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Adapting Video for VI Learners

Visual Impairments

What matters to teachers is not the eye condition producing the visual impairment, but its functional effects in learning settings (in our particular case, its effect on viewing video materials). Here is a list of common (and some rarer) eye conditions, with a note of which of the effects we have described are likely to result from it.

This list is just indicative, to help you when someone has presented you with a terse, medically oriented description of a student's problems. You will always need to talk through the effects of any condition with the student and maybe other professionals. Remember that conditions and effects vary in severity; that some problems can affect different parts of the field of view; and that the person may be suffering from more than one impairment.

DIABETIC RETINOPATHY Retinal changes occurring in long standing cases of diabetes mellitus. In general the amount of the retinopathy is related to the duration of the disease rather than the severity of the disease. Both eyes are involved but usually to differing degrees. Visual acuity is unaffected unless the central macular area is involved.

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DIPLOPIA The seeing of one object as two.

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DIVERGENT SQUINT The eye turns outward to the temporal side.

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ENUCLEATION Complete surgical removal of the eyeball.

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ESOTROPIA A manifest turning inward of the eye (convergent strabismus or crossed eye).

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EXOPHTHALMOS Abnormal protrusion of the eyeball.

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EXOTROPIA Abnormal turning outward from the nose of one or both eyes (divergent strabismus).

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ECCENTRIC FIXATION Fixation, where the object of regard is not imaged on the fovea. In this condition the patient feels they are looking straight ahead at the object, but in fact the image is stimulating an area just outside the fovea.

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FLOATERS Small particles consisting of cells or fibrin which move in the vitreous.

GLAUCOMA Increased pressure inside the eye; 'hardening of the eyeball', caused by accumulation of aqueous fluid in the front portion.

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GLIOMA Malignant tumor of the retina.

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HEMIANOPIA Blindness of one half of the field of vision of one or both eyes.

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HETEROTROPIA (CROSS EYE; STRABISMUS:SQUINT) An obvious or manifest deviation of the visual axis of an eye out of alignment with the other eye.

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HYPEROPIA, HYPERMETROPIA (LONGSIGHT) A refractive error in which, because the eyeball is short or the refractive power of the lens weak, the point of focus for rays of light from distant objects (parallel light rays) is behind the retina; thus accommodation to increase the refractive power of the lens is necessary for distance as well as near vision.

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HYPERPHORIA A tendency of one eye to deviate upward.

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HYPOPLASIA A congenital absence of nerve fibres

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IRIDOCYCLlTIS Inflammation of the iris and ciliary body.

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IRITIS Inflammation of the iris; the condition is marked by pain, inflammation, discomfort from light, contraction of pupil, discoloration of iris. It may be caused by injury, rheumatism, gonorrhea, tuberculosis.

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KERATITIS Inflammation of the cornea; frequently classified as to type of inflammation and layers of cornea.

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KERATOCONUS Cone shaped deformity of the cornea.

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MACULA DEGENERATION Affection of the most sensitive part of the retina, the macula. A central degenerative condition of the retina in which the photoreceptors (the rods and cones) in the macular area lose their function, due to the disruption of the underlying pigment epithelium. The disease is usually age related but may occur in younger age groups (eg; Best's disease).

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MACROPHTHALMOS Abnormally large eyeball, resulting chiefly from infantile glaucoma.

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MICROPHTHALMOS An abnormally small eyeball.

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MONOCULAR VISION Vision in one eye only

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MYOPIA (NEAR/SHORTSIGHTEDNESS) A refractive error in which, because the eyeball is too long in relation to its focusing power, the point of focus for rays of light from distant objects (parallel light rays) is in front of the retina. Thus, to obtain distinct vision, the object must be brought nearer to take advantage of divergent light rays (those from objects less than twenty feet away).

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NIGHT BLINDNESS A condition in which the sight is good by day but deficient at night and in faint light.

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NYSTAGMUS An involuntary, rapid movement of the eyeball; it may be lateral, vertical, rotary, or mixed

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OPTIC ATROPHY Degeneration of the nerve tissue which carries messages from the retina to the brain.

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OPTIC NEURITIS Inflammation of the optic nerve.

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PHOTOPHOBIA Abnormal sensitivity to and discomfort from light.

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PRESBYOPIA A gradual lessening of the power of accommodation due to a physiological change which becomes noticeable after the age of forty.

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PTOSIS A paralytic drooping of the eyelid.

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RETINAL DETACHMENT A separation of the retina from the choroid causing blindness.  

RETINITIS Inflammation of the retina.

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RETINITIS PIGMENTOSA A hereditary degeneration and atrophy of the retina. There is usually misplaced pigment.

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RETINOPATHY A disease of the retina, due to various causes.

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RETINOPATHY OF PREMATURITY/RETROLENTAL FIBROPLASIA A disease of the retina in which a mass of scar tissueforms in the back of the lens of the eye. Both eyes are affected in most cases and it occurs chiefly in infants born prematurely who receive excessive oxygen.

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SCLERITIS Inflammation of the sclera; the white part of the eye a tough covering which, with the cornea, forms the external, protective coat of the eye.

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STEREOSCOPIC VISION (STEREOPSIS) Ability to perceive relative position of objects in spacewithout such cues as shadow, size and overlapping. Not possible with monocular vision.  

STRABISMUS Squint; failure of the two eyes simultaneously to direct their gaze at the same object because of muscle imbalance.

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TUNNEL VISION Contraction of the visual field to such an extent that only a small area of central visual acuity remains, thus giving the affected individual the impression of looking through a tunnel.

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UVEITIS Inflammation of the vascular coat of the eye.

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