Four prevalent, different types of blindness – Perkins School for the Blind

Most people think of blindness in the simplest terms: a person who can’t see. In actuality, blindness is more complex. In fact, there are many different types of blindness and visual impairment.

Some blind people truly see nothing, while others see light, shadows or objects that are close by. Vision loss can start at birth or gradually decline. Blindness can stem from a problem with the eye itself or be caused by a disorder in the brain. 

Different types of blindness can affect anyone: you, your parents, a friend, your child or anyone else. Learn more about the types of blindness that exist. 

CVI

CVI, or cortical/cerebral visual impairment, is the leading cause of modern day blindness in children. Unlike ocular forms of visual impairment, CVI is a brain-based disorder, and often coexists with an additional visual impairment.

Since the issue exists in the brain, people with this diagnosis have challenges processing what their healthy eyes are seeing. A child with CVI, for example, may see the world as a swirling mass of color.

Today, CVI is the fastest growing cause of blindness in children in the U.S. Too few educators and medical professionals are equipped to diagnose and intervene. Meaning countless kids are missing out on crucial opportunities to develop and thrive. When a specially trained educator works with a child with CVI and his or her family, the child’s life can improve dramatically. There is even a possibility of helping the child recover use of their vision to varying degrees.

Watch this video and hear one family’s journey with CVI.

Want to learn more about CVI? Visit CVINow.org for more information about CVI, diagnosis, research and methods that can help children with the disorder.

Retinitis Pigmentosa

Retinitis pigmentosa is a genetic disorder, which affects up to one in 4,000 people in the U. S. and across Europe, according to the U.S. National Library of Medicine. People with this eye condition often have trouble seeing at night and experience a loss of peripheral vision due to the gradual breakdown in cells of the retina. It’s most commonly detected in early childhood, and can lead to total blindness later in life. 

Interested in learning more about the symptoms and diagnosis of retinitis pigmentosa? Start here for a brief overview.

For people and families diagnosed with this condition, it’s important to understand the effects and progression of the disease in order to optimize quality of life. At Perkins School for the Blind, students with this eye condition learn to achieve their full potential and become strong capable adults. Watch one blind youtuber talk about her life with Retinitis Pigmentosa. 

Macular Degeneration

Macular degeneration is another one of the leading causes of vision loss, affecting an estimated 10 million people in the U. S. 

There are a few types of this condition, but the most common is called dry macular degeneration. This type of visual impairment is found in adults, and causes a person’s central vision to deteriorate. In children, a genetic disorder called Stargardt Syndrome looks very similar to macular degeneration because of the way both conditions affect one’s vision. 

Diagnosis of macular degeneration can be done during routine visual exams or eye screenings. Find the help you or your loved one needs to diagnose and live with Macular Degeneration from the Macular Degeneration Foundation.

Retinopathy of Prematurity

Retinopathy of prematurity is an eye disease which occurring in babies born prematurely. It begins when blood vessels in the eye leak or bleed, resulting in scarring of the eye and retinal detachment. Although surgeries can lessen the severity of the visual impairment, children born with the condition often have little to no eye sight. 

Retinopathy of prematurity can manifest at birth, but cannot be detected without proper eye examination. Despite the severity of vision loss often connected to this condition, people with this diagnosis are more than capable of achieving their goals. Check out this article illustrating accomplishments of young blind people, some of whom have retinopathy of prematurity.

The spectrum of blindness and visual impairment varies widely from person to person. There are countless types of vision loss which affect everyone differently at different stages of life. The many types of blindness can be due to genetics, cancer, difficulties at birth, or other diseases discovered later in life. No matter the cause or symptoms, though, people with all types of blindness can live fulfilling lives with the right adaptations, assistance and services. A little research and the right questions are key to the success of a loved one or friend with a visual impairment. 

Perkins School for the Blind is always here to provide resources and support. We offer a wide variety of educational and services and resources on our campus and in public schools to support children and young adults with blindness.  

Visit our Services page for more information.

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Partial, total, congenital, and more

Blindness has many types and causes, ranging from injuries and infections to neurological or congenital conditions. People can categorize blindness based on its cause or whether a person has complete or partial blindness.

Blindness is a general term that includes people with low vision and those who cannot see. A wide range of conditions can cause it in newborns, children, and adults.

This article will discuss types of blindness and some examples of its causes.

Healthcare professionals divide types of blindness into the following categories:

• Total blindness: This is when a person cannot see anything, including light. Only 15% of individuals with eye disorders have total blindness.
• Low vision: Low vision describes visual impairments that healthcare professionals cannot treat using conventional methods, such as glasses, medication, or surgery.
• Legal blindness: “Legal blindness” is a term the United States government uses to determine who is eligible for certain types of aid. To qualify, a person must have 20/200 vision or less in their better-seeing eye, even with the best correction.
• Visual impairment: Visual impairment is a general term that describes people with any vision loss that interferes with daily activities, such as reading and watching TV.

People can also categorize types of blindness by their cause. Below are just some of the potential conditions that can result in vision loss.

Visual impairments are most common in older adults. Potential causes include:

• Age-related macular degeneration (AMD): AMD is an eye disorder that occurs when aging damages the macula, which controls sharp, straight-ahead vision.
• Cataract: A cataract is a cloudy area that develops over the eye’s lens. These can cause clouding or blurring of vision, color fading, and reduced night vision.
• Diabetic retinopathy: This diabetes complication is more likely to develop in older adults. It occurs when high blood sugar levels damage the tiny blood vessels supplying the retina.
• Glaucoma: Glaucoma is an eye disease that damages the optic nerve at the back of the eye. It is more common in people aged 60 years and over and can cause vision loss.

Eye injuries can lead to vision loss or blindness in some cases. They may occur due to:

• playing sports
• physical violence
• motor vehicle crashes
• chemical burns
• exposure to toxins
• falls or collisions
• objects such as darts, bullets, explosives, or fireworks

Many infectious diseases can result in vision loss. Some examples include:

• Trachoma: This is a bacterial infection that can cause eye itching, irritation, discharge, and eyelid swelling. Trachoma is the cause of more vision loss and blindness than any other infection worldwide, but it is rare in the U. S.
• Shingles: The same virus that causes chickenpox also causes shingles. When shingles affect the eyes, it may lead to corneal scarring, ulceration, and perforation, resulting in severely decreased vision.
• Cytomegalovirus (CMV): CMV is a herpes virus that can cause CMV retinitis, a severe viral infection that destroys the retina and damages the optic nerve. This is more common in people with compromised immune systems.
• Histoplasmosis: Histoplasmosis is a fungal lung infection. The infection can move from the lungs to the eyes, causing ocular histoplasmosis syndrome and vision loss.
• Keratitis: This is inflammation of the cornea that typically occurs due to a bacterial, viral, or fungal infection. Without treatment, it can result in severe complications that permanently damage vision.
• Syphilis: Syphilis is a sexually transmitted infection (STI) that can affect the eyes, leading to vision loss and permanent blindness in some cases.
• Toxoplasmosis: This occurs due to a parasitic infection. Some people are at risk of ocular toxoplasmosis, which causes retinal inflammation. Without treatment, it may lead to progressive vision loss.
• Uveitis: Uveitis is inflammation of the middle layer of the eye, known as the uvea, which can lead to loss of peripheral vision and complications that cause blindness.

Several noninfectious conditions can also lead to blindness. These include:

• Amblyopia: Amblyopia or “lazy eye” is an impairment that occurs in one or both eyes due to a breakdown in how the eye and brain work together. Without treatment, amblyopia may cause vision loss.
• Stroke: If a stroke damages part of the brain responsible for sight or eye movement, people can experience vision changes or loss.
• Retinopathy of prematurity (ROP): ROP is an eye disease that occurs in premature infants when atypical blood vessels develop in the retina. Advanced ROP may cause retinal detachment and blindness.
• Cancer: Certain types of cancer, such as orbital tumors, may cause complications, including retinal detachment and blindness.

Nutritional blindness occurs due to a vitamin A deficiency. This may lead to:

• xerophthalmia, which causes dry eyes and inflammation
• keratomalacia, which is drying and clouding of the cornea
• corneal necrosis, or the death of cells and tissue in the cornea

According to the World Health Organization (WHO), 250,000–500,000 children with vitamin A deficiency lose their sight each year.

Snow blindness occurs when the sun’s UV rays reflect off ice or snow, damaging the cornea and the conjunctiva. Snow blindness can also refer to the freezing of the cornea or severe drying of the cornea’s surface due to dry air.

It typically occurs in people who ski, climb mountains, or go snowmobiling. Although snow blindness is temporary, repeated exposure to UV rays without sunglasses may result in other eye disorders that cause permanent vision loss.

Night blindness, or nyctalopia, is when people experience poor vision in dimly lit environments or at night. Despite the name, people with night blindness are not blind but may have difficulty seeing in places such as movie theatres, restaurants, or driving at night.

People can develop night blindness due to eye conditions, such as nearsightedness, cataracts, and retinitis pigmentosa. Vitamin A deficiency may also cause it.

Several genetic conditions can cause blindness.

The blindness may be present from birth, in which case, it is known as congenital blindness. In some cases, though, blindness develops later on. Examples include:

• Leber hereditary optic neuropathy (LHON): LHON is an inherited disease that transmits from birth parent to child. It causes clouding and blurring of vision, progressing to blindness.
• Oculocutaneous albinism: Albinism is when a person does not have melanin in their hair, skin, or eyes. This can sometimes affect vision.
• Retinoblastoma: This type of eye cancer can be hereditary, occurring due to changes in certain genes.
• Inherited retinal diseases (IRDs): IRDs are rare conditions that can lead to vision loss and blindness. Genetic mutations in more than 260 genes may cause IRDs. IRDs may include conditions such as:
  • retinitis pigmentosa
  • choroideremia
  • Stargardt disease
  • cone-rod dystrophy
  • X-linked retinoschisis

Blindness can also occur due to congenital abnormalities, such as:

• anophthalmia, which is when a fetus does not develop one or both eyes
• microphthalmia, which is when one or both eyes are very small
• coloboma, which is when part of the eye does not develop in the typical way
• infantile glaucoma

Other causes of congenital blindness include:

• congenital cloudy cornea
• congenital cataracts
• optic nerve lesions
• cerebral visual impairment, which occurs due to brain damage
• ophthalmia neonatorum, which is an eye infection newborns can get if their birth parent has an STI

Color blindness does not cause blindness or vision loss. However, people with the condition see colors differently from others. It tends to run in families.

Color blindness can make it difficult for people to distinguish between certain colors, such as red and green or blue and yellow. Some people are completely color blind and cannot see any color. However, this is uncommon.

Age-related eye diseases, such as AMD and cataracts, are the leading causes of low vision and blindness in the U.S.

According to the Centers for Disease Control and Prevention (CDC), about 12 million people in the U.S. have some form of vision impairment, and 1 million are blind.

There are several ways to categorize blindness. Certain types describe how much vision loss a person has, ranging from some impairment to complete blindness. People may also categorize blindness based on its causes, which vary widely from congenital conditions to those that occur later in life.

The most common causes of blindness are age-related, including conditions such as AMD and glaucoma. Blindness can also result from injuries, infections, vitamin A deficiency, UV damage, congenital abnormalities, and many other conditions.

Color blindness: types, symptoms, signs, treatment, correction.

From Gretchyn Bailey; reviewed by Gary Heiting, OD

Color blindness is not a form of blindness at all, but merely a deficiency in color perception.

If you are colorblind, you may find it difficult to distinguish between certain colors, such as blue and yellow or red and green.

Color blindness (or more precisely color vision deficiency) is a hereditary disease that is more common in men than in women. According to Prevent Blindness, an estimated 8 percent of men and less than 1 percent of women have color vision problems.

The most common form of color blindness is red-green color deficiency.

Disturbances in the perception of blue and yellow shades are much less inherited. This blue-yellow color deficiency usually occurs in men and women equally.

Color blindness: Signs and symptoms

Do you find it difficult to distinguish between blue and yellow or red and green? Are you ever told that the color you think you see is different?

If so, this indicates that you have a color vision deficiency.

Contrary to popular belief, color blind people who see everything in gray are rare.

Most people who are considered “color blind” can see colors, but they perceive some colors as blurry and easily confused with other colors, depending on what kind of color vision deficiency they have.

If you have a color vision disorder, although you could normally see the entire spectrum of colors, then you should definitely consult an ophthalmologist. Sudden or gradual loss of color vision can indicate a number of health problems, such as the development of cataracts.

The color blindness test will help you determine what type of color vision deficiency you have.

SEE. ALSO: Color blind glasses

What are the causes of color blindness?

Color blindness occurs when the light-sensitive cells in the retina do not respond appropriately to changes in the wavelength of light that allow people to see different colors.

The photoreceptors in the retina are called rods and cones. There are many more rods in the human retina (approximately 100 million) and they are more sensitive to light, but the rods are not able to perceive colors.

About 6-7 million cones are responsible for color vision in the human retina; these photoreceptors are located in the central area of ​​the retina called the macula.

The center of the macula is called the fovea; this tiny area (0.3 mm in diameter) where the concentration of cones in the retina is highest is responsible for our sharpest color vision.

Inherited forms of color blindness are often associated with a deficiency or complete absence of certain types of cones.

In addition to genetic differences, other causes of defects or deficiencies in color vision include:

• Parkinson’s disease (PD). Because Parkinson’s disease is a neurological disease, the light-sensitive nerve cells in the retina that process vision can become damaged and lose their function.

• Cataracts. Clouding of the natural lens of the eye due to cataracts can lead to “washing out” of color vision, causing colors to appear less vibrant. Fortunately, vivid color vision can be restored with cataract surgery, during which the clouded natural lens of the eye is removed and replaced with an artificial intraocular lens..

• Certain medicines. The anticonvulsant drug tiagabine has been shown to impair color vision in about 41 percent of people who take it, although this side effect resolves over time.

• Leber’s hereditary optic neuropathy (HONL). In this form of hereditary optic neuropathy, some degree of color blindness can occur even in carriers of the disease who do not have any other symptoms. With this disease, a red-green color deficiency is predominantly observed.

• Kallman syndrome. This is a hereditary disease associated with damage to the pituitary gland, which can lead to incomplete or unusual gender development, for example, of the genitals. Color blindness can be one of the symptoms of this disease.

Color blindness can also develop due to damage to retinal cells during aging. Injury or damage to the areas of the brain where visual information is processed can also lead to color vision deficiency.

Treatment Options for Color Blindness

University of Washington researchers report that monkeys have been cured of color blindness through gene therapy.

Although these results in animals look promising, gene therapy will not be used in humans until proven safe.

There are currently no treatment options for color blindness. But some strategies can help colorblind people improve their eye function in a colorful world.

Most people can adapt to color vision deficiency without any problems. But some professions, such as those involved in graphic design and working with electrical wiring of different colors, require accurate color perception.

If you realize at an early age that you are colorblind, then it is worth choosing a career that does not require accurate color perception.

Diagnosing color vision deficiency at an early age can also prevent learning problems during the school years, especially as many learning materials rely heavily on color perception.

If your child has a color deficiency, be sure to talk to their teachers so that they can take this into account when preparing their lessons and presentations.

Color blind lenses

To enhance color perception, some people use special lenses that are filters and can be presented as contact lenses or spectacle lenses.

One example is the colorblind glasses developed by EnChroma. EnChroma’s tinted lenses for color-blind glasses, made with patented light-filtering technology, allow people with common forms of color blindness to see a wide range of vibrant colors that most of us take for granted, according to the company.

If you have a color vision deficiency, you should contact your local optometrist to see if colorblind glasses are suitable for you.

You can also learn how to get around the inability to distinguish certain colors. For example, you can sort your clothes so you don’t wear mismatched colors. (Ask your friends or family who have normal color vision to help you with this.)

Learn to recognize some colored objects by their order, not by color. In addition, you can download

different apps designed for Android and Apple devices to help you identify color.

See your optometrist for additional help and advice if you have difficulty distinguishing colors or if you suspect your child may be color blind.

Is red-green color deficiency hereditary?

The most common hereditary form of color vision deficiency is the red-green color vision deficiency. It is caused by a fairly common X-linked recessive inheritance.

Mothers have a set of X-X chromosomes carrying genetic material, while fathers have a set of X-Y chromosomes. Chromosomes are taken from both mother and father, which
determine the sex of the child.

When an X chromosome from one parent pairs with an X chromosome from the other parent, the child will be a girl. When an X chromosome from the mother pairs with a Y chromosome from the father, the child will be a boy.

If you have X-linked recessive color vision deficiency, your mother is a carrier of the gene or is colorblind herself.

With this inheritance of red-green color deficiency, fathers pass on the X-linked gene to their daughters, but not to their sons, since the son cannot receive the X-linked genetic material from his father.

A daughter who inherits a gene for color blindness from her father will be a carrier of such a gene, but will not be color blind herself – unless, of course, her mother is a carrier of the gene for color blindness, and she did not inherit it from her mother. If a daughter inherits X-linked characteristics from both her father and mother, then she will be colorblind.

When a mother passes on this X-linked characteristic to her son, he will inherit a color vision deficiency and it will be difficult for him to distinguish between red and green colors.

A daughter can also be a carrier, but she will only develop this form of color blindness if both father and mother pass on the X-linked gene to her. Therefore, there are more color blind men than
women.

Page published on Monday, November 16, 2020

Attention blindness and other “normal” blindness

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Interesting

90 002 7 min

02/24/2021

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In this article we will tell you: repetition

– Op! Coin in hand! And now rrrr! AND…. – Max once again tried to hide the naughty ruble between his fingers, but he slipped out of his hands, fell to the floor with a clang and rolled away.

During the holidays, Max decided to master the art of illusion. But the tricks described in the book that he bought for this occasion turned out to be much more difficult than he thought.

Lucy decided to support her son:

– Listen, can you do this trick a little slower? That way the coin doesn’t fall out of your hand.

“Yes, but you will see how I hide it!” And the “trick” of the trick is that I do it quickly, and you don’t have time to notice where the coin has gone.

“Hmm, I can blink. Then I won’t see anything!

Psychologists say that our eyes do not notice much. And not only at the performances of illusionists. There are a number of situations in which a person becomes “blind” to the objects and events around him, even if his vision is excellent.

Inattentional blindness

When we focus on something, we do not notice unexpected events that are not related to what is in the center of our attention.

In 1975, scientists Daniel Simons from the University of Illinois and Christopher Chapris from Harvard (USA) conducted an experiment that later became known as the “Invisible Gorilla”.

Its participants were asked to watch a video in which the athletes played basketball and count the number of innings from one of the teams. In the middle of the game, a man dressed as a gorilla suddenly appeared on the field. He walked between the athletes, punched himself several times in the chest, looked at the players and left.

It would seem that such a character is impossible not to notice! However, it turned out that only half of the participants in the experiment paid attention to the gorilla man. The rest were so busy counting passes that they just didn’t see this character.

A few years later, Simons repeated the experiment. This time, he recorded a new video and alerted viewers to the appearance of a man in a gorilla suit. The participants in the experiment had to count the number of ball passes made by girls in white T-shirts.

Not everyone completed this task. It turned out that the attention of the audience was focused on the gorilla. Most of the subjects did not notice two changes that occurred during the video: the color of the curtain changed from red to yellow, and one of the girls left the frame. Only 17% of viewers paid attention to at least one of these changes.

It turns out that people who are focused on counting passes do not see the gorilla in the center of the screen. And those who are looking forward to the appearance of a man in a gorilla costume do not notice how the situation in the frame is changing.

Blindness to change

We do not notice a change if it happened at the moment when we were distracted, blinked, or shifted our gaze to another object.

In 1998, Daniel Simons and another colleague Daniel Levin conducted such a study: the experimenter approached a passerby on the street and asked for directions to a certain object. In 15–20 seconds after the start of the conversation, two fictitious workers carrying the door passed between the interlocutors.

At that moment, when the subject did not see the experimenter, the latter imperceptibly changed places with one of the workers. As a result, when the door was taken away, a completely different person was in front of the passerby. Almost 50% of the subjects did not notice what had happened and continued the conversation.

Ironically, even when the differences between the experimenter and the fictitious worker were made even more obvious (for example, they put a bright helmet on the second), the subjects still did not notice the substitution. As it turned out, they could describe in detail the appearance of the person who approached them with a question, but did not see how much she had changed after the “trick” with the door.

Simons and Levin conducted a similar experiment with videos. The subjects were shown a small film in which the main character and some minor elements changed at the moment of changing the angle of the shooting. According to the results of the experiment, it turned out that 70% of the audience did not notice the substitution of the main character. As for the change in less significant details (clothing, furniture, accessories), no one paid attention to them!

Blindness to repetition

If two identical objects appear in front of us in succession, it is likely that we will not notice the second one.

Various scientists are interested in this phenomenon. One of them is Nancy Kanwisher, a neuroscientist, professor at the Massachusetts Institute of Technology and researcher at the McGovern Institute for Brain Science.

In 1987, she conducted the following study: a group of subjects were presented with a series of words from which they had to make a sentence. In cases where the same words appeared on the screen in succession, the subjects almost always lost sight of the second one. A similar experiment was carried out with letters – and people again turned out to be “blind to repetition.”

On the next test, they were shown letters of different colors. It turned out that if different letters are painted in the same shades, then our brain perceives them as identical and does not notice the second in a row.

The phenomenon of repetition blindness is due to the fact that the brain does not have time to transfer data about the second object from short-term memory to long-term memory before a new piece of information appears in front of it.

If word processors didn’t underline repeated words with a red squiggly line, our messages, letters, and articles would be far less compelling to read. Try disabling this feature in Word and see for yourself.

Banner blindness

We do not notice intrusive advertising on the Internet

In 2018, representatives of the American consulting company Nielsen Norman Group shared the results of a study, during which they were once again convinced that Internet users very often do not notice ads.

Over the years of living in the digital age, we have learned to focus only on what can bring us real benefit. This is, for example, a search bar, a navigation bar, an article title.

Jakob Nielsen, Ph.D., founder and director of the Nielsen Norman Group, coined the term “hot potato phenomenon”: Internet users treat ads in a similar way: when they even glance at an ad, they don’t look back at this place, even if there may be something useful there.