Screen enlargement is one of several intervention strategies which has allowed many persons with visual impairments to gain or maintain positive employment outcomes, achieve their educational goals, enhanced their quality of life and increased their overall independence. The demand for this technology has created a diverse selection of screen enlargement software and hardware solutions.
To gain a better understanding of those screen enlargement alternatives available to the public, we will explore ways in which screen enlargements accomplished from simply using a larger monitor to the behind the scenes look at how the computer accomplishes enlargement of text and graphics.
Before we think about screen enlargement, perhaps we should ask ourselves why use screen enlargement at all? Are there any contraindications to screen enlargement use? Are there other alternatives which would allow the individual to access the computer system more freely and still make the best use of their functional vision?
I do not recommend consideration of screen enlargement alternatives for persons with visual impairments until they have had a low vision examination and have been exposed to other low vision alternatives which are less intrusive or restrictive. I now require a low vision examination report from field staff referring clients to me for technology evaluations. This accomplishes a number of important things which save my time, the client's time and may provide more holistic solutions for the client. Firstly, I am made aware of what the client's functional vision is like, to some extent. Usually an examination by a qualified low vision examiner will tell me if the client makes use of eccentric viewing techniques to use as much functional vision as possible. Also it will relay information about field restrictions in the client's vision to consider which may, when combined with little acuity,preclude or contraindicate extensive screen enlargement. A low vision examiner will possibly recommend low vision aids to help the client access a computer or similar reading materials at the same focal length. This would be included in the report as well as an indication as to whether the client experiences or is likely to experience photophobia, or light sensitivity, which might indicate a need to adjust contrast and color on the computer screen. The light sensitivity might be exacerbated by glare from harsh lighting in the room, bouncing off of the computer's screen. Keep in mind that, to a degree,filters and colored gels or acetate screen covers may offer sufficient glare reduction and color contrast to preclude the need for software intervention.(I shall take this opportunity to relay an evaluation story to you.)
This story relates directly to the color and glare issue. I was performing an assistive technology evaluation for a person who worked on a terminal in a retail showroom. The person complained of not being able to read the computer screen due to the lighting (florescent) of the room and the color of the screen (amber). Their vision seemed to become worse as the day progressed,by their own account. An assistive technology staff person who attended the evaluation with me recommended some colored acetate he brought with him to help filter some of the lighting glare and augment the color of the characters on the screen. We custom manufactured a screen cover on the spot which helped the person see the characters better, still the glare was continuing to annoy her. I sized up the showroom where she worked and described it to my blind coworker. Then we hit upon a solution. I asked if we might borrow two of the hundreds of thick catalogs which lined the showroom. I lifted the computer monitor to a height nearly level with the user's line of sight.This accomplished two things, one of which was to reduce fatigue caused by looking toward the floor. The second was not so apparent as I did not describe the room to you. The computer was situated so that the user had to face a large picture window as many catalog showrooms have. This window was on the west side of the building. When the sun crossed its apogee, afternoon time, sunlight streamed in through the window into the user's eyes.Moving the monitor up covered the user's eyes, eliminating the major source of eye fatigue in the office for all of the workers on that computer. The client's eyes widened in an expression of revelation as she exclaimed that she could now see the screen and further modification would not be necessary.
The low vision exam can also tell me if the client has a medical condition related to the eye condition which causes him or her to have fluctuating visual acuity or fields.
Lastly, a low vision exam will indicate whether the client has a prognosis in which the visual condition is degenerating to the degree that low vision aids may not sufficiently keep up with the loss of vision whereby additional support through screen enlargement might be recommended.
The client will have been informed of various low vision aids which might eliminate the need for screen enlargement or reduce the amount of screen enlargement needed. A person who would need screen enlargement at 2X magnification on a 14"e; computer monitor with the proper prescribed low vision aids and eye ware may be able to use a 20" monitor with no software screen enlargement at all. This may significantly increase the freedom of the individual by not providing something else to go wrong on the computer system. A computer system is not unlike an automobile. Each extra that is added like air conditioning,power steering, cruise control, power windows and door locks, etc. is something else which can reduce overall performance (gas mileage for example) and is something else to break down or cause interference with another system of the vehicle. Adding software screen enlargement to a computer must take up at least some portion of precious conventional memory in the computer and could cause problems with other software application packages which access the same memory addresses, use up large amounts of memory, often redraw the computer screen or write to the same code page. I have had this happen with a software based screen enlargement package and Windows. When toggling between DOS and Windows session using the Alt Enter or Alt tab keyboard commands, the screen was redrawn by Windows to the same location,naturally, used by the screen enlargement package. The only problem with this was that the enlargement package was not sophisticated enough to known change in the display had occurred and that Windows redraw the screen.The result was a page which was split vertically in the middle, the left margin against the right side of the split, the right margin against the left side of the split and garbage on the lower quarter of the screen. No big deal, right? I only had to invoke the short cut key commands to turn the enlargement off then on again to refresh the enlarged screen but, to someone who was not familiar with the behind the screens methods used to enlarge the picture, this might have been a seemingly unsolvable problem whereas I found it to be simply annoying. Secondly, I have 20/20 vision,so I am not always as in tune with my clients as I should be in terms of walking in their shoes. I sometimes will try to duplicate their visual condition with low vision simulators in order to help come to a solution tailored to the person for whom I am customizing the computer. One such time, the aforementioned screen enlargement and Windows anomaly occurred and I was really disoriented. I had no idea what had happened even though I had seen the problem through 20/20 eyes before. To the person with a visual acuity loss or field loss, this was much more than annoying, it was frustrating,confusing, and somewhat embarrassing.
I do recommend screen enlargement for persons who have exhausted all means of low vision aids to easily access the computer screen or who may need screen enlargement as a means of reinforcing what they hear from a speech package. Their visual acuity may require screen enlargement which is too great to allow the user to work efficiently on the computer so they maybe using speech synthesis. Some speech synthesizers do not offer sufficient range of pitch and tone or fidelity to be easily understood. In these cases,as for someone newly in need of screen access alternatives just learning the speech package, screen enlargement may offer a reinforcement of what is being iterated by the speech system. (A picture is worth a thousand words.)
Computer screen enlargement may be necessary for someone who needs enlargement in addition to that provided by low vision aides prescribed for them.
Screen enlargement software might benefit someone for whom an increase in picture contrast through use of different color combinations is necessary.
Screen enlargement intervention may be indicated for persons who might benefit from or smoothed characters or different type fonts than standard font.
Persons who experience days in which their visual acuity fluctuates such as in some diabetic conditions or conditions where medications they need to take causes their vision to fluctuate may need screen enlargement here and there.
A person may be using prescribed low vision aids but their prognosis indicates that their visual acuity is diminishing more rapidly than a fixed prescription can accommodate alone. Screen enlargement may help the person continue to use as much of their functional vision as possible for an extended period of time.
The following stages are a generalization of how some screen enlargement is achieved. This might help us understand why screen enlargement glitches or conflicts occur and how we might avoid those conflicts and glitches.
Stage One, User Input
The computer user enters a key combination or mouse control function which prompts the TSR (terminate and stay resident) screen enlargement program to do something to the screen.
Most screen enlargement packages intercept the normal operation of the computer by using interrupts. Next, the keystroke(s) intercepted from the user a reprocessed and the information on the screen is monitored for changes. If the user has entered a "hot key" of the screen enlargement package,the package may process a series of instructions and return to the normal cycle of computer processing where the interrupt occurred.
Stage Two, Copying of BIOS Text
During this stage, the information on the unenhanced screen is copied to memory, either computer memory as in the case of software based enlargement or into the memory of the video card in the case of hardware enlargement.We are basically taking a picture of the screen for reference later.
Stage Three, Conversion
The picture which was taken of the screen is bit mapped in such a way that scaling can take place. This is the way that Windows screen enlargement is handled. DOS based systems may take only the text that is available from the picture and rather than bit map it, use pre-made pictures of text characters to construct a new picture in the window area. This difference between the way DOS and Windows enlargement packages are handled is the root of why windows based enlargement is not always as efficient as DOS based enlargement.I shall explain why when we discuss software issues.
For DOS based software, the enlarged text characters are cropped and then displayed. For Windows based enlargement, the picture enlargement is mathematically calculated and cropped, then displayed.
Stage Four, Screen Modifications
Any user preferences are handled, ie. character scrolling, color mapping,etc.
Interrupts and Address
Hardware systems, such as Telesensory's VISTA VGA, are a combination of a VGA video card with 1 megabyte of memory, a special chip with programmable options for handling video changes, and a software support package which includes smooth fonts and instructions which are sent to the video card for video processing. The hardware part of the system, the card that replaces the video card of the PC, has a setting for interrupts and address locations for the card to reside in. The trouble with this is that the other cards in the PC such as SCSI controller cards, I/O cards, game and sound cards use similar interrupt and address settings. If you have a machine, for example,that has a SCSI card with an address setting of Hexadecimal 0340 and a soundcard with an interrupt setting of 7 you will have to change these settings,the default, on the VISTA VGA card. This is easily done on this card with the flip of a small set of switches on the card, called DIP switches. the dip is an acronym for dual in line package and is not important to remember.What is important is that the switches are an easy way of making changes on the card rather than the jumper method whereby a little sleeve would fit across two pins on the circuit board, itself, shorting the two together,completing a circuit. This is more time consuming as they are somewhat hard to find and, because of the nature of the way circuit boards are laid out,are seldom in one location on the board like the DIP system. Telesensory makes the adjustment simple by way of the clear, concise instructions inthe manual. This manual is very important, especially since inserting morethan one video card in your PC can destroy one card, both, or the the PC. The instructions walk the user step by step through safely installingthe unit. I have installed these units over fifty times in the past two years, and have not had a single board fail, destroyed or operate in anyway other than indicated in the manual.
This brings up more positive aspect of direct line video processing such as this hardware concept. While installation may be a little more tricky than the software versions, sometimes requiring a sighted assistant, I have not had a single unit fail to perform as expected. In computers where software products failed to perform due to the limitations listed in the software issues section, the VISTA VGA product was able to handle multiple sessions,mainframe support, fast response, seamless operation, and consistent quality.This is not a shameless endorsement of any particular product and I am not in any way associated with the company which produces the product, I am merely relating my experience with the equipment listed here.
Accessibility
This is more of a problem with speech synthesizers than with screen enlargement products, but, is still an issue. If there is a problem with a hardware screen enlargement product, one must open the computer and remove the card to have it repaired. With the software based screen enlargement products,one merely needs to reinstall the software and can be up and running in minutes. Again, not to endorse a particular product, but this should rarely happen with the hardware product. It stands to reason, as I have not had to repair or reinstall any video cards, adaptive or otherwise, due to corruption or breakdown. I have had to reinstall software products from time to time depending on their software protection scheme. I have had trouble with hardware screen enlargement systems and conflicts with some versions of BIOS, the chip that handles the internal s of your PC. This is rare and more a product of the BIOS chip, I suspect, rather than the screen enlargement product as I have had this happen randomly on machines which were next to each other off the assembly line; different bios version, same motherboard, chips and hardware internal s. That tells me it is a PC problem, not an adaptive technology problem, necessarily.
Transferability
If you wanted to use the same screen enlargement product at home and work,moving the enlargement package from machine to machine would be laborious to say the least. Software products may easily be transferred, installed on a diskette, carried in your pocket, demonstrated on various PC's, etc.
Limited Number of Slots in the Host
Hardware systems, as we have discussed, require at least one slot in the PC. When one looks at adapting a machine which has a network interface card,Separate I/O card, SCSI card, sound card, internal Modem, etc., there may not be any room left for the additional adaptive hardware card. This will usually not be the case; however, as the video card will usually need to be removed, creating an open slot for the replacement adaptive video card.
As mentioned earlier, software screen enlargement products offer their own unique bonuses and problems.
Concurrent Session Support
When emulating a terminal on a mainframe system, does the screen enlargement product have enough memory and the right memory handling scheme to maintain picture integrity. As mentioned earlier, memory is finite. Some software screen enlargement products corrupt the picture when many switches between sessions occurs. The hardware version does not have this problem as it directly displays the modified image from the circuit board to the screen, storing the BOIS information on the board. Some software based products do not pollbios as frequently or update quickly enough to handle many sessions with much switching between sessions.
Network and Mainframe Support
As it sounds, does the product support network and mainframe sessions? Some software based products require the same sections of memory to do their magic as the network software or mainframe terminal emulation software.
Cross-operating System Support
Is the software capable of handling more than one operating system. For example, The new IBM screen enlargement product works under OS/2, supporting dos, OS/2 and Windows based applications. Most of the other popular products such as the VISTA VGA, Zoomtext PLUS, LP DOS Deluxe, Magic Deluxe, and others work with DOS and Windows.
Memory Conflicts and Usage
As indicated in the hardware discussion, software based systems require addresses and interrupts that application packages may also require, causing a conflict and system problems.
Learning Curve
The ability to quickly learn the product is of great importance. If the user interface makes sense, if the user manual is written clearly and enlarge print, the user will be able to start sooner and increase their productivity.
Ease of Use
This goes hand in hand with the learning curve issue. If the software is easy to use, it will be open to a wider audience. Support from coworkers is possible when the product is simple and straightforward. This is important in employment situations, school settings and public library settings.
Consistency of Quality
Does the product doe what it claims to do on each system on which it is installed, again and again without frequent reinstallations? Does the format for use of the product stay similar in subsequent upgrade versions, reducing the need for retraining?
Software Installable on Floppy Disk
Is it necessary to install the software portion of the product on a hard disk drive? Some people are still using PC's without hard disks. Also, some macintosh users are using Mac Pluses with only floppy disks on a Mac network.
There are features which are particular to some package and others that seem to be the norm. Depending on the visual condition of the person for whom you are adapting the computer system, some packages or maybe even one package could be singled out from this list of features.
User Interface Features
Supports Separate Keypad/Input Devices - Some screen enlargement packages allow the user to make the adjustments to the screen through keyboard input(hot keys), mouse control, or both.
Keyboard Support - Some screen enlargement programs allow the user to redefine what key combinations control the product. This is an important feature for those users who have a limited range of motion or who have application programs which use the original adapted key configuration.
Loads Configurations Automatically - This refers to the ability to use a simple command which could be called from within a batch or initialization file to load a custom configuration for the user.
Visual Menu System - This feature may be useful to reduce the learning curve of the product and aid anyone who is teaching the end user to use the product.
Compatible with Other Adaptive Software/Hardware - This is one of the most important features of a screen enlargement product. The more other technology and the screen enlargement product work together, the more efficient the end user will be in accessing the computer.
Ability to Use Command Line Parameters - Some packages allow the user or installer to add command line parameters to custom load the product with features like specific magnification size, presentation view, color mapping,etc. This is a valuable tool to use when setting up a system in a classroom or for a setting where multiple users are accessing the same computer.
Multi-Version and Type of Operating System Support - Does the software come with versions for say DOS and Windows?
Compatible with Numerous Display Platforms - Simply, does the product support numerous video formats? These formats are listed here for IBM PC compatible systems: Monochrome; CGA (Color Graphics Array); EGA (Enhanced graphics array); VGA (Video Graphics Array); XGA (Extended Graphics Array); SVGA(Super VGA)
Software: Will it fit onto a single disk (portability) - As previously discussed,this feature is helpful for folks who use multiple systems of for those of us who use network terminals without hard disk drives.
Ability to Load the Program into High Memory, Ability to Access Extendedor Expanded Memory - These features are similar in nature, offering the installer more flexibility and the user more choice of what application programs run concurrently with the screen enlargement in place.
The following is a list of important user features offered by screen enlargement products for computers. Most are self explanatory.
Enlargement Options: Enlargement Size Adjustable; Enlarge Entire Screen;Enlarge A Single Line; Enlarge A User Defined Window (This refers to enlarging a window on the screen which, while moveable, is only moved for initial placement. This makes it possible, for example, to enlarge just half oft he screen or a section of screen.); Enlarge A User Defined Moveable Glass
(This refers to a magnifying glass type of object window which could be moved easily and was designed to be used like a hand held magnifier.)
Tracking Options: Bar Tracking/Highlight Tracking; Color Change Detection/Tracking;Mouse Tracking; PC Cursor Tracking; Screen Reader Tracking; Ability to TurnOff Tracking; Graphic Identification/Enlargement
Font Technology: Choice of Multiple Fonts; Smoothed or Anti-aliases Fonts
Review Options: Page Review/Scrolling Available; Ability to Read/Review an Entire Document, Not Just the Current Screen
Justification Options: This refers to justification similar to what first appeared with word processing packages. Focus could be placed on and enlargement would home in on a justified area on the screen. These include the following:Center Justification; Full Justification; and Right Justification .
Color Control: Variable Color Combinations for Foreground and background colors; Remapping of Colors Supported (This differs from the above in that colors are changed for certain aspects of the application program. For example,if you chose yellow characters on a black background for the above, all characters, menu items, highlights, etc. would be in yellow and black, making it difficult to see highlights and other application features. the user change all red characters to yellow, for example, leaving all the other colors alone.)
Service and Support: As with any product one buys, service and support after the sale can make the difference between a wise investment that pays for itself and a disaster waiting to happen.
Windows Version Included With DOS Product On PC Based Systems: This is important now that Windows has a firm hold on the operating system market. continued dos support is important because some applications have not made the leap to Windows and Windows 3.1 is still DOS tied. This is the reason that the user has to pay more for a DOS version with Windows included and cannot buy a Windows only version but could buy a DOS only version. There may bea few exceptions to this.
Daniel A. Aunspach is a Rehabilitation Engineer
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