Increased use of computers in the workplace has
brought about the development of a number of health
Eye related symptoms are the most frequently
occurring health problem in computer uses.
Many individuals who work at a computer video display
terminal (VDT) report high levels of job-related
complaints and symptoms, including ocular
discomfort, muscular strain and stress.
The level of discomfort appears to increase with the amount of
VDT use, and symptoms appear to be different to other near-
Up to 90% of the 70 million US workers using computers for more
than 3hrs per day experience it in some form.
Based on current evidence it is unlikely that the use of VDTs
causes permanent changes or damage to the eyes or visual
However, some workers may experience continued impaired or
reduced visual abilities, such as blurred distance vision, even after
The extent to which an individual may experience symptoms is
largely dependent upon his/her visual abilities in relation to the
visual demands of the task being performed
High visual demands of VDT work make many individuals
susceptible to the development of eye and vision-related
Uncorrected vision conditions, poor VDT design and workplace
ergonomics and a highly demanding visual task can all contribute
to the development of visual symptoms and complaints
These visual and ergonomic problems can often significantly
affect worker comfort and ultimately performance.
Uncorrected or undercorrected myopia, hyperopia and
astigmatism which under normal circumstances are harmless
Underlying accommodative disorders can lead to decreased
amplitude of accomodation or infacility of accommodation
Presbyopic patients may have have an improper add prescribed
or spectacle design is incorrect (no intermediate distance,
Binocular visual problems can become manifest with deviation of
phorias and strabismus
Transient induced myopia from excessive near work..
Mostly after prolonged usage.
Transient phenomenon, may continue long after use.
Ocular Surface Mechanisms
Enviromental factors (fans, ventilation, static, dust)
Reduced blink rate (up to 60% reduction).
Increased exposure (horizontal gaze with wider palpebral fissure).
Systemic or ocular cause for dry eye.
Extra ocular mechanisms
Contrast and resolution of the display
– Maximum contrast (black letters on white background)
– Radiation exposure is extreemly low and not harmful.
Viewing distances and angles
– the top of the screen should be below the horizontal eye level of the
operator and tilted back slightly (10o
) away from the operator.
– VDT at arms length
Extra ocular mechanisms
– General workplace lighting, glare and images reflected on the VDT
– ? The value of filters
– Compromise required between that amount of light needed to
enhance VDT screen visibility and reduce reflections and glare and
that needed to perform other office reading and work tasks. Older
individuals will generally require more light than younger individuals to
perform the same tasks comfortably
– Do not place computers in front of windows
– Enviromental factors (fans, air conditioning, dust,
– Ergonomics (chair, table, keyboard, VDT
– Lighting, anti-glare filters, display quality
– Regular work breaks
– Glasses (NB presbyopes)
– By far the most common cause is Dry Eye
Children and computers
Children often have a limited degree of self-awareness.
Children are very adaptable.
Children are not the same size as adults.
Children often use computers in a home or classroom with less
than optimum lighting.
Have the child's vision checked.
Strictly enforce the amount of time that a child can
continuously use the computer.
Carefully check the height and arrangement of the
Carefully check the lighting for glare on the computer
Reduce the amount of lighting in the room to match the