22.11.13
Visual Impairment and Blindness caused by Accidents | Group 2
The eye is the most
important sensory organ, which influences our way in which we see the world.
Eyesight comes so naturally to us that we often tend to take it for granted. Our
eyes and our brain work together to see. The eye is made up of many different
parts, including the cornea, iris, lens, and retina that together help us to
focus on light and images. Our eyes then use special nerves to send what we see
to our brain, so that our brain can process and recognise it. Our eyes helps us
to distinguish between light and dark, they can perceive colours, recognise
spatial contrasts and adapt instantly and effortlessly to any distance and all
light conditions.
One of the causes of
blindness or partial blindness affecting people of all ages is accidental
damage to the eye. Injuries to the eyes can occur in a wide variety of ways.
The obvious types of injuries that can harm the eyes are sharp objects, like
knives or scissors puncturing the eye. Others include:
- Assaults or attack
- Auto accidents
o Car / Truck / Motorcycle / Bus collisions
o Drunk driving
- Bright lights
- Chemicals
- Electric shock
- Head trauma
- Sharp objects
- Dog bites / Animal attacks
- Fire and explosions
- Hazardous work environments
- Foreign particles entering the eye
Assaults or
Attacks
Violent crime can
result in loss of sight or blindness if there is any sort of trauma caused to
the head or face. Injuries to eyes can be caused during assaults or attacks
when a victim is being struck by another person or object or as they fall.
Bright Lights
Bright lights that damage
the eyes can also cause temporary or permanent blindness. In particular Welders
and others working in similar professions are more prone to such accidents.
Other dangerous bright lights could come from explosions, lasers, searchlights
or defective electrical objects. To avoid such risks protective goggles should
be worn in any hazardous situation.
Head Trauma
An impact to the head
or face or any type of head trauma can lead to loss of sight or blindness
either directly or through brain injury. Obviously, an impact to the face or
head can be caused by any type of accident such as a car accident, an accident
at work or a slip, trip or fall.
Sharp Objects
Sharp objects found
almost anywhere can cause terrible injuries to eyes resulting in loss of sight
or blindness. One can come into contact with dangerous sharp objects at
work, at home or in a public place such as a supermarket or school.
Foreign Particles
Our eyes are designed
in such a way that they are protected to some degree from foreign particles
getting into them. Our eyelashes and the protective socket around our eyeballs
help prevent the intrusion of particles to a certain extent. However it is
still possible for particles or other substances to damage the eyeball causing
loss of sight or blindness. This can happen at work for example whilst
using machinery, particularly if protective gear is not worn.
Chemicals
If chemicals come
into contact with your eyes they can cause burns resulting in loss of sight or
blindness. This can be due to splashes and spillages. The employers should
provide Training and safety equipment to the employees working with chemicals
Electric
Shock
Electric
shocks can also result in blindness either because of the shock itself or as a result
of the eye being exposed to a sudden bright flash of light.
Auto
Accidents
Accidents caused due to sideswipe collisions, head on
head collisions,
rear-end accidents, and other types of traffic collisions as well as accidents involving any type of vehicle in which the driver or operator was under the influence of drugs or alcohol can result in injury to the eyes.
rear-end accidents, and other types of traffic collisions as well as accidents involving any type of vehicle in which the driver or operator was under the influence of drugs or alcohol can result in injury to the eyes.
Blindness By Birth | Group 1
Blindness is the condition of lacking visual perception due to physiological or neurological factors. Various scales have been developed to describe the
extent of vision loss and define blindness
Visual acuity (VA) is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain. Visual acuity is a measure of the spatial resolution of the visual processing system. VA is tested by requiring the person whose vision is being tested to identify characters (like letters and numbers) on a chart from a set distance. Chart characters are represented as black symbols against a white background (for maximum contrast). The distance between the person's eyes and the testing chart is set at a sufficient distance to approximate infinity in the way the lens attempts to focus.
An ophthalmologist is a doctor
who specializes in eye problems. Visual impairment and blindness in children
pose a special problem for ophthalmologists, as many eye care practitioners are
not familiar with performing pediatric eye examinations and measuring visual
acuity in infants. Infants are unable to verbalize their complaints, and
history from parents and care takers may lack important details. However, the
first year of life is also the time when the visual system develops and
binocular vision is formed. If a
visual deficit at this age is not treated in a timely manner, amblyopia and
permanent visual deficit can occur. Hence, early diagnosis and prompt treatment
is essential.
The burden of blindness, measured in blind-person
years (i.e., the no of years spent as a blind individual), due to childhood
blindness is second most common cause of avoidable blindness. Studies worldwide show that many of
the causes of blindness in children are either preventable or treatable (ie,
avoidable). Even children who
have visual loss that cannot be clinically treated can be helped with low
vision devices and rehabilitation. Childhood blindness affects the individual,
their family, and the community. Blindness also has implications for infants’
development, education, and future social, marital, and economic prospects.
Nearly 80% of all sensory input and 75% of early learning comes from vision.
Early onset visual loss can have profound consequences on a child’s motor,
social, emotional, and psychological development.
Severe Visual Impairment (SVI) and blindness in infants must be detected as early as possible to initiate immediate treatment to prevent deep amblyopia. Although difficult, measurement of visual acuity of an infant is possible. The causes of SVI and blindness may be prenatal, perinatal, and postnatal:
Severe Visual Impairment (SVI) and blindness in infants must be detected as early as possible to initiate immediate treatment to prevent deep amblyopia. Although difficult, measurement of visual acuity of an infant is possible. The causes of SVI and blindness may be prenatal, perinatal, and postnatal:
·
Prenatal:
Congenital anomalies such as anophthalmos (missing an eye), microphthalmos
(small eye), coloboma ( hole in one of the structures of the eye, such as the iris), congenital cataract, infantile glaucoma, and neuro-ophthalmic lesions
are causes of impairment present at birth.
·
Ophthalmia neonatorum(conjunctivitis contracted
by a newborn), retinopathy of prematurity, and cortical visual impairment are
acquired during the perinatal period
·
Postnatal
conditions (ie, those acquired after birth) are unusual
during infancy.
While few medical or surgical options are available for congenital anomalies or neuro-ophthalmic disorders, many affected infants can still benefit from low vision aids and rehabilitation. Ideally, surgery for congenital cataracts should occur within the first 4 months of life.
If one is completely blind, one can see nothing. If one is partially blind, one might experience the following symptoms:
·
cloudy
vision
·
the
inability to see shapes
·
seeing
only shadows
·
poor
night vision
·
tunnel
vision
A child’s visual system begins to develop in the womb, but will not be fully formed until about 2 years of age. By 6 to 8 weeks of age, a baby should be able to fix his or her gaze on an object and follow its movement. By 4 months of age, the child’s eyes should be properly aligned (not turned inward or outward).
A pediatrician will screen the baby for eye problems shortly after
birth. At 6 months of age, parents should have an eye doctor or pediatrician
check the child again for visual acuity, focus, and eye alignment. The doctor
will look at the baby’s eye structures and see whether the baby can follow a
light or colorful object with his or her eyes.
The following conditions can cause vision impairment or blindness in
infants:
- infections, such as pink eye
- blocked tear ducts
- cataracts
- strabismus (crossed eyes)
- amblyopia (a lazy eye)
- ptosis (a droopy eyelid)
- congenital glaucoma
- retinopathy of prematurity (when the blood
vessels that supply the retina are not fully developed in premature
babies)
- visual inattention (delayed development of the
child’s visual system)
A child should be able to pay attention to visual stimuli by 6 to 8
weeks of age. If he or she child does not react to light shining in his or her
eyes or focus on colorful objects by 2 to 3 months of age, or if it is noticed
that the child has crossed eyes or any other symptoms of impaired vision, the
child’s eyes must be examined right away.
Symptoms of visual impairment in young children include:
- constant
eye rubbing
- extreme
sensitivity to light
- poor
focusing
- chronic eye
redness
- chronic
tearing of the eyes
- a white
instead of a black pupil
- poor visual
tracking (following an object with the eyes)
- abnormal eye
alignment or movement (after 6 months of age)
Tests
Orthoptic evaluation of an infant requires
patience. Jampolsky’s dictum of “one toy-one look” should be used to examine
the infant’s ocular motility in the nine cardinal directions of gaze. An
assortment of soft toys, brightly colored objects, and even mobile phones can
be used to arouse the child’s interest. The objects should not make noise as
the child will be attracted through the auditory and not the visual signals,
which would defeat the purpose of the examination.
Visual acuity can be formally assessed using
forced preferential looking tests (eg, Cardiff cards), with the child sitting
comfortably on a parent’s lap. The test is based on the psychological percept
that humans are attracted to novel stimuli. If the child is shown a line
drawing at one end of the card sheet and the other end is kept blank, the child
will divert its eyes to the drawing rather than the blank area. The line
drawings are made progressively finer to estimate higher orders of form vision.
Worth’s ivory fall test and small sweets commonly used to decorate cakes,
“hundreds and thousands”, can also be used. The child picks up the small sweets
if it is able to see them. At first, bilateral vision is tested followed by
monocular testing. The mother should be asked to occlude the infant’s eyes one
at a time, and report on the infant’s response. If the infant objects to
occlusion of one eye, this may indicate the visual acuity of the other eye is
poor.
Brain Plasticity
People
who have been blind from birth make use of the visual parts of their brain to
refine their sensation of sound and touch, according to an international team
of researchers led by neuroscientists at Georgetown University Medical Center
(GUMC).
Using functional magnetic resonance imaging (fMRI), the researchers found that the blind use specialized "modules" in the visual cortex that process the spatial location of an object when a person localizes it in space. More generally, they believe that the different functional attributes that make up vision, such as analysis of space, patterns, and motion, still exist in the visual cortex of blind individuals. But instead of using those areas to understand what the eyes see, the blind use them to process what they hear and touch because the same components are necessary to process information from those senses.
"That tells us that the visual cortex in the blind takes on these functions and processes sound and tactile information which it doesn't do in the sighted," he says. "The neural cells and fibers are still there and still functioning, processing spatial attributes of stimuli, driven not by sight but by hearing and touch. This plasticity offers a huge resource for the blind."
Using functional magnetic resonance imaging (fMRI), the researchers found that the blind use specialized "modules" in the visual cortex that process the spatial location of an object when a person localizes it in space. More generally, they believe that the different functional attributes that make up vision, such as analysis of space, patterns, and motion, still exist in the visual cortex of blind individuals. But instead of using those areas to understand what the eyes see, the blind use them to process what they hear and touch because the same components are necessary to process information from those senses.
"That tells us that the visual cortex in the blind takes on these functions and processes sound and tactile information which it doesn't do in the sighted," he says. "The neural cells and fibers are still there and still functioning, processing spatial attributes of stimuli, driven not by sight but by hearing and touch. This plasticity offers a huge resource for the blind."
Dreams
A series of questionnaire and interview
studies conducted in the 1970s led to four generalizations about the
dreams of the blind:
1. People born blind, and who never experienced visual imagery in
waking life, have no visual images in their dreams.
2. People who became blind before the age of five rarely experience
visual imagery in their dreams.
3. People who became blind between the ages of five and seven
sometimes retain some visual imagery and experience it in their dreams.
4. Most people
who became blind after the age of seven continue to experience at least some
visual imagery in their dreams, but the clarity and frequency of the imagery is
often reduced with time.
Several
studies in sleep laboratories, in which blind participants were woken up during
REM sleep for the collection of dream reports, reported similar results.
A more recent study analyzed a sample of
372 dreams from 15 blind adults—some born blind, and others who went blind
later in life. Again, the study found that people blind since birth or very
early childhood experienced no visual imagery, and people blinded later in life
did retain some visual imagery from their sighted waking lives and experienced
it while dreaming.
Bibliography:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3119278/
http://en.wikipedia.org/wiki/Blindness
http://en.wikipedia.org/wiki/Visual_acuity
http://www.sciencedaily.com/releases/2010/10/101006131203.htm
http://www.healthline.com/health/blindness
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3119278/
http://en.wikipedia.org/wiki/Blindness
http://en.wikipedia.org/wiki/Visual_acuity
http://www.sciencedaily.com/releases/2010/10/101006131203.htm
http://www.healthline.com/health/blindness
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