June 26, 2002 For Immediate Release

For Information Contact Ellen Yu or Steven Clark Andover Communications 201-947-4133

STUDY REVEALS MAJOR DIFFERENCES IN COMPUTER VISION TESTS

(Beaverton, OREGON) A landmark study called "Comparison of Tests of Accommodation for Computer Users" recently published by the AOA Journal of Optometry, found conclusively that with prepresbyopes, traditional printed testing methods are unable to accurately and reliably generate the same near Rx that the PRIO tester indicates.

"With the increased use of computers in the workplace and at home, optometrists are finding more patients presenting with symptoms of Computer Vision Syndrome," write authors Robert Hutchinson, O.D., David Kolker, O.D., and Erik Nilsen, Ph.D. "Among these symptomatic individuals, research supports that accommodative disorders are the most common vision findings. While many tests exist to determine the status of a patient's accommodative mechanism, most optometrists in a typical busy practice setting will utilize only one or two tests to quantify the accommodative status of a patient."

This study examined several nearpoint tests of accommodation at a computer working distance for subjects separated into prepresbyope (ages 18 to 37) and presbyope (ages 45 to 68) groups. Tests included the reduced Snellen, NRA/PRA midpoint, cross cylinder, dynamic retinoscopy, and the VDT simulator (PRIO Vision Tester).

All of these tests use a high resolution, high contrast printed image as the target—except PRIO. The PRIO tester replicates the Gaussian light distribution of the pixels on a typical computer screen, thereby simulating the accommodative demand of a computer screen.

The researchers found a surprisingly large difference among the testing devices in the prepresbyopic group. Specifically, the study revealed among prepresbyopes that:

When using the reduced Snellen testing, in only two (2) cases out of 30 did the doctor arrived at the same add power indicated by the PRIO method. When using a near binocular cross cylinder test, zero patients indicated the same add power as the PRIO test. When comparing the Snellen-derived add to the PRIO-derived add, 10 subjects (33%) showed a difference of -0.75D or more (less plus than PRIO). When comparing the NRA-PRA midpoint-derived add to the PRIO-derived add, 20 subjects (66%) showed a difference of -0.75D or more (less plus than PRIO). The add powers resulting from the PRIO test had a statistically significant difference from those found by other testing methodologies. There is no way to reliably predict the PRIO add power from the results of any of the other testing methodologies.

In the presbyopic group, the tests yielded much more similar results, ranging from a mean add power of 1.44D for the cross cylinder test up to 1.61D for the PRIO test. The difference in add power indicated by the PRIO test is small, but is statistically significant.

However, Dr. Cary Herzberg, a computer vision expert who practices optometry in Aurora, Illinois, said that while his anecdotal findings confirm the results of the study for prepresbyopes, he has found that significant differences exist among early presbyopes as well (ages 42-47).

"In my experience the Gaussian image is most effective in diagnosing CVS with prepresbyopes, but I have also found that the Gaussian or PRIO method can make a significant difference with presbyopes," said Dr. Herzberg. "In some cases I get 0.50D to 0.75D of additional add power using the PRIO method, that I would not have found with the older methods of testing. And a 0.25D error has been shown to cause visual problems for many computer users."

Is More Plus Better?
Are tests that indicate more plus better for the comfort of the patient? To answer this, researchers in an earlier study1 had subjects who suffered from CVS wear two pairs of prescription glasses for two weeks each, in a double blind crossover experiment. Experimental glasses were prescribed using the PRIO test and control glasses were prescribed using a reduced Snellen card. Additionally, data was collected on the frequency and severity of symptoms of the subjects in their work environment.

Results indicated that the glasses prescribed using the PRIO tester were preferred by over 70% of the participants. Also, visual stress symptoms were significantly reduced in frequency and severity for these glasses over the control glasses.

"We've been saying to ECPs for years, "Are you comfortable being off by 0.75 or more for a significant percentage of your patients?"" said Jon Torrey, President of PRIO Corporation. "This study in the AOA Journal confirms it. "Close" may work for horseshoes, but doctors can and should do better than "close enough.""

Other recent studies on CVS have shown that:

Computer users make more mistakes in their data than workers using printed, solid images. (Source: Wilkinson, Robinshaw: 1997) Accommodative disorders are most prevalent among computer users. (Sources: Sheedy, Parsons: 1990; Hokoda, 1985; Sheedy, Fowler: 1993) Computer eyeglasses are more effective at reducing CVS than ergonomic interventions. (Source: Butzon, Sheedy, Nilsen, 2002)

For more information on PRIO, call 1- or visit www.prio.com.

References:
1. Reducing Visual Stress Symptoms of VDT Users With Prescription Eyeglasses, Nilsen, et. al., Human Factors in Computing Systems, CHI '95 Short Papers, 1995.

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