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Low Vision = Useable Vision |
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| Low Vision |
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| The person is said to have low vision when conventional spectacles, contact lens or medical and surgical intervention cannot improve vision and finds difficulty in daily routine activities in everyday life
Everyday tasks, such as reading, shopping, cooking, watching television and writing can seem challenging.
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| Causes of Low Vision |
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Vision is a complex sense with an ability to perceive details, color, and contrast and distinguish objects. These capacities can diminish with advancing age or can occur because of any eye diseases or ocular trauma or birth defect.
There are varieties of eye diseases affecting vision, depending on site of their involvement some common problems are
Corneal Pathology – Any injury or damage to the cornea (black shining part in front of the eye) result in clouded image and increased glare sensitivity and the reading print appears hazy or reduced in contrast.
Glaucoma – Chronic elevated eye pressure can cause optic nerve damage and loss of peripheral field of vision and also reduces the contrast. The print can appears faded and words are difficult to read.
Macular Degeneration/Dystrophy - It is the ageing process, but can occur at younger age also. Macular is the central area of retina, which due to degeneration gets distorted. This can cause decrease in central vision where a person can notice a black spot in front of his eye. The print can appear distorted and segments of words be missing.
Diabetic Retinopathy - In advanced or long term diabetics there can be leaking of retinal blood vessels which can effect the macular, or the entire retina, the person can have variable amount of vision and print may appear distorted or blurred with patchy shadows while reading.
Birth/Inherited Diseases: Albinism, Micropthalmos, Cone dystrophies, Cerebral palsy, etc.
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| Signs of Low Vision |
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- Difficulty to recognize a familiar face
- Difficulty reading and writing
- Difficulty doing things that require seeing well up close, such as cooking, sewing, or fixing things around the house
- Reading the instructions on medication
- Difficulty picking out and coordinating the color of clothes
- Finding it hard doing things at work or home because lights seem dimmer than usual
- Unable to read street and bus signs or the names of store
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| Types of Low Vision |
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- Reduced Peripheral Vision
- Reduced Central Vision
- Disabled Colour Vision
- Reduced ability to adjust to light, contrast and glare
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| Low Vision Devices |
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| Low vision devices are categorized as either optical or non-optical devices.
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| Optical Low Vision Devices |
Optical devices use lenses or combination of lenses to provide magnification. They are available in many types and different strengths.
Magnifying Glasses – Available from low to high power, useful for reading and writing, can be worn as normal reading glasses.
Hand Held Magnifiers - Used for reading, seeing labels or price tags.
Stand Magnifier - Rest on reading material, some are available with inbuilt illumination. Greater magnification can be achieved with this type of magnifier.
Telescope –Telescope used for distance magnification, like looking at board in classroom or watching television. They are available as hand held or spectacle mounted.
Video Magnifiers – Electronic Magnifier or CCTV which produces enlarged image on television screen or monitor. Tabletop magnifiers make it easy to read books and magazines.
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| Non Optical Devices |
Non optical devices are used in form of enlarged image or to bring images closer to the eyes thus providing magnification. These are available as adaptive devices like large print magazines, calendar, playing cards, timer, calculators etc.
- Large print books, illuminated watches, telephone, clock etc
- Writing guides, Typoscope, reading guides
- Instrument that provide voice instruction (i.e. computers, calculators, telephone)
- Bold felt tipped pen, dark pencils
- Absorptive Lenses
- Good illumination adjustable lights and stands
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| Comprehensive Low Vision Services |
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Specially trained professionals provide low vision services.
When there are no other avenues to pursue medically or surgically for the patient, Low vision specialist will conduct a comprehensive Low Vision Examination and will offer a wide array of proven techniques to help the patient maximize their usable vision with the goal of living independently in their environments,
The services include
- Functional vision assessment
- Clinical vision assessment
- Prescription of non-optical and optical low vision devices
- Training to use the low vision devices
- Follow-up care as needed, for low vision instruction and training
- Low vision rehabilitation, mobility training, and counseling.
- Guidelines for environmental modification
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