Sight is anything that is seen with the
. Catch sight of; to perceive with
the eyes. The ability to see; the visual faculty. The range of
act of looking or seeing or observing.
million people in the world are
, around one in every 200 people
on Earth. Another 246 million have low vision to degrees that impose
moderate or severe limits. Vision loss also affects hundreds of millions
more people. Often relatives, devoted to aiding
those who can’t see.
Many become blind after many years of slow and progressive retinal
Blind - Sight Problems
provides sustainable medical, surgical, and educational services through
volunteer ophthalmic surgeons with the objectives of restoring sight and
preventing blindness to disadvantaged individuals worldwide.
American Foundation for the Blind
is a decreased ability to see to a degree that
causes problems not fixable by usual means, such as glasses. Some also
include those who have a decreased ability to see because they do not have
access to glasses or contact lenses. Visual impairment is often defined as
a best corrected visual acuity of worse than either 20/40 or 20/60. The
term blindness is used for complete or nearly complete vision loss. Visual
impairment may cause people difficulties with normal daily activities such
as driving, reading, socializing, and walking.
Near-sightedness is a condition of the eye where light focuses in front
of, instead of on, the retina. This causes distant objects to be blurry
while close objects appear normal. Other symptoms may include headaches
and eye strain. Severe near-sightedness increases the risk of retinal
detachment, cataracts, and glaucoma.
clouding of the lens in the eye which leads to a decrease in vision.
Cataracts often develop slowly and can affect one or both eyes. Symptoms
may include faded colors, blurry vision, halos around light, trouble with
bright lights, and trouble seeing at night.
Cataract Diagnosis and Treatment
using LED technology to measure
cataracts at a molecular level.
is a group
of eye diseases which result in damage to the optic nerve and vision loss.
The most common type is open-angle glaucoma with less common types
including closed-angle glaucoma and normal-tension glaucoma. Open-angle
glaucoma develops slowly over time and there is no pain. Side vision may
begin to decrease followed by central vision resulting in blindness if not
treated. Closed-angle glaucoma can present gradually or suddenly. The
sudden presentation may involve severe eye pain, blurred vision,
mid-dilated pupil, redness of the eye, and nausea. Vision loss from
glaucoma, once it has occurred, is permanent.
is a medical condition which may result in
blurred or no vision in the center of the visual field. Early on there are
often no symptoms. Over time, however, some people experience a gradual
worsening of vision that may affect one or both eyes. While it does not
result in complete blindness, loss of central vision can make it hard to
recognize faces, drive, read, or perform other activities of daily life.
Visual hallucinations may also occur but these do not represent a mental
is the ability of people who are cortically blind
due to lesions in their striate cortex, also known as primary visual
cortex or V1, to respond to visual stimuli that they do not consciously
Testing Sight - Eye Exams
- stand 20 feet from the
at eye level
(cover one eye but don't close the eye or press on the eye). 20/20 vision
means that the test subject sees the same line of letters at 20 feet that
person with normal vision sees at 20 feet. 20/40 vision means that the
test subject sees at 20 feet what a person with normal vision sees at 40
20/40 - Able to pass Driver's License Test in all 50 States. Most
printed material is at this level.
20/80 - Able to read alarm clock at
10 feet. News Headlines are this size.
20/200 - Legal blindness. Able
to see STOP sign letters.
Eye Test Game
Eye Exam Seeing Test
20 20 20 Rule
is every 20 minutes, stare
and focus at an object 20 feet or more away for 20 seconds. This helps
Improve Vision Naturally
Glasses Off App
How to See Without Glasses
ZEISS Vision Care
OD = Right Eye
OS = Left Eye
DV is your prescription which corrects your
ability to see
things far away (distance vision)
NV means your prescription is
for reading only (near vision)
refers to the clarity of vision. Visual acuity is
dependent on optical and neural factors, i.e., (i) the sharpness of the
retinal focus within the eye, (ii) the health and functioning of the
retina, and (iii) the sensitivity of the interpretative faculty of the
brain. A common cause of low visual acuity is refractive error (ametropia),
or errors in how the light is refracted in the eyeball. Causes of
refractive errors include aberrations in the shape of the eyeball, the
shape of the cornea, and reduced flexibility of the lens. Too high or too
low refractive error (in relation to the length of the eyeball) is the
cause of nearsightedness (myopia) or farsightedness (hyperopia) (normal
refractive status is referred to as emmetropia). Other optical causes are
astigmatism or more complex corneal irregularities. These anomalies can
mostly be corrected by optical means (such as eyeglasses, contact lenses,
laser surgery, etc.).
is an organ which reacts to
and pressure. As a sense organ, the mammalian eye allows vision.
Human eyes help provide a three dimensional
, moving image, normally coloured in daylight. Rod and cone cells in the retina allow conscious
light perception and vision including color differentiation and the
perception of depth. The human eye can distinguish about 10 million
and is possibly capable of detecting a single photon
How Human Eye Works
Anatomy of the Eye
are organs of the
They provide organisms vision, the ability to process visual detail, as
well as enabling several photo response functions that are independent of
vision. Eyes detect light and convert it into electro-chemical impulses in
is the branch of medicine that deals with the anatomy, physiology and
diseases of the eyeball.
Lateral Geniculate Nucleus
is a relay center in the thalamus for the visual pathway. It receives a
major sensory input from the retina. The LGN is the main central
connection for the optic nerve to the occipital lobe. In humans, each LGN
has six layers of neurons (grey matter) alternating with optic fibers (white
is the third and inner coat of
the eye which is a light-sensitive layer of tissue. The optics of the eye
create an image of the visual world on the retina (through the cornea and
lens), which serves much the same function as the film in a camera. Light
striking the retina initiates a cascade of chemical and electrical events
that ultimately trigger nerve impulses. These are sent to various visual
centres of the brain through the fibres of the optic nerve. Neural retina
typically refers to three layers of neural cells (photo receptor cells,
bipolar cells, and ganglion cells) within the retina, while the entire
retina refers to these three layers plus a layer of pigmented epithelial
is a paired nerve that transmits visual information from the
retina to the brain. The optic nerve is derived from optic stalks during
the seventh week of development and is composed of retinal ganglion cell
axons and glial cells. In humans, the optic nerve extends from the optic
disc to the optic chiasm and continues as the optic tract to the lateral
geniculate nucleus, pretectal nuclei, and superior colliculus.
Wills Eye Hospital
Prosthetic Iris Devices
A. Academy of Ophthalmology
Review of Ophthalmology
National Institutes of Health
Animal Eyes Pupil Shapes
is vision in which
creatures having two eyes use them together.
is a Retinal prostheses for restoration of sight to
patients blinded by retinal degeneration meant to partially restore useful
vision to people who have lost their photoreceptors due to retinal
diseases such as retinitis pigmentosa.
is a experimental bionic eye visual device intended
to restore functional vision in those suffering from
partial or total
Argus Retinal Prosthesis
is an electronic retinal implant.
with Sound Augmented Reality
Eye Music: Hearing Colored Shapes
Andrew Bastawrous: Get your next eye exam on a Smartphone
White Eye Detector App
is an eye examination that can detect dysfunction
in central and peripheral vision which may be caused by various medical
conditions such as glaucoma, stroke, pituitary disease, brain tumours or
other neurological deficits. Visual field testing can be performed
clinically by keeping the subject's gaze fixed while presenting objects at
various places within their visual field. Simple manual equipment can be
used such as in the tangent screen test or the Amsler grid. When dedicated
machinery is used it is called a perimeter.
VisualFields easy Eye Exam App
capture high-quality images
of the front and back of an eye.
is sold under the trade name Avastin, is an
angiogenesis inhibitor, a drug that slows the growth of new
Diplopia is a Computer Game
that has been designed using the
latest research to help people with
(lazy eye) and
strabismus (crossed eyes)
Brain training video games help low-vision kids see better
Computer Vision Syndrome
Protecting your Vision
Color-Binoculars App helps color blind individuals distinguish colors in
their everyday lives
vision science and optical technology. The only specialty
eyewear that alleviates red-green color blindness, enhancing colors
without the compromise of color accuracy.
Association for Research in
Vision and Ophthalmology
branch of medicine concerned with the eye and
SyncBraille is one of the smallest, lightest, and most
affordable, portable Braille Displays
Refreshable Braille Display
Periscope Braille Tablet
- Speech Recognition
is a miniature smart
camera that can attach to any pair of glasses. The device takes a photo of words
and reads them to the blind.
Brain-sensing technology developed by Stanford scientists allows typing at
rate of 12 words per minute
, could provide a way for people with
movement disorders to communicate.
VoiceOver Gesture Support, Text to Speech, Braille Display
Vision Correcting Light Field Display
Vision-impaired & Low Vision Tool
Daniel Kish: How I use Sonar to Navigate the World
is a technique that uses sound propagation to navigate, communicate with
or detect objects.
device is an electronic travel aid which fits on
the top fold of the white cane.
BuzzClip, wearable ultrasound for visually impaired people
How new technology helps blind people explore the world
(video and text)
Narrator Text–to–Speech Utility
JAWS Screen Reader
The Read 'n Style Pen:
Turn any text to audio. The world's first
digital reading tool created by and for
Dizzy Head Spins
refers to the ways in which people and
other animals communicate and interact via the sense of touch. As well as
providing information about surfaces and textures, touch, or the haptic
sense, is a component of communication in interpersonal relationships that
is nonverbal and nonvisual. Touch is extremely important for humans and is
vital in conveying physical intimacy. Haptics is a branch of
is the ability of humans to detect
objects in their environment by sensing echoes from those objects, by
actively creating sounds – for example, by tapping their canes, lightly
stomping their foot, snapping their fingers, or making clicking noises
with their mouths – people trained to orient by echolocation can interpret
the sound waves
reflected by nearby
objects, accurately identifying their location and size. This ability is
used by some blind people for acoustic wayfinding, or navigating within
their environment using auditory rather than visual cues. It is similar in
principle to active sonar and to animal echolocation, which is employed by
bats, dolphins and toothed whales to find prey.
Daniel Kish's echolocation in action
Talking Barcode Scanners
Sheila Nirenberg: A Prosthetic Eye to treat Blindness
Can Blind People Draw?
Ron Mccallum: How Technology allowed me to Read
The Blind Woman Who Saw Rain
Suppression of an eye
is a subconscious adaptation by a person's brain
to eliminate the symptoms of disorders of
. The brain can eliminate double vision by ignoring all or
part of the image of one of the eyes. The area of a person's visual field
that is suppressed is called the suppression scotoma (with a
meaning, more generally, an area of partial alteration in the visual
field). Suppression can lead to
Aphantasia: How It Feels To Be Blind In Your Mind
voice activated search and information.
Be My Eyes
Smartphone App that allows a blind person to use friends and
family to help identify things using video.
How Do A Blind Person & A Deaf Person Communicate? (with Rikki Poynter)
Lechal Haptic Footwear
Injecting a benign virus that carries good copies of a malformed gene in the
Visual Cortex Activity in Early and Late Blind People
Leber Congenital Amaurosis
is an eye disorder that primarily affects
the retina, which is the specialized tissue at the back of the eye that
detects light and color. People with this disorder typically have severe
visual impairment beginning in infancy. The visual impairment tends to be
stable, although it may worsen very slowly over time.
People with Disabilities are Gifts from
are the most common eye color in the world with over 55% of the
world's population having brown eyes.
are around 5-8% of the world's population. Hazel eyes are
similar to brown eyes, although they are typically lighter in
color, and have more of a green-yellow tint. Hazel eyes have a
higher concentration of melanin (pigment) around the eye's
border, which can result in a multi-colored appearance that
varies between copper and green depending on the lighting.
are around 8% of the world's population.
History of Eye Color
are often confused with hazel eye color, yet is entirely
separate and distinct. Green eye color is the rarest color found
around the world, and it is estimated that only around 2% of the
world's population has green colored eyes. Green eye color is
a result of a mild amount of pigmentation in the eye with a
golden tint. When combined with the natural blue scattering of
the eye, the colors mix to give a green appearance. Green eye
color is most common in northern and central Europe, but can
also be found in western Asian cultures on rare occasion.
are also quite rare. Silver eyes are the result of a very low
amount of pigmentation in the eye, which reflects a gray-silver
appearance. Amber eyes show off a yellow-copper tone, which
results from the yellow colored pigment lipochrome.
are very rare worldwide, and are most common in Asia and South
American countries. Amber eye color can range from golden yellow
to a more copper tone.
a polygenic phenotypic character determined by two distinct factors: the
pigmentation of the eye's iris and the frequency-dependence of the
scattering of light by the turbid medium in the stroma of the iris.