6. VDU, CVS, Visual screening

General facts about VDU:

THESE ARE ALL OUT OF DATE NOW

96% of working Americans use the internet as an integral part of their job.
• Almost 30% of the world’s population are internet users.
• Adults in the USA spend an average of 9.7 hours per day looking at digital media
• American children (8-18 years) spend approximately7.5 hours viewing entertainment media every day (comprising 4.5 hours watching television, 1.5 hours on a computer and over an hour playing computer games).
• Pre-schoolers spend up to 2.4 hours per day watching electronic screens
• On average, users may check their smartphones about 1500 times per week or 221 times per day
• When people first wake up, 35% reach for their phones, ahead of coffee (17%), a toothbrush (13%) or their significant other (10%).
• Some screen sizes require small text which the observer frequently holds very close, closer than had previously been adopted for hard copy printed materials.
• These increased visual demands may give rise to a variety of symptoms which have been termed computer vision syndrome (CVS) or digital eye strain (DES)

What is computer vision syndrome (CVS)?

• The American Optometric Association defines CVS (DES) as the combination of eye and vision problems associated with the use of computers.
• Some reports suggest up to 90% of computer users may experience visual symptoms.
• Musculo-skeletal problems are also common - Musculo-skeletal injuries associated with computer use may account for at least half of all reported work-related injuries in the USA
• Prevalence of these symptoms increases significantly if VDU use exceeds 4 hrs/day

General signs and symptoms of CVS:

• headaches
• neck or shoulder tension
• general pain or discomfort when sitting at VDU
• back pain
• pain in arms, wrists or shoulders
• excessive physical fatigue
• heavy eye lids or forehead
• general fatigue and drowsiness

Ocular signs and symptoms of CVS:

• eyestrain
• headaches
• ocular discomfort (itching and burning eyes)
• dry eyes (or excessive tears)
• excessive blinking
• general contact lens discomfort
• diplopia
• enhanced sensitivity to light
• blurred near vision
• blurred vision when looking into the distance after prolonged computer use

Caution of CVS symptoms:

• Prevalence of symptoms vary according to investigation, with single assessments showing a higher rate of symptoms than longitudinal studies
• Symptoms are higher in those poorly motivated at work, and in those performing repetitive and/or uninteresting tasks
• This suggests that ‘some’ symptoms might be psychosomatic or hysterical

Difficulties of correcting presbyopia for CVS:

• Correction of presbyopia can be problematic for patients who spend extended periods of time viewing digital screens.
• Difficulties may be most severe when viewing desktop monitors placed at fixed viewing distances (> 40 cm) and gaze angles.

These screens are generally placed at or just below primary gaze and as such the use of a standard bifocals, with the near segment placed for a target positioned in downward gaze and providing clear vision for a viewing distance around 40 cm, may be inappropriate.
• Varifocal lenses produce similar difficulties

OPTIONS FOR TREATING PROBLEMS WITH PRESBYOPIA AND CVS

• Altering screen position/distance
• Monovision correction: works for a low percentage of people. Prescribe the distance prescription in the dominant eye and the near prescription in the non-dominant eye.
• Single vision near lenses: work really well. Cut down presbyopic add as screen is a little further away (intermediate add), also allows px to look at papers on the desk in the surrounding areas. Remove the specs when looking at distance.

What are the 2 potential ocular causes of CVS?

1)Inappropriate oculomotor responses

2) Dry eye

1)Inappropriate oculomotor responses as an ocular cause of CVS:

not enough evidence:

• Inappropriate accommodative and vergence responses have been cited as contributing to the symptoms associated with VDU use.
• However, there is little objective data detailing how these parameters change during VDU use.
• In general: CVS associated with accommodation and vergence disorders seem to be a result of viewing a visually demanding near target for an extended period of time, and not specific to the digital display. Same problem even if looking at paper material not just VDU.

2) Dry eye: 8 factors that cause dry eye as an ocular cause of CVS

Reports of dry eye, burning and grittiness may result from one or more of the following factors:
1. environmental factors producing corneal drying (e.g. air conditioning)
2. reduced blink rate with VDU use
3. incomplete blinking with VDU use

4. Increased corneal exposure. Desktop computers are commonly used with the eyes in the primary position, whereas hardcopy text is more commonly read with the eyes depressed. The increased corneal exposure associated with the higher gaze angle could also result in an increased rate of tear evaporation.
5. Age and gender. The prevalence of dry eye increases with age and is higher in women than men
6. Systemic diseases and medications (e.g. Incidence of dry eye may be greater in patients with arthritis, allergies, or thyroid disease. Incidence may also be higher in patients taking antihistamines, anti-anxiety medications, antidepressants, oral steroids, or vitamins).
7. Contact lens wear
8. Ocular pathology (e.g. Obstruction of the lacrimal glands

Thus, some factors associated with dry eye symptoms do appear to be directly related to computer use (e.g. position of the monitor (producing increased corneal exposure), reduced blink rate, increased partial blinking and other environmental factors)

Non-ocular causes of CVS:

• poor design or organization of the workstation (which may be a
significant cause of symptoms such as back, neck, shoulder and wrist pain)
• inappropriate lighting
• glare: REFLECTIONS ON SCREEN
Note: ocular and non-ocular causes of CVS could be additive, thereby increasing the magnitude of symptoms.

What are the general issues with CVS?

There is no reliable evidence that VDUs cause any permanent damage to the eyes
• There is little evidence that VDU users per se are more likely to become myopic (distance from the screen and myopia development: children hold their phones really close to their eyes: short working distance for a prolonged period of time, not the VDU itself)
• There are no health hazards from either ionising or non-ionising radiation emitted from VDUs. Tints or filters which claim to cut out harmful radiation are superfluous
• 10% of users will require spectacles specifically for display screen equipment (e.g. presbyopes).
• Treatment: both ocular and non-ocular factors must be addressed. Rest and regular breaks appear essential. The relevant regulations are the Health and Safety (Display Screen Equipment) Regulations 1992. Regulation 4, is concerned with the daily activities of users and states: 'Every employer shall so plan the activities of users at work in his undertaking that their daily work on display screen equipment is periodically interrupted by such breaks or changes of activity as reduce their workload at that equipment

*rest and regular breaks

DSE 1992 and College Guidelines (2005)

-Regular sight tests must be offered to all habitual users of VDU/DSE

-FREE SIGHT TETS MUST BE PROVIDED FOR USERS ON THEIR REQUEST or where theres visual difficulty in carrying out display work- test repeated at appropriate intravels

-Where glasses or other corrective appliances are necessary the employer must provide those free of charge, but only to
the extent of the cost of basic frames and the lens prescription necessary to do the display screen work.
-in addition, if a user’s normal corrective appliance (spectacles or contact lenses) is unsuitable for DSE, employers are
required to provide ‘special’ spectacles specifically for DSE

-optom to carry out full eye exam

-It remains that the prescription or written statement is
the property of the patient. The same legal and professional considerations with regard to referral apply as for any other eye examination.
-Confidentiality of clinical information about the employee must be maintained at all times and clinical information should
only be divulged to an employer if it is relevant to the employee’s work at the DSE and then only with the patient’s written consent.

What are the health risks associated with VDU??

• Asthenopia

TYPES OF ASTHENOPIA

1. Refractive, including astigmatic
2. Accommodative
3. Colour
4. Heterophoric
5. Hysterical
6. Photogenous/ Glare
7. Miscellaneous

• Facial rash/dermatitis – from dust particles attracted to the screen due to static electricity ?
Solutions offered: antistatic carpets; clean VDU with antistatic solutions
• Photosensitive epilepsy – induced by flicker (and, more rarely, high spatial frequency detail)
• Radiation – various reports conclude that there is no risk of ill health from radiation

PRESBYOPIC PX AND VDU

• Bifocals or SV reading glasses are typically set for 40cm viewing distance, which is shorter than the usual screen distance
• Bifocal/varifocal wearer needs to bend the neck to focus
• Pre-presbyopes may need a low add
• May need an intermediate add for mid to late presbyopes
• Most presbyopes function best with single vision lenses provided the lenses satisfy all near vision task needs (viewing the monitor and reference material)

How do tints and coating help problems with VDU?

• Tinted lenses may help computer users, particularly those who are light sensitive and have worn tinted lenses routinely
• However, visibility of hard copy is reduced with tinted lenses
• Most popular colours are light grey or light pink - the latter works well with over head fluorescent lighting
• Anti-reflection coatings provide
• Increased visibility
• Improved appearance
• Fewer ghost images
• But do not eliminate glare on the monitor
• UV coatings
• No documented evidence that any significant UV radiation is emitted from the computer screen
• Point of Discussion: Blue light at bedtime – should filters to cut transmission of blue light be use

Problems with colour and VDU:

Most displays are in colour, or make extensive use of colour to guide information
• Inappropriate use of colour can cause stereoscopic and accommodative difficulties

Heterophoria and VDU

• With lower text contrast (through misuse of colour &/or grey levels), fusional mechanisms may be less effective
• Prolonged maintenance of fusion will cause fatigue
• As gaze is directed higher, compared with normal reading, convergence will be reduced

Hysterical and vdu

• Probably of low incidence
• There is evidence to show that this occurs more in individuals who are technophobic or have been asked to change working practices.

What is Photogenous asthenopia?

• VDU luminance typically varies from 10 to 100 cd/m2 (but could be higher)
• Typical consulting rooms have an ambient luminance of 250 cd/m2
• If windows are present in the room, ambient luminance may rise significantly
• Such variations require changes in adaptation levels, particularly if the background luminance of the screen is low
• Sudden changes in luminance might cause disability glare - more likely in older users

Miscellaneous - wrist, hand and finger pains:

• Repetitive strain injury (RSI) due to prolonged use of keyboard, thought to be form of tendinitis
• Possibly due to sustained abnormal positioning of wrists/forearms causing stress on the tendons
• There is a greater proportion of sufferers than found with individuals who used standard typewriters
• Keyboards with different rests, key tensions, shapes etc are available

What is the advice youd give to px when problems with VDU?

Varying tasks may help user
• Rest breaks do not necessarily reduce productivity, and may improve it
• Rest breaks should be taken before the onset of fatigue
• A 5-10 min break every hour is better than a 15 min break every 2 hours
• 20/20/20 rule: every 20 minutes spent looking at a screen, a person should look at something 20 feet away for 20 seconds

• fist under chin for children, don’t read phone/ipad lying down.

What are the aims of visual screening?

• To identify those who are experiencing eye problems and to determine if the symptoms are related to visual defects or environmental factors or a combination
• To detect those people who have defective vision but who do not present with symptoms that result in them seeking optometric attention

What are the obligations and rights with visual screening?

• Many employers offer screening to determine whether users need a full sight test
• Any person failing screening must be referred for full eye examination
• DSE Regulations (1992) state that the employer must provide an eye examination for habitual user of a VDU
• Screening is not limited to VDU users
• Employees have the right to opt out of screenin

What are the advantages of industrial screening?

• Better selection of personnel - Visual ability can be used in the selection of new employees, or transferring existing employees to new tasks.
• Identification of employees with visual disabilities - These may be due to an uncorrected refractive error or ocular pathology. Near vision problems are commonly found.
• Improved employee-employer links
• Improved visual efficiency, which may yield increased productivity
• Fewer accidents, and therefore reduced insurance costs
• Reduced absenteeism, as the task is less visually fatiguing
• Easier settlement of compensation claims

3 different methods of vision screening, with advantages and disadvantages

1) Modified clinical technique (MCT)
• Carried out by qualified personnel (e.g. optometrists or ophthalmologist)
• Advantages: Flexibility - tests can be selected depending on visual functions considered to be important for the task; determine refractive error type and magnitude; detection of pathology, detection of strabismus; more reliable than instrument screeners, leading to fewer false referrals
• Disadvantages: Expensive due to the use of eye care professionals; time consuming.

(2) Instrument screeners
• Advantages: Operation by lay technicians; speed of screening; low cost
• Disadvantages: Lack of flexibility of tests and testing distance; do not detect pathology/strabismus; The awareness of the actual target distance may induce proximal accommodation and convergence even when distance viewing conditions are simulated
(3) Computer programs (may dominate in future)

Vision screening for children in Australia

•The cost effectiveness of paediatric vision screenings, the nature of the tests included in the screening batteries and the ideal screening age has been the cause of much debate.
•Results suggest there is no agreed vision screening protocol for children in Australia. This appears to be a result of the lack of strong evidence supporting the benefit of such screenings.
•While amblyopia, strabismus and, to a lesser extent refractive error, are targeted by many screening programs during pre-school and at school entry, there is less agreement regarding the value of screening for other visual conditions, such as binocular vision disorders, ocular health problems and refractive errors that are less likely to reduce distance visual acuity.
•The screening programs that are offered are ad hoc and poorly documented

Vision screening for children in the US

• In the US, paediatric vision screening is more common and is incorporated in routine child health assessments and school health programs.
• However, there remains little agreement about when children should be screened, which conditions should be targeted, protocols that should be used and which screening personnel are best equipped to provide service

Vision screening for children in the UK

• In the UK, the 1997 NHS review suggested that preschool vision screenings may not be as beneficial as had been previously thought, arguing that the conditions being targeted (amblyopia and refractive error) were ‘minor’ problems and that there was minimal evidence to demonstrate that treatment was beneficial.
• Following this NHS report, Logan and Gilmartin (2004) examined the evidence-base for the content, provision and efficacy of children’s vision screenings that specifically targeted refractive error, amblyopia, binocular vision and colour vision. They recommended children receive a vision screening between the ages of five and six years (for detection of significant refractive error, colour vision and previously undetected amblyopia) as well as at the age of 11 years to assess for the development of myopia