What is Dry Eye? Why Does It Happen?

By | 17 February 2021

What is Dry Eye?
Dry eye is the decrease in the moisture of the eye surface due to the lack of tears or the irregularity of the tear film layer due to excessive evaporation. The tear film layer is renewed with each blink.

Tears provide protection of the eye from external factors, moisturizing the cornea and conjunctiva, which are the transparent layer of the eye, and provide nutrient and oxygen support to the cornea. Also, it prevents damage to the eye surface during the movements of the eyelid and suppresses the growth of microorganisms by mechanical heating and antimicrobial activity.

To protect the eye surface, there must be a continuous tear film. Any damage to the tear film will affect the ability to see easily.

Dry Eye Symptoms

  • Dry eye feeling,
  • Burning, stinging, feeling of sand in the eye,
  • Eyestrain
  • The uncomfortable feeling from smoke and air conditioning,
  • Light sensitivity,
  • Tearing,
  • Blurred vision,
  • Difficulty wearing contact lenses, discomfort when wearing contact lenses.

Why are dry tears so important?

Tears form a thin film on the transparent layer in the front of the eye. This layer provides protection of the eye from external factors, moistening of the cornea and conjunctiva, which are the transparent layer of the eye, and the nutrient and oxygen support of the cornea. Also, it prevents the damage of the eye surface during the movements of the eyelid and suppresses the reproduction of microbes with mechanical heating and antimicrobial activity. To protect the eye surface, there should be a continuous tear film layer. Any damage to the tear film layer affects the ability to see easily.

Why Does Dry Eye Occur?
a) Decreased tear film quality
The tear film layer consists of 3 basic layers. These are mucus, aqueous (aqueous), and oily (lipid) layer. Problems with any of these layers can lead to dry eye complaints.

Mucous layer: The innermost layer of mucus covers the surface of the eye. If there is not enough mucus layer to cover the surface of the eye, there may be punctate epithelial defects on the corneal surface.

Aqueous layer: This layer, which is produced by the tear glands and contains some salt, cleans the eye and removes foreign bodies and irritants from the eye. In the insufficient production of this layer, the oil and mucus layers contact each other and cause a thread-like tear.

Oily (lipid) layer: This layer, which forms the outermost layer of the tear film layer, is secreted by the meibomian glands on the lid edges. This lipid-containing layer prevents the aqueous layer in the middle from evaporating suddenly. In the absence of this layer, the aqueous layer evaporates quickly and causes dry eye symptoms. Meibomian dysfunction with frequent symptoms of dry eye; can coexist with rosacea, blepharitis, and other skin diseases.

b) Decreased tear production
Due to hormonal changes, tear production has decreased in postmenopausal women and people over 50 years of age.

Rheumatic diseases such as lupus, Sjögren’s syndrome, rheumatoid arthritis, diabetes, and antidepressants or some allergy or hypertension drugs reduce tear production. Tear production is also affected in cases that cause damage to the tear glands such as LASIK, surgical procedures such as cataract surgery, radiation.

c) Eyelid problems
The blinking movement provides an even distribution of tears on the eye surface. Decreasing the frequency of blinking increases the time the eye stays open, increasing the number of tears evaporating. Therefore, physical eyelid diseases such as entropion (inverting of the eyelid), ectropion (eyelid turning out), or a decrease in the number of blinking due to psychological reasons can cause dry eye symptoms. Also, if the distance between the eyes is too great, it causes a change in the angle of vision, so the size of the eye in contact with the air changes. As the part that comes into contact with air increases, evaporation increases, and dry eye symptoms may occur.

d) Medicines
Birth control drugs, some antidepressants, are threonine derivative drugs used in acne treatment, pain relievers such as ibuprofen and naproxen, antihistaminic and decongestant drugs, centrally acting antihypertensives, and diuretics may cause dry eyes.

e) Other reasons
Environmental factors can also cause the eye surface to dry out. Wind, air conditioning systems, sun, and dry environments can increase the evaporation of tears, leading to dry eye symptoms. Prolonged use of a computer, watching television, working or driving can reduce the frequency of blinking and dry the eye surface.

What are the most common complaints of dry eye syndrome?
Stinging, burning, dryness, the feeling of sand, and blurred vision. Blurred vision usually increases at the end of the day and when you focus on something for a long time. The most important complaints of the patients are sensitive to light, sticky secretion around the eyes, tearing in the eyes, increased discomfort in the eyes in smoking and windy weather, and the feeling of heaviness in the eyes while reading a book. Patients with dry eyes have difficulty wearing contact lenses. A doctor should be consulted when there are complaints such as redness, pain, and tiredness in the eyes.

What are the most important risk factors?
Aging, being a woman, a history of laser or cataract surgery, radiation therapy, using drugs that can cause dry eyes, diabetes, goiter, rheumatic diseases increase the risk of dry eye. Also, diets containing low vitamin A and omega-3 fatty acids increase the risk of dry eyes.

What are the complications?
Eye infections can occur more frequently in dry eyes, as tears protect the surface of the eye from infections. Also, if untreated, eye irritation, corneal surface deterioration, and vision problems may occur in patients.

How is the disease diagnosed?
Detailed examination of the patient by an ophthalmologist who is an expert in the subject is very important in the diagnosis of the disease.

Measurement of the number of tears: measured by the Schirmer test. Marked special filter papers are placed on the lower eyelid edge and waited for 5 minutes. At the end of the time, the amount wetted with tears on the paper indicates the number of tears.

Determination of tear quality: The tear break-up time and the tear evaporation time are measured. Also, the health of the surface of the cornea and conjunctiva are evaluated with special dyes such as fluorescein, lissamine green, and Rose-Bengal.

Tear density measurement (osmolarity): It is an important and new method in the diagnosis of dry eyes.

Recently, we often hear dry eyes, is it a new disease brought about by today’s conditions?
Dry eye disease is a decrease in the moisture of the eye surface due to insufficient tear release or irregularity of the tear film layer due to excessive evaporation. Dry eye is not a new disease, but it is more common today due to changes in living and environmental conditions. At the same time, because the disease is better known, it comes to the fore more frequently.

Will malnutrition, vitamin deficiency affect the eye fold?
The deficiency of vitamin A affects the moisturizing inner layer of the tear, causing dry eye disease. Also, zinc, magnesium, and vitamin B6 deficiency negatively affect tears. The fat-containing layer of the tears is adversely affected by the Omega 3 deficiency.

Does dry eye occur in children?
Dry eyes are not common in children. When there is a dry eye, the diagnosis is often overlooked. In addition to causes such as eyelash allergy and eyelash root inflammation (blepharitis), intensive computer use is the most common cause of dry eye in children.

Does the lens dry the eye? Should those with dry eyes wear glasses instead of lenses?
People with severe dry eye disease cannot produce enough tears to keep the contact lens moist and wet. Therefore, they feel uncomfortable when they wear contact lenses. These patients should use additional tears compatible with the contact lens. Those with severe dry eyes should avoid wearing contact lenses.

Does the incidence of dry eye increase with pollen in spring?
When patients with dry eyes are exposed to allergens, they are affected more than normal and their complaints increase. In some patients, both dry eye and allergic conjunctivitis may coexist. Allergy and dry eye complaints appear more exaggerated in these patients. Environmental factors can also cause the eye surface to dry out. Wind, air conditioning systems, sun, and dry environments increase dry eye complaints by increasing the evaporation of tears. Being in smoking environments and smoking also negatively affect dry eyes.

Could the increase in dry eye incidence in recent years be due to intense computer use?
Using computers for a long time, being air-conditioned and dry in office environments, watching television, working for long hours, and driving can reduce the frequency of blinking and dry the eye surface.

How do dry eyes affect social life? why does it make you unhappy?
In dry eye syndrome, complaints such as stinging, burning, feeling of sand penetration and loss of image quality make the patient uncomfortable and unhappy in business life and social life. Burness in vision generally increases at the end of the day and when a point is focused for a long time. Also, sensitivity to light, sticky mucus around the eyes, smoking, and windy weather increase eye irritation. Patients with dry eyes have difficulty wearing contact lenses. All these factors become a source of serious stress and anxiety in daily life.

 

The computer screen should be slightly below eye level. To look at the computer screen above eye level, it is necessary to open the eyes more, this will increase dry eyes. In long working periods, it is necessary to take 5-minute breaks to close the eyes and rest or to make the blink more frequent. Patients should be advised to pay attention to frequent eye breaking while using a computer.