Low Vision Rehabilitation
As one of Nevada's few centers for the partially sighted, we take pride in going the extra mile to help those patients for whom regular glasses are no longer functional. Adjustment to any vision loss is difficult. It takes self-acceptance, determination, support of family and friends, and learning new techniques to fully utilize any remaining vision. The goal of Low Vision Services is to enable people with partial vision loss to improve their ability to use their remaining vision so they can be independent and better able to meet the demands of everyday living.
What is Low Vision?
Low Vision is a visual impairment not correctable by standard glasses, contact lenses, medicine, or surgery that interferes with a person’s ability to perform every day activities. This means that any patient that is not 20/20 may be a low vision patient. Partially sighted patients have a best corrected visual acuity between 20/70 and 20/200. Legally blind patients in the United States have remaining vision in the better eye after best correction of less than 20/200 or contraction of the peripheral visual fields in the better eye (A) to 10 degrees or less from the point of fixation; or (B) so the widest diameter subtends an angle no greater than 20 degrees.
What is Low Vision Rehabilitation?
Low vision rehabilitation is the management of individuals who have a congenital or acquired impairment of visual acuity, visual field, and/or other functional vision factors. This loss of vision can interfere with the process of learning, vocational or avocational pursuits, social interaction, and activities of daily living. Low vision rehabilitation involves a continuum of care, which begins with medical and surgical intervention and proceeds through to the prescription of low vision devices and vision rehabilitation services.
Insurance Coverage and Payment
Most patients with medical insurance have coverage for parts of the low vision evaluation, but devices are typically not covered by medical insurance. Some vision plans do cover devices. In order to qualify for services typically patients must be 20/70 or worse best corrected in better eye, have a central scotoma or general constriction of field or have a hemifield loss. Some assistance is available from local service groups and we also accept CareCredit.
What Can Be Expected When Having a Low Vision Evaluation?
The initial evaluation includes a functional based history, measures of visual acuity, refraction, contrast sensitivity, field of vision, binocularity, cognitive state, mobility and other tests as needed. Devices may or may not be prescribed at this visit. This visit is often 60-90 minutes. Follow up evaluations often include a review of goals, confirmation of visual stability, device selection and training. These visits tend to last 10-60 minutes.
How Can My Vision be Helped?
For patients with central vision loss often caused by macular degeneration we often talk about the three B’s; bigger, bolder, brighter. Often patients with central vision loss suffer from decrease contrast, so by making the darks darker and the lights lighter we can improve the ability to make out the target. Brightness is often linked to boldness in the fact that more light on a target tends to enhance contrast. The disadvantage of increasing brightness is that we often also increase debilitating glare at the same time, so one must be careful about how much light and the placement of a lamp to control the glare. Making the target bigger is the most familiar way to improve the low vision patient’s ability to see small targets. This works best for patients with mainly central loss and good peripheral vision. There are two ways to help patient’s with peripheral vision loss from conditions like glaucoma or traumatic brain injury. We can expand the field of view for those with tunnel vision or we can shift the field of view toward the better seeing side in patients with hemifield losses.
How Many Devices Might I Need?
Most patients need 3-6 devices usually totaling around $750. This is equivalent to a good pair of no-line bifocals and is more functional for the low vision patient.
What Types of Devices are Available to Help?
Good lighting is generally known to be one of the best and inexpensive ways to improve vision. A light moved twice as close is 4 times as bright, so having an adjustable lamp is key to reducing glare and maximizing brightness. For patients with certain conditions different colors and types of lighting may be useful.
Contrast or Absorptive Filters:
Filters can absorb uniformly across all wavelengths (i.e. grey sunglasses) which reduces glare but also reduces contrast and total light reaching the eye. We can also selectively absorb certain wavelengths bands (i.e. yellows, oranges, plums) which allows us to reduce glare and increase contrast and potentially acuity. Disadvantages to colored filters include the alteration of color perception and may not be safe for driving and recognition of traffic lights.
Yellow or amber filters provide the most contrast enhancement but least glare reduction. Yellow filters are typically used for indoor activities. Plum filters provide the least contrast enhancement and the most glare reduction. Plum filters are a great choice for outdoors.
While magnification is the most familiar way to improve vision for the low vision patient, it is often misused by patients resulting in poor vision and frustration. Here are a few tips on magnification as it applies to low vision:
- The higher the power the smaller the diameter of the lens
- The peripheral optics of higher powered lenses are typically so distorted they are useless and can be cut out of the lens
- Large high powered lenses with good peripheral optics are very expensive and usually very heavy
- In order for a 2x magnifier to show the patient the whole page at one time, it would need to be twice as large as the page
- Higher powers require a closer working distance
- A 4x magnifier typically requires a working distance of 16cm for maximum clarity and field of view
- Higher powers have smaller fields of view
- Holding the magnifier closer to the eye will expand the field of view
Hand magnifiers are familiar and easy to use for most patients. They come in many designs, sizes and powers and are very travel friendly. They do require at least one hand for use and holding the magnifier steady causes fatigue very quickly, so they are great for short to intermediate length tasks (reading a menu, sorting the mail, seeing the price on a label). They are often best used with patient’s distance glasses.
This type of magnifier is perfect for longer term tasks like reading the newspaper or a magazine as they stand on the page. This allows for less fatigue and shaper vision as the magnifier is not reliant on a shaky hand to hold it steady. Like hand magnifiers, they come in a variety of size and styles and some are even portable. They are typically best used with the patient’s reading correction.
Prism Glasses and Head Borne Microscopes:
Prism glasses are very easy to use for most patients as they are similar to a strong pair of reading glasses. They allow the patient to be hands free and the field of view is very wide as the magnification lens is very close to the eye. They do require the patient to hold things much closer than they are used to and do require an adaption period. Head borne microscopes are for those patients that require a higher power or are limited to usable vision out of one eye only. Both of these device types are not recommended for wear while walking.
Telescopes are a great way to make the distance world easier to see. They can be hand held or spectacle mounted for greater ease of use. When mounting in glasses, they can be mounted high for use while walking or driving, or they can be mounted low for reading or hobbies. Fixed focus or variable focus for near and far activities can also be made. Learning to use telescopes can be a daunting task, as they have a small field of view, usually between 8-12 degrees and often require more training to use proficiently.
Electronic Magnifiers and Telescopes:
Electronic devices are the wave of the future in low vision and have become the primary assistive device used in our clinic. These devices allow for variable contrast and magnification so that the device can grow and adapt with patient as their vision changes. Styles come in moble, stationary and even head bourne models. Patients find the more comfortable working distance preferable to optical magnifiers and often a larger field of view can be obtained at higher magnifications.
Field Expansion and Shifting:
Magnification is not the only way to help patients see better. Sometimes making objects smaller allows us to fit more field of view into a smaller window of vision. Using high minus lenses or reverse telescopes to shrink the image, can help the mobility of patients with tunnel vision. This drawback of making targets smaller is a reduction in acuity (i.e. a 20/20 patient with a reverse 2x telescope is now 20/40 through the scope). Prisms and mirrors can be used to shift the image from the blind side over to the sighted side for patients with hemifield losses. These devices are typically very difficult devices to learn to use.
Daily living devices and simple tips:
Sometimes using a magnifier or telescope is not the best answer. Using larger playing cards, talking watches, books on tape, large size checks, bold pens, talking blood glucose meters can make life easier than trying to use a visual aid. Use contrasting cutting boards and measuring cups when cooking, for example, put your coffee in a white cup and your milk in a dark cup to help the liquid stand out from the background. Tablet readers like Kindles and iPads allow for larger fonts and adjustments in contrast that may be more comfortable than using a magnification device.
High Quality Magnifiers
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