Lecture about Visual Important

ALL ABOUT VISUAL IMPAIRMENT Visual or vision impairment (VI or VIP) is the partial or total inability of visual perception. In the absence of treatment such as corrective eyewear, assistive devices, and medical treatment, visual impairment may cause the individual difficulties with normal daily tasks, including reading and walking. Vision loss can happen for a variety of reasons, causing the types of visual impairments to cover a wide spectrum. As a rule, visual impairment cannot be fixed simply by glasses or contact lenses. There are stages of vision loss. What we call blindness is when a visual impairment results in total or near-total vision loss. The World Health Organization (WHO) International Classification of Impairment, Disabilities, and Handicaps (ICIDH) system is used to classify the types of visual impairment. This system, as the name suggests, is used to classify disorders, impairments, disabilities, and handicaps. Definition of impairment Impairment is defined as “any loss or abnormality in an anatomical structure or a physiological or psychological function.” Similarly a disability is “any restriction or lack (resulting from an impairment) of ability to perform an activity in the manner or within the range considered normal for a human being.” This places an individual in a handicap that is a person’s disadvantaged position in society due to an impairment or disability. Definition of visual impairment Visual impairment is defined as the limitation of actions and functions of the visual system. The National Eye Institute defines low vision as a visual impairment not correctable by standard glasses, contact lenses, medication or surgery that interferes with the ability to perform activities of daily living. Types of visual impairment According to the CDC and the World Health Organization the classification of visual acuity and impairment includes (1, 2). Low visual acuity means vision between 20/70 and 20/400 with the best possible correction, or a visual field of 20 degrees or less. Blindness is defined as a visual acuity worse than 20/400 with the best possible correction, or a visual field of 10 degrees or less. Legal blindness in the US means visual acuity of 20/200 or worse with the best possible correction, or a visual field of 20 degrees or less. Visual acuity of 20/70 to 20/400 (inclusive) is considered moderate visual impairment or low vision. Causes of visual impairment Types of impairment are different for different causes of visual impairment. In total vision loss for example there may be total darkness of the visual fields. Other types include visual impairment in glaucoma, age-related macular degeneration and so forth. (1-5). Visual impairment in glaucoma This condition is due to the rise of normal fluid pressure inside the eyes. The type of vision is usually like a tunnel. The intact vision remains in the center while progressively the peripheries start decreasing. The center of the tunnel reduces in size progressively till total vision is lost if left uncorrected. Age-Related Macular Degeneration A central area of woolly or cottony opacity obscures the central part of the vision. The peripheries may be normally seen. AMD usually blurs the sharp, central vision that is needed for closely viewed activities like reading, sewing, and driving. This is a painless condition. Cataract There is general clouding of the vision. As the whole eye lens is affected the blurring of vision may be diffuse until it is totally lost. There may be other symptoms like photophobia – inability to see the light; diplopia – double vision etc. Cataracts are very common in older people. Diabetic Retinopathy Diabetes leads to damage of the smaller arteries and blood vessels at the back of the eyes over the retina. Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness in adults. Usually vision impairment in diabetics begins as black spots or floating shapes that appear in the field of vision. Slowly complete vision may be lost if left unchecked. Near sightedness Myopia or near sightedness or short sightedness means a person can see nearby objects clearly but distant objects appear blurred. High myopia may lead to vision impairment. Retinitis Pigmentosa This is a genetic or inherited condition. Initially it manifests as night blindness. As the disease progresses there may be a tunnelling of vision with loss of peripheral vision followed by complete blindness. Amblyopia Also called “lazy eye,” this functional problem often causes decreased vision in one or both eyes, but it doesn’t include any detectable damage to the retina. The brain tends to shut down vision in one eye to favor the good vision in the other eye. Depending on the situation, the treatment may be something as simple as wearing a patch on the good eye so the weaker eye can strengthen. Aniridia Aniridia is the incomplete formation of the iris. It is usually a congenital anomaly, but it can also result from an injury where an object penetrates the eye. This condition often causes poor vision and sensitivity to light. Sometimes corrective and tinted lenses can help resolve the problem. Achromatopsia Achromatopsia can develop due to malformation or partial/total absence of cones in the eye, which makes it difficult to distinguish colors. It’s important to note that this is different from color blindness. This hereditary condition often includes some vision loss in bright light. The severity of achromatopsia differs across patients, with the most severe cases unable to see any colors at all. Astigmatism When the eye is unable to focus completely at any distance, it usually results from a spoon-like shape of the normally spherical cornea. This shape bends light rays unequally, which prevents vision focus. Most people have some degree of astigmatism and slight astigmatism may not be a problem, but more severe cases require special glasses or surgery. Color Blindness What we call “color blindness” is not blindness at all, but a deficiency in how certain people perceive color. There are different types of color blindness, with red-green and yellow-blue types the most common forms. For the most part, males are more likely to be color blind than females. To deal with color blindness, the individual must learn other ways to recognize important information, such as recognizing the state of traffic lights by the positioning of the light rather than by the coloring. Hyperopia (Farsightedness) This vision loss occurs when an individual can clearly see objects that are far away but not focus on objects nearby. Basically, light rays from a distant object strike the retina before the eye can focus. This is a common visual disorder and glasses or contact lenses are usually used to correct this problem. Myopia (Nearsightedness) The opposite of hyperopia, people with myopia can see objects that are near but cannot see objects that are in the distance. In this case, the light rays enter the eye and come to a focus before reaching the retina. A simple solution to this vision loss is glasses or contacts, however, some may be eligible for surgery to correct the vision. Macular Degeneration The deterioration of the macula causes loss of focused central vision, which challenges acuity and color discrimination. This vision loss can affect all ages, but is most common in older people; in fact, it is the most common form of vision loss in people aged 50 or over. The most common form of the macular degeneration is Stargardt’s Disease. Optic Nerve Atrophy When the optic nerve atrophies, this dysfunction results from the optic nerve not being able to send electrical impulses to the brain. The most common cause of the atrophy of the optic nerve is poor blood flow, but the condition may result from trauma, toxins, or radiation as well. The lack of communication between brain and optic nerve results in vision loss, which may include blind spots. Retinal Detachment A condition caused by the separation of the retina from the pigmented cell layer that maintains the retina, retinal detachment can cause severe myopia. Usually caused by a slight retinal tear that begins to experience fluid passing from the vitreous into the sub-retinal space, the tear disrupts the eye structure. This condition tends to require surgery to restore normal sight. Visual impairments can be caused by many different types of situations including infections and trauma. Whether the infection occurs before birth or during life at some point, vision loss can be the result of localized infection. Head injuries can also cause vision impairments. With so many different types of visual impairments, it’s important that society creates a world that is accessible to everyone. At StrongGo, we work towards greater accessibility every day with our detectable dome tiles that help signify to people with low vision an intersection or mass transit platform. Crossed Eyes (strabismus) Strabismus occurs when the eyes do not line up or they are crossed. One eye, however, usually remains straight at any given time. Common forms of strabismus include: Esotropia – one or both eyes turn inward toward the nose. Exotropia – one or both eyes turn out; also called wall-eyed. Hypertropia – one or both eyes turn up. Hypotropia – one or both eyes turn down. If detected early in life, strabismus can be treated and even reversed. If left untreated strabismus can cause amblyopia. Lazy Eye (amblyopia) Amblyopia — often called lazy eye — is a problem that is common in children. Amblyopia is a result of the brain and the eyes not working together. The brain ignores visual information from one eye, which causes problems with vision development. Treatment for amblyopia works well if the condition is found early. If untreated, amblyopia causes permanent vision loss. Types of blindness Partial blindness: You still have some vision. People often call this "low vision." Complete blindness: You can't see or detect light. This condition is very rare. Congenital blindness: This refers to poor vision that you are born with. The causes include inherited eye and retinal conditions and non-inherited birth defects. Legal blindness: This is when the central vision is 20/200 in your best-seeing eye even when corrected with glass or contact lenses. Having 20/200 vision means that you have to be 10x closer or an object has to be 10x larger in order to see compared to a person with 20/20 vision. In addition, you can be legally blind if your field of vision or peripheral vision is severely reduced (less than 20 degrees). Nutritional blindness: This term describes vision loss from vitamin A deficiency. If the vitamin A deficiency continues, damage to the front surface of the eye (xerophthalmia) This type of blindness can also make it more difficult to see at night or in dim light due to retinal cells not functioning as well. Xerophthalmia Xerophthalmia is pronounced "zeer-of-thal-mee-uh” or “zeer-op-thal-mee-uh.” The Greek root words literally mean “dry eye.” Vitamin A deficiency can cause health problems throughout your body, including the eyes. Xerophthalmia is a group of eye signs and symptoms that can result in blindness. Treatment consists of taking vitamin A. Written by Syed Irfan Abid Bukhari Syed Irfan Abid Bukhari is a Audiometerist by profession, lecturer by vocation and a writer by passion. I pride myself on my service, and i'd love to hear from you!