Computer Vision Syndrome: Its Cause, Treatment and Potential for the Modern Ophthalmic Practice

By Lee Prewitt, ABOM

In the United States, approximately 281 million people go about their daily lives, working, going to school or enjoying the golden years. As our culture becomes more and more fast paced, Americans are embracing technology like never before. We have devices that will entertain, help to cook our meals, relax and help us be more efficient at work. One device however has permeated our lives so much thataccording to the U.S. Census Bureau60 percent of adults and more than 89 percent of children ages five to 17 use it: the computer. During the course of their day, 50 million workers, 47 million school children and a staggering 7.6 million seniors over 65 are either online or using a computer. This last segment of users (seniors over 65) is expected to surge to 16.3 million by 2007.

CVS AND ITS SYMPTOMS
All of these people will potentially have one problem in common. They will all be susceptible to Computer Vision Syndrome or CVS. What is CVS? The American Opto-metric Association defines Computer Vision Syndrome as:

Computer Vision Syndrome (CVS) is a complex of eye and vision problems related to near work which are experienced during or related to computer use. CVS is characterized by visual symptoms which result from interaction with a computer display or its environment. In most cases, symptoms occur because the visual demands of the task exceed the visual abilities of the individual to comfortably perform the task.

Eyecare for computer users should be different from the eyecare required for every day visual tasks. The major difference between computer eyewear and dress eyewear is the stress placed on the visual system when performing intensive task-specific work coupled with the visual environment associated with computer usage that is not encountered in the normal course of ones daily routine.

The visual system components that are utilized during computer usage are comprised of frequent ocular movement, constant accommodation, and demands on the muscles for vergence. Eye movement, focusing, and alignment require constant and repetitive musculature movements. It is estimated that the eyes will utilize between 30,000 and 50,000 musculature movements in a typical workday. The extraocular muscles control movement and vergence. They are the superior and inferior oblique, superior and inferior rectus, and the medial and lateral rectus muscles. These six muscles move the eye about the orbit and control and maintain our gaze. The ciliary muscle, part of the ciliary process, is responsible for near-visual focusing.

Symptoms of CVS occur whenever the requirements of the visual task exceed the visual systems ability to deliver. In many respects, CVS can be classified as a musculoskeletal disorder or repetitive stress injury similar to carpal tunnel syndrome. In fact, OSHA, the governing body of the work-place, has recognized CVS as a legitimate occupational malady associated with prolonged computer usage. CVS is now more common than carpal tunnel syndrome occurring in seven out of 10 workers compared to one out of five sufferers of carpal tunnel syndrome. Although CVS and its causes have been attributed to numerous ergonomic factors, this paper will focus on the visual causes and its solutions.

UNDERSTANDING RESTING POINT, GAUSSIAN IMAGES AND LAG OF ACCOMMODATION
There are three key definitions to understanding how the visual system reacts to computer images. The first is Resting Point.

When an individual is daydreaming, just looking off into the distance at nothing in particular or zoning out, the eyes are focused on the natural resting point that is inherent in all of us. This focal plane is unique to each individual and is that point in space that the eyes will come to focus without any consideration of accommodation or convergence.

The second is Gaussian image.

The human eye has no problems in discerning a printed image. The image is well defined, has excellent contrast against the background and most importantly has sharp edges for the eye to lock on to. This has been a human skill since man has had to hunt for survival. On the contrary, a computer image is an image comprised of pixels. Each pixel is a point of light on the computer screen that has a Gaussian effect.

A Gaussian image is one that is very bright in the center and fades to nothing on the edges. Think of a bell shaped curve. The image is brightest in the central region of the bell curve but very faint as it radiates outward. The human visual system has an extremely difficult time holding focus on this type of image. So what happens when the eye cant hold an image? It resets itself to its unique resting point. However that is not likely to be where the user is trying to view the computer screen. The brain sends out its signals to focus on the screen and the muscles in the eye that control the lens flex and refocus. Now that wont work well either because the human eye has a difficult time focusing on the pixilated image. So it resets itself to its natural resting point and so on and so on. A Catch-22 ensues.

What happens to a muscle that is repeatedly flexed over a long period of time? Fatigue sets in, the muscle gets tired and does not function as efficiently. It is commonly accepted knowledge that fatigued eye muscles can lead to headaches. Headaches cause tension, which in turn can lead to tight muscles in the neck, shoulder and back. Welcome to Computer Vision Syndrome.

The third is Lag of Accommodation
Lag of accommodation is defined as the difference between the natural resting point and the focal plane on which one is attempting to focus. Lag of accommodation is independent of all eye conditions. It affects myopes, hyper-opes and emmetropes equally. In conducting a computer vision exam, an Optometrist is able to determine a correction that will neutralize the lag of accommodation that we all experience.

RESEARCH

PRIO Corporation, a leading researcher into CVS and its solutions have patented a vision tester device for the exam room that duplicates the Gaussian effects of the computer screen. In a study of 970 patients in 17 states conducted by PRIO, doctors found that 90 percent exhibited a lag of accommodation in excess of 0.37D, 50 percent exhibited a lag of accommodation in excess of 0.75D, and 25 percent exhibited lag of accommodation in excess of 1.75D or more. Clearly patients could be made more comfortable if the lag were reduced to zero.

In a survey of 1,307 optometrists, just over 14.25 percent of patients presented themselves with symptoms primarily associated with computer usage. If one extrapolates this to the computer user population, nearly 15 million will experience some symptom of CVS. That represents a huge number of people suffering on a daily basis and an enormous opportunity for lens care.

REMEDIES
A SPECIAL PAIR OF GLASSES A doctor of optometry diagnoses the problem and writes a prescription to stop the cycling of accommodation. This solution is a task specific pair of computer glasses. However the patient already has a habitual pair of glasses. Wont they work for the computer? The simple answer is no. The patients general use glasses have not been corrected or compensated to negate the lag of accommodation effect when viewing a computer screen. In fact, a study conducted by the Ohio State University College of Optometry found that test subjects who had a dedicated pair of computer glasses had a greater reduction in CVS symptoms that those subjects who relied upon their general purpose prescription.

LENSES THAT CAN BE USED

The types of lenses available to correct CVS are single-vision lenses, traditional bifocal, trifocal or progressive addition lenses and task-specific computer progressive lenses. The latter design of lenses is a progressive addition style of lens developed with the computer environment in mind. They are designed for a wide near zone, edge to edge viewing at the intermediate or computer screen and a short distance beyond to about 10 to 15 feet. This paper focuses more on this group of lenses. Research conducted by Department of Optometry and Visual Science, Buskerud University College, Kongsberg, Norway concluded that lens designs that cover from near distances to about 2 meters or 6.5 feet work well compared to designs trying to cover greater ranges.

NEAR VARIABLE FOCUS (NVF) LENSES

Near variable focus lenses, as computer progressives have become known, are manufactured by many lens companies. Shamir Office, Nikon OnLine, SOLA Access and PRIO Browser are some of the special, task-specific designs that are available. All of these lenses give the wearer a wide near, wide clear intermediate and minimal distortion. Near variable focus lenses differ from traditional progressive addition lenses in two ways, the intermediate field of view and the magnitude of peripheral blur.

A traditional progressive has a far, intermediate and near zone. Due to the larger power difference between the near and far zones a considerable amount of unwanted peripheral blur and a narrower intermediate is created as a compromise. This is uncomfortable for the computer user. To use the intermediate zone, the wearer is required to elevate their head. This causes the neck to be held at a 20-degree inclination from the norm, an uncomfortable position to hold ones neck for long periods of time

For a computer user, this creates an unnatural head position that will lead to musculoskeletal problems over time. In fact, a study conducted by the University of Missouri-St. Louis found that 76 percent of presbyopic progressive lens wearers preferred their task-specific computer eye-wear to their normal daily eyeglasses.

In creating designs for near variable lenses, designers wanted a lens that gave clear vision with minimal distortion from 1.3 feet out to about 10 feet. By effectively removing the far zone component, designers are able to create a lens with an extremely wide zone of intermediate power above the 180-line and a smooth, short transition into the reading zone. Two things happen in this design. One is that the inherent peripheral blur that is common in progressive designs is greatly minimized since the power shift is not as extreme as in progressive addition lenses. Secondly, the peripheral aberration that is left over can be spread over a greater lens surface area thus softening the impact of the unwanted astigmatism

This creates a lens that is optimized for all wearers. Emmetropes and progressive wearers alike have good utilization and adaptation. Using near variable focus lenses is also good for musculoskeletal ergonomics. Since the computer operator can maintain optimal vision at the plane of the computer screen, the head can be at a more natural 15-degree angle. This is the optimal position and drastically reduces the neck and back pains of CVS.

The majority of computer lenses can best be described as having a range or degression, a loss of power from reading to intermediate. These lenses are progressive in design but instead of adding power, they are designed to reduce power. To fit a patient with a near variable focus lens, start with the patients full distance and reading add. Select the lens digression that is desired (either select the power shift to achieve the dynamic power you want or allow your lab to select the lens power recommended by the lens manufacturer) and place the order. The lenses received back from the lab will have the full reading prescription at the bottom of the lens and will digress or be reduced by the power shift as the eye moves up the lens.

For example, an emmetrope, who requires a +1.00D add might be fit with a Shamir Office with the recommended 075 degression. The lenses received back from the lab would measure +1.00D sphere at the reading level and +0.25D at the top and about +0.625D at the fitting cross. This prescription provides clear close up vision and at the computer screen. Distance vision is not completely corrected and as a result is slightly blurred.

In fitting computer progressive lenses, it is recommended to follow the manufacturers fitting guide. When a fitting cross exists, most recommend fitting the lens at pupil center. Refer to the attached table for a complete guide. Minimum B measurement of around 29mm are also required. This does allow for a wide range of frame selections including a majority of todays fashion designs.

Lens Rxs range from +6.00 to -6.00D sphere, cylinders to 4D and up to three power shifts or degressions are available. Nikon OnLine offers a 1.67 index lens with a 2.00 degression and is currently the only high-index lens on the market. The more the degression, the farther out the wearer will be able to see. This is especially important to the high-add wearer where there is no reserve of accommodation left.

LIGHT CONTROL

Light is another component of CVS that bears worth mentioning. Although many may consider this an environmental ergonomic factor, it has a strong bearing on the application of ophthalmic lenses. Two factors that can be controlled in the design of computer glasses are glare control and visible spectrum control.

Anti-reflective treatments applied to the lens surface will be beneficial to the user as visual performance through the lens is enhanced by reducing distracting glare. Anti-reflective lenses greatly improve the performance of lenses by eliminating visual noise from reflections. A study performed in 1993 by the Indiana University School of Optometry concluded that it is 67 percent easier to see with AR lenses as opposed to non-AR. Three light conditions were analyzed: normal light, bright light from the front (driving) and bright light from behind or overhead as in office type lighting. Image contrast was significantly improved in all conditions with anti-reflective lenses.

The second component, visible light management involves fluorescent lighting in the workplace. Office lighting is rich in short wavelength blue light. The human eye has a difficult time focusing with an abundance of this scattered blue light. A UV400 filter on the lens will help attenuate a portion of this spectrum of light. UV400 filtering will decrease by about half of fluorescent tubes blue light output creating a room light that is less harsh and more visually comforting.

WHAT DOES THIS ALL MEAN TO YOU?

Consider each of the following as a significant growth opportunity for the progressive ophthalmic practice

• In the United States alone, over 60 percent of the population (18 and over) uses a computer, according to the U.S. Census Bureau. In the working population, nearly 40 percent are online at work. 70 million use a computer for work-related tasks at least one hour per day. Nearly 90 percent of school age children between the ages of five to 17 use a computer. This includes online research, completing school assignments and playing games. Children are a very susceptible population of computer users for many reasons. Chief among them is childrens ability to remain engaged in an enjoyable task with intense concentration for hours at a stretch. This prolonged activity without any form of breaks can cause accommodative issues, eye irritations and musculoskeletal discomfort. In fact, American children are reporting moderate amounts of musculoskeletal discomfort and this discomfort can be associated with computer usage.
• In a very surprising development, seniors aged 65 and over numbered more than nine-and-a-half million online users. That was a 25 percent increase from the previous year and the senior market is projected to be over 16 million online users by 2007. Email is the number-one activity cited by this age group.
• As the American workforce becomes more service-based more workers will be using computers to complete and gather the information needed to perform their jobs efficiently. Laboratory studies have shown task performance decreases 4 to 19 percent with relatively small amounts of visual degradation. In another study conducted by the University of Alabama School of Optometry, results showed productivity increase of between 2.5 and 28.7 percent among test subjects who were corrected for refractive errors at the computer. The study also found a cost benefit ratio of 9:1 in favor of providing computer eyewear. Productivity gains outweighed associated costs of providing an eye exam and glasses.
  
  Computer Vision Syndrome is widespread covering nearly every demographic of the population. Over 14 percent of all eye exams are for CVS symptoms and 41 percent of those people purchased task specific eye-wear to alleviate the problem. This demonstrates a practice growth segment available to all offices. Optical professionals are uniquely positioned to provide profitable solutions for their patients. Take a look at the following scenario:
• On average in 2002, optometrists conducted 2,104 complete eye exams including refractions, according to an AOA economic survey.
• As reported earlier, 14 percent of all patients present themselves with symptoms of computer vision syndrome.
• That represents on average 305 patients per year with CVS-related problems for the typical practice.
• Jobson Optical Research reported an average frame cost of $120 and progressive addition lenses $208. No data was available for near variable focus lenses. For our purpose we will assume an average of $168 for computer lenses and an average for anti-reflective lenses of $69, according to a Jorgenson Optical Supply lens survey.
• This gives us an average of $357 for frame, lens and anti-reflective coating.
• Multiplied by the number of patients that present with CVS symptoms, there is about $108K in potential revenue from CVS solutions. This hypothetical scenario represents a healthy target to increase revenue and better meet patient needs.

THE FUTURE

Near variable focus lenses have huge market potential beyond usage as a computer lens. This category of lens is ideally suited for any office environment, home, hobbies and numerous other work situations. Yet the market share for this product is still small. Raanan Naftalovich, CEO, Shamir Insight, Inc. recognizes that this type of lens could eventually replace single-vision readers. He says, So much of what we do today at the near range is well beyond 1.5 feet. Why do we limit our visual range to just that? Shamir Office offers the patient a lens that is comfortable at near and extends beyond to about six feet. Single-vision readers are limited to just 1.5 feet. When a patient goes to their eyecare provider, they want the latest advancement. Not medicine that is 200 years old. This will be the reading lens of the 21st century.

Computer vision syndrome and its symptoms are here and affecting millions of people from all demographics on a daily basis. Optometrists, opticians and ophthalmologists who embrace CVS and its solutions will position themselves for continued practice growth as they educate their patient base about the symptoms and solutions to all those nagging and persistent vision problems they encounter.