Most often, changing the glasses will not improve distance vision dramatically. To improve distance vision we have hand held telescopes as shown being demonstrated in (fig. A). These can be used for short term viewing tasks like when traveling and needing to see signs. These same telescopes can be miniaturized and mounted into a pair of glasses for more continued use like seeing lectures and chalkboards in class (fig.B). In very limited cases the bioptic or spectacle mounted telescope can be used for driving.
These are similar to the lenses that are used in the reading glasses of the microscopes but are mounted on a handle or with a stand to allow the patient to see small print at a longer working distance. The disadvantage is the loss of the field of view. Some of these systems have lighting built into them.
Often the simplest of devices such as standard hand held and stand magnifiers are the best solution for improving an individual's ability to use their remaining vision. Shown is an array of common magnifiers that would be used in the clinical setting. Most of these will have better optics and lighting than those found over the counter and more importantly will be correctly prescribed to the patient's acuity and demands of the task or activity being assessed.
There are a number of electronic magnification systems, self focusing telescopes and video displays with virtual reality mountings that can be very beneficial in helping individuals improve vision function. These prescribed devices are especially helpful in letting individuals maintain employment. A big asset to those who are visually impaired is the new and constantly improving video magnification systems.
They range from the standard closed circuit television which allows one to read printed material and do a variety of near tasks under high magnification, yet with comfort and proficiency (fig. A). Newer systems are designed so that one views a magnified world through a video display mounted as glasses (like virtual reality glasses) as shown in fig. B. Our clinic is constantly updating the technology available for the visually impaired.
Light and Contrast
There are filters or sunglasses designed for the special needs of the visually impaired. These will allow individuals to function in brightly lighted areas or dim areas where they are unable to use their vision at present. Special lamps and lighting is very important to the successful use of most prescribed devices.
Lighting is very important for all patients, no matter what the cause of vision loss. It is important to note that there can be too much light as well as too little light when it comes to maximizing visual performance. The appropriate amount of lighting and type of lighting (fig. A) will be evaluated in the clinical assessment as well as the need for filters and special sun glasses (fig. B).
In almost all cases it is important that the individual being prescribed an optical (or even non-optical) device be given some instruction in its use and care. More importantly, the instructional sessions make sure that the intended prescription, which is based on clinical data, actually works for the intended tasks. The instructional sessions will give the patient an opportunity to use the device to read the materials or perform activities they will be using at home instead of just reading some small print on a clinical chart. For example, it will give the individual an opportunity to bring in the quilting project that was discontinued months ago and work with the new optical prescription to verify its practicality before having to purchase the prescription. As with all new devices, the more one uses the device, the more proficient they will become. Our training sessions allow for this time to be spent with the device (or a simulated Rx) in more normal settings such as home and outdoors. It is not until the doctor, instructor and patient are happy with the actual performance with the device, that it will be prescribed.
We cannot replace the eye or its normal functioning. These prescription devices will allow an individual to perform specific tasks or activities. The patient will need to learn to use almost all of these systems and training is provided in this clinic.
The success of the rehabilitation program is totally dependent on the patient's participation and willingness to modify their lifestyle and accept the performance limitations of the prescribed devices. While this may sound very negative, the positive side is that low vision prescriptions will allow the patient the opportunity to do things they would otherwise be unable to do.
Text and photos used with permission by Randall Jose, OD, FAAO