By Alan Innes, OD
Low vision patients typically seek care because they have lost the ability to carry out the activities they engage in on a daily basis because of an impairment in their vision. The impairment can be acquired or present at birth due to hereditary or congenital anomalies of the eye and visual system. Traditional care and treatment of these patients is usually based on magnification of the image of the object they are attempting to see.
Magnification can be achieved by several methods. One of the ways is to simply have the patient move the object, printed material, for example, closer to them or for the patient to physically move closer to the object if it is too large to move. An example of the latter would be a patient moving closer to their TV to see the image on the screen more clearly. In either case the shift in the relative position of the patient and the object creates an increase in the visual angle.
Most patients do not have the depth of focus or field to allow them to see the image clearly at significantly reduced working distances. Optical devices such as hand magnifiers, stand magnifiers and microscopic spectacles are often prescribed. These devices provide a “clear” (useful) image at the working distance required by the magnifier or spectacles. The working distance depends on the level of loss the patient has experienced and can be anywhere between the normal distance of 16" (40cm) in cases with minimal loss to as close as one to two inches in patients with profound loss.
For many patients, however, the fact that the ability to read has been restored can be offset by difficulty adapting to the changes in posture necessitated by the close working distance. If the patient decides on a pair of microscopic spectacles, for example, they have no choice but to hold the material at the focus of the microscope. If a hand magnifier is chosen, the material still has to be held at the focus of the lens, but the patient has the option of holding the magnifier at any distance they choose. The downside to doing things this way is that the field of view decreases with increased working distance.
For many of the patients who fail with spectacles, hand or stand magnifiers, electronic magnification systems are the ultimate solution because they have features that allow the patient to select from a wide range of magnification factors at normal or close to normal working distances. Electronic devices come in two basic varieties: computer software and video. One of the best known software packages for enhancing the output on a computer monitor display is a program called Zoom Text by Ai Squared. Zoom Text has features that allow the user to increase the size of the characters on the display. It also has a “lens” that can be used to further enhance (magnify) the display. The latest version, Zoom Text 9.0 magnifier/reader, has added some new features and expanded those already available in earlier versions. 9.0 offers a screen reader which, as the label implies, reads the text on the screen to the user. Another feature, xFont, provides improved quality and clarity of text at all magnifications levels. In addition, the range of magnification has been extended from 2-16X to 2-32X. Reading zones, text finder and automatic adjustment of settings whenever the user switches programs round out the upgrades in Zoom Text.
Video devices, as the label implies, have a video camera as their basic component. Most models come with a built in display. CCTV systems are the best known of the electronic magnification devices. CCTV systems employ a video camera mounted vertically in line and beneath the monitor and a movable platform on which the print is placed. The video camera, which can be analog, digital or a hybrid transmits the signal to the monitor that displays the image of the text or picture for the patient to see. Recently introduced versions of CCTV systems include the Clearview from Tieman Group Optelec, the Neo from Assist Vision, the Merlin and Acrobat from Enhanced Vision Systems, and SmartView and My Reader from HumanWare. Most of these systems have a number of models that range from a basic black and white system to color systems with controls for changing the focus, magnification, color select, polarity of the image, windowing and underlining the display. The magnification range on most of the available CCTV systems is from about 2.5X to approximately 70X. Some of these video systems, such as the Clearview Plus and the SmartView are available in four configuration. The Merlin is available in three configurations. The Clearview can be completely customized to incorporate more advanced features.
My Reader is a relatively new introduction to the video magnifier market. It has a couple of features that set it apart from most of the prior generation CCTV systems. My Reader has the ability to scan text and control the presentation of the text through a technology called Smart Sense. Through this technology My Reader has the ability to capture (scan) a full page of text, a process similar to what one might do in scanning a document to be downloaded into a computer, with the push of a button. It can then present the print as a wrapped paragraph (column layout) as a continuous line (row layout) and one word at a time (word layout). Navigating the text is done through a control on the panel rather than an XY pallet as is found in most video CCTV systems. Scrolling is done through a dial on the control panel. My Reader can also be folded up for easier transport (this is relative since the unit weighs 22 pounds) should the user wish to take the unit with them to a remote site.
Modified versions of the standard CCTV system are essentially hand held devices. Earlier versions include the Max, the Magni-Cam and the Primer. These are small hand held devices resembling a computer mouse. The Primer is one example of this class of video magnifier. These devices contain a control for changing the magnification. The Magni-Cam and Primer l require the use of a TV or monitor to display the print. The Max also requires the use of a TV. However, it is available in two other packages that incorporate separate display components. The Max Panelutilizes a 10" flat panel LCD monitor to display the text. When coupled to a 20" TV or monitor, the Max provides a magnification range of 16X to 28X.
The other types of video devices include portable devices that rest directly on the reading material and head mounted video devices. These “pocket” video display magnifiers look, in many cases, like oversized PDAs. The difference, of course, is that the magnifiers are composed of a small video camera and a display. All of the components are contained within a single casing. In some cases the display can be unfolded from the base and elevated to accommodate the patient’s preferred posture or for writing. Examples of portable video systems include the PocketViewer from HumanWare, the Quicklook by Ash Technologies Limited, available through HumanWare distributors and Freedom Vision, the Traveller+ by Tieman Group Optelec and the Slider by Assist Vision. A recent entry in this category is the Amigo by Enhanced Vision Systems. Like the Traveller, the Amigo has a display that can be folded up away from the body of the unit.
The PocketViewer and Quicklook both have 4" color as well as black and white displays. The Quicklook has a camera that can be pointed to the side so the user can write and view what they are writing on the display. The magnification range for the two devices is 2X to 7X and 2X to 5.5X respectively. Each device weighs approximately 10 ounces.
The Traveller+ provides the user with a magnification range of 4X to 16X on a 6.4" color display, which can be unfolded up from the base of the device. Other features include a control for changing polarity of the print and auto-focusing. There is also a pocket version called the Compact. The Compact has a 4" color display with a 4X and 8X magnification mode. Another feature allows the user to set the display to a yellow on black and yellow on blue display mode. Also included in this group is the Clear Note, which is a laptop accessory that utilizes the laptop monitor to display the text.
The Amigo has a 6.5" color display and offers six viewing modes and freeze frame that allows the user to take a “picture” of the object. The magnification is digital and ranges from 3.5X to 14X.
The Slider from Assist Vision is much thicker than the other pocket video devices. It has an external camera with a collar for changing the magnification. Viewing mode and contrast controls are on the front side of the unit. The camera stand can hold a pen or pencil.
Head mounted video devices consist of a miniature video camera and a mirror onto which the camera image is projected through an optical system. Although there were earlier attempts, such as the LVES, (often referred to as the “Elvis”) to design and market head-mounted devices, the best known contemporary example of this is the Jordy by Enhanced Systems. It has a video camera and display in one unit and is worn in the same way a pair of spectacles would be worn. It looks similar to a video game “helmet” and is a lightweight, versatile system. Its features include magnification, contrast, viewing mode (color or black and white), object locator, brightness and automatic preset magnification controls located on a separate module that also holds the battery when the A/C adaptor cannot be used. The magnification range is approximately 30X. The Jordy also incorporates auto-focus, a reading lens that slides over the port when desired, and an adjustable head strap. Enhanced Vision Systems also has an adaptor called the Jordy Stand, into which the unit can be mounted. In this configuration the unit serves the same purpose as the camera in a dedicated CCTV system. It can also be plugged into a television or monitor so that the output can be viewed on the display in the head set.
The Jordy also exists in a modified version called the Flipper Port. In this configuration the camera is separate from the display unit. It is mounted on a stand that has rollers on the struts on which it is mounted. The camera can be rotated 180 degrees around the horizontal axis to allow the wearer to point the camera at reading material lying on a flat surface or material that is positioned vertically such as a sign mounted on a wall. The headset looks very similar to the Jordy and is worn in the same way. (The Max Port uses the same head set as the Flipper Port, although the Max provides the input.) The controls are located on the camera stand in this configuration. Both systems are designed to be worn over the patient’s distance spectacles.
This article provides an overview of the various classes or types of video magnification devices. It does not include all the models available at the present time.
Alan Innes, OD, is associate clinical professor of Optometry at the State University of New York College of Optometry. He is the instructor of record for the ophthalmic optics course taught in the professional program. He also supervises interns in the low vision and ophthalmic dispensing clinics at the college.