Seeing The Brain Through The Eyes
A neurosurgeon at the University of Cape Town is pioneering a way to diagnose a brain condition through patients eyes.
Since ancient times, the eye has been seen as a portal to the innermost secrets of the human mind and body a window to the soul. Taking a more literal approach to this metaphorical truth, Dr Llewellyn Padayachy, a paediatric neurosurgeon at the University of Cape Town has spent the past five years or so researching a novel diagnostic method that uses ultrasound and the eye as a window to the brain.
What you do as a paediatric neurosurgeon is treat a condition called hydrocephalus more than anything else, Padayachy explains. And the sad thing is, a lot of the children we treat, without a doubt, present to us much later than they should.
More often than not, the reason for this is that the children come from impoverished rural areas, where the condition would not have been picked up in a primary healthcare clinic, due to a lack of resources.
While accurate data regarding the number of hydrocephalus cases on the African continent is sparse, conservative estimates put it at some 100 000 cases annually. In the United States, it affects about one million people in every stage of life: from infants to the elderly.
Undergoing this sort of procedure is highly traumatic for any patient and even more so for babies and young children.
Journey of discovery
From rural clinics to the final frontier
Story: Nadia Krige. Photo: Pexels, Pixabay.
Iris Is The Colorful Part
Behind the cornea are the iris, the pupil, and the anterior chamber. The iris is the colorful part of the eye. When we say a person has blue eyes, we really mean the person has blue irises! The iris has muscles attached to it that change its shape. This allows the iris to control how much light goes through the pupil .
The pupil is the black circle in the center of the iris, which is really an opening in the iris, and it lets light enter the eye. To see how this works, use a small flashlight to see how your eyes or a friend’s eyes respond to changes in brightness. The pupils will get smaller when the light shines near them and they’ll open wider when the light is gone.
The anterior chamber is the space between the cornea and the iris. This space is filled with a special transparent fluid that nourishes the eye and keeps it healthy.
Biometric Identification And Diagnosis Of Disease
The bifurcations and other physical characteristics of the inner retinal vascular network are known to vary among individuals, and these individual variances have been used for biometric identification and for early detection of the onset of disease. The mapping of vascular bifurcations is one of the basic steps in biometric identification. Results of such analyses of retinal blood vessel structure can be evaluated against the ground truth data of vascular bifurcations of retinal fundus images that are obtained from the DRIVE dataset. In addition, the classes of vessels of the DRIVE dataset have also been identified, and an automated method for accurate extraction of these bifurcations is also available. Changes in retinal blood circulation are seen with aging and exposure to air pollution, and may indicate cardiovascular diseases such as hypertension and atherosclerosis. Determining the equivalent width of arterioles and venules near the optic disc is also a widely used technique to identify cardiovascular risks.
The retina translates an optical image into neural impulses starting with the patterned excitation of the colour-sensitive pigments of its rods and cones, the retina’s . The excitation is processed by the neural system and various parts of the brain working in parallel to form a representation of the external environment in the brain.
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Lobes Of The Brain And What They Control
Each brain hemisphere has four sections, called lobes: frontal, parietal, temporal and occipital. Each lobe controls specific functions.
- Frontal lobe. The largest lobe of the brain, located in the front of the head, the frontal lobe is involved in personality characteristics, decision-making and movement. Recognition of smell usually involves parts of the frontal lobe. The frontal lobe contains Brocas area, which is associated with speech ability.
- Parietal lobe. The middle part of the brain, the parietal lobe helps a person identify objects and understand spatial relationships . The parietal lobe is also involved in interpreting pain and touch in the body. The parietal lobe houses Wernickes area, which helps the brain understand spoken language.
- Occipital lobe. The occipital lobe is the back part of the brain that is involved with vision.
- Temporal lobe. The sides of the brain, temporal lobes are involved in short-term memory, speech, musical rhythm and some degree of smell recognition.
S Of The Eye And Their Functions
There are several physical and chemical elements that make up the eye. The eye is linked together with the nervous system, which allows the brain to take in information from the eyes and make the appropriate decisions on how to act upon this information. The nerves must be kept in prime condition or the brain may start to receive false images, or you will not take in enough information to get an accurate perception of your environment.
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The Color System Of The Eye
Cone cells contain a pigment through which light must pass beforereaching the receptor. There are three pigments: One passes violet,with a wavelength of 430 nm one passes blue-green, with a wavelengthof 530 nm and the last pigment passes yellowish-green, with awavelength of 560 nm. In fact, these optical filters have filterskirts, meaning they pass light of other wavelengths, but with reducedsensitivity. Any monochromatic light actuallyactivates cone cells of multiple pigments, but at differentsensitivities. This also explains why we can see light with wavelengthsshorter than 430 nm, and longer than 560 nm.
No conecells, however, can truly perceive red. The closest we really get isyellowish-green. What we call red is really an opticalillusion, supplied by the brain by means of extrapolation. Oursensitivity to red is dramatically reduced compared to other colors,and our visual acuity in the red end of the spectrum is extremely bad.Everyone knows not to focus a projector using a redtest pattern. This is why the red gun in color-video equipment needsthe least resolution to be satisfactory .
Folk wisdom has many sayings about believing what you hear andbelieving what you see. The visual sense is just as prone to illusionas the auditory pathway, and equally filled with mystery andmisunderstanding. Maybe belief should rest not on the particularsensory pathway but rather on our understanding of the ways and meansthrough which we view the world.
The Eyes Are Windows Into The Brain
The eyes are a window into the workings of the brain. Many studies show that eye movements are closely linked to cognitive processes such as attention, memory, and decision-making. Eye movements not only reflect certain aspects of brain function, providing information about our thoughts and desires to others, but might also influence and actively participate in them.
The eyes also provide a glimpse into the aging and diseased brain. We now know that changes in eye movements accompany the changes that occur in the brain as a result of both normal aging and neurodegeneration. Eye movements may therefore prove to be important indicators of these processes, and there is growing interest in using them as a marker for early signs of conditions such as Alzheimers and Parkinsons diseases. Though the research is still in the early stages, it suggests that eye-tracking technology might eventually be useful in diagnosing such diseases.
Scanning the field
There are four basic types of eye movements. Vestibulo-ocular movements are reflexes that stabilize our eyes relative to the outside world to compensate for head movements vergence movements simultaneously rotate the eyes in opposite directions to align the fovea of each eye to a near or distant object and smooth pursuit movements are slow tracking moves that keep a moving object on the fovea.
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Ventricles And Cerebrospinal Fluid
Deep in the brain are four open areas with passageways between them. They also open into the central spinal canal and the area beneath arachnoid layer of the meninges.
The ventricles manufacture cerebrospinal fluid, or CSF, a watery fluid that circulates in and around the ventricles and the spinal cord, and between the meninges. CSF surrounds and cushions the spinal cord and brain, washes out waste and impurities, and delivers nutrients.
Where Do Emotions Come From
The limbic system is a group of interconnected structures located deep within the brain. Its the part of the brain thats responsible for behavioral and emotional responses.
Scientists havent reached an agreement about the full list of structures that make up the limbic system, but the following structures are generally accepted as part of the group:
- Hypothalamus. In addition to controlling emotional responses, the hypothalamus is also involved in sexual responses, hormone release, and regulating body temperature.
- Hippocampus. The hippocampus helps preserve and retrieve memories. It also plays a role in how you understand the spatial dimensions of your environment.
- Amygdala. The amygdala helps coordinate responses to things in your environment, especially those that trigger an emotional response. This structure plays an important role in fear and anger.
- Limbic cortex. This part contains two structures, the cingulate gyrus and the parahippocampal gyrus. Together, they impact mood, motivation, and judgement.
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The Brain And The Eye
The eye works like a camera. The iris and the pupil control how much light to let into the back of the eye, much like the shutter of a camera. When it is very dark, our pupils get bigger, letting in more light when it is very bright our irises constrict, letting in very little light.
The lens of the eye, like the lens of a camera, helps us to focus. But just as a camera uses mirrors and other mechanical devices to focus, we rely on eyeglasses and contact lenses to help us to see more clearly.
The focus light rays are then directed to the back of the eye, on to the retina, which acts like the film in a camera. The cells in the retina absorb and convert the light to electrochemical impulses which are transferred along the optic nerve to the brain. The brain is instrumental in helping us see as it translates the image into something we can understand.
The eye may be small, but it is one of the most amazing parts of your body. To better understand it, it helps to understand the different parts and what they do.
ChoroidA layer with blood vessels that lines the back of the eye and is between the retina and the sclera .
Ciliary BodyThe muscle structure behind the iris, which focuses the lens.
CorneaThe very front of the eye that is clear to help focus light into the eye. Corrective laser surgery reshapes the cornea, changing the focus to increase sharpness and/or clarity.
FoveaThe center of the macula which provides the sharp vision.
ScleraThe white outer coating of the eyeball.
Causes Of Neurological Vision Loss
- stroke or brain attack, where part of the brain is damaged by a haemorrhage or blockage in a blood vessel of the brain
- traumatic brain injury for example, after a car accident or fall
- infection, such as meningitis or cytomegalovirus
- lack of oxygen, such as near-drowning or a heart attack, which can interrupt the flow of blood to the brain
- disease, such as a brain tumour or multiple sclerosis.
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How The Eyes Communicate With The Brain
When we decide to look at something, a brainstem structure called the pons is called into action. It controls eye movement, constantly telling our eye muscles to move toward the correct stimulus of light .
When light enters the eye through the pupil, it strikes in the retina called rods and cones. Rod cells are responsible forperipheral vision and night vision, while cone cells react to brighter light, color and fine details.
When light hits its corresponding rod or cone, the cell activates, firing a nerve impulse through the optic nerve the middle man between the eye and the brain.
This impulse travels across countless nerve endings and eventually ends up with our pal the occipital lobe, where its processed and perceived as a visible image. This is eyesight.
Since an image isnt much help without meaning, the occipital lobe sends this visual information to the hippocampus in the temporal lobe. Here its stored as a memory.
All of this happens within the tiniest fraction of a second, allowing us to perceive the world in essentially real time.
The human brain is an incredibly complex web of neurons and synapses. And the more we understand about its mind-boggling ability to process and make sense of random collections of light, the more we can appreciate the equally complex world around us.
STILL HAVE QUESTIONS ABOUT YOUR BRAIN AND VISION? Talk to an eye doctor near you to schedule an appointment.
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The Cerebellum Coordinates Eye And Hand Tracking Movements
In the article and abundant reference material below you will learn why Mendability exercises such as Memory of weight and color or Maze in front of mirror to stimulate brain plasticity to improve brain function and eventually lead to growth and health, including in the cerebellum.
The cerebellum is a region of the brain that plays an important role in motor control. It is also involved in some cognitive functions, such as attention and language, and in some emotional functions, such as regulating fear and pleasure responses.
Note: The text below does not include the tables from the original article. To read the article with its data you may wish to contact the authors directly.Nature Publishing Group http://neurosci.nature.com
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Is Eye Part Of Brain
The eye may be small, but it is one of the most amazing parts of your body and has a lot in common with the brain. The eye is the only part of the brain that can be seen directly this happens when the optician uses an ophthalmoscope and shines a bright light into your eye as part of an eye examination.
Gross Anatomy Of The Eye
The eyeball is a sphere approximately 24 mm in diameter. There is asmaller bulge in the front, containing the structures that admit lightinto the eye. The eye socket is an opening in the skull called theorbit, where fatty tissues, connective tissues and muscles cushion andprotect the eyeball.
Movement of the eye is controlled by six muscles for each eyeball.One pair controls up-and-down movement, one pair controls side-to-sidemovement, and another pair controls diagonal movement. The eyes are inconstant involuntary motion, moving 30 to 70 times per second. Theseastonishing movements are called saccades. The eye is inconstant, restless search for parts of the visual field with thegreatest light-dark contrast. Amazingly, we are completely unaware ofthese movements. To prove that to yourself, stand before a mirror andgaze into the reflection of your left eye. Now shift your gaze to thereflection of your right eye. Notice two things: There was no blur asyour eyes moved, and you saw no reflection of moving eyes in themirror.
Behind thecornea is a chamber containing a clear, colorless liquid called theaqueous humor. This fluid is 99% water the remainder is a kindof clear serum found in blood. The aqueous humor is also found behindthe iris and around the lens. It provides nutrients to the transparentparts of the eye. See Figure 1.
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Part : The Ear And The Brain
To understand how clients will respond to sound systems, and tohelp protect your hearing, consider the intricate and surprisingauditory pathways.
COMPARE FOR A MOMENT THE EYE and the ear. There is no question thatthe eye is more sensitive to the human environment. The dark-adaptedeye needs only 0.5 attojoules of energy at its retina to perceivelight. The ear needs about 100 joules of energy 20 orders ofmagnitude more at the eardrum to perceive a sound.
The dynamic range of the two sensory organs is also dramaticallydifferent, but the ear is much more versatile. The range from thethreshold of perception to the threshold of damage is about 90 dB inthe case of the eye. Thats an amazing dynamic range by any estimation.The dynamic range of hearing in an audiologically normal person is fiveorders of magnitude greater: 140 dB.
Consider also the frequency response of seeing and hearing. This isthe range of frequencies over which the sensory organ operates. The eyecan sense light ranging in frequency from infrared to ultraviolet .This is a range of about 0.7 octaves. The ear of a young person ofmoderate tastes, on the other hand, can hear sounds from around 20 Hzto 20 kHz, 10 octaves.
Both the eye and the ear are connected to the brain, and the sensorymechanisms of both interact in intimate and complex ways with it. Wederive more information about the world than the sensory organs alonecan provide. Consider this analogy from Albert Bregman:
GROSSANATOMY OF THE EAR
Functional Differences Between The Flocculus/paraflocculus And The Nodulus/uvula
The vestibulocerebellum has many functions and lesions produce a variety of abnormalities. Are there overriding principles about the functions of the two areas within the vestibulocerebellum? One simple hypothesis is that the flocculus and paraflocculus are more concerned with the relatively immediate and fast-acting aspects of ocular motor function that relate to the needs of the fovea . On the other hand, the nodulus and ventral uvula are more concerned with the duration and axis of eye rotation in response to low-frequency, sustained rotational stimuli, and so determine the orientation of images on the retina relative to upright. Recent evidence however indicates that an intact nodulus and uvula are also necessary for the proper function of the high-frequency t-VOR as well as smooth pursuit . Thus there does not appear to be an absolute compartmentalization of functions of the VOR and pursuit among the different parts of the vestibulocerebellum, and, as will be discussed below, the dorsal vermis and underlying fastigial nuclei also play a role in smooth pursuit. Such redundancy is certainly an advantage during locomotion, considering the vital role vestibular and pursuit responses play in stabilizing gaze on stationary targets or in following targets that are also moving in the environment.
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