Update
Motivated by the launch of the Eye Guide MC wearable device for Parkinson’s Disease, I have updated this article, originally published September 2017, with some more information about the role of dopamine in the eye, and also about the emerging field of Neuro-optometrics.
Indeed, in addition to the breath and the muscles of the inner ear, the eyes represent another direct portal into the Autonomic Nervous System, with pragmatic possibilities for progressive symptom reduction. For example, in a recent episode of the Huberman Lab podcast, Prof. Andrew Huberman stated that stimulating/expanding peripheral vision can immediately increase range of motion and hence motor control of the body.
As discussed in the original article below, the eyes also appear to be linked to the dopaminergic systems of the brain. This has now been practically demonstrated by a fellow person with Parkinson's Disease, Sandra McDonough, who has invented a simple wearable device which constantly stimulates her peripheral vision and vestibular system at the same time. The Eye Guide MC website includes a video demonstrating that when Sandra wears this device, her tremors stop immediately, and she can walk normally, without the standard shuffling gait associated with PD, which she lapses back into when she removes it. Recently, this device has been launched to the market, with the hope it can benefit many more people with PD.
I have also previously found that I can stave off the wear off of a dose of dopamine supplementing PD drugs by doing eye intensive work, especially if it also includes hand eye co-ordination, writing being an example. However, once I stop doing the focussed work, the symptoms then become suddenly apparent again. This too illustrates a link between the eyes and dopamine systems in the brain.
Indeed, very direct scientific evidence now exists for the links between Parkinson’s Disease, dopamine, and the eyes, as discussed in the scientific journal paper
Neurochemical Systems of the Retina Involved in the Control of Movement.
Here are some abridged notes from the article.
"Dopamine (DA), serotonin (5-HT), and melatonin (MEL) occur naturally in mammalian retina."
"The retina may exert control over deep brain function and may be importantly involved in the [cause], progression, and treatment of disorders such as Parkinson’s disease (PD). "
"...study was undertaken to determine how retinal dopamine (DA), serotonin (5-HT), and melatonin (MEL) neurotransmitter systems might be involved in the control of movement . Results illustrate that specific retinal neurotransmitter systems participate in the normal control of bodily motor function. Retina is functionally linked to nigro-striatal dopamine (NSD) system control over motor function: there is a neurological system running between the retina and the pineal gland that communicates with crucial hypothalamic and midbrain structures..."
"...injection of [tiny] quantities of anti-Parkinsonian drugs into the eye can restore impaired NSD system function. The observed behavioral recovery occurs even though the variables of anatomical distance and compartmentalization of the retina render the two events anatomically unrelated...a deeper examination of both clinical and experimental manifestations of this disease reveal that impaired visual function is shared and that dopamine (DA) deficiency of the retina is, in fact, a bi-product of the disease as well..."
"..While the role of the NSD system in PD sits as the core proposition upon which the entire arsenal for treating this disease has been developed, this presents problems with interpretation since DA deficiency in the retina and NSD system occur together. At the very least, to imply cause and effect, good scientific procedure would dictate that retinal and NSD involvement would each have to be studied individually to determine their participation in the possible sequelae of events underlying this disorder."
Another very intriguing article I read recently details how specially designed glasses can improve trauma symptoms and other issues. We already know the link with eyes and trauma exists through the success of EMDR - Eye Movement Desensitisation Reprocessing - based therapies, but this takes these concepts much further.
"Use of therapeutic 'brain' eyeglasses to modify the frequency, amount and direction of light on the retina can often help accelerate recovery from symptoms of brain injury or chronic stress levels. The glasses also can sometimes improve patient comfort and range of tolerance to environmental changes and decrease hypersensitivity to sensory stimuli."
"Research has demonstrated the retina is a piece of brain tissue that is part of our body’s central nervous system. It not only sends the brain environmental signals obtained through eyesight, but also registers luminance levels (external light) dispersed across the retina. Concurrently, the retina receives feedback signals from the body through informational pathways in the brain. This continuing process of feeding environmental signals forward for further brain processing while receiving feedback signals from various brain structures makes the retina a two-way portal for influencing and monitoring body functions and thought processes, primarily below the level of consciousness"
"The role of neuro-optometric rehabilitation as a non-invasive approach to brain function and visual and neurological disorders continues growing in importance. Using different lenses, prisms, mirrors, filters and other optometric interventions to stimulate the retina allows eye professionals now trained in advanced neuro-optometric techniques to evaluate possible hidden dysfunctions in mind-eye connections and neurologic disruptions that can impact a person".
Introduction (from September 2017)
I've been researching eye problems, and the role of vision, in Parkinson's Disease. I discovered much information which is both profound and unfamiliar, but very important for people with Parkinson's (PwP) to grasp. As usual, I have self-experimented with ideas developed from these concepts, and have indeed found practical solutions which are helping me. I am therefore now sharing this full report on the subject, in case it is helpful to others too.
Eye Problems and Vision Symptoms of Parkinson's Disease
The following is based on the major scientific review article:
The retina in Parkinson's disease.
A number of studies have found strong evidence for significant visual problems in the PwP population. These eye issues tend to worsen when a PwP is an "off" state, but improve again when they are "on" due to l-dopa supplementation. Visual problems that are strongly correlated with PD include:
visual acuity;
contrast sensitivity;
color vision;
motion perception;
visual disturbances, hallucinations.
Sufficient evidence exists that these can be linked to dopamine deficiencies in the retina, and cannot all be ascribed to just being age related or to the cognitive decline (brain damage) of PD. Indeed, physical and structural changes to the eye and retina are also implicated in PD, as determined by a number of modern eye examination methods.
"The Parkinsonian retina may therefore exist in an inappropriately dark-adapted ([ow contrast vision] state. This, in turn, [leads] to lower spatial and temporal resolving potential and an ultimate impact on visual acuity, and colour perception. Evidence is now emerging that visual dysfunction directly contributes to [the] more traditional ‘motor’ complications of PD "
The Role of Dopamine in the Eye
Note in the above, I emphasized dopamine and its shortage is important in the eye. For most PwP, this link between dopamine and vision will come as unexpected, because, while we are informed at diagnosis that our PD is due to dead dopamine producing cells in a small part of our brains called the Substantia Nigra, we are typically not being properly informed that the dopamine deficiency issues are much more widespread, including in the gut
THE GUT, DIGESTIVE SYSTEM AND PARKINSON'S DISEASE,
but also in the retina too.
Indeed, according to the scientific review article mentioned above, the role of neurotransmitters in the eye has been known since at least the 1960s, when dopamine producing cells - dopaminergic neurons - were found in the retinas of animals, and later in humans. Since then, several types of dopaminergic neurons have been discovered in the retina and it is now known their functions are strongly affected by light levels. They have a pivotal role in the processing of visual information through the retina. Different types of photo-receptors in the eye can either be switched on or off due to the concentration of dopamine in the retina.
It has also been found that there is a significant diurnal variation in levels of dopamine in the eye, with higher levels in the day and lower levels at night, and hence time of day and even the weather/seasons impact on the complex feedback between the functions of the photo-receptors and dopamine concentration in the visual system - and ultimately on PD symptoms.
"This circadian rhythm is in counterphase with the retinal concentrations of melatonin, and indeed, dopamine and melatonin have mutually inhibitory effects on each other's production—acting as a ‘biological clock’ for the retina. Because of this light-sensitive variation in dopamine concentration, it has been postulated that dopamine plays a role in the transition from a dark- to light-adapted state".
Dopamine is therefore important in the eye at multiple levels, and helps to control the processing of visual information in a complex way, stimulating some photo-receptors and inhibiting others. Neuro-chemical measurements found evidence for depleted levels of dopamine in the eyes of PwP. Post-mortem studies of PwP indicated that the level of dopamine in the retina after death was much lower if the person had not taken any l-dopa medications within about a day of the death, as compared to those who had taken their last l-dopa pill more recently.
Epithelial Layers in the Eye
In my article,
LEAKY BLOOD BRAIN BARRIER AND PARKINSON'S DISEASE,
we discussed how leakage issues with epithelial cell membranes, a special form of protective and moisturizing tissue, are prevalent in PD. The malfunctions of these epithelial layers are due, for example, to chronic dehydration, nutritional deficits, infection. Places where epithelial layers occur include in the skin, the gut lining, the blood brain barrier, the mouth and sinuses - all of which are implicated in the major and common symptoms of PD.
Such epithelial layers also occur in the eye. For example the retina-blood barrier, which has functions including, but not limited to, light absorption, nutrient transport from blood to eye, secretion and immune response. These retinal cells, like those in the Substantia Nigra, are meloncytes - they are black. The Conjunctiva also contain epithelial cells, lining the inside of the eyelids and covering the white of the eye. Conjunctiva help lubricate the eye with mucous and tears, with immune surveillance, and protection of the eye against microbes. Given that problems with epithelial layers are common in PD, it is highly probable that malfunctions of the eye's epithelial cells are also widespread in PwP. Indeed, dry eyes, bloodshot eyes and eye strain problems are very common, for example.
These epithelial layers and their associated mucous membranes also appear to be places where natural microbiomes are being found to have essential roles in our health. The role of imbalanced gut bacteria profiles in particular is coming to the fore in the treatment of Parkinson's Disease, for example. Interesting, it is now also emerging that the eye also has its own microbiome, and imbalances in the types of bacteria here too can affect health or be used as indicator for problems.
Compounding Side-Effects of Parkinson's Drugs
Unfortunately, according to Drugs.com, many of the common PD medications can exacerbate eye problems in PwP. Possible side-effects related to the eye are listed as:
ropinerole: "double vision or other eye or vision problems";
sinemet: "inability to move the eyes; increased blinking or spasms of the eyelid; large, hive-like swelling on the eyelids; blurred vision; double vision";
amantadine: "irritation and swelling of the eye; decreased vision or any change in vision";
Interventions (nutritional support, movement therapies, mental health support, stress management techniques, etc.) which can help minimize PD drug burden may therefore be appropriate for helping to keep eyes as healthy as possible.
What Can We Do?
Armed with the above knowledge, is there anything we can do about it? I have been implementing various strategies to see if these help and I do strongly believe these are cumulatively benefitting me and reducing my symptoms over time.
The main thrust is to look after our eye health. In this regard, many of the strategies I discussed for blood-brain-barrier health follow over directly: keeping our bodies very well hydrated; avoiding inflammation and stress as best we can; making sure our nutritional support is maximized. In terms of nutrition specifically for the eyes, Dr Axe recommends two special anti-oxidants, Lutein (the "eye vitamin") and Zeaxanthin, as well as Zinc and Omega 3 supplementation too. I have been taking all of these for several weeks and do feel my eyes are less sore and dry now. The A, C, E vitamins are also recommended by Dr Axe.
Like most of the rest of our body parts, exercising the eyes and visual brain functions will also be most important to maintaining their health, see:
EYE EXERCISES AND PARKINSON'S DISEASE.
In this regards, I also recommend the work of Dr Eric Cobb of Zhealth Education. Dr Cobb gives a lot of free information on his blog about vision health and provides powerful, but quick exercises to practice daily, as well as running a commercial "vision gym" for pro-athletes. Importantly, Dr Cobb shows us just how - unexpectedly - important the eyes and vision are in direct connection to movement and stress reduction: hence eye exercise has very profound relevance for people with PD. I also recommend stimulation of the cranial nerves which are responsible for the muscles that move the eyes:
THE CRANIAL NERVES AND PARKINSON'S DISEASE.
Bright light therapy continues to be one of the most impactful and safe, long term answers to reducing PD symptoms, and I hope the above article helps to explain why I am such a proponent in strategic light therapy for Parkinson's and strongly recommend PwP to consider this too: