Dry eye is a condition in which the eyes don’t produce enough tears for adequate lubrication of the eyes. It is a very common condition, particularly in older individuals.
It is also known as dry eye syndrome (DES), keratoconjunctivitis sicca (KCS), or keratitis sicca.
It affects around 5–34% of the general population. Among older people, about 70% of individuals are known to suffer from dry eye. Also, it is more common among postmenopausal females.
Dry eye leads to an uncomfortable feeling and can cause vision problems or other complications.
For mild cases, certain lifestyle changes and regular use of artificial tears is able to provide relief in the majority of cases. For severe cases, specific medications, procedures like punctal plugging, or surgery may be carried out.
Composition of Tears
When a person blinks, a film of tears spreads over the eye. This helps to keep the surface of the eye, moist, smooth, and clear. The tear film is essential for good vision.
The tear film is made of three layers:
- An oily or lipid layer
- A watery or aqueous layer
- A mucous layer
The oily or lipid layer is the outermost layer of the tear film. It helps to make the tear surface smooth and prevents tears from drying up too fast. This oil is produced by the meibomian glands present in the eyelids.
The watery or aqueous layer is the middle layer of the tear film. This layer cleans the eye and washes away any foreign particle that enters the eye. This layer is produced by the lacrimal glands present near the eyelids.
The mucus layer is the innermost layer of the tear film. It helps to spread the watery layer over the surface of the eye. In the absence of mucus, tears will not be able to stick to the eye. It is produced in the conjunctiva.
All the layers need to be produced in an adequate amount so as to have a good quality tear film.
Normally, the eyes produce tears constantly which helps them to stay moist and lubricated.
If any external particle enters the eyes, the eyes get irritated and produce a lot of tears in an effort to wash away or get rid of that particle.
However, at times the eyes are unable to make enough tears due to defects in one or more layers resulting in dry eyes.
Causes of Dry Eye
Decreased tear production
- Aging: Tear production reduces with age. People more than 50 years of age are more prone to dry eyes.
- Menopause: About one-third of all post-menopausal females have dry eyes. This occurs due to deficiency of hormone estrogen.
- Certain diseases: Diabetes, rheumatoid arthritis, lupus, scleroderma, Sjogren’s syndrome, thyroid disease
- Nutritional deficiency: Diet low in vitamin A or omega-3 fatty acids can lead to dry eyes.
- Taking certain medicines
- Diuretics for high blood pressure
- Beta-blockers, for heart diseases or high blood pressure
- Decongestants used as cold medicines
- Antihistamines for allergy
- Sleeping pills
- Anxiety and antidepressant medicines
- Heartburn medicines
- Hormone replacement therapy
- Oral contraceptive pills
- Lasik eye surgery for refractive error
- Damage to tear glands due to inflammation or radiation
Increased tear evaporation
- Exposure to wind or dry air (such as continuous exposure to a heater or air conditioner)
- Smoky environment
- Not blinking enough, which occurs when eyes are concentrating, such as during reading, driving, watching television or working at a computer or smart-phone
- Using contact lenses for a long time
- Diseases of eyelids
- Out-turning of the lids (ectropion)
- In-turning of the lids (entropion)
- Swollen or red eyelids (blepharitis)
Imbalance in tear composition
Defect in any of the three layers – oil, water, or mucus can cause dry eyes.
- Meibomian gland dysfunction
- Inadequate oil (meibum) secreted from meibomian gland
- Blocked meibomian glands
- Blepharitis (inflammation of the eyelids)
- Other skin disorders
Symptoms of Dry Eye
Usually, both eyes are affected. Common symptoms include:
- A scratchy feeling, like a sensation of having something in the eye
- Stinging or burning sensation in the eyes
- Stringy mucus in or around the eyes
- Redness of eyes
- Sensitivity to light
- Eye fatigue
- Blurred vision
- Watery eyes, which is the body’s response to the irritation of dry eyes
- Difficulty wearing contact lenses
- Difficulty with nighttime driving
Complications of Dry Eye
The tears protect the surface of the eyes from infection. In the absence of adequate tears, there is an increased risk of eye infections.
Damage to the surface of the eyes
Severe dry eyes, if not treated may cause abrasion of the corneal surface and corneal ulcers leading to defects in vision.
Difficulty in performing routine activities
Dry eyes can cause an uncomfortable sensation and may cause difficulties in performing day to day activities, such as reading, watching television, etc. This may lead to decreased quality of life, headaches, or even depression.
A detailed patient’s history to know about the signs and symptoms, general health problems, medications, etc is taken. Underlying health disease which is causing the dry eyes must be investigated and diagnosed accordingly.
Dry eyes can be diagnosed with a complete eye examination.
The test carried out by an ophthalmologist can detect reduced tear film in the eyes.
The Rose Bengal test
This test is used to measure the functioning of the lacrimal glands. A non-toxic dye – Rose Bengal is instilled in the eyes. In case of dry eyes or a complete lack of tear film, the dye is taken up by the healthy epithelial cells and the eyes will display extensive staining with Rose Bengal.
It is a test used to measure the degree of dryness of the eyes. A small piece of filter paper is kept inside the lower eyelid for five minutes to measure the production of tears. The wetness is then measured with a ruler. Reduced wet area indicates dry eye.
Prevention and Self-care Tips
- Avoid dry or windy places.
- Avoid smoky environment. Stop smoking, if you do so. If you do not smoke, try to stay away from other people when they are smoking.
- When using hair dryers, heaters, air conditioners or table fans, make sure that the air does not blow directly towards your eyes.
- When outdoors, wear wraparound sunglasses or glasses with sides so as to prevent drying of eyes from winds or sun.
- When indoors, use a humidifier near you to keep the surrounding air moist.
- Reduce your screen time, watching TV, or spending a long time reading as it tends to make the eyes dry.
- Keep your computer screen below eye level. This prevents opening the eyes wider to view the screen thereby, slowing the rate of evaporation of the tears.
- If it is necessary to perform a task for a long period which requires your eyes to concentrate, ( such as reading a book or working on a computer) take frequent eye breaks. Follow the 20-20 rule. After every 20 minutes, look at a distance 20 feet away for about 20 seconds. Alternatively, you can close your eyes for a few minutes.
- Make a conscious effort to blink regularly as it helps to spread the tears evenly over your eyes.
- Drink plenty of water (around 8 glasses) every day to prevent dehydration.
- Avoid medicines that can cause dryness of eyes as a side effect.
- Applying warm compresses on the eyes and then pressing the edge of the eyelid with a finger helps to squeeze out the clogged oils and loosen up the clogged glands. It also reduces the associated inflammation.
- Nutritional supplements containing essential fatty acids like omega-3 fatty acids can decrease dry eye symptoms. Fish such as salmon, sardines, herring and cod; nuts including flaxseed, chia seeds, and walnuts are a natural rich source of omega-3 fatty acids and should be included in daily diet.
Treatment for dry eye depends on treating the underlying cause. Certain treatments can help to ease the symptoms and prevent complications from occurring.
The most common treatment for mild dry eye is with artificial tears available commonly in the form of eye drops. They act as moisture replacement therapy and can be obtained as over the counter drugs meaning without a prescription.
Artificial tears are usually of watery consistency. They provide quick relief. However their effect is usually short-lived, and hence they need to be used frequently throughout the day to get adequate relief.
Artificial tears having a high viscosity are available in the form of gels and ointments. These provide lubrication for a longer time. But they cause significant blurring of the vision for several minutes after applying them and so unsuitable for use during the daytime. They are usually recommended for bedtime use only.
Cyclosporine (Restasis) or lifitegrast (Xiidra)
These drugs may be given in addition to artificial tears. Besides lubrication, they reduce the inflammation associated with dry eyes and helps the body to produce more natural tears.
Steroid eye drops
These may also be prescribed for a brief period to reduce the underlying inflammation associated with dry eyes. However they should not be used for prolonged period of time as they can cause serious side-effects like high eye pressure or cataracts.
Punctal plugs may be used to retain tears on the surface of the eye for a longer time.
A punctal plug is a small, sterile device made of collagen or silicon that is inserted into the openings (called puncta) of tear ducts that are located in the inner corner of the upper and lower eyelids.
As a result, the tears can no longer drain away from the eye through these ducts and remain on the surface of the eye for a long period.
In severe cases, a minor surgical procedure that seals the tear ducts that drain tears from the eyes (punctal occlusion) may be carried out to relieve dry eyes.
Meibomian gland expression
This treatment is helpful in cases when the meibomian glands produce inadequate oil (meibum) due to inflammation and blockage.
In this procedure, firstly warm compresses are applied to the eyelids. The clogged contents of the meibomian glands are then squeezed out using a forceps-like device.
Surgery may be required in certain cases like entropion or ectropion when the lids are either turned abnormally inwards or outwards. In such cases, surgery can fix the eyelids and help to retain the tears on the eyes.
In severe cases, the drainage holes (punctum) may be permanently plugged to allow the eyes to maintain an adequate amount of tears.
Long-Term Outlook or Prognosis
Dry eyes usually don’t cause permanent loss of vision. It may cause an uncomfortable feeling in the eyes which can be reduced with proper treatment. If left untreated, complications such as eye infections and ulcers may occur and need to be treated.
- Donnefeld ED, et al. Safety of Lifitegrast Ophthalmic Solution 5.0% in Patients With Dry Eye Disease: A 1-Year, Multicenter, Randomized, Placebo-Controlled Study. Cornea. 2016 Jan. 35(6):741-8.
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- The definition and classification of dry eye disease: report of the Definition and Classification Subcommittee of the International Dry Eye WorkShop. 2007. Ocul Surf. 2007 Apr. 5(2):75-92.