What Is Low Vision?
Vision loss that cannot be corrected by ordinary eyeglasses, contact lenses, medication or surgery. A person with low vision has extremely limited sight that interferes with daily activities..
You can still see something. And with the help of vision aids, you can stay independent.
– Worse than 6/18 in the better eye
– Significant field loss
– Impaired function
What Causes Low Vision?
Low vision can be caused by a number of diseases in the eye. An injury to the eye can also result in low vision. And some people are born with low vision.
The macula may break down, causing loss of central vision (macular degeneration).
The blood vessels may become weak and leak fluid into the eye (diabetic retinopathy).
The optic nerve may be damaged by glaucoma (increased eye pressure) and be unable to send messages to the brain.
Low vision can be caused by a number of diseases in the eye. An injury to the eye can also result in low vision. And some people are born with low vision.
The macula may break down, causing loss of central vision (macular degeneration).
The blood vessels may become weak and leak fluid into the eye (diabetic retinopathy).
The optic nerve may be damaged by glaucoma (increased eye pressure) and be unable to send messages to the brain.
Stroke/ brain injury
Retinitis pigmentosa
Optic Nerve disease
Albinism
Nystagmus
Cortical Visual Impairment
What are the Symptoms?
The symptoms of low vision depend on the cause of the vision loss and where the problem is in the eye. Symptoms can include:
Blank spots, dark spots or wavy lines in the centre of your vision
Blurred, hazy or cloudy vision or double vision
Loss of side (peripheral) vision or colour vision.
Goals of Low Vision Management?
¬ Increase functionality - Make the most of the remaining vision
¬ Provide link to community resources and support services
¬ Education
Functional Effects of Low Vision
- Loss of central vision (visual acuity)
· Difficulty reading
· Problems writing/ completing paperwork
· Inability to recognize distance objects and faces
- Loss of peripheral vision (visual field)
· Location of scotoma important!
· Generalized loss of visual field difficult to compensate for
· Mobility and independent travel
· Reading may require adaptations
· Glare and contrast
· Need for additional lighting
· Problems with glare
· Increased adjustment to changes in illumination
· Visual discomfort and fatigue
Staying Independent
Using vision aids can help you do the things you need and want to do. There are many kinds of vision aids. Low-vision centres and some doctors sell these aids. They also train you to use your aids. And they will talk with you about proper lighting.
Working with Your Eye Doctor
Your eye doctor will check your eyes and help you get the vision aids that will work best for you. Or, he or she may refer you to a low-vision specialist (an eye doctor who is trained to treat low vision). You'll most likely have glasses prescribed for you, too. Many vision aids are designed to be used along with glasses. Be sure to wear your glasses as directed.
Magnification
Using vision aids can help you do the things you need and want to do. There are many kinds of vision aids. Low-vision centres and some doctors sell these aids. They also train you to use your aids. And they will talk with you about proper lighting.
Working with Your Eye Doctor
Your eye doctor will check your eyes and help you get the vision aids that will work best for you. Or, he or she may refer you to a low-vision specialist (an eye doctor who is trained to treat low vision). You'll most likely have glasses prescribed for you, too. Many vision aids are designed to be used along with glasses. Be sure to wear your glasses as directed.
Magnification
¬ Enlarges image on retina to stimulate more retinal cells
¬ Can be achieved in many ways
– Relative Distance
– Relative Size
– Optical / Angular
– Electronic
Low Vision Devices
¬ Distance
1. Hand held telescopes
2. Mounted telescopes
3. Electronic systems
Electronic Distance Systems
¬ Near Devices
· Spectacles
– Prismatic ½ eyes
– Full-field microscopes
· Magnifiers
– Hand held vs. stand
– Illuminated vs. non-illuminated
· Tele microscopes
· Electronic Devices
¬ Field enhancement
¬ Non-optical
· Glare reduction devices
· Contrast enhancement devices
· Computer software
· Accessory devices
– Talking watches, clocks, etc
– Writing guides
– Tactile markers
CCTV CAMERA
When traditional optical low vision aids don't help accomplish a task, electronic aids might help. Closed-Circuit Television (CCTV) systems help people who need greater magnification than reading glasses, magnifiers, and microscopes provide [Figure 6]. CCTV systems also allow the user to adjust the size, brightness, and contrast of the magnified image to best match the user's vision. The user can even read white letters on a black background to decrease glare. CCTV systems have historically been far more expensive and far less portable than other near vision aids. Newer CCTV designs, however, such as the MagniCam®, are now smaller, more versatile, more portable, and less expensive then previous CCTV systems. Other electronic aids help users see far away objects.
When traditional optical low vision aids don't help accomplish a task, electronic aids might help. Closed-Circuit Television (CCTV) systems help people who need greater magnification than reading glasses, magnifiers, and microscopes provide [Figure 6]. CCTV systems also allow the user to adjust the size, brightness, and contrast of the magnified image to best match the user's vision. The user can even read white letters on a black background to decrease glare. CCTV systems have historically been far more expensive and far less portable than other near vision aids. Newer CCTV designs, however, such as the MagniCam®, are now smaller, more versatile, more portable, and less expensive then previous CCTV systems. Other electronic aids help users see far away objects.
Few Instruction before the use of Low Vision Aids
Proper Lighting
ü Along with vision aids, you need good lighting to help you see. For improved lighting:
ü Use a portable light with an adjustable arm. Place it close to what you're reading or doing.
Sit near a window during the day. At night, make sure there is plenty of lighting in the room.
Sit near a window during the day. At night, make sure there is plenty of lighting in the room.
ü Try a visor, a hat with a brim or special lenses to reduce glare from lighting or the sun.
Tips for the Family
ü You can help your loved one learn to use vision aids and see better.
ü Go to the doctor with him or her and learn what vision aids are available.
ü Make sure the person gets what he or she needs.
ü Help the person learn to use the vision aids.
ü Encourage him or her also to wear glasses as directed by the eye doctor.
