Dry eye is a very common ocular disorder consisting of an altered tear film with an incidence that has increased significantly in recent years and is often underestimated in its importance.
The tear films
The tear film is a fluid, transparent film that lines the outer structures of the eye. The main functions of the tear film are defence, lubrication, nutrition and cleaning of the ocular surface, and, together with the eyelid, it is the main defence against corneal and conjunctival bacterial infections.
The tear film is composed of three layers:
- Mucosal, the innermost in direct contact with the corneal surface
- Aqueous, intermediate, the thickest of the three
- Lipid the outermost and in direct contact with the external environment
Each of these layers has a specific role:
- the mucous layer firmly anchors the aqueous layer to the surface of the corneal cells, preventing it from slipping off
- the aqueous layer is the vehicle for nutrients, oxygen, and contains many substances with a protective character, such as some immunoglobulins of the immune system.
- the lipid state serves to limit friction and evaporation, and must be continuously distributed over the surface by the eyelids because it tends to form globules as it does with fat suspended in a bowl of broth.
Dry eye can be distinguished into two forms:
- Hypolacrimia: from reduced tear production
- Dyslacrimia: from excessive evaporation. This is the most common form.
There are many contributing causes of dry eye:
- Advanced age. Over the years, atrophy of the lacrimal glands occurs causing a progressive qualitative alteration of the tear itself.
- Menopause. In women going through this stage of life, due to hormonal imbalances, the lacrimal glands undergo progressive atrophy.
- Contact Lenses. Their prolonged use can greatly increase tear evaporation as well as induce ocular surface changes.
- Eyelid changes. Chronic inflammation of the eyelid rim such as blepharitis, which, by affecting certain glands, can result in alterations to the composition of the tear film.
- Medications. Antidepressants, antihypertensives, antiarrhythmics, antiulcer, antihistamines, diuretics, hormones, and immunosuppressants can inhibit tear production.
- Environmental factors. Constantly being stationed in unhealthy environments due to air conditioning, excessive ventilation, high temperature, low humidity, working at furnaces …., can turn a transient discomfort into a real pathological dryness
- Attention activities. Work or recreational activities that require attention such as computer work, video games, reading…., reduce blinking by altering the distribution of the tear film favouring its evaporation.
- Surgical and presurgical interventions. These can result in transient anatomical damage and that can cause dry eye. In these cases, untimely therapeutic intervention may cause this condition to become chronic, turning it into a full-fledged pathological dryness.
Symptoms
Symptoms are numerous but can all be traced to ocular surface changes:
- Sensation of sand or foreign body in the eye
- Burning
- Itching
- Photophobia (discomfort with light)
- Difficulty in eyelid opening upon awakening
- Wet eye sensation
- Difficulty blinking
- Visual fogging
Symptomatology can be exacerbated by particularly unfavourable environmental conditions, such as exposure to wind, in the presence of smoke, air conditioning, heating or during moped use, or in the presence of smog.
The physician may often observe the so-called red eye that is associated with dry eye when an inflammatory state is established.
Therapy
Therapy is replacement in nature based on eye drops or gels with moisturizing and lubricating action.
However, when dry eye is accompanied by inflammatory phenomena (red eye), the use of an exclusively lubricating and moisturizing artificial tear may be insufficient. In this case, the ophthalmologist will choose a product that combines a lubricating and moisturizing effect with an anti-inflammatory action that is particularly useful in reducing this complication.
Therefore, an accurate diagnosis by the ophthalmologist is necessary.