Positioning the Monitor : OSH Answers: What should you know while setting up (selecting) a proper viewing distance?
Looking at far distances does not cause eyestrain - it is the muscular effort required to focus on objects at close distances that strains the eyes. The distinction between "far distance" and "close distance" is never "razor sharp". It is not only individual but it also can change over time, for example, due to age.
Accommodation* and convergence** are the two main functions, which govern the viewing of objects at closer distances. The shorter the viewing distance, the greater the muscular effort required for accommodation and convergence, and which, in turn, increases the risk for eye discomfort. A greater viewing distance, on the other hand, eliminates the risk for eyestrain but can make the resolving of the finer images or characters displayed on the computer screen more difficult. Consequently, the right viewing distance is the one at which the computer operator can easily read the screen without experiencing eyestrain.
The eyes have a default accommodation distance, called the Resting Point of Accommodation (RPA) and a default Resting Point of Vergence (RPV). In practical terms, at distances greater than the RPA and RPV, there is no need for either accommodation or convergence. Under these conditions, individuals with perfect (20/20) vision or those with properly corrected vision are not likely to experience eyestrain (assuming they take appropriate eye "rest breaks" from focussing on the screen).
Numerical values of RPA -- around 75 cm (about 30 in.)-- and RPV -- around 80 cm (about 32 in.)-- are close to each other which makes setting the right viewing distance simple. The viewing range 40 cm to 70 cm (about 15 - 27 in.) provides visual comfort for majority of computer users. In the situation where the recommended viewing distance is too great for the operator to see images clearly it is better to increase the font size (images) than to force a shorter viewing distance.
Health and Safety Services: Working Safely at your Computer:
For a good start - work though Birkbeck's interactive safety training package at:
http://www.learninglink.ac.uk/keepfit/index.htm (takes only 20 mins.)
This site is also very good with regard to adopting best posture when sitting. http://www.posturite.co.uk/art-of-sitting
You should also try out the stretching exercises at the following link: http://www.bbk.ac.uk/so/guidance/stretch2
General guidance for home or office
1...Adjust the backrest of your chair to fully support your lower back, and sit well back into the chair.
2...Adjust the seat height until your forearms are horizontal and wrists straight while using the keyboard. Bring the keyboard close to the edge of the desk just leaving enough room for a gel filled wrist rest if you want one or to rest the heel of your hands. Avoid- pushing your keyboard forward to keep papers in front of it. If you do this you will probably lean forward to reach it and your back will no longer be supported by your chair. Do not rest your wrists on the edge of the desk or bend your hands up at the wrist. Keep a soft touch on the keys and do not overstretch your fingers. Place the mouse right beside the keyboard so that you do not have to stretch - use a mouse mat with a gel filled wrist rest if you wish.
3...When you have the seat height right, if your feet do not rest comfortably on the floor use a footrest – get a purpose made one or a suitably sized box.
4...The screen should be approximately at arm's length. Adjust the height so that your the top of the screen is at eye level when sitting upright and looking straight ahead. If you need to look at the keyboard to type the screen can be lowered to avoid repeated neck movements. Adjust the angle of the screen to suit your sitting height.
5...Do not lean over to read documents. Use a document holder, and place it beside the screen at the same distance, height and angle as the screen.
6...Position the workstation so that windows or lights are not in the same ahead line of sight - sit sideways to windows, and use blinds to cut out unwanted light. Avoid any remaining reflections from windows or lights on the screen by adjusting the screen angle.
7...Adjust the brightness of the monitor screen to suit the lighting conditions in the room. Note that for persons with light sensitivity who require low screen lighting - this can be difficult to achieve on some flat screen models - consult your DSE assessor if this is the case.
8...If there is a flicker or any other deterioration of the image on the screen, make adjustments or report the matter for repair.
9...Keep the screen clean
10.. Sitting in the same position and staring at the screen for long periods is undesirable so if your time at the keyboard is not interrupted naturally by phone calls, discussions with colleagues etc, plan to break the work up with other work activities which do not involve similar movements of the arms and wrists and preferably require some walking about. Drink some water. There is no set legal length for such breaks. 5-10 minutes each hour is often mentioned but just how long and how frequently depends on the person and the task. Little and often is best. Some staff use the free software from http://www.workrave.org/ to remind themselves to take a break. Whatever, make sure you give your eyes, muscles and joints that needed break from sitting, staring, typing and clicking. 'Don't wait until you ache.'
11.. On-line Marking - if you have a lot of on-line marking to do, make sure that you have adequate time to fit in the necessary breaks from computer work outlined above. If you feel that you would not get through your workload by the deadline if you took such breaks then you should discuss the situation with your line manager.
12..Eyesight. If your eyesight is good or is satisfactorily corrected by spectacles or contact lenses, you should have no difficulty using a display screen. If you wear bifocals or varifocals you may find that you need a separate pair of spectacles to work at the display screen comfortably. (Most wearers of reading glasses find that their reading prescription is suitable for display screen work). If you are quite sure that your work station is satisfactory and yet you get headaches or "eyestrain", or if you cannot achieve a layout that is comfortable, you should consider visual problems. It would then be appropriate for you to have your eyesight tested.
13.. Eyetests. If you are an employee of Birkbeck and using a display screen forms a substantial part of your work, you will be entitled to an eye test paid for by Birkbeck. The College has an arrangement with a local optician for this purpose. See: http://www.bbk.ac.uk/so/guidance/eyetests
14.. Modern printers are relatively silent but any older noisy printers should be fitted with a hood or put in an unoccupied room.http://www.bbk.ac.uk/so/guidance/eyetest
15..If you wish your workstation to be assessed for safety, first complete the self-assessment form at: http://www.bbk.ac.uk/so/forms/dseassess and pass this to your school/department DSE workstation assessor or safety coordinator. See here for contact list: http://www.bbk.ac.uk/so/contact/co-ords . If you experience symptoms of discomfort in your limbs or back which you think are related to working with your computer you should report this to your school/department DSE workstation assessor or safety coordinator or the Health and Safety Officer.
16.. Working when pregnant. The Health and Safety Executive advise that computer screens do not constitute any risk to users who are pregnant or to their unborn child. Nevertheless, staff who may still have concerns about this area should contact the Health and Safety Officer or HR department. In exceptional circumstances, and where practicable, the member of staff will be given alternative duties or alternative methods of work.
17.. Laptops/notebooks.
Increasingly, staff are choosing to use a laptop/notebook in their Birkbeck offices instead of non-portable screens and base units. Where this is the case, a docking station should be used to provide best ergonomic benefit. A docking station consists of an external keyboard, an external mouse and a platform to raise the screen to a suitable height. Adjustable plastic platforms can be purchased from office suppliers fairly cheaply. Alternatively, packets of A4 or telephone directories can be used to provide suitable and stable platforms.
In depth good guidance on laptop use here from UCL: http://www.ucl.ac.uk/uclic/research/projects/laptops
18.. Homeworking. Essentially, make sure your home set-up is as good as that in your office. Duplicate all the conditions you have at work - good chair, desk, screen height etc. Birkbeck has a homeworking policy at: http://www.bbk.ac.uk/so/policies/home
Looking at far distances does not cause eyestrain - it is the muscular effort required to focus on objects at close distances that strains the eyes. The distinction between "far distance" and "close distance" is never "razor sharp". It is not only individual but it also can change over time, for example, due to age.
Accommodation* and convergence** are the two main functions, which govern the viewing of objects at closer distances. The shorter the viewing distance, the greater the muscular effort required for accommodation and convergence, and which, in turn, increases the risk for eye discomfort. A greater viewing distance, on the other hand, eliminates the risk for eyestrain but can make the resolving of the finer images or characters displayed on the computer screen more difficult. Consequently, the right viewing distance is the one at which the computer operator can easily read the screen without experiencing eyestrain.
The eyes have a default accommodation distance, called the Resting Point of Accommodation (RPA) and a default Resting Point of Vergence (RPV). In practical terms, at distances greater than the RPA and RPV, there is no need for either accommodation or convergence. Under these conditions, individuals with perfect (20/20) vision or those with properly corrected vision are not likely to experience eyestrain (assuming they take appropriate eye "rest breaks" from focussing on the screen).
Numerical values of RPA -- around 75 cm (about 30 in.)-- and RPV -- around 80 cm (about 32 in.)-- are close to each other which makes setting the right viewing distance simple. The viewing range 40 cm to 70 cm (about 15 - 27 in.) provides visual comfort for majority of computer users. In the situation where the recommended viewing distance is too great for the operator to see images clearly it is better to increase the font size (images) than to force a shorter viewing distance.
Health and Safety Services: Working Safely at your Computer:
Here you will find lots of good-practice advice for working at the PC in your office, your home set-up and your laptop - wherever you use it.
For a good start - work though Birkbeck's interactive safety training package at:
http://www.learninglink.ac.uk/keepfit/index.htm (takes only 20 mins.)
This site is also very good with regard to adopting best posture when sitting. http://www.posturite.co.uk/art-of-sitting
You should also try out the stretching exercises at the following link: http://www.bbk.ac.uk/so/guidance/stretch2
General guidance for home or office
1...Adjust the backrest of your chair to fully support your lower back, and sit well back into the chair.
2...Adjust the seat height until your forearms are horizontal and wrists straight while using the keyboard. Bring the keyboard close to the edge of the desk just leaving enough room for a gel filled wrist rest if you want one or to rest the heel of your hands. Avoid- pushing your keyboard forward to keep papers in front of it. If you do this you will probably lean forward to reach it and your back will no longer be supported by your chair. Do not rest your wrists on the edge of the desk or bend your hands up at the wrist. Keep a soft touch on the keys and do not overstretch your fingers. Place the mouse right beside the keyboard so that you do not have to stretch - use a mouse mat with a gel filled wrist rest if you wish.
3...When you have the seat height right, if your feet do not rest comfortably on the floor use a footrest – get a purpose made one or a suitably sized box.
4...The screen should be approximately at arm's length. Adjust the height so that your the top of the screen is at eye level when sitting upright and looking straight ahead. If you need to look at the keyboard to type the screen can be lowered to avoid repeated neck movements. Adjust the angle of the screen to suit your sitting height.
5...Do not lean over to read documents. Use a document holder, and place it beside the screen at the same distance, height and angle as the screen.
6...Position the workstation so that windows or lights are not in the same ahead line of sight - sit sideways to windows, and use blinds to cut out unwanted light. Avoid any remaining reflections from windows or lights on the screen by adjusting the screen angle.
7...Adjust the brightness of the monitor screen to suit the lighting conditions in the room. Note that for persons with light sensitivity who require low screen lighting - this can be difficult to achieve on some flat screen models - consult your DSE assessor if this is the case.
8...If there is a flicker or any other deterioration of the image on the screen, make adjustments or report the matter for repair.
9...Keep the screen clean
10.. Sitting in the same position and staring at the screen for long periods is undesirable so if your time at the keyboard is not interrupted naturally by phone calls, discussions with colleagues etc, plan to break the work up with other work activities which do not involve similar movements of the arms and wrists and preferably require some walking about. Drink some water. There is no set legal length for such breaks. 5-10 minutes each hour is often mentioned but just how long and how frequently depends on the person and the task. Little and often is best. Some staff use the free software from http://www.workrave.org/ to remind themselves to take a break. Whatever, make sure you give your eyes, muscles and joints that needed break from sitting, staring, typing and clicking. 'Don't wait until you ache.'
11.. On-line Marking - if you have a lot of on-line marking to do, make sure that you have adequate time to fit in the necessary breaks from computer work outlined above. If you feel that you would not get through your workload by the deadline if you took such breaks then you should discuss the situation with your line manager.
12..Eyesight. If your eyesight is good or is satisfactorily corrected by spectacles or contact lenses, you should have no difficulty using a display screen. If you wear bifocals or varifocals you may find that you need a separate pair of spectacles to work at the display screen comfortably. (Most wearers of reading glasses find that their reading prescription is suitable for display screen work). If you are quite sure that your work station is satisfactory and yet you get headaches or "eyestrain", or if you cannot achieve a layout that is comfortable, you should consider visual problems. It would then be appropriate for you to have your eyesight tested.
13.. Eyetests. If you are an employee of Birkbeck and using a display screen forms a substantial part of your work, you will be entitled to an eye test paid for by Birkbeck. The College has an arrangement with a local optician for this purpose. See: http://www.bbk.ac.uk/so/guidance/eyetests
14.. Modern printers are relatively silent but any older noisy printers should be fitted with a hood or put in an unoccupied room.http://www.bbk.ac.uk/so/guidance/eyetest
15..If you wish your workstation to be assessed for safety, first complete the self-assessment form at: http://www.bbk.ac.uk/so/forms/dseassess and pass this to your school/department DSE workstation assessor or safety coordinator. See here for contact list: http://www.bbk.ac.uk/so/contact/co-ords . If you experience symptoms of discomfort in your limbs or back which you think are related to working with your computer you should report this to your school/department DSE workstation assessor or safety coordinator or the Health and Safety Officer.
16.. Working when pregnant. The Health and Safety Executive advise that computer screens do not constitute any risk to users who are pregnant or to their unborn child. Nevertheless, staff who may still have concerns about this area should contact the Health and Safety Officer or HR department. In exceptional circumstances, and where practicable, the member of staff will be given alternative duties or alternative methods of work.
17.. Laptops/notebooks.
Increasingly, staff are choosing to use a laptop/notebook in their Birkbeck offices instead of non-portable screens and base units. Where this is the case, a docking station should be used to provide best ergonomic benefit. A docking station consists of an external keyboard, an external mouse and a platform to raise the screen to a suitable height. Adjustable plastic platforms can be purchased from office suppliers fairly cheaply. Alternatively, packets of A4 or telephone directories can be used to provide suitable and stable platforms.
In depth good guidance on laptop use here from UCL: http://www.ucl.ac.uk/uclic/research/projects/laptops
18.. Homeworking. Essentially, make sure your home set-up is as good as that in your office. Duplicate all the conditions you have at work - good chair, desk, screen height etc. Birkbeck has a homeworking policy at: http://www.bbk.ac.uk/so/policies/home
