Dry Eye: Symptoms and Causes of Dry Eye

Dry eye can be defined as the heterogeneous group of diseases in which the tear film, due to qualitative or quantitative alterations, fails to maintain adequate ocular surface moisture. It manifests itself as the subjective sensation of dryness or lack of tears, which causes various symptoms of ocular discomfort such as rubbing, itching, stinging, grit, blurred vision, burning or lack of lubrication.

Nowadays it is known to be the most frequent problem in ophthalmology, although fortunately it is only rarely very serious. It is mainly suffered by women after menopause, due to hormonal changes, while it also occurs with advancing age, systemic diseases and pharmacological treatments, but in fact anyone can be affected.

Types of Dry Eye

Any diagnosis of dry eye must be defined by three parameters:

• Cause
• Histopathology: the type of dacryogland affected.
• Severity

Causes of Dry Eye

The causes of dry eye can be gathered in 10 groups, where the first 5 usually affect numerous exocrine glands (eyes, nose, mouth, vagina, skin), while the last 5 usually affect only the glands of both eyes, of only one eye, or even a single glandular variety of one eye:

1. Age-related origin: with age everyone ends up having a pan-exocrinopathy sicca, affecting eyes, mouth, throat, etc. Age-related dry eye is usually mild to medium (grade 1 or 2).
2. Hormonal origin: If testosterone decreases or there are not enough testosterone receptors, the gland starts to hypofunction. Women, since they have very few androgens, when menopause arrives and their androgen status decreases may start to develop dry eye. Therefore: castration, aging, hypoovarianism, antiandrogen treatment, ovariectomy, postmenopause, estrogenic contraceptives and lactation are situations in which tear secretion decreases and mild dry eyes occur.
3. Pharmacological origin: There are multiple drugs capable of producing ocular dryness due to secondary exocrine hyposecretory effects: anxiolytics, antidepressants, sleeping pills and hypnotics, antiparkinsonians, antihistamines, anticholinergics, arterial antihypertensives, diuretics, etc.
4. Immunopathic or immunological origin: We can distinguish two groups: autoimmune processes to exocrine glands or Sjögren’s syndrome and immunological processes to non-exocrine tissues, but which include the glands, affecting them. Some infectious diseases, such as Epstein-Bar virus infection, seem to favor the autoimmune attack against the exocrine glands.
5. Hyponutritional origin: Dry eye due to malnutrition or lack of vitamins was the most frequent cause of severe dry eye for millennia, and continues to be so today in underdeveloped countries. In developed countries they are rare, and are usually caused by intestinal malabsorption (alcoholism, Crohn’s disease, intestinal resections, etc.) or by following diets lacking in fats. Other deficits that may cause dry eye are: severe degrees of hydric dehydration, vitamin B2 avitaminosis, vitamin B12 avitaminosis and iron deficiency and potassium depletion.
6. Glandular dysgenesis: These are due to embryo-fetal malformations, which can have a genetic or occasional origin. In the first case they can be hereditary and in the second case not. They can affect several exocrine systems, or only the lacrimal of one or both eyes, or even only one of the 3 glandular subsystems of the eye.
7. Inflammatory origin: Inflammation, generally infectious, of the lacrimal glands, affecting the aqueous glands, which affect the mucous membrane covering the eyeball.
8. Traumatic origin (Destructions by physical or chemical agents): Destruction of the glands can lead to dry eyes. The severity of traumatic dry eyes is very variable according to the traumatic affectation. Sometimes it can acquire severe degrees.
9. Neurodeprivative origin: Lacrimal secretion has a nervous stimulation that can be altered in cases of facial paralysis or nervous lesions. Similarly, fatigue, drowsiness and anxiety also decrease tear secretion. Restricted REM sleep reduces the already low secretion during sleep.
10. Tantalic eyes: Tantalic eyes are those in which even though they have normal or even excessive tear secretion, their ocular surface cannot take advantage of it. Dry eyes are those that have a normal tear production and the cornea cannot take advantage of the tear, either due to alterations of the epithelium that cause the tear to slide over the cornea or because the eyelids cannot adequately extend the tear over the corneal surface.

Histopathological classification

Dry eye can also be classified according to the lacrimal gland that is affected:

Frequently dry eye is due to dysfunction of the three types of dacryoglands that form the lacrimal: aqueous, mucous, and lipid. It can affect one of the three subsystems, two or all three, and although initially only one is affected, in the course of the disease all of them are usually affected secondarily.

Most dry eyes are included in diseases affecting many exocrine glands:

• Nose: dryness, itching, anosmia.
• Mouth: thirst, dense saliva, saliva expulsion when speaking, taste alterations and halitosis or bad breath.
• Throat: thirst, hoarseness, phlegm and dysphonia.
• Vagina: itching, painful intercourse.
• Seminal glands: dense sperm.
• Skin: dryness, itching.
• Ear: earwax plugs AND itching of the ear canal.

Often, the dryness suffered by a gland does not correspond to the sensation felt by the patient: usually the greatest discomfort is usually felt in the eyes, then in the mouth. Dryness of the throat, nose and vagina usually occupy a medium degree. While dryness of the ear and skin often goes unnoticed.

Classification by clinical severity of dry eye

The degree of severity of dry eye is expressed in 5 grades: subclinical, mild, medium or moderate, severe and disabling.

• Grade 1 minus or Subclinical: The patient has incipient dry eye, but only feels symptoms of dryness in situations of overexposure (use of contact lenses, exposure to wind, fan, air conditioning, etc.). At this stage the patient is usually unaware that he/she has dry eye. The symptoms felt transiently are: sensation of dryness, gritty sensation, eye fatigue and blurred vision that disappears momentarily when blinking. Generally in this grade the patient is unaware that he/she already has dry eye.
• Grade 1 or Mild: The patient frequently notices symptoms of dryness such as itching, photophobia or fatigue, even in normal environmental situations. Often at this stage the patient confuses dry eye with other diseases such as conjunctivitis, infections or allergies.
• Grade 2 or Moderate: In addition to the above symptoms, there are reversible signs characterized by the presence of lesions of the ocular surface, such as epithelial erosion, punctate keratopathy, hyperemia of the exposed conjunctival trigones, or leghorn. These signs can be diagnosed with the slit lamp. New subjective symptoms of ocular dryness also appear, such as difficulty in opening the eyes upon waking in the morning, tingling or burning.
• Grade 3 or Severe: Permanent or irreversible signs appear due to dryness of the ocular surface: corneal hypoesthesia, ulcerations and nephelium of the corneal stroma, leukomas, squamous metaplasia of the ocular surface, corneal neovessels, conjunctival scars, retraction of the lacunar sulci (between the nasal conjunctival trigone and the semilunar plica, and between the semilunar plica and caruncle). These lesions persist and worsen if the dry eye condition progresses, and do not disappear completely if the tear secretion improves.
• Grade 3 plus or disabling: Corneal damage causes more or less severe vision loss: disabling central corneal ulcers, central corneal scarring, corneal epithelial keratinization.

Treatment of Dry Eye

There are a multitude of treatments, but they are not usually curative since in most cases the etiology cannot be treated, and the disease usually persists for life.

Treatments that will improve the quality of life of the patient with dry eye can range from hygienic and environmental measures, to etiological treatments when possible, as well as tear substitutes, drugs that stimulate tear secretion, mucosecretors and mucolytics, immunosuppressants, or cases in which surgical techniques and regenerative agents enriched with platelets or serum are needed.

Dry Eye Prevention

To delay as much as possible the ocular dryness and that it affects the eye as little as possible, with adequate environmental and dietary means and avoiding certain medications and situations whenever possible.