Low Vision

Question 1

Using the Snellen fraction measurement, what are the ranges for normal vision to low vision to blindness?

Answer 1

• Normal - 20/12— 20/25
• Near Normal- 20/30– 20/60
• Moderate low vision- 20/70—20/160
• Severe low vision- 20/200 (legally blind)
• Profound low vision 20/500
• Near Blindness-20/1200
• Blind- No light perception

Snellen Fraction (20/20)

• Optotypes
• Acuity = the smallest line of optotype that can be read with good accuracy.
• 20/20 = Standing as a distance of 20 feet, the viewer can see the letter that a person with normal vision can see at 20 feet.
• 20/200 = Standing at a distance of 20 feet, the viewer can see a letter that a person with normal vision can see at 200 feet.

Question 2

What are the Snellen fractions for some functional daily activities, and at what level is independence affected?

Answer 2

• Newsprint requires 20/50 vision
• Driving a car requires 20/40 – 20/60
• Menu at McDonald’s requires 20/80 vision
• Microwave controls require approximately 20/100 vision
• Grooming requires 20/50 – 20/100 vision
• Independence is threatened when vision falls below 20/60

Question 3

What are some of the common diagnoses that can cause low vision and what are their signs and symptoms?

Answer 3

• Macular Degeneration (AMD)
  
  • Age-related macular degeneration is an acquired retinal disorder caused by degenerative changes in the retinal pigment epithelium with subsequent degeneration of the rods and cones
  • •Signs and Symptoms
  • Blurred central vision
  • •Central vision is lost making it difficult to see detail
  • •Central scotoma
  • •Increased need for light
  • •Glare sensitivity and slower recovery time going from outdoors to indoors
  • •Charles-Bonnet syndrome
• Cataracts
  
  • •Opacification of the crystalline lens resulting in decreased visual acuity.
• Signs & Symptoms
• Glare Sensitivity
• Decreased acuity
• Increased myopia in nuclear sclerotic cataracts
• Decreased contrast sensitivity
• Glaucoma
  
  • •Glaucoma is an optic nerve disease caused by decreased blood flow to the optic nerve resulting in peripheral field loss leading to central vision loss when severe.

Signs and Symptoms:

• Glare
• Increased IOP
• If not treated, glaucoma can destroy the peripheral vision
• Poor control of IOP can lead to blindness
• Diabetic Retinopathy
  
  • •Diabetic retinopathy results from the vascular complications of both insulin-dependent and non-insulin dependent diabetes

•After 20 years, nearly all insulin dependent diabetics and 60% of non-insulin dependent diabetics have some form of diabetic retinopathy

Common Complaint:

•floating spots or blind spots

Signs and Symptoms:

• After 20 years, nearly all insulin dependent diabetics and 60% of non-dependent have some form of DR
• Timely dx and proper treatment will eliminate the risk of severe vision loss

Question 4

What are some of the questions that can be asked when getting a visual history from a client?

Answer 4

During evaluation- assess vision and needs:

• ( Low Vision Screen)
• Vision history?
• Last eye exam?
• Glasses or special devices to see?
• What size print do they do best with?
• Do they use a special lamp at home?
• Do they have difficulty with color or contrast?
• What IADLS have been affected?
• How is this person’s independence compromised? Risk factors?
• How well can the patient perform his IADLS despite his vision loss?
• What compensatory techniques is he trying?
• What LV techniques are going to fit his lifestyle, motor and cognitive functional level?

Question 5

What are the four principles of low vision adaptation? Give 2 examples of each principle that can be used as an intervention.

Answer 5

• Magnification
• Lighting
• Contrast
• Position

Question 6

List some common symptoms in vision following a traumatic injury.

Answer 6

• After an injury to the brain, it is estimated that 20 to 40 percent of the time, there are interruptions to the neurological system that controls eye movement, regulates focusing, and accurately interprets visual information.
• Approximately 80 percent of the information about the environment is received through vision; therefore, visual deficits can cause significant difficulties performing daily activities. Unfortunately, this is a deficit that is often overlooked after a brain injury.
• Common visual symptoms include:
• Double vision
• Difficulty with visual tracking and scanning
• Difficulty focusing or maintaining focus
• Misalignment of eyes
• Light sensitivity
• Contrast sensitivity
• Decreased eye–hand coordination
• One of the many ways Pate Rehabilitation addresses visual deficits is through use of the Sanet Vision Integrator.

Using a 50” touch screen monitor, the SVI is designed to improve visual abilities for a wide range of patients with visually-related problems due to stroke and traumatic brain injury

Question 7

List at least 2 technologies that are being used for low vision.

Answer 7

•The SVI can be used to enhance the following visual abilities:

Pursuits, saccades, fixation stability, eye-hand coordination, visual reaction time, speed and span of recognition, automaticity, and contrast sensitivity, plus visual and auditory sequencing and memory.

•The CentraSight treatment program uses a tiny telescope that is implanted inside the eye to improve vision and quality of life for individuals affected by End-Stage AMD. End-Stage AMD is the most advanced form of age-related macular degeneration (AMD). The CentraSight treatment program involves four steps: 1) diagnosis, 2) candidate evaluation, 3) implantation and 4) rehabilitation.