Common Visual Impairment Types Explained with Physics Examples
Types of Visual Impairment
Visual or vision impairment is the decreased ability to see usually associated with age and cannot be cured by prescription glasses or other medicines and surgical processes. The term blindness is used for the condition that involves the loss of complete vision. Visual impairment ranges from low to severe. The most recurrent causes of visual impairment throughout the world are uncorrected refractive errors, cataracts, and glaucoma. There are different types of visual impairment; conditions like near and farsightedness, presbyopia, and astigmatism are caused by refractive errors. Blindness is caused by cataracts. Visual impairments are often related to the increasing age and other conditions that it causes. Other disorders, such as age-related macular degeneration, corneal clouding, and diabetic retinopathy, can also give rise to visual impairment.
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Vision Problems
As we discussed earlier, there are various factors that give rise to different types of visual impairment. Refractive errors are caused when the shape of the eyes resists one from focusing well. It is a vital problem of a visually challenged person. Cataracts are the one that causes visual impairment for people that are old-aged, though cataracts can also harm the vision for middle-aged people as well. There are many causes of cataracts, such as cortisone medication and diabetes. Here in this section, we will discuss the two most important causes of visual impairment-
Cataracts- 33% of the visual impairment cases are caused by cataracts and it is one of the leading causes of blindness that doubles the prevalence with every ten years after one has reached the age of forty. It is most common among adults rather than being in the case of children. Inspire of the progress in the medical domain; cataracts remain of the leading factors in case of visual impairment.
Glaucoma- Glaucoma causes around 2% of all the visual impairment cases around the world. It causes visual field loss as well as damages the optic nerves. It is funny that pediatric glaucoma can be acquired after a cataract-removal surgery.
Solution to Vision Impairment and Optical Aids
The development that we have witnessed in the medical domain over the years has given us many solutions to vision impairment. Telescopes, magnifying glasses are blessings to a visually challenged person. Some other ways are also there, such as Braille that has given a visually challenged person the ability to read and write. That uses the technology of raised dots; each set of dots represent an alphabet. People with low visual impairment are often given glasses or contact lenses according to their needs, which we will discuss later in the following section.
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Low Vision Aids: Depending on the severity of the visual impairment, optical aids can range from reading glasses to small scale telescopes. However, low vision devices are not made for all purposes. They are used with a specific purpose in mind. People that have been contracted with low vision impairment, the specific one that is called a negative visual impairment in medical terminology, are often administered with magnifying glasses that are often mounted in spectacles that give them a wide variety. A negative visual impairment is a condition where the visually challenged person has trouble looking at a far distance. Though low vision aids help a visually challenged person to view things clearly, it does not bring back the vision that has already been lost. Various kinds of low vision aids are popular these days, and the aids have been varied throughout the centuries. In the early days, people used to fasten a rope in the spectacle and hang those in the neck, or some used to hold the spectacle in front of their eyes manually. Some used to use magnifiers or small telescopes. These low vision aids can save the remaining vision from getting lost.
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Solved Examples
1. What are the Low Vision Devices for Students?
NuEyes, DaVinci Pro, Sirecues are some of the devices that can be used for visually impaired students.
2. Name a Device Used by Blind Person.
Tape recorders, speech compressors, reading machines, optacon, Braille printers are some of essential devices that are used by a blind person.
Did You Know?
There are almost 36 million people around the world that are blind. Around 217 million have moderate or severe distance vision impairment. Low and middle-income countries take up to 90% of the visually impaired people in the world. Cataract surgery and correction of refractive errors are one of the most cost-effective surgeries in the medical domain. 51% of all blindness is due to age-related problems or cataracts.
FAQs on Types of Visual Impairment: Key Concepts, Causes & Solutions
1. What does the term 'visual impairment' actually mean?
Visual impairment refers to a decreased ability to see that cannot be fully corrected by standard means like glasses or contact lenses. It encompasses a wide range of vision loss, from partial sight to complete blindness. It is primarily defined by a loss of visual acuity, where the eye cannot see objects with the same clarity as a person with normal vision.
2. What are the most common causes of visual impairment?
The leading causes of visual impairment globally are primarily due to diseases and conditions that affect the eye's structure and function. The most common causes include:
Refractive Errors: Conditions like myopia (nearsightedness) and hypermetropia (farsightedness) that are uncorrected.
Cataracts: A clouding of the eye's natural lens, which is a major cause of blindness, particularly in older adults.
Glaucoma: A condition that damages the optic nerve, often due to high pressure inside the eye.
Age-Related Macular Degeneration (AMD): Deterioration of the macula, the part of the retina responsible for sharp, central vision.
Diabetic Retinopathy: A complication of diabetes that affects the blood vessels in the retina.
3. What are the main types of visual impairment?
Visual impairments are broadly categorised based on how they affect vision. The primary types include:
Myopia (Nearsightedness): Distant objects appear blurry while close objects are clear.
Hypermetropia (Farsightedness): Close objects appear blurry, and in some cases, distant objects may also lack sharpness.
Presbyopia: An age-related condition where the eye's lens loses its flexibility, making it difficult to focus on close objects.
Astigmatism: Vision is blurred at all distances due to an irregularly shaped cornea or lens.
Cataracts: Causes an overall cloudiness or dimming of vision.
4. How do refractive errors like myopia and hypermetropia differ in terms of what happens inside the eye?
The key difference between myopia and hypermetropia lies in where light is focused relative to the retina. In myopia (nearsightedness), the eyeball is often too long or the lens too curved, causing light to focus in front of the retina. This makes distant objects look blurry. In hypermetropia (farsightedness), the eyeball is typically too short or the lens not curved enough, causing light to focus behind the retina. This makes it difficult to see nearby objects clearly.
5. Why is a cataract a leading cause of blindness, especially in older adults?
A cataract is the clouding of the eye's natural lens, which is made mostly of water and protein. With age, these proteins can start to clump together, creating cloudy areas on the lens. This cloudiness prevents light from passing through clearly, leading to blurry or dim vision. Because this process is a natural part of ageing, it is extremely common in older adults. If left untreated, the cataract can become so dense that it blocks most light, resulting in blindness. Fortunately, this type of blindness is often reversible with surgery.
6. How do corrective lenses in spectacles actually work to fix vision problems?
Corrective lenses work by precisely bending, or refracting, light before it enters the eye to ensure the image focuses correctly on the retina. For myopia, a concave lens is used. This lens diverges light rays, effectively moving the focal point backward onto the retina. For hypermetropia, a convex lens is used. This lens converges light rays, moving the focal point forward onto the retina. The power of the lens is carefully prescribed to compensate for the specific refractive error of the individual's eye.
7. What are the common signs that might indicate a visual impairment?
Recognising the signs of visual impairment is crucial for early detection and treatment. Common characteristics include:
Difficulty reading small print or seeing distant objects clearly.
Frequent squinting or tilting the head to see better.
Increased sensitivity to light and glare.
Seeing halos around lights.
Poor night vision.
Changes in colour perception.
8. Are there solutions for visual impairment other than wearing glasses?
Yes, while glasses are a common solution, several other options exist. Contact lenses offer a wider field of view and are a popular alternative. For more permanent correction of refractive errors, surgical procedures like LASIK reshape the cornea. For conditions like cataracts, cataract surgery, which involves replacing the cloudy lens with an artificial one, is a highly effective solution. Additionally, for those with low vision, various aids like magnifiers and electronic devices can significantly improve daily functioning.
9. What is the difference between being visually impaired and being legally blind?
While related, these terms have distinct meanings. Visual impairment is a broad term for any level of vision loss that impacts a person's ability to perform daily activities. Legal blindness, however, is a specific, defined threshold of vision loss. In most places, it is defined as having a visual acuity of 20/200 or less in the better eye even with corrective lenses, or a visual field of 20 degrees or less. A person can be visually impaired without being legally blind, but a legally blind person falls under the umbrella of visual impairment.
