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Sunday / June 16.
HomemieyecareBeat The Nine To Five Dry Eye

Beat The Nine To Five Dry Eye

Eye irritations such as dry eye are common in office environments. The cause of eye irritations is multi-factorial. Symptoms include stinging, burning, dry, scratchy, sore, gritty and itchy eyes. Control of office environment, workstation design and an appropriate treatment plan helps relieve these symptoms.

Several factors associated with dry eye in office environments are:

1. Low Relative Humidity

Sustained low relative humidity causes impairment of precorneal tear film, resulting in an increased tear evaporation rate. It has been shown that a 20 per cent decrease of relative humidity will increase the rate of tear film evaporation by 100 per cent and relative humidity greater than 40 per cent helps stabilise tear film and reduce irritation caused by desiccation.1,2 However, relative humidity greater than 60 per cent should be avoided because of the higher risk of dust mite proliferation.3

2. High Room Temperature

It was suggested that a 1ºC decrease in room temperature was associated with a 19 per cent decrease of reported eye symptoms.4 Elevated room temperature will disrupt the stability of the lipid layer of the tear film.5 A room temperature between 20 and 22ºC may reduce eye irritation symptoms by avoiding excessive tear film evaporation.6

Eyedrops are well proven to be effective in relieving dry eye symptoms. However, preservatives found in artificial tears may be harmful to corneal epithelium and cause irritation.

3. Indoor Air Velocity

High horizontal or downward air velocity along the head region increases evaporation of water from the eye, causing dry eye symptoms.7

4. Video Display Unit (VDU) Work

Blinking is essential in the coating and redistribution of the tear film with each blink. Computer users are more likely to suffer from dry eye symptoms because of changes in blinking pattern during VDU work. Studies show that blink frequency can be reduced by a factor of two to three times during VDU work2 and is also dependent upon the type of computer tasks.8,9 Blink frequency during an active computer task requiring vision and hand-eye coordination was 69 per cent lower than that during a passive task like watching a film on a VDU;8,9 squinting at a computer screen may further reduce blink frequency by half.10 Squinting can provide two benefits: it improves visual acuity and decreases retinal illumination from glare sources. However, the more people squint, the less they blink. A reduction of blink frequency will result in tear film thinning and allows formation of dry spots on the cornea, causing an increase of dry eye symptoms.

5. Contact Lens Wear

43 per cent of soft contact lenses wearers have dry eye symptoms.11
Higher tear evaporation with contact lens wear is a major factor contributing to contact lens-induced dry eye. It was found that tear film evaporation at normal relative humidity (40 per cent) with contact lenses is similar to the evaporation at low relative humidity (30 per cent) without contact lenses.12 This means contact lens wear can be equated to putting someone in a low-humidity environment, when in fact the environmental humidity is normal.

6. Makeup

There is a significant association between the use of eye makeup and a thin lipid layer of the tear film. It was proposed that oils in the eye makeup may be able to displace the phospholipids in the tear film and disrupt the formation of lipid layer on the cornea.13

Reducing Dry Eye Symptoms

To reduce ocular irritation and dry eye symptoms in office environments, the following preventive measures and intervention may be considered:

Workstation

  • Maintenance of relative humidity is important. A relative humidity level above 40 per cent helps maintain tear film stability.
  • Lowering room temperature may reduce tear film evaporation. The optimal room temperature is between 20 and 22 ºC.
  • Avoid ventilation directed at your eyes.
  • Adjust the position of the monitor. Downward gaze may minimise loss of water from the tear film. It was found that lowering the gaze angle by 25º decreased the exposed area by seven per cent during an active task.9
  • Change font and font size of characters displayed on the monitor to avoid squinting. Among the different fonts, Verdana and Arial were shown to be the most legible, while Times New Roman and Franklin were the least legible.14
  • Remove any bright light glare on the computer screen by moving the screen, lowering the light level or using an anti-reflection screen. Make sure that the computer monitor screen is not in front of a bright background (e.g. bright window). Glare will induce squinting which is strongly associated with a reduction of blink frequency.
  • Alternate between work with a high and low degree of visual and cognitive demands. A computer task with high visual demands will reduce blink frequency more significantly.
  • Micro-breaks every one to two minutes and exercise of complete blinks help restore normal tear film stability.

Optometric Intervention

Lubricating eye drops may be used in the treatment of dry eye symptoms from various causes. For contact lens wearers, contact lens rewetters may be instilled directly on contact lens before insertion or while on eyes. Eye drops containing lubricating agents such as sodium hyaluronate are well proven to relieve dry eye symptoms.15 However, preservatives found in artificial tears may be harmful to corneal epithelium and cause irritation.16,17 Therefore, a preservative-free eye drop or an eye drop with preservatives that decompose into natural tear ingredients upon instillation is recommended. An example of decomposable preservatives is stabilised oxychloro complex, or SOC (e.g., OCUPURE preservative, Abbott Medical Optics Inc). When exposed to light, SOC will be converted into sodium ions, chloride ions and water. It has been shown that SOC produced fewer observable effects on the morphology of rabbit corneal epithelial cells compared to other products tested.17

The use of high-water content lens materials was found to be strongly related to dry eye in lens wear.18 The odds of dry eye occurring with high- water content contact lens materials is two to three times greater than that associated with non-ionic, low-water content. Lens surface characteristic may also have an impact. The non-ionic high-water content lens materials in general are more often associated with dry eye than the ionic high-water content lens materials.18 Refitting patients with low-water content hydrogel or silicone hydrogel lenses may be helpful.19

Manage near point stress to prevent squinting (e.g. reading or computer glasses).

Others

Dry eye symptoms are associated with a reduction of blink frequency during intensive VDU work which requires a high level of mental alertness. Therefore, it has been proposed that specific “relaxation” exercises (e.g. yoga) can relieve visual discomfort during the use of computer by restoring blink frequency towards normal.20

Dr. Gunter Wong graduated from the optometry program at the Hong Kong Polytechnic University. He gained his Master of Optometry degree from the University of New South Wales and his PhD from the University of Hong Kong. His research interest is orthokeratology, visual perception and dyslexia. He is currently the training manager of Abbott Medical Optics Inc.

References:
1. Uchiyama E, Aronowicz JD, Butovich IA, et al. Increased evaporative rates in laboratory testing conditions simulating airplane cabin relative humidity: an important factor for dry eye syndrome. Eye Contact Lens 2007; 33:174-176.
2. Wolkoff P. “Healthy” eye in office-like environments. Environ Int 2008; 34:1204-1214.
3. Wolkoff P, Kjærgaard SK. The dichotomy of relative humidity on indoor air quality. Environ Int 2007; 33:850-857.
4. Mendell MJ, Fisk WJ, Petersen MR, et al. Indoor particles and symptoms among office workers: results from a double-blind cross-over study. Epidemiol 2002; 13: 296-304.
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6. Wolkoff P, Nøjgaard JK, Frank C, et al. The modern office environment desiccates the eyes? Indoor Air 2006; 16:258-265.
7. Murakami S. Analysis and design of micro-climate around the human body with respiration by CFD. Indoor Air 2004; 14(Suppl 7):156-164.
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12. Guillon M, Maissa C. Contact lens wear affects tear film evaporation. Eye Contact Lens 2008; 34:326-330.
13. Franck C. Fatty layer of the precorneal film in the “office eye syndrome”. Acta Ophthalmol (Copenh) 1991; 69:737-743.
14. Sheedy JE, Subbaram MV, Zimmerman AB, et al. Text legibility and the letter superiority effect. Hum Factors 2005; 47:797-815.
15. Condon PI, McEwen CG, Wright M, et al. Double blink, randomised, placebo controlled, crossover, multicentre study to determine the efficacy of a 0.1per cent (w.v.) sodium hyaluronate solution (Fermavisc) in the treatment of dry eye syndrome. Br J Ophthalmol 1999; 83:1121-1124.
16. Pisella PJ, Pouliquen P, Baudouin C. Prevalence of ocular symptoms and signs with preserved and preservative free glaucoma medication. Br J Ophthalmol 2002; 86:418-423.
17. Huth S, Huang L, Kao E, et al. Effects of contact lens rewetting solutions with various preservative systems on corneal surface epithelial morphology in a rabbit model. Poster presented at: The 32nd BCLA Conference; June 2008; Birmingham, UK.
18. Ramamoorthy P, Sinnott LT, Nichols JJ. Treatment, material, care, and patient-related factors in contact lens-related dry eye. Optom Vis Sci 2008; 85:764-772.
19. Chalmers R, Long B, Dillehay S, et al. Improving contact-lens related dryness symptoms with silicone hydrogel lenses. Optom Vis Sci 2008; 85:778-784.
Telles S, Naveen KV, Dash M, Deginal R, et al. Effect of yoga on self-rated visual discomfort in computer users. Head Face Med 2006; 2:46.