Jul
2003

Lens Choices:

 

With computers in nearly every workplace and home, Computer Vision Syndrome (CVS)—the dry eye, eye fatigue and blurring caused by looking at computer monitors—is rampant. In addition to the strain and fatigue symptoms in the eye, CVS, which the American Optometric Association identified in 1995, also manifests in the back, neck and brow, caused by computer users shifting position to compensate for blur in the intermediate.
The optical solution for CVS, known clinically as asthenopia, is Near-Variable Focus (NVF) lenses, a specialized progressive lens design featuring a wide intermediate corridor to optimize vision for computer use.
From eye exam to lens ordering, successful dispensing of this high-tech, second-pair lens requires low-tech methods. The first step in NVF lens dispensing is the lowest-tech method of all. “It comes down to talking to the patient,” says Eric White, OD, of Complete Family Vision Care in San Diego, Calif. “You can only find out if patients are using a computer and if they’re experiencing symptoms [of CVS] by asking about the vision problems they’re having.”
As part of the pre-exam, many dispensaries have patients fill out a lifestyle questionnaire including questions about vision tasks such as computer use. “A lot of patients have either heard of CVS or are just instinctively aware that working at the computer is causing some discomfort,” says John Gunning, OD, of Family Vision Centers in Chillicothe, Ohio. “But often it is the optometrist who has to put the relationship between the symptoms and their computer use together for the patient.”

Untapped Niche
According to the U.S. Census, 143 million adults use a computer every day and an estimated 54 million children use a computer at home and/or school. Industry observers estimate that NVF lenses account for less than 5 percent of progressive lens sales, suggesting the niche is under-sold and CVS is going undiagnosed by most eyecare professionals.
“As clinicians, we are only beginning to understand eyestrain and that computer use is a visually distinct task that actually causes a reduction in blink rate,” says James Sheedy, OD, Ph.D., associate professor at Ohio State University’s College of Optometry. “There are also accommodative issues. Computer users who require a prescription can have more problems accommodating in the intermediate. Computer lenses can be a solution for these patients.”
Dr. Sheedy, who launched a CVS web site (www.doctorergo.com) and is currently conducting a Microsoft-funded study of CVS issues, admits progress in addressing computer-related vision problems has slowed in recent years. “With the current administration in office, there’s less interest in health and safety workplace issues,” Dr. Sheedy notes. “It sets an unfortunate tone.”
The task-specific, computer lens is more often than not an out-of-pocket patient expense, which ECPs cite as the factor most inhibiting the presentation of NVF lenses to patients. “Even though the lenses cost less than progressives, patients are hesitant to spend the money,” says Stephen Rozenberg, OD, of 10/10 Optics in New York. “On the other hand, you get a really high satisfaction rate among patients. They love these lenses. You’re literally taking away their headaches. You don’t get that patient satisfaction with other lens products. As an optometrist, that is a big incentive.”
Kent Daum, OD, Ph.D., associate professor, University of Alabama at Birmingham, School of Optometry, has found, “there are some plans, especially with some unions, that will pay at least partly for a computer eye exam and even for the lenses. Sometimes the patient will come in with a voucher from their human resources manager, but we have had cases in my private practice where we’ve identified a CVS problem, then contacted the health plan and found some benefit was offered.”
Dr. Daum released a study last year that found dispensing an NVF lens to computer users can improve productivity by 3 percent. “If you multiply it over the workforce, it means billions of dollars to employers,” says Dr. Daum. “Getting the message to employers about productivity gains with these lenses will certainly boost demand and interest.”

Computer Exam
The most effective eye exam for computer users emphasizes intermediate distance from the eye—generally 16 to 24 inches, which is where the computer monitor is situated. Not everybody’s work station is exactly the same distance. A lap top’s screen, for instance, is closer to the user than a desk top screen. To optimize the individual’s intermediate zone, patients are asked to measure the distance of the monitor from their eyes by the optometrists. In the case where the home computer is a different distance than the work unit, eye doctors recommend using an average distance and the computer lens refraction is based on that individualized distance.
Typically, an eye exam refracts for the distance and near zone and in presbyopic patients when an add-power is required, the full add-power is for the near zone; the intermediate portion of the progressive lens is half the add-power of the near. In standard progressive lenses, the intermediate corridor is basically the transition portion from near to distance, thus any variations in that intermediate zone power are not a priority. “With progressives, if there is a blur at the intermediate, patients adapt because they are under-using this area,” says Dr. Daum. “With computer use, it’s the area they use the most, so it is appropriate the refraction optimizes the patient’s prescription at that point. When patients use regular progressives, they are constantly moving their head and squinting at the computer because there’s such a relatively small spot where the intermediate vision is clear.”
Many ECPs, instead of just using a Snellen chart, refract this intermediate power using the Prio Vision Tester System, manufactured by Prio Corp. The system is based on the theory that accommodation is not only affected by the intermediate distance, but by the screen itself where the characters—formed by a series of flashing spots called pixels—flicker. Pixels are less defined and more difficult to focus on than printed characters. They have a Gaussain or “bell-shaped” energy curve when measured by a light meter and can disrupt the patient’s Resting Point of Accommodation. The Prio device enables the refraction to compensate for the accommodation issue related to the unique visual task of viewing pixels at an intermediate distance.
During the refraction, ECPs position the Prio device, which simulates pixels, to the exact distance of the patient’s computer monitor. “Computer use is a vision intensive task because of the screen and the intermediate,” explains Dr. Rozenberg. “I will ask the patient to measure their eyes to their computer screen and refract from that distance, performing retinaoscopy using the Prio tester to see how their eyes are accommodating at that focal point.”
The refraction itself relies more on the OD’s judgment than automated ophthalmic instrumentation. “By using the retinascope with Prio, you can identify more subtle changes in accommodation,” says Larry Wan, OD, of Family Eye Care Center in Campbell, Calif. “Autorefractors won’t detect these measurements. After I have the intermediate power, I ‘trial lens’ the patient for the intermediate zone to verify the result and make any necessary modifications on the prescription.”
Sometimes the refraction will be different for computer use than for regular wear, “it’s a task-specific lens and sometimes it’s a task-specific refraction. Optometrists shouldn’t be afraid of that,” notes Dr. Wan.
“Many patients benefit from even quarter of diopter changes in NVF lenses,” says Dr. Rozenberg. “But, I’ve also seen differences of a half or a whole diopter using Prio and I’ve seen differences in each eye. As an OD, you have to use your judgment, listen to the patient and see their reactions.”

 






Patient Diversity

While the majority of CVS complaints seem to come from presbyopes, other patients can have intermediate zoneaccommodative issues associated with computer use. “The market probably holds as much second-pair sales potential as any,” says Nina Rivetta, optician/owner of Sunset Optics in Erie, Pa. “You can’t prejudge a patient’s CVS problems. I’ve had LASIK patients who’ve complained about computer use and after the exam, an add power in the intermediate zone helps them.”
Hyperopes can also have accommodative issues with the intermediate zone that a regular prescription will not correct. “Hyperopes seem to have more complaints with computer use than myopes, especially with latent hyperopes and NVF lenses are a great solution for them,” says Dr. Gunning.
Dr. Wan prescribes NVF lenses to pediatric patients. “Kids use computers in the school, do nearly all their homework on computer and they play a lot of computer or video games. The combination of the intermediate zone and the monitors cause what appears to be unique accommodative issues to children. Often when they stop looking at the screen, they will have problems focusing.”
Some ECPs point to the proliferation of over-the-counter “readers” marketed for computer use and sold at computer and office supply stores as an indication the eyecare community needs to do a better job recognizing the need for NVF lenses as a CVS remedy. “With OTC readers, people are basically self-refracting themselves and not getting glasses properly fit,” says Rivetta. This creates an opportunity when they get their eyes examined because the NVF lenses perform so much better.”

Fitting and Ordering
Just as the NVF refraction is more hands-on, dispensing and ordering requires more attention by the ECP. “Especially when a practice is first ordering their NVF lenses, it’s best not to use automated ordering,” says Mike Sutton, vice president/sales and marketing of Rite-Style Optical, an independent wholesale lab in Omaha, Neb.
In general, NVF power ranges are a -2.00D to +4.00D, with add powers .75 to 3.00. For specific power ranges and increments of add power, check with the manufacturer and/or with your wholesale lab. The distance zone is either minimal or non-existent depending on the lens.
Ordering NVF lenses is similar to ordering other progressives. However, when refracting for the intermediate sometimes the optimum intermediate power exceeds 50 percent of the near zone power. This generally won’t affect how the lenses are ordered from a lab though, since generally only the near power is lited on the Rx order form. Prio Corp., which also markets two NVF lenses, has its Shazam! software program that calculates what it calls “total near” power, so labs can process a Prio NVF lens with the prescribed intermediate and near zone powers. “Sometimes depending on the lens and the Rx, you have to decide between over or under correcting a zone or tweak the lens by manipulating the segment height,” says Dr. Wan. “If the patient works mainly on the computer and has minimal near zone needs, you can get away with over-correcting that zone but make the zone slightly smaller.”
Other recommended tips include, “taking monocular near PDs and taking a precise fitting height from the lower lid,” says Michael Palkovicz, president of I-See Optical, an independent wholesale lab in Blackwood, N.J. “Do not go below the suggested fitting height by the manufacturer and select a good size frame so the intermediate has ample room.”
In spite of the complexities and extra considerations for dispensing NVF lenses, ECPs who have taken the time to succeed in this niche have found that patients easily adapt to the lenses. “There’s been very few reports of adaptation problems. Patients get it almost instantaneously,” says Sutton. “They’re no longer seeing a blur they were working around.” LT

 

 








 

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