ReVision Study: Real Visual Conditions at the Visual Display Unit: A Field Analysis

Abstract

Purpose. In this interventional study, the character size of the main work task of computer workers in their offices was recorded, compared with the guidelines of the German Social Accident Insurance and adjusted to the recommendations. Subjectively estimated changes in productivity were recorded.

See: https://www.aaopt.org/detail/knowledge-base-article/revision-study-real-visual-conditions-at-the-visual-display-unit-a-field-analysis

Methods. The habitually used character size of the capital letter E was recorded on 152 visual display units, by using a ruler template. The productivity under this setting was subjectively assessed by the subject on a scale of 1 (low) and 100 (high). In case of failure to comply with the guidelines, the character size was increase to the lower limits of the recommendation range of 22 angular minutes. Two weeks after the initial visit, it was recorded whether the subjects continued to use the modified character size and how the estimated productivity changed as a result of the intervention. Reasons returning to the old character size were recorded.

Results. The analyzed character size was 14.3 angular minutes and falls statistically and clinically significant below the recommendation range by 7.71 ± 3.53 angular minutes (95% CI; 7.14 to 8.28, P < .001, paired T-Test). Transferred (for a viewing distance of 70cm) to Arial, as a realist sans-serif typeface, the lower limits of recommendations are 18 pt, the recorded character size was 11 pt. Half of the sample assumed compliance with the recommended range, in only 4% of all cases this could be confirmed. After intervention, the subjectively estimated productivity decreased significantly by 23 points on average (95 % CI; 16,90 - 30,06, P < .001, paired T –Test). In 71% of the cases the recommended character size was not compatible with the work task. A correlation between the undershoot compared to the lower limits of the recommendation and symptoms of the computer vision syndrome could not be demonstrated.

Conclusion. The recommended character size was not adhered to at the workplaces investigated. From the viewpoint of the screen workers, the adjustment to the lower limit of recommendation leads to a reduction in productivity and is not compatible with the work task. In general, solutions for the continuous increase of visual stress at the visual display unit have to be developed. An unrealistic range of recommendations does not seem to be very helpful.

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ReVision Study: Real Visual Conditions at the
Visual Display Unit: A Field Analysis
OLIVER KOLBE, M.ENG.¹; JENNIFER MÜLLER, B.SC.¹; PROF. DR. STEPHAN DEGLE¹;
PROF. DR. HABIL. CHRISTOPH ANDERS²
¹UNIVERSITY OF APPLIED SCIENCES JENA/GERMANY ²DIVISION OF MOTOR RESEARCH, JENA UNIVERSITY
HOSPITAL, JENA/GERMANY
PRESENTED AT:

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INTRODUCTION
Motivation
To reduce the burden of computer workers guidelines and recommendation were published by the German Social Accident
Insurance (DGUV). [1] Few literature [2, 3] show that computer workers fail to use character sizes in-between the limits
of recommendation (22 - 31 angular minutes). An increased visual load is conceivable.
During ergonomic workplace consultations, display setups with the top line on the screen above the horizontal visual axis can be
observed. Reasons for this are manifold:
screens are arranged according to recommendations that originate from the 90s, where cathode ray tubs were used
widely
some screen workers use screen stands or arrange packs of copy paper below the display, to raise the top line on the
screen further
some types of monitors cannot be adjusted in height or even tilted.
Weidling and Jaschinski [4] and Jaschinski et al. [5] showed that even a slight gaze reduction leads to a lower level of
musculoskeletal complaints.
Purpose
In this interventional study, the character size of the main work task of computer workers in their offices was recorded, compared
with the guidelines of the German Social Accident Insurance and adjusted to the recommendations. Subjectively estimated
changes in productivity were recorded.
Further, ergonomic workplace setups (display height, display type etc.) that are used in the field should be recorded.

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METHODS
The habitually used character size of the capital letter E was recorded on 152 visual display units, by using a ruler template, see
Fig. 1. The productivity under this setting was subjectively assessed by the subject on a scale of 1 (low) and 100 (high). In case
of failure to comply with the guidelines, the character size was increase to the lower limits of the recommendation range of 22
angular minutes. Two weeks after the initial visit, it was recorded whether the subjects continued to use the modified character
size and how the estimated productivity changed as a result of the intervention. Reasons returning to the old character size
were evaluated.
Computer vision syndrome was evaluated with a translated (German) version of the computer vision syndrome questionnaire
(CVS-Q). [6]
Fig. 1: Transparent ruler template to measure character size [7]

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RESULTS (PRIMARY ENDPOINT)
Character size
The analyzed character size was 14.3 angular minutes and falls statistically and clinically significant below the lower limits of
the recommendation range by 7.71 ± 3.53 angular minutes (95% CI; 7.14 to 8.28, P < .001, paired T-Test), see Fig. 2. This
average character size corresponds to a reduction of 35% of the lower and 54% of the upper limits of the recommendation range.
Transferred to the point size (and mm) of a sans-serif typeface (Arial) viewed in an average display distance of 70 cm the
recorded character size was 11 pt (2.9 mm), the limits of recommendations are 18 pt (4.5 mm) - 26 pt (6.4 mm).
Fig. 2: Mean and 95% CI of character size in arcmin (left) and mm (right)
compared to limits of recommen-dation [1] (green);
N = 152
Half of the sample assumed compliance with the recommended range; in
only 4% of all cases this could be confirmed.
There was no statistically significant correlation between the amount of the deviation in character size and the score of the
Computer Vision Syndrome Questionnaires (Pearson: r = -.061;
P = .452).

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RESULTS (SECONDARY ENDPOINT)
Performance
After intervention, the subjectively estimated productivity decreased from 90.2 to 66.8 points significantly by 23.4 points on
average (95 % CI; 16,90 - 30,06, P < .001, paired T–Test) see Fig. 3.
Fig. 3: Mean and 95% CI of subjective estimated performance before and after
intervention,
N = 100
In 52% of the cases, the subjects did not keep the adjusted character size and
decreased it within two weeks (follow up). Main Reasons for returning to
smaller sizes was a missing compatibility with work task in 71% of all cases.
There was no statistical significant difference in the loss of performance between user with display sizes greater or equal
and smaller than 27'' (95 % CI; -23.50 to 14.58, P = .643, paired T – Test).
Ergonomic Setup (key facts)
at least two displays could be found in 63% of all analyzed workspace
23"/24'' was the most common display size (62%)
wide screen displays could be found in 80% of the cases
there was no correlation between display size and character size (Pearson: r = - .026, P = .747)
the top line of the display was 39.0 mm ± 64.18 mm below eye level (95 % CI; 28.68 to 49.25, P < .001, paired T-test),
however in 23% of the cases the display was above the eye level

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CONCLUSION
The recommended character size was not adhered to the workplaces investigated. The incensement of the character size to the
lower limit of recommendation leads to a reduction in productivity and is not compatible with the work task, e.g. the missing
overview within a spreadsheet. A significantly reduced character size results in a permanently increased visual burden and can
put greater strain on the screen worker, depending on the individual's ability to compensate.[3] The study revealed poor
knowledge of the screen worker about the correct character size. Compared to Bartha et al. [3] only little evidence about a
correlation between subjects' complaint level (CVS-Q Score) and the character size could be found. This might be reasoned in
methodological differences due two different utilized questionnaire.
In general, solutions for the continuous increase of visual stress at the visual display unit have to be developed. An unrealistic
range of recommendations does not seem to be very helpful.

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REFERENCES
[1] German Social Accident Insurance (Ed.) VDU and office workplaces - guidelines for design: [Information 215-410.
Bildschirm- und Büroarbeitsplätze - Leitfaden für die Gestaltung]; 2019
[2] Bababekova Y, Rosenfield M, Hue JE, Huang RR. Font size and viewing distance of handheld smart phones. Optometry and
vision science 2011;88:795–7
[3] Bartha MC, Allie P, Kokot D, Roe CP. Field observations of display placement requirements and character size for
presbyopic and prepresbyopic computer users. Work 2015;52:329–42.
[4] Weidling P, Jaschinski W. The vertical monitor position for presbyopic computer users with progressive lenses. How to reach
clear vision and comfortable head posture. Ergonomics 2015;58:1813–29.
[5] Jaschinski W, Konig M, Mekontso TM, Ohlendorf A, Welscher M. Comparison of Progressive Addition Lenses for General
Purpose and for Computer Vision: An Office Field Study. Clinical & experimental optometry 2015;98:234–43.
[6] Segui MdM, Cabrero-Garcia J, Crespo A, Verdu J, Ronda E. A reliable and valid questionnaire was developed to measure
computer vision syndrome at the workplace. Journal of clinical epidemiology 2015;68:662–73
[7] Employers' Liability Insurance Association (Ed.) [Verwaltungsberufsgenossenschaft], Set up and design software in a user-
friendly way. The most important tips and information at a glance [Software nutzerfreundlich einstellen und gestalten. Die
wichtigsten Tipps und Infos auf einen Blick] 2018
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AUTHOR INFORMATION
Oliver Kolbe
Research Gate: https://www.researchgate.net/profile/Oliver_Kolbe (https://www.researchgate.net/profile/Oliver_Kolbe)
LinkedIn: https://www.linkedin.com/in/oliver-kolbe/ (https://www.linkedin.com/in/oliver-kolbe/)
Jennifer Müller
Research Gate: https://www.researchgate.net/profile/Jennifer_Mueller22
(https://www.researchgate.net/profile/Jennifer_Mueller22)
Prof. Dr. Stephan Degle,
Research Gate: https://www.researchgate.net/profile/Stephan_Degle (https://www.researchgate.net/profile/Stephan_Degle)
LinkedIn: https://www.linkedin.com/in/stephan-degle-85a18a89/ (https://www.linkedin.com/in/stephan-degle-85a18a89/)
Prof. Dr. Christoph Anders
Research Gate: https://www.researchgate.net/profile/Christoph_Anders (https://www.researchgate.net/profile/Christoph_Anders)

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ABSTRACT
Purpose. In this interventional study, the character size of the main work task of computer workers in their offices was recorded,
compared with the guidelines of the German Social Accident Insurance and adjusted to the recommendations. Subjectively
estimated changes in productivity were recorded.
Methods. The habitually used character size of the capital letter E was recorded on 152 visual display units, by using a ruler
template. The productivity under this setting was subjectively assessed by the subject on a scale of 1 (low) and 100 (high). In
case of failure to comply with the guidelines, the character size was increase to the lower limits of the recommendation range of
22 angular minutes. Two weeks after the initial visit, it was recorded whether the subjects continued to use the modified character
size and how the estimated productivity changed as a result of the intervention. Reasons returning to the old character size were
recorded.
Results. The analyzed character size was 14.3 angular minutes and falls statistically and clinically significant below the
recommendation range by 7.71 ± 3.53 angular minutes (95% CI; 7.14 to 8.28, P < .001, paired T-Test). Transferred (for a viewing
distance of 70cm) to Arial, as a realist sans-serif typeface, the lower limits of recommendations are 18 pt, the recorded character
size was 11 pt. Half of the sample assumed compliance with the recommended range, in only 4% of all cases this could be
confirmed. After intervention, the subjectively estimated productivity decreased significantly by 23 points on average (95 % CI;
16,90 - 30,06, P < .001, paired T –Test). In 71% of the cases the recommended character size was not compatible with the work
task. A correlation between the undershoot compared to the lower limits of the recommendation and symptoms of the computer
vision syndrome could not be demonstrated.
Conclusion. The recommended character size was not adhered to at the workplaces investigated. From the viewpoint of the
screen workers, the adjustment to the lower limit of recommendation leads to a reduction in productivity and is not compatible
with the work task. In general, solutions for the continuous increase of visual stress at the visual display unit have to be
developed. An unrealistic range of recommendations does not seem to be very helpful.

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REFERENCES
[1] German Social Accident Insurance (Ed.) VDU and office workplaces - guidelines for design: [Information 215-410.
Bildschirm- und Büroarbeitsplätze - Leitfaden für die Gestaltung]; 2019
[2] Bababekova Y, Rosenfield M, Hue JE, Huang RR. Font size and viewing distance of handheld smart phones. Optometry and
vision science 2011;88:795–7
[3] Bartha MC, Allie P, Kokot D, Roe CP. Field observations of display placement requirements and character size for
presbyopic and prepresbyopic computer users. Work 2015;52:329–42.
[4] Weidling P, Jaschinski W. The vertical monitor position for presbyopic computer users with progressive lenses. How to reach
clear vision and comfortable head posture. Ergonomics 2015;58:1813–29.
[5] Jaschinski W, Konig M, Mekontso TM, Ohlendorf A, Welscher M. Comparison of Progressive Addition Lenses for General
Purpose and for Computer Vision: An Office Field Study. Clinical & experimental optometry 2015;98:234–43.
[6] Segui MdM, Cabrero-Garcia J, Crespo A, Verdu J, Ronda E. A reliable and valid questionnaire was developed to measure
computer vision syndrome at the workplace. Journal of clinical epidemiology 2015;68:662–73
[7] Employers' Liability Insurance Association (Ed.) [Verwaltungsberufsgenossenschaft], Set up and design software in a user-
friendly way. The most important tips and information at a glance [Software nutzerfreundlich einstellen und gestalten. Die
wichtigsten Tipps und Infos auf einen Blick] 2018;

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