Automated Vision Screening Equipment and Environment
Automated vision screeners are instruments used to conduct vision testing to ensure that individuals comply with specific vision standards required in the workplace. The instruments contain simple visual slides (pictures or optotypes) which are presented to each eye and both eyes at various simulated distances. Automated vision screeners have varying degrees of automation or computerisation. Most vision screeners test near and far visual acuity, depth perception (stereopsis), night vision, peripheral vision and colour vision. Some include an assessment of visual acuity at an intermediate distance which is used for workers working on computers or digital display screens. Because vision screening is not always performed in a clinic, these instruments need to be portable and easy to use therefore compact and light. To obtain accurate and reliable results, automated equipment should:
Have a comprehensive range of tests.
Have a standardised light source to ensure true colour testing.
Have an adjustable viewing function and should be easy to clean.
Be light and compact and portable.
Conducting vision testing on large groups needs to be completed quickly and accurately and therefore the length of time it takes to go through all the automated tests should be considered when purchasing an automated machine and the time and ease it takes to complete the reports should be considered. Some automated vision screeners compile the reports electronically and others don’t and therefore handwritten reports are required. The manufacturers provide the templates and guidelines for interpreting results, these should be checked against legislative requirement and action and exclusion criteria set by the OMP.
Tests Performed by an Automated Vision Screener
Most vision screeners test the following parameters:
Visual Acuity – both eyes simultaneously as well as individual left and right eyes (using random-dot (TNO), Landholdt or Snellen letters)- Far and Near vision testing
Muscle Balance / Phoria (Horizontal)
Muscle Balance / Phoria (Vertical) and
Figure 6.4: Example of a Optotype / Plate from an Automated Vision Screener5
Preparation of the Vision testing Room
In order to obtain the best results possible these general requirements for the room where automated vision screening is performed should be in place.
The room should be quiet – so that the worker being tested can hear the instructions and concentrate on the test being performed
The room should be well ventilated – to prevent infections, unpleasant odours or stuffiness which may distract the worker being tested
The room should be private – privacy ensures confidentiality which encourages trust and honesty. When taking a history, a worker may not be honest or provide an answer to personal medical and other history if the room is not private.
There should be hand washing facilities – as part of hygiene and the standard universal precautions required in healthcare.
The room should be easy to clean and hygienic.
Floors and surfaces should be washable and slip-proof.
The lighting should be adequate and adjustable – see details under each test.
Direct sunlight and glare on all equipment must be eliminated – usually the light source is above and in front of the test to avoid glare.
The size of the room must match the test being performed – see details under each test. In the automated test there should be enough room for the technician to conduct the test and maintain social distancing required in terms of Covid-19 rules (1.5 – 2m)5.
The workstation should be at a comfortable height for the worker being tested and the technician.
A chair should be provided for both the worker and the technician, neither should have wheels on them to prevent sliding. Chairs may need to be adjustable to accommodate tall and short people as most tests need to be done at eye level.
There should be enough space for additional equipment like printers and stationary draws.
At the beginning of the day examine the unit using the following basic checklist (each machine has a specific daily checklist):
Is the machine plugged in?
Are the lights inside the machine working?
Do the appropriate lights go out when the “occlude” buttons is selected?
When advancing to the next test does the slide change? Does the test rotate from 1 test to another?
Avoid positioning the instrument where strong glaring light will shine directly into the instrument or into the subject’s face.
Is the software licensed and updated?
Are the manufacturers reports for the specific machine in use available?
Are the automated questions for each test available in the testing room?
Is the printer plugged in and working correctly?
Vision screening policies and procedures should be in the room in a file?
Preparation of the Automated Vision Screener
All screeners require electricity and have a power switch to switch operations on and off. The machine needs to be opened and locked into position. The height can be adjusted by the worker being tested to ensure it is at the correct height. The machine must be positioned near the edge of a table or counter at a height comfortable for the worker. In all automated tests, the client sits comfortably, looking straight ahead for all the tests.
The tester needs to be positioned on the side of the person being tested. The plates are arranged to test each eye and both eyes with the operator asking a specific question for each plate (see figure 6.4)7,10. The operator advances the test from one slide to the next using the keyboard or computer software (if used). The operator records the results on the template for the specific machine used and interprets the results.
At the beginning of the day dust the unit and lenses with a soft, alcohol and water-dampened cloth. The soft foam headrest must be cleaned using a disinfectant solution between each assessment. The exterior of the instrument must be cleaned with a soft cloth dampened in a mild solution of soap and water. Use dust cover to protect the instrument and prevent dust accumulation when not in use.
Keypad and cables
All automated vision screeners come with an operator keypad with a cable that is inserted into the back of the vision screener and is interchangeable within the same make and model machine. With extended use, the cable can fray internally at the junctions of both ends, and the buttons sometimes with age don’t respond therefore, this must be checked daily prior to use.
The keypad and cables should be wiped with a slightly damp cloth containing soap and water, ammonia-based cleaners, or bleach-based cleaners. If alcohol-based disinfectants are used on the cable these will need to be replaced more frequently as alcohol dries the cable coverings and they crack.