Dry Eye

Causes of Dry Eye

Dry eye is caused either by too little tear production or by excessive evaporation of the tears that are produced.

1. Too Little Tear Production

Too little tear production can be caused by a rheumatic disease called Sjögren’s syndrome. Besides dry eyes, Sjögren’s syndrome also causes a dry mouth. In Sjögren’s syndrome the tear gland is destroyed by an inflammatory reaction of unknown cause. Sjögren’s syndrome can also occur together with other rheumatic diseases.

When reduced tear production is not caused by Sjögren’s syndrome, it results from the following:

• Advancing age
• Diseases that destroy the tear gland (e.g. the form of thyroid disease that affects the eyes)
• Blockage of the ducts of the tear gland (e.g. eye diseases such as trachoma)
• Certain neurological diseases (e.g. Riley–Day syndrome)

2. Excessive Evaporation of the Tears

Excessive evaporation is caused by factors such as contact lens wear and computer use. Problems with the secretions of the oil glands at the base of the lashes also cause excessive evaporation by making the oily component of the tears insufficient.

Symptoms of dry eye

• Stinging
• A foreign-body sensation
• Burning
• Sticky discharge
• Blurred vision
• Redness
• Sensitivity to light
• A feeling of tiredness

Diagnosis

• Tear break-up time: normally the tear film should remain on the surface of the eye for at least 10 seconds after each blink. Dry areas not covered by tears forming on the surface in less than 10 seconds (that is, the tear film breaking up) are abnormal and indicate insufficient tears.
• Schirmer test: after the eye has been numbed with anaesthetic drops, paper strips marked in millimetres are placed on the lower eyelids. After five minutes, at least 10 mm of the strip should be wet. Less than 5 mm of wetting means dry eye.
• Assessing the surface of the eye with dyes: dyes called fluorescein or rose bengal are applied to the surface of the eye. They stain dry areas on the surface and cells shed because of dryness. The presence and amount of staining show whether there is dry eye and how severe it is.

Treatment

• General measures: humidifying the rooms you spend time in, placing containers of water on radiators, using cool-mist humidifiers and so on.
• Artificial tear drops: they moisten the eye. Preservative-free artificial tears have no toxic effect at all.
• Drops that increase tear secretion: these drops increase the amount of tears produced.
• Punctal plugs: tears drain towards the nose through openings called “puncta” on the inner side of the lower and upper eyelids — which is why our nose runs when we cry. In people with dry eyes, plugs are placed in the puncta to stop the existing tears from draining into the nose, so that the tears stay on the surface of the eye.