Vision Rehabilitation: Overview
Mark E. Wilkinson, OD, FAAONovember 20, 2017
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This is Mark Wilkinson from the University of Iowa Department of Ophthalmology & Visual Sciences. In this presentation, I will provide an overview of vision rehabilitation care.
In this presentation, I will be discussing:
What low vision is.
Why all individuals with visual impairments should be referred for a low vision rehabilitation examination.
Components of the structured vision rehabilitation examination.
Core principles of low vision rehabilitation.
Worldwide, in 2017, the Vision Loss Expert Group estimated there were 36 million people who are blind and 217 million people with severe or moderate visual impairment of their distance vision.
This group also estimated that there will be almost 115 million cases of blindness and 588 million people with severe or moderate visual impairment in 2050.
According to the National Eye Institutes', National Eye Health Education Program, low vision is defined as a visual impairment, not correctable by standard glasses, contact lenses, medicine, or surgery, that interferes with the person's ability to perform every day activities.
The importance of this definition is that it uses a functional definition; vision loss that interferes with a person's ability to perform activities of daily living, as opposed to a specific level of visual acuity or visual field loss, for a person to be considered visually impaired.
In keeping with the aforementioned definition of low vision, low vision rehabilitation may be necessitated by any condition, disease or injury that causes a visual impairment serious enough to result in functional limitations or disability.
This means that there is no required amount of visual acuity or visual field loss necessary, before an individual can be referred for low vision rehabilitation care.
It is important to note that low vision rehabilitation is the only non-surgical treatment modality for vision loss.
Let's consider a few of the many different causes of visual impairment.
First, a person can have vision loss secondary to retinal diseases such as macular degeneration, diabetic retinopathy, myopic degeneration and retinitis pigmentosa.
Vision loss can also occur from optic nerve diseases such as glaucoma, optic atrophy, ischemic optic neuropathy and Leber's Hereditary Optic Neuropathy.
A person can also have media opacities that result in vision loss. Media opacities include cataracts, keratoconus, corneal scarring or vitreous hemorrhages.
Finally, brain injuries, such as strokes causing hemianopsias and cortical vision loss are additional causes of visual impairment.
One way to think about visual impairments, is based on where the pathology is in the visual system. Is the pathology in the ocular media, the retina or in the brain?
Additionally, we need to consider the pathology's effect on the visual field.
When we consider how the pathology causing vision loss is affecting the patient's visual fields, there are 3 options. The person could have no visual field defect, just overall blurring of vision. This could be caused by refractive media problems, or macula problems where there is impaired central resolution without an absolute scotoma.
Alternately, the person could have central vision loss with an absolute central scotoma, secondary to macula dysfunction.
Finally, the person could have peripheral field loss, in a sector, quadrant or generalized constriction. This could be caused by problems with the retina or the visual pathways.
It is important to appreciate that low vision rehabilitation is an integral part of the
continuum of eye care that is provided to people of all ages, who have experienced a loss of vision.
You might ask, how can I easily determine who needs low vision rehabilitation services? Dr. Roy Cole developed the following 1-minute screening tool for determining who needs low vision rehabilitation services.
To use this tool, simply ask your patients; do you have trouble doing what you want to do because of your vision? For example: Reading your mail? Watching television? Recognizing people? Paying your bills? Signing your name? Walking stairs, curbs, crossing the street or driving?
Next ask, during the past month, have you often been bothered by: Feeling down, depressed or hopeless? Also, have you had little interest or pleasure in doing things?
These two questions are ~90% effective in detecting depression.
If your patient answer yes to any of the above 8 questions, and you are not able to ameliorate the cause of their visual difficulties or depresssion, the patient should be referred for additional vision care and/or vision rehabilitation services and/or mental health services.
Dr. Cole's take home message is this, think about implementing vision rehabilitation strategies when…
Visual acuity is 20/40 or worse
Visual field is 20 degrees or less
Or, when your patient has one or more functional complaints related to their decreased vision.
It is important to understand that the goal of low vision rehabilitation is to maximize function. In so doing, you will enhance the patient's potential, increase their independence and improve their overall quality of life.
Achieving the patient's low vision rehabilitation goals is accomplished by the use of prescriptive optical and electronic magnification devices as well as patient education, which includes teaching strategies to enhance functional abilities.
Also, referral should be made for any needed additional vision rehabilitation services you are not able to provide. Those additional services may include such things as vocational assistance, mobility training and counseling.
When we consider the need for counseling, it is important to recognize that depression is not uncommon among the elderly in general, with about 3% estimated to be clinically depressed. What is important to know is that depression is even more common among those that have experienced a significant loss in vision, where reports indicate that up to 30% are clinically depressed.
This is important because one study found that 64% of those with major depression will not use vision rehabilitation services or devices. With this in mind, it is critically important to recognize that individuals with vision loss and depression need counseling, as well as education and problem-solving therapy to treat their depression. Often, the depression will need to be treated before the patient will be responsive to vision rehabilitation services.
There is a structured process that is used with doing a low vision examination. That process starts with a detailed case history, that includes the past ocular and medical history, the patient's developmental history and educational history, as well as their reported visual and functional difficulties.
After the history has been completed, the exam will start with measurement of distance and near visual acuity. Near acuity will include documentation of the testing distance. The patient's current glasses will be checked against their refraction. Once their distance refraction is determined, their predicted reading add power will be estimated.
After best corrected vision has been determined for distance and reading, a variety of visual function tests may be performed, including contrast sensitivity testing, confrontation and/or non-threshold related formal visual field testing, color vision testing and Amsler grid testing.
Various devices will next be reviewed for distance and/or near vision enhancement, based on the patient's specific needs and desires for vision enhancement.
Instruction and training in how to use the recommended device(s) will next be provided. If appropriate, the recommend device(s) will be dispensed.
The information gathered during the structured low vision rehabilitation examination is the basis for the development of the individualized vision rehabilitation plan for each patient.
The vision rehabilitation plan is guided by the individual's specific needs and functional abilities.
Here are a few examples of visual acuity charts used for individuals with vision loss. These charts allow for greater accuracy of acuity measurement. For more information about visual acuity testing of distance and reading vision, go to www.eyerounds.org/video/refraction/visual-acuity-testing/index.htm
Not every patient who is visual impaired needs a trial frame refraction. However, if you are going to provide care for individuals who are visually impaired, you should be comfortable refracting with a trial frame. For more information about doing a trial frame refraction, go to www.eyerounds.org/video/refraction/trial-frame-refraction/index.htm
There are a variety of additional tests of visual function you may wish to use in assessing the functional visual abilities of your patients who are visually impaired. My most frequently used tests are non-threshold related full field perimetry and contrast sensitivity testing. Other useful tests are color vision testing, Amsler grid testing and to a much lesser extent for me glare testing.
It is important to know how to determining the starting reading correction power, based on the person's best corrected reading vision.
Let's now talk about the different categories of devices individuals with vision loss will use to enhance their functional abilities.
Optical options include specially powered spectacles and loupes. There are also hand and stand magnifiers, as well as hand held and spectacle mounted telescopes for distance and near vision enhancement. Special filters and absorptive lenses to reduce light sensitivity from a variety of different conditions are also available.
Electronic magnification options include full size and hand held, as well as transportable video magnifiers and head borne devices. These devices can be used for both distance and reading vision enhancement.
The use of computers can be enhanced with text to speech, voice dictation and screen enlarging software.
Additionally, IDevices, smart phone and tablets all have accessibility options and apps that can be used to enhance readability and the usefulness of these devices in general.
It is important to remember that low vision rehabilitation is the only non-surgical treatment modality for vision loss.
With this in mind, individuals with vision loss that is affecting their functional abilities and quality of life should be referred for a low vision rehabilitation examination.
It is important to remember that there is a structured process, to be followed in a sequential manner, when evaluating all individuals who are visually impaired. By following this process, the evaluation of individuals with vision loss can be performed in an effective and efficient manner.
Finally, it is important to remember that each individual's needs and visual functioning is different. For this reason, there is no way to generalize a rehabilitation/treatment plan for a given diagnosis or visual acuity.
Wilkinson ME. Vision Rehabilitation: Overview. EyeRounds.org. Posted November 20, 2017; Available from: http://www.eyerounds.org/tutorials/vision-rehabilitation-overview.htm