What is Low Vision?
What is Low Vision?
Low vision is defined as vision that is not correctable with spectacles, contact lenses, surgery, or medication.
Low vision can be due to:
- congenital problems or disorders
- traumatic injury to the eye or brain
- systemic diseases
- adult onset diseases
- aging related diseases
- a loss of acuity (ability to see detail)
- loss of peripheral vision or parts of the field of vision
- constant double vision (diplopia)
- loss of contrast sensitivity
- reduced or loss of color vision
- reduced or loss of depth perception
These disorders can prevent a person from completing their daily routines. Specialized microscopic and telescopic lenses, along with other types of prescriptive magnifiers are used to perform simple visual tasks like reading, writing, watching TV, hobbies, performing an occupation, traveling more independently, and in some cases even driving a car. In addition to prescribed optical devices, the loss of vision can be compensated for through the use of electro-optical devices such as portable video magnifiers and reading machines, or heads-up display devices as found in virtual reality technology. Sometimes a significant improvement in visual performance can be realized with new medical care or simple training techniques.
Low Vision Specialists
Low vision is a very specialized area within the eyecare field. Although both Optometrists and Ophthalmologists can provide low vision care, not every general eyecare practitioner is experienced in this specialty area. Low vision specialists use a variety of specialized testing procedures to identify a patient's visual abilities and they have special knowledge and expertise of the variety of optical devices that are available and how they may be used in the vision rehabilitation process.
During the course of a low vision examination, the eyecare professional's goals are: (American Optometric Association)
- To evaluate the functional status of the eyes and visual system.
- To assess ocular health and related systemic health conditions and the impact of disease or abnormal conditions on visual functioning.
- To provide appropriate optometric low vision intervention to improve the patient's visual functioning, taking into account the patient's special vision demands, needs, and adjustment to vision aids.
- To counsel and educate patients regarding their visual impairment and ocular and related systemic health status, including recommendations for treatment, management, and future care.
- To provide appropriate referral for services that are outside the expertise of the low vision clinician.
Low Vision Examination
A low vision examination defines the extent of the handicap of vision loss for the individual through extensive case history, consulting with other professionals and evaluating the individual's ability to perform tasks and activities. Magnifiers, telescopes, computer adaptive technology, and electronic reading systems are prescribing options for achieving specific vision goals.
The comprehensive low vision examination may include, but is not limited to, the following procedures:
- Comprehensive history - The nature and duration of the vision disorder along with visual, medical and family history. Especially important is the assessement of the vocation, avocational, and educational requirements.
- Distance visual acuity - quantification of the vision remaining.
- Specialized refraction - using hand instruments to better simulate the vision normally used by a low vision patient.
- Visual Fields - performed mostly for functional purposes rather than for diagnostic purposes. Determines the extent of the field of vision (peripheral vision).
- Binocular vision - with low vision, the two eyes will often interfere with one another causing blurred, double, or swimming vision.
- Contrast sensitivity - to determine the visual response to loss of lighting and contrast.
- Near acuity - single letter acuity is determined as well as paragraph or reading material.