Dry eye syndrome

Dry eye syndrome is the most common reason for a visit to an eye doctor.

It is a multifactorial disease of the ocular surface that results in a wide range of symptoms, including discomfort, visual disturbance, tear film instability and potential damage to the ocular surface. There is increased osmolarity of the tear film and quite often a chronic inflammation of the ocular surface.

Dry eye syndrome is a malfunction of patient¨s Lacrimal Functional Unit, which comprises the lacrimal glands and ocular surface. The ocular surface consists of cornea, conjunctiva and meibomian glands and eyelids, together with nerves that link them.

The reasons of dry eye syndrome are:

  • Decreased tear production in some patients
  • Increased tear evaporation
  • Incorrect quality of tears in most of the patients

These reasons cause patients’ Lacrimal Functional Unit to malfunction and start the irritating symptoms

Dry eye is a general term referring to abnormalities of the tear layer which normally coats the surfaces of the eyes. In most cases the main reason is not the amount of tears, but the inadequate quality of tears caused by the improper functioning of the lipid secreting meibomian glands that provide clear vision and protect sensitive surface tissues.

Symptoms of dry eyes

Patients will present some of the following symptoms:

  • Tired eyes when reading, watching TV, computer work
  • Foreign body sensation
  • Sore eyes
  • Gritty eyes
  • Fluctuating vision
  • Eyelids stick shut at night
  • Burning eyes
  • Contact lens intolerance
  • Excessive mucus discharge
  • Watery or running eyes
  • Irritation by smoke
  • Increased sensitivity to light (photophobia)
  • Blurred vision

Grading of dry eyes

The mildest form of dry eyes can be managed with artificial tear supplements, warm lid therapy and environmental changes. The majority of people suffer from dry eyes from time to time.

The next level,is moderate dry eye symptoms; these affect vision more and also have an impact on life quality because of more severe symptoms like chronic pain, light sensitivity and eye sensitivity

The severe dry eye might lead to damage of the outer ocular surface like conjunctiva and especially the cornea, leading to ulceration of the cornea, a possible infection and severe impairment of daily life, including visual impairment.

Causes of dry eyes

The major risk factors are increased age and being female, but dry eye syndrome is a very common symptom and condition affecting almost everybody to some extent during life.
Dry eye syndrome has a wide variety of causes:

  • Meibomian Gland Dysfunction (MGD)
  • Blepharitis- either anterior or posterior
  • Ocular surface disease/allergic conjunctivitis
  • Systemic diseases like Sjögrens syndrome, Rheumatoid Arthritis, SLE,
  • Thyroid disease
  • Eye conditions like ocular rosacea and corneal dystrophies
  • Rosacea, atopia
  • Eyelid conditions
  • Eye injuries and burns
  • Idiopathic reasons
  • Blink disorders

Diagnostics

Dry eye symptoms are common but a thorough examination should include measuring the amount of tear production and quality of tears, as well as a clinical examination to evaluate the condition of the tissues.

Measurement of tear film stability

The normally functioning eye has a tear film that is continuously available and blinking maintains the tear film. In patients with dry eyes, the tear film is unstable and it breaks up faster. Therefore, the tear break-up time is shorter. You can demonstrate the symptoms by forcing your eye to be open and you will have a feeling of dryness in your eyes, forcing you to blink or close your eyes.

Tear Break Up Time (BUT)
This measures the interval between the individual’s last complete blink and the break-up of his or her tear film.
This simple test involves the use of fluorescein and a slit lamp.
A BUT lower than 10 sec suggest a dry eye
BUT can be measured with a keratograph now, removing the need for fluorescein, and it is called NIBUT. A value of less than 15 seconds suggest of a dry eye.

Schirmer
Schirmer is a tear volume test that measures the quantity of dry eyes but does not reveal the quality of the tears. In rare cases the amount of tears in insufficient, but in most cases the question is about the quality of tear production. A value below 5 or 6 suggests lack of tears, 6-10 is borderline and above is normal.

Height of Tear Menisci
this can be measured simply with a slit lamp by adjusting the height of the light to match the height of the tear film on the lower lid
A height of less than 0.2mm suggests dry eyes.

Staining
Staining serves as an indicator of the health of the ocular surface.
Fluorescein is the most widely used method for staining the cornea and conjunctiva and the result is evaluated with a slit lamp.
A Rose Bengal test identifies devitalized tissue. It is best done 3-5 minutes after installing the drops. A pattern of interpalbebral cornea and bulbar conjunctiva is typically seen with a deficiency of aqueous tear secretion.
Lissamine green stains the dying cells of ocular surface and the result is observed with a slit lamp.

Osmolarity
In dry eye conditions the strength or osmolarity of tears is increased and is called hyperosmolarity. It can be tested with a device that collects a nanoliter of tears and analyzes the osmolarity of tears. Normal values lie around 304mOsm/kg whilst values over 320mOsm/kg suggest a dry eye condition.

Treatment of dry eyes

Treatment of dry eyes

The aim of treatment is to decrease the symptoms and increase the quality of life. In some cases the symptoms cannot be cured completely.
The treatment options:
1)Enviromental counselling:
-moisturizing of the air at home, in office
-effect of air conditioning, computer work, the flow of air, the effect of travelling by plane, the effect of smoking and consumption of alcohol
2)The use and type of lubricating drops according to patients needs
3)The use of medical drops like corticosteroid, antibiotics
4)Lid hygiene and local treatment with warm compresses
5)The treatment of normalizing the secretion of meibomian glands with Thermoflo
6)Systemic medication

After a thorough examination and a detailed treatment programme most, if not all, patients get satisfactory results, decreased or vanished symptoms and increased quality of life. Dry eye is a very common symptom and there are treatment options other than only using lubricating tears, which quite often are not enough to resolve the symptoms.