back in! -------- (Expect a book review, people. Expect it!)

Visual field loss

The most known causes for visual field loss are eye disease (see picture) or damage of some sort to one or both of the eyes. This is the case for the gentleman featured above.

 Often, however, visual field loss can present more subtly on a cortical level. Cortical vision loss can occur developmentally or due to various kinds of brain injury. Whatever the cause of the visual field loss, the symptoms and the suffering associated are similar. Because of the complexity of the brain, cortical vision loss is very personal and presents itself differently in each patient.

This image gives you an idea of how various cortical disturbances can lead to
different types of visual field loss 
Measurements of visual field loss are performed following the quadrant schematic. I’m not going to get into all the possible types of vision loss but it is important to know that various types of visual training, sometimes including the use of prisms, are available to improve visual brain function. Even when it is impossible to recover vision in a certain field, training can systematically improve adaptation by optimizing residual abilities. Relearned environment scanning can avoid future accidents, elevate quality of life and increase independence.

One very interesting aspect about visual field loss is that some patients lose conscious awareness of what is seen in a field due to damage to the primary visual pathway or the visual cortex but can still intercept valuable visual information through unconscious visual processing. This is called blindsight. In case of blind sight a partially blind patient might be able to perform saccading or pointing to an object in the blind field, be able to use information from the blind field to better execute perceptual tasks in the intact field or even be able to ‘guess’ features of an object in the blind field at much higher rates than chance. There is indeed a neurological basis for these peculiar skills. Even more interesting for the cause of vision rehabilitation is that these latent abilities can be trained to eg. improve maneuvering. --- Also check out this video on blindsight

Visual-spatial neglect

Many patients with visual field loss are aware of the fact that they have lost vision in a certain field yet some aren’t. That’s where things get even more tricky. Some patients with visual-spatial neglect are in some sort of ‘denial’ about their missing visual field. It simply doesn’t exist in their mind. People with visual-spatial neglect think they have an accurate representation of their environment and don’t really feel the need to compensate for their visual deficit. This too can present in a number of degrees. There’s personal, peripersonal or extrapersonal neglect. People with personal neglect do not only ignore half of their visual space but also ignore half of their own body image to a greater or lesser extent. Peripersonal neglect indicates the neglect of space within arm’s reach and extrapersonal neglect adds the neglect of space beyond arm’s reach.

The presence of moderate to severe visual-spatial neglect can disrupt a variety of daily activities such as dressing, eating, reading, writing, walking, returning to work, and driving. Patients with left visual-spatial neglect will typically veer to the left when walking or bump their left shoulder on the doorframe. (BINGO) -- Vision Rehabilitation

Since most eye doctors aren’t even capable of detecting or treating any brain based vision dysfunctions which are often literally staring them in the face, it is no surprise visual-spatial neglect often goes undetected. In my case bumping my shoulder and what seem minor mishaps were less worrisome to me than, say, double vision. Nonetheless, many with more severe visual-spatial neglect, but without associated motor deficits, go undiagnosed and untreated following stroke or TBI.

They may be misdiagnosed as having dementia, as family and caretakers are unable to understand why a person might end up with their pants on backward (when they put them on, they only acknowledged one leg, so there was no frontward or backward choice), or why they forget to finish a task or put away tools. It is not always as easy as noticing that they do not finish food on one side of their plate. Patients with visual-spatial neglect are frequently misdiagnosed as having visual field deficits by vision care practitioners who are unaware of the possible diagnosis or visual-spatial neglect. -- Vision Rehabilitation

Indeed, it is not always easy to determine whether a patient has visual field loss, visual-spatial neglect or both! That’s why appropriate testing has to be done in order to get answers to those questions and get appropriate treatment.

Visual field loss and visual-spatial neglect in strabismic and amblyopic patients

As for the connection between strabismus, visual field loss and visual-spatial neglect, it is clear there must be a considerable incidence of neglect among strabismics. Suppression of part of the visual field to deal with misaligned eyes can be seen as self-induced visual field loss. This suppression of one of the eyes, be it permanently or alternately, leads to a reduced field of vision. In my case it is no surprise I bump into doors with my left shoulder as my left eye was traditionally the ‘lazy’ one. Even now with a field of vision that is as binocular as ever, I still tend to suppress peripheral vision coming from my left eye in more stressful situations requiring focus. Clearly this also affects my body image as I seem to be less likely to take into account the existence of my left side while moving.

The most common location for the lesion causing left spatial inattention is thought to be the right parietal lobe. In most patients, corresponding lesion to the left parietal lobe causes mild or transient visual-spatial neglect of the right space. It has been hypothesized that the right hemisphere modulates attention to both hemi-fields, where the left hemisphere modulates attention mainly to the right hemi-field only. Thus, damage to the left parietal lobe may cause an imbalance in allocation of attention from the pre-injury state, but damage to the right parietal lobe, common in middle cerebral artery infarct or aneurysm, causes marked visual-spatial neglect, as this is the major cortical substrate for orienting and allocating selective attention to the left hemifield. (!) In very young children, this hemispheric dominance for spatial attention is not yet fully developed (!) as evidenced by line-bisection tasks at age 4-5 years (!). Children show adult-like bisection with a slight leftward bias in bisection by 7-8 years of age. -- Vision Rehabilitation

That solves the mystery then. At the age of three my bispherical development went array and I developed amblyopia, strabismus and visual-spatial neglect. In addition to the distorted body map and frequently missing visual fields, unreliable alignment of the visual axes produces conflicting input to answer the basic ‘where am I?’ and ‘where is it?’ questions. Answering those two questions are the two primary objectives of the visual system preceding the ‘What is it?’ and the ‘What to do about it?’ questions. In developmental strabismus, neglect might in fact be a way of dealing with these conflicting inputs. To resolve the conflict one side has to foot the bill. That’s why, at this point in my rehabilitation, I am putting a lot of emphasis on not only aligning the eyes but also paying attention to my entire visual field and doing activities that promote bilateralism. Again it seems to come down to the magic three: the integration of visual input, vestibular input (balance) and proprioceptive input (self awareness and body image).

I'll try to be more practical about what I actually DO to integrate those types of sensory input next time. :)

Friday, July 11, 2014

Session 75: Trusting yourself

I had another training session on Tuesday. I did more 'feeling depth' in anaglyph pictures by reaching out for them with my fingers. It's very exciting how that keeps working. This practice also enhances physiological diplopia. That makes sense given that this ability is based on positioning your eyes correctly, seeing the object of interest single and everything after it double. When my hand is singled out and the object of interest is singled out, that's where it should theoretically be in space. It isn't really, because it's just an anaglyph stereogram of course. That sounds pretty obvious but it wasn't when I first started doing this exercise. It takes accuracy.

I'm so astonished by the fact that this is starting to work out for me. My training optometrist/vision therapist Sofie (as opposed to the supervising optometrist who does the check-ups) said: "Yeah, just trust yourself. That's how it should be." After all these years of double vision, it's hard to trust my vision. The illusion of seeing is believing is gone. It feels like it was all just one crazy conspiracy designed to screw with me. So I guess trusting myself would be a good start. In this spirit, my brain is finally starting to interpret the normal alignment of the visual axes. Sweet.

Of the supervising optometrist I already knew from the very first meeting he thought my case was hopeless and I should not even start training, but Sofie had never said this with so many words.  She'd always been patient. For the first time she now admitted: "I never thought you would ever get to this stage of correctly interpreting stereograms by reaching out for them." There's always been progress but this new feat is very outspoken. It's added functionality and that is what we have been laying the groundwork for all along. I like it. It's like the first time you used WiFi. It's awesome and incredible, yet it's 'normal'.

Earlier, when listening to the book 'Phantoms in the Brain', I was struck by an anecdote very similar or related to using fingers to sense depth and develop binocular depth perception.

"... Many stroke patients, like Bill, with dyscalculia also have an associated brain disorder called finger agnosia: They can no longer name which finger the neurologist is pointing to or touching. Is it a complete coincidence that both arithmetic operations and finger naming occupy adjacent brain regions, or does it have something to do with the fact that we all learn to count by using our fingers in early childhood? The observation that in some of these patients one function can be retained (naming fingers ) while the other ( adding and subtracting) is gone doesn't negate the argument that these two might be closely linked and occupy the same anatomical niche in the brain. It's possible , for instance, that the two functions are laid down in close proximity and were dependent on each other during the learning phase, but in the adult each function can survive without the other. In other words, a child may need to wiggle his or her fingers subconsciously while counting, whereas you and I may not need to do so. ..."
V. S. Ramachandran, Sandra Blakeslee - Phantoms in the Brain: Probing the Mysteries of the Human Mind page 19

This excerpt demonstrates the intimate interaction of seemingly unrelated neurological functions during developmental processes. Body image, (ocular) movement, counting, seeing, whatever... They all cross contaminate each other and create synergies. Right now I have to use my fingers to judge depth in a similar fashion as a kid learning how to count with his fingers. As I'll develop further and my vision matures, dependence on finger reference will decline. For now however, it's all still highly connected. That's why it's obvious that if I want to see better, the movement of my eyes and their integration in a moving body will have to be perfected further. Nonetheless, it's not only about getting both eyes to work together. It's about getting the two sides of the body, notably the two brain hemispheres, to work together. That's a tough job and that's why I'm tired a lot of the time. Unlike a normal job, this job goes on every waking hour. Even though it's exhausting, I'm very excited about it. The elimination of Convergence Insufficiency and the integration of balance, proprioception and other senses are now entering a critical phase.

In order to integrate my visual streams, vestibular system and proprioception, I'm trying to move a moderate amount every day. Biking, walking, two-footed football juggling, ... Not brute force movement, but activities that emphasize (eye) movement, balance and taking in the environment. It makes me kind of dull and tired afterwards as my visual accuracy diminishes but it's beneficial in the long haul. That's training. Stress yourself, get a little worse and tired and then get better. In contrast to the twenty years that have come before, this time there is a clear plan and a road to follow. My eyes have never been on the verge of permanently aligning themselves, making it possible to integrate all these factors for the first time since I was three years old. If all these sensory input streams start completing each other instead of competing with each other, I will be set up for life.

More about sensory integration over the next few weeks and months!

Thursday, July 3, 2014

Setting goals for July 2015

Much of VT comes down to setting small but attainable goals for yourself and then reaching them. Then doing that again, and again, and again. Three years ago a goal would be 'any reduction of the strabismus angle is a win'. So the first two years I would systematically halve my strabismus angle until I saw my first single image in years. After that I would have to solidify by increasing binocular motility and improving my vestibulo-ocular reflex (VOR) so single vision can be sustained while moving. That's what I've been doing the last year and a half.  Managing the drama, engineering my own brain and putting more wood behind fewer arrows seems to be paying off. So far so good.

Here we are, July 2014. What will be my goals for July 2015?

- Eliminate Convergence Insufficiency and Divergence Insufficiency. My viewing for mid range distances between 2m to 10m is getting more and more comfortable. That's why driving is not thát taxing anymore. I'm not too worried anymore of running out of energy behind the wheel and relapse into double vision. I'm not venturing any road trips yet but at least I can drive somewhere for 30 minutes, enjoy an activity and drive back without going to my limit. Good start.

What remains to be conquered are the very short and, albeit less urgent, long distances. Most of all, I want to get rid of my Convergence Insufficiency by next summer. At this moment reading is still a problem, along with computer work and even using a cell phone.

Two days ago my cell phone died and I had to buy and configure a new one. It's not very complicated but it's just a tough convergence job. That's just one example. Of course not being able to read with ease leaves one stranded on a much broader level. Reading should be a basic skill or you are left to the wolves. Even for someone as well-informed as me it's easy to get worked up and frustrated about this inability to accomplish 'easy' tasks without great physical discomfort. Fortunately, I know exactly what's wrong and I'm very aware of what I have to do to fix it, namely be patient and work on it gradually. Achieving comfortable reading will be a major liberation.

- Be able to seamlessly use spherical flippers up to +-2 and prism flippers up to 4 diopters. My ultimate ambition is to be able to do this even while bar reading. Bar reading, c'est mon dada.

These flippers make tasks artificially hard and require great visual flexibility. If you can handle these flippers while doing all kinds of visual tasks your visual system is working quite 'effortlessly'. If I would manage to eliminate the CI and handle these stressors, my afferent visual system will be strong enough to supply the visual cortex with a robust and high quality visual information stream. THAT'S THE DREAM, DUDE! Hahaha. No seriously! Since stereovision is first generated at the level of the visual cortex, it needs to be supplied well. If the afferent pipelines to the visual cortex can be firmly established, the supply of solid visual information will broaden my binocular visual field of focus (as opposed to tunnel vision) and hopefully generate some stereo. Then we can finish and solidify the process by further strengthening the link with the dorsal 'where and how' stream and the ventral 'what' stream. These visual improvements will in turn supply the motor side of things with more accurate information to base (eye) movement upon. Once that happens the downward cycle has been turned into an upward one.

- Stereovision
If I'm lucky achieving the first two goals will lead to this result. The magic might just be around the corner.

- 75kg
I used to weigh 73kg. For the last three years I've been stuck at 68kg after losing a lot of weight due to circumstances. Nowadays I'm entering the seventies again but I need more reserves, especially since 73kg was on the skinny side of the spectrum already considering my height. I'm eating a lot of good food and staying fairly calm so I should just continue to gain weight from now on. I think we've had the worst.

- Running 5K under 20 minutes again
Accomplishing the aforementioned goals will be a tough job. Even if it would be accomplished by December 2015 rather than July 2015, I'd still be happy! On the other hand, if it would go unexpectedly swell and it would work out faster than I'd hoped, I'd like to participate in a 5K run again. A month ago I ran 5K after a long period of inactivity and I did it in 22min50'. My biggest problem while running was vision. Yes, that's right! By the end of my run I was getting motion sick for lack of visual stability. I started closing my eyes during the final patches of my run and that felt much better! When I get carsick in the backseat, I also close my eyes. For the moment, that's the best way to eliminate the incongruity between visual and other sensory input.
"The intrinsic role of vision in counterbalancing gravitational forces and in visually guided movement is reflected in clinical tests of standing and walking balance. Separate scores for times executed with eyes open and eyes closed help differentiate the contributions of visual input from the somatosensory and vestibular input. Under normal circumstances, the ability to offset postural sway is significantly better with eyes open as compared with eyes closed. A patient with ABI who has compromised antigravity processing due to visual imbalance will have little difference in their ability to maintain balance with eyes open versus eyes closed. When vision is interfering with, rahter than supporting balance, the patient may even initially exhibit better balance with eyes closed as compared with eyes open." - Vision Rehabilitation

As a 14 year old kid I'd run 5K in 18min50. If it weren't for all this ophthalmology and surgery nonsense, my performance would be peaking right now. I honestly think that if I can accomplish the above goals, I'll just go back to 'my natural state' and run it in under 20 minutes again.

Many of these goals are actually not separate goals. Many of them would be happy consequences of increased control of my vision. Improved visual enjoyment, reading, productivity, sports performance, ...  Continuing to develop my vision is the lever to make all of this happen.

I still believe these vision problems are just a bump in the road. A bump maintained by people who have a stake in it. Everyone, including my behavioral optometrist, had written me off but nowadays it seems I'm considered a 'feasible case'. We've already done the impossible so I'd like to finish by doing the possible. :)