Vision Fatigue

This article is from Synergy June 2001 the Society of Radiographers UK magazine published with permission of the author Carol Perry.

An article based on a dissertation submitted for a M.Sc in Medical Imaging at Sheffield Hallam University and funded by a Bryan Macey Award

Carole Perry M.Sc., DCR
Senior Radiographer
Bassetlaw Hospital

Karen Booth MEd, TDCR, HDCR, DCR
Principal Lecturer, School of Health and Social Care,
Sheffield Hallam University

Introduction

Do you suffer from dry, itchy or sore eyes? Do you sometimes have blurred or double vision? Do you suffer headaches on a regular basis? If you do, then you might be suffering symptoms of vision fatigue. Vision fatigue, or asthenopia is a condition, classified by a collection of symptoms, thought to be linked to regular use of a visual display screen (VDU)1. The condition is classified as a collection of symptoms which are thought to be linked to the use of VDUs2. Ultrasound display monitors along with CT and MRI monitors are classified as VDUs. The Society of Radiographers has always maintained that this equipment should be subject to VDU assessments in line with legislation3.

Current legislation requires Occupational Health Departments (OHD) to undertake baseline screening prior to employment, or when staff are identified as working on a regular basis with any VDU. Staff should then be regularly monitored or reassessed when experiencing vision problems.

From my role as a health and safety representative, it became apparent that not all OHDs agreed that the ultrasound monitor should be classified as a VDU under the current legislation. As a consequence, vision tests for sonographers are not considered for funding. In order to try and resolve this issue, I decided to undertake a study to ascertain the extent of vision fatigue in sonographers and to identify any factors which might affect the incident rate.

The decision to limit the research to ultrasound was twofold, firstly there had been some research into muscular problems for sonographers which discovered some vision problems.4,5,6,7,8 Secondly ultrasound has been practised since the early seventies, and it now accounts for more than 25% of all imaging procedures performed worldwide9.

The ability of a sonographer to perform a visual task efficiently and correctly depends on their visual capabilities. It follows therefore that any discomfort which may affect the operator’s performance should be reduced to the lowest level possible. Although there are some similarities between the viewing of the ultrasound monitor and the computer screen in an office environment, the actual operating conditions differ. The sonographers will determine their stance and position according to the needs of the patient and the diagnostic task.

Research Study

Data was collected by means of a postal questionnaire distributed to forty hospitals. (The hospitals were selected from two groups, firstly all local hospitals identified by a member of the Trent Ultrasound Group, secondly from the base hospitals of the members of the Health and Safety Forum of the SOR). It consisted of 32 questions determined through a process of interview and observation of sonographers at three local hospitals. The return rate was high at 85% and 149 completed questionnaires were evaluated for the research project.

The sample consisted of 129 females and 20 males which gave a broad cross section of ages, experience and grades. The main purpose of the research was to determine the prevalence of vision fatigue symptoms; this was done by the inclusion of two questions with multiple-choice answers to identify vision problems at the end or during and after the working day.

The results are given below.

Figure 1

76 (50.3%) indicated three or more symptoms whilst 21(14%) of the respondents did not identify any symptoms. To minimise any inherent bias only those respondents who identified three or more symptoms were looked at in detail. It has been thought that some symptoms of vision fatigue could be related to personal factors i.e. uncorrected refractive errors1, transient personal problems or relatively mild complaints, setting three or more symptoms as the threshold, should remove any bias.

Personal factors such as gender were studied and it was determined that there was a statistical significance that females are more likely to suffer from symptoms than males (p=<0.01). The full figures can be seen below:

Gender analysis Table 1

	Males	Females	Totals
More than 3 symptoms	5	71	76
Less than 3 symptoms	15	58	73
Totals	20	129	149

From the 76 respondents who had three or more symptoms other risk factors were examined. Thirty wear glasses or contact lenses to scan and although not identified as statistically significant, it does appear to indicate that the wearers of glasses/contact lenses have a higher risk of experiencing symptoms. Figures for eye infections were 12(8%) and regular headaches 13 (8.7%).

In line with VDU legislation risk assessments should take place so a comparison of risk assessment or its absence with the level of symptoms was undertaken. The graph below is scaled on two axes, the left side shows the symptom numbers where a yes/no answer was given. The right side shows symptom numbers where the respondents did not know if a risk assessment was in place.

Figure 2

The graph seems to show a distinct pattern with the exception of dry eyes. Here the level of symptoms is much higher where risk assessments are in place.

Some research has shown that the use of dimmer lighting5 would reduce symptoms, this was not proved in this study. Dimmer lighting was not available for 63 (42%) and 33 (23%) only had it available in certain rooms but no significant difference in symptoms with respondents who had dimmer lighting was identified.

Regular breaks away from VDU screens are advocated in the VDU regulations, however no difference was logged in symptom levels where this was taking place. Time spent reporting individual scans could provide the break away from the screen that enables the sonographer’s eyes to relax and minimise symptoms.

Work pressures on the sonographers were shown to be high. 78 (52%) of the respondents cannot set their own pace, and only 4 of 149 sonographers said that they never felt pressured as a result of patient expectations of the service. Additional comments in the questionnaire responses, showed that in obstetric scanning the pressure from patients is high, with an expectation of the service that is not linked to the medical aspects of the scan. The “first” photograph and determining the baby’s sex, were identified as the parents’ priorities, “ A family day out” according to one respondent. Other figures, which showed only 3 (2%) never felt tired at the end of the day, but 119 (79%) usually felt stressed, confirmed the strain on sonographers on a daily basis.

Questions were asked as to how the individual sonographers would like to change equipment design, the two most popular requests are not available:

• Less heat generated
• Curved design of workstation to allow a more comfortable sitting position.

All the other requests logged within the research are already available on some models of equipment.

Additional comments expressed were:

• Risk assessments might make a difference, but they have doubts about management actually taking them on board.
• They have been continually treated with derision by occupational health departments, who still insist that ultrasound equipment is not a VDU and therefore they are not entitled to eye testing.
• Firm guidelines are needed from the Society of Radiographers as to what should be provided by departments.
• They would like eye tests as standard health surveillance annually for ultrasonographers.
• Manufacturers of ultrasound equipment should make it more ergonomically friendly.
• No matter what risk assessments are in place, if sonographers do not change their working practice they will experience pain and discomfort.

Discussion

Health problems facing sonographers are not limited to vision, within the questionnaire the question was asked, “How do you feel at the end of the day” the three highest responses were:

• Tired 98%
• Drained 81%
• Stressed 80%

These percentages indicate the pressure on sonographers. It must follow therefore, that the risks of other factors affecting their visual performance must be enhanced. Problems with back pain and neck pain were also identified with figures comparable with other studies.6,7,10,11,12,,13

The display screen equipment regulations (DSE)14 gave specific guidance on employer’s responsibilities to provide eye tests and specific prescriptions appropriate for the task involved. The obtuse wording in the guidance notes quoted by Ungar15, has led to confusion by OHDs in hospitals of their role. They seem to be reluctant to accept that ultrasound workstations are classified as VDUs and that the sonographers are entitled to the protection afforded by the regulations.

Within the study only 9 (6%) sonographers had received a hospital funded eye test, 109 (73%) had paid privately. The DSE regulations do state that full eye tests by a competent person (Reg. 5 (1) & 5(2) should be provided, however it is accepted that vision screening initially can be used to monitor or pinpoint individuals with problems. Staff can then be referred for a full eye test if required or requested. The sight test itself must include a reference to the distance at which the screen is viewed16. This cannot be generalised. The initial observational study measured eye to screen distances varying from 30 cm. to 100 cm. Any corrective lens prescribed would be varied by the operator’s (a) vision defects and (b) the eye to screen distance. If sonographers are to lobby for vision screening, it must be the type of screening suitable for them. The individual’s unique eye to screen distance must be taken into account. Within this study glasses and contact lens wearers 89 (60%) out numbered non-spectacle wearers 60 (40%). Research has also shown that the wearers of bifocal and varifocal lenses were more likely to fail vision-screening tests17. It has also been said that varifocal lenses are unsuitable for VDU use18. Prescription lenses for reading were worn by 9 sonographers out of 38, the distance that this prescription is based on is 25 – 35 cms8. If a full eye test showed that a prescription unique to the sonographers work was needed then that should be paid for by their employer.

From literature certain factors had been evidenced as possible influences over the symptoms of vision fatigue. These were either A. personal i.e. age, incorrect glasses or B. workplace i.e. lighting, dry environment, equipment, demands of the service. The taking of regular breaks and varying the workload away from continual VDU employment, has been supported by the guidance regulations14 as a way of minimizing symptoms. This was not proved in this research, there was no difference in symptom levels for those taking regular breaks or between full and part time workers. Bergquist19 has found a definite link between symptoms and working without a break.

Employers are required to carry out VDU risk assessments of workstations, but 77 (52%) respondents did not know if one had taken place. It could be argued that if they didn’t know; then there is a greater likelihood that one is not in place. Local protocols for ionizing radiation are displayed within every x-ray room in accordance with legislation; it should be feasible therefore for this to be applied to VDU assessments.

Blink rate was monitored in the observation study. It was noted that the higher the blink rate, the lower the number of symptoms. This has been attributed to the “stare” factor20. As the operators tend to fixate their eyes on a small portion of the screen to determine an abnormality, they forget to blink. Therefore the covering of the eye dries, thus becoming irritable and itchy 18. The figures within this study 43 (29%) itchy eyes and 62 (42%) dry eyes would seem to indicate that sonographers have a reduced blink rate when scanning.

Not all sonographers had been involved in the choice of new equipment. The reasons given for this related to monetary restraints or that the radiologists decided on the equipment.

Conclusion

The full investigation did show a high prevalence of vision fatigue within its target population as 50.3% identified three or more symptoms. Certain factors had an impact on the figures, females and the wearers of glasses are more likely to show symptoms, and symptom levels increase with age.

Some recommendations were made in the full research study, these included:

• Further comparative studies with general radiographers and other digital imaging groups should be undertaken.
• Appropriate vision screening and testing protocols should be in place for all sonographers.
• Lobbying of manufacturers, to design equipment that is user and ergonomically friendly without compromising image quality.
• Patients for obstetric scanning should be made aware of the medical considerations of the scan by the referring clinician.
• Monitoring of workload parameters where possible to reduce the pressure on staff.

(This article cannot give full details of the research study but anyone who wishes to contact me for further information can do so through Eleanor Ransome at the Society of Radiographers.)

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