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Computer Simulation of Visual Impairments


Introduction Screenshots User Guide Project Report Links

Glaucoma / Retinitis Pigmentosa Macular Degeneration Diabetic Retinopathy Hemianopia with Macular Involvement Hemianopia with Macular Sparing Cloudy Cataracts Double Vision Cataracts Yellow / Brown Cataracts Colour Blindness Myopia / Hyperopia


Glaucoma

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Cause: The optic nerve is damaged at the point where it leaves the eye. This may be caused by increased intracocular pressure (pressure of the fluid inside the eye) or by weakness in the optic nerve. In the normal eye, the ciliary body (a layer of cells behind the iris) secretes a watery fluid called aqueous. This fluid then flows through the pupil before leaving the eye via the trabecular meshwork (drainage channels between the back of the cornea and the iris).

Primary open angle or chronic glaucoma occurs when these drainage channels become slowly blocked and the eye pressure rises, causing damage to the optic nerve. The field of vision gradually becomes impaired. Acute angle closure glaucoma occurs when there is a sudden and more complete blockage to the flow of aqueous caused by the apposition of the lens to the back of the iris.

Symptoms: Reduction in the peripheral field of vision (tunnel vision).

Glaucoma / Retinitis Pigmentosa

Computer Simulation of Glaucoma / Retinitis Pigmentosa

Retinitis Pigmentosa

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Cause: retinitis pigmentosa is the name given to a group of hereditary eye conditions that affect the retina's ability to respond to light.

Symptoms: Reduction in the peripheral field of vision (tunnel vision) and difficulty in seeing in poor light.

Glaucoma / Retinitis Pigmentosa

Computer Simulation of Glaucoma / Retinitis Pigmentosa

Macular Degeneration

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There are two types of macular degeneration:

Cause: Wet macular degeneration results in a build-up of fluid under the retina. This causes bleeding and scarring which leads to sight loss. Dry macular degeneration is caused by pigmentary changes at the macula.

Symptoms: Macular degeneration usually occurs in both eyes, but it may be asymmetrical. In the early stages central vision may be disturbed or blurred. Straight lines may seem wavy and objects may become distorted or appear an unusual size or shape. Peripheral vision is unaffected. Eventually, central vision may be completely lost resulting in a blank patch or dark spot. This central area of visual distortion or loss moves as the patient tries to look around it.

Macular Degeneration

Computer Simulation of Macular Degeneration

Diabetic Retinopathy

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Cause: diabetic retinopathy affects the fine network of blood vessels within the retina. It is usually graded in three main stages according to how severe it is.

Symptoms: Peripheral vision will be initially preserved. Some central vision loss may occur. As the condition progresses to Proliferative diabetic retinopathy, pigment or blood in the vitreous may cause blurred or patchy vision with floaters or blobs.

Computer Simulation of Diabetic Retinopathy

Hemianopia

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Hemianopia is also known as Hemianopsia.

Cause: Damage to the brain as a result of stroke, tumour or trauma.

Symptoms: Loss of vision in one half of the visual field.

Hemianopia with macular involvement

Computer Simulation of Hemianopia with Macular Involvement

Hemianopia with macular sparing

Computer Simulation of Hemianopia with Macular Sparing

Cataracts

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Cause: A cataract is the opacification (clouding) of all or part of the lens which prevents light passing through. Cataracts often form slowly with age. The lens turns from being clear to yellow and then eventually to brown.

Symptoms: Sensitivity to glaring light. Blurred or misty vision, multiple images, double vision or ghost images. Print appears hazy. Colours may appear faded, and contrast is limited.

Cataracts - cloudy vision

Computer Simulation of Cataracts - Cloudy Vision

  Cataracts - double vision

Computer Simulation of Cataracts - Double Vision

Cataracts - yellow vision

Computer Simulation of Cataracts - Yellow / Brown Vision

Colour Blindness

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Colour blindness is the reduced ability to discriminate between different wavelengths of light.

Cause: The retina contains three types of cone cells. The short-wave (blue), medium-wave (green) and long-wave (red) cone cells each contain a different photosensitive pigment. They have peak sensitivities in the blue, green and red wavelengths of the visible spectrum. colour blindness is the result of deficiencies in the cone photopigments, which can be classified into three main types:

Symptoms:

Colour blindness

Computer Simulation of Colour Vision

Myopia

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Myopia is also known as short-sightedness.

Cause: Refractive error. Parallel light rays are focussed in front of the retina when the eye is in its relaxed state. This is because the eyeball is too long for the natural converging power of the cornea and lens.

Symptoms: The eye can see close objects clearly whist distant objects appear blurred.

Myopia / Hyperopia

Computer Simulation of Myopia / Hyperopia

Hyperopia

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Hyperopia is also known as Hypermetropia or long-sightedness.

Cause: Refractive error. Parallel light rays are focussed behind the retina when the eye is in its relaxed state. This is because the eyeball is too short for the natural converging power of the cornea and lens.

Symptoms: The eye can see distant objects clearly whist close objects appear blurred.

Myopia / Hyperopia

Computer Simulation of Myopia / Hyperopia


Stephen Ratcliffe. 2005