Low Vision

Knoxville Low Vision Specialists

Nearly 14 million Americans have low vision – vision loss that interferes with daily activities. It occurs when visual acuity (the numerical value of eyesight) is below 20/60 and is not correctable with medical treatment, surgery, or conventional glasses.

Studies indicate the majority of people with vision loss are adults who are not totally blind (only able to detect slight motion, light, or none at all). Often you may hear the term “partially sighted” to indicate low vision. Today, this term is replaced with “Visually Impaired.”

Many people have heard or even used the term “Legally Blind” to describe what they perceive as their lack of good vision. However, this term has a “legal” definition that goes beyond sight without your glasses or contacts. The term is used by the US Federal Government to determine eligibility for vocational training, rehabilitation services, schooling, disability benefits, low vision devices, and tax exemption programs. Unfortunately, it is not a very functional definition and does not tell us exactly what the person can or cannot see. The definition has 2 parts, the first based solely on visual acuity (the smallest figure/letter seen on a typical eye chart) and the second based on the limits of the person’s visual field (the total area a person can see without moving the eyes from side to side).

Part 1: A visual acuity of 20/200 or less in the better-seeing eye with the best conventional correction (glasses or contact lenses).

Part 2: OR a visual field of 20 degrees or less (also known as tunnel vision) in the better-seeing eye.

In both of these definitions, it should be assumed the lesser-seeing eye is the same or worse.

What Causes Someone to Have Low Vision?

Most conditions causing low vision are related to 2 basic categories:

• Acquired conditions

• Congenital (occurring at birth) or Hereditary (occurring after birth by genetic mutation).
  
  

Acquired Conditions:

• Macular degeneration

• Diabetic retinopathy

• Ischemic Optic Neuropathy

• Optic Atrophy

• Glaucoma

• Retinal Artery / Vein Occlusions

• Cortical Blindness
  
  

Congenital/Hereditary Conditions:

• Ocular Albinism

• Nystagmus

• Cone-rod dystrophy

• Juvenile Glaucoma

• Congenital cataract

• Stargardt’s maculopathy

• Retinitis Pigmentosa

What are some typical functional problems experienced with low vision?

The vast majority of persons with low vision experience difficulty with reading. This could be books, magazines, newsprint, mail, or labels of all types. In today’s digital world, difficulty accessing computers and cell phones is also a frequent complaint.

Other widely experienced difficulties include: watching TV, managing the checkbook/finances, driving safely, recognizing faces of friends/family, sewing/crafting/woodworking, managing medications, cooking, and household chores.

With both central and peripheral vision loss, mobility can be greatly impacted. This can make travel very challenging, especially on steps, curbs, or in crowded areas.

Light sensitivity is a common occurrence with many visual conditions and can increase the difficulties of many of the problems mentioned above.

Luckily, there are solutions to many of the problems above using adaptive techniques, optical devices, and training.

What is Low Vision Rehabilitation?

A person with diminished sight must learn how new strategies to adapt to the world around them in order to maintain independence and safety. The process of learning is called Low Vision Rehabilitation and is accomplished by 1) identification/setting specific goals, 2) introduction of low-vision devices that meet visual demands, and 3) training in the use of prescribed devices and adaptive strategies that assist independence.

In addition to efforts provided in the office, there are many outside services available to further assist the person with visual impairment to maintain independence and safety whether in their home, at a workplace or school, or out in the community. These outside services include federal, state, and local government-supported agencies, school programs, and not-for-profit programs.

Listed below are common low-vision devices that could be prescribed by your low-vision specialist:

Devices for Near

• Higher power reading glasses

• Handheld (pocket style) illuminated magnifiers

• Illuminated, stand-type magnifiers

• Near focused telescopic devices

• Electronic video magnifiers

• Computer adaptive (magnification) software

Devices for Distance

• Hand-held monocular telescopes

• Binoculars

• Spectacle-mounted telescopes

• Head-borne Video devices