Dry eye: is it more severe in people suffering from depression?

Dry eye syndrome can be related to depression and other neurological disorders. In this article we elaborate on this specific aspect.

Introduction

La dry eye syndrome or DED (Dry Eye Disease) is a multifactorial disease characterised by altered tear production, which can affect both the quantity of tears produced and their composition.

It is one of the most common eye disorders and presents symptoms such as eye discomfort, pain, dryness, foreign body sensation, visual disturbances and tear film instability.

The discomfort caused by this disease negatively affects the quality of life, not only with regard to vision, but also because it affects the normal performance of daily activities in general.

Pathology

Dry eye syndrome or 'dry eye', referred to in medical parlance as 'dry keratoconjunctivitis', is a multifactorial condition that affects the tear film and ocular surface and results in symptoms of discomfort, visual disturbances, and tear film instability with potential damage to the ocular surface.

It is accompanied by an increase inosmolarity of the tear film and theinflammation of the ocular surface.

The tear film

The tear film is a film that covers the corneo-conjunctival surface and forms the interface between the eye and the external environment.

It consists of three layers, respectively: lipidic, aqueous and mucous.

The aqueous part of the tear film is the most abundant and contains electrolytes and numerous proteins, including lysozyme with antibacterial properties.

It is produced by the main and accessory lacrimal glands.

Functions

The tear film performs numerous functions:
- lubricates the eye, creating a smooth surface on the cornea on which the eyelids can slide easily.
- nourishes the cornea, which, being devoid of blood vessels (avascular), receives nutrients and oxygen precisely through the tear film.
- protects the eye from bacterial and viral infections and removes its waste substances

Dry eye types

Depending on the causes, two main forms of dry eye can be distinguished:

1) from hyposecretion

2) from evaporation.

Hyposecretion forms

Hyposecretion forms, in which there is a reduced functioning of the lacrimal glands, include forms related to autoimmune diseases, first and foremost Sjögren's syndrome.

Other autoimmune diseases include rheumatoid arthritis, systemic lupus erythematosus, polyarthritis nodosa, Wegener's granulomatosis, systemic sclerosis and other connective tissue diseases.

Then there are the hyposecretive 'non-Sjögren' forms of dry eye, the most important of which is age-related.

Evaporation forms

Dry eye due to excess evaporation can be classified according to the conditions that cause it, into 'intrinsic' (e.g. in the case of Meibomian gland dysfunction or eyelid and orbital abnormalities) and 'extrinsic' (due to contact lens wear or topical drugs with preservatives.

Among the forms of dry eye from excess evaporation are those related to eye diseases such as allergies and conjunctivitis and vitamin A deficiency.

Risk factors

The main risk factors can be summarised as follows:
1. Age: ageing causes progressive atrophy of the lacrimal glands.
2. Gender: women between 40 and 60 are more affected by dry eye, probably due to the new hormonal balance following the menopause.
3. Use of certain drugs: hormones, immunosuppressants, antihypertensives, antihistamines, antidepressants and others.
4. Climatic-environmental factors: air conditioning, dry climate, cigarette smoke, wind, smog.
5. Prolonged use of computers and television.
6. Nutritional deficiencies: insufficient vitamin A intake.
7. Use of contact lenses.

Contact lenses

It has been established that wearing all types of contact lenses results in alterations to the ocular surface and the tear film.

The magnitude of these effects varies depending on the lens material, the way it is worn and the characteristics of the wearer.

Silicone hydrogel lenses generally result in fewer harmful effects.

However, the risk of corneal infection and inflammation remains high, especially in the case of recurring night-time lens wear.

In the case of predominantly daytime use, damage to the ocular surface can also result from the use of certain solutions for daily lens cleaning, to which the eye can be or become particularly sensitive.

Oxidative stress

In recent years, dry eye, like other eye diseases such as glaucoma and keratoconus, has been associated with oxidative stress.

The surface of the eye is also particularly exposed to environmental agents (wind, temperature variations, ultraviolet radiation) and irritants that make it vulnerable to oxidative stress.

Mechanical factors such as contact lens wear or eye surgery can also be causes of oxidative stress on the ocular surface.

Symptoms

Patients with dry eye may present a wide variety of symptoms, such as burning, foreign body sensation, difficulty in opening the eyelids, especially upon waking, blurred vision, photophobia (discomfort from light), and pain (in severe cases).

These symptoms are often accompanied by clinical signs such as redness, mucous hypersecretion, and suffering of the corneo-conjunctival epithelium.

Diagnosis

Dry eye syndrome is a very common condition, the diagnosis of which can be made using numerous tests, some of which are used to diagnose qualitative changes in the tear film (such as the tear film rupture test), while others measure quantitative tear deficits (such as the Schirmer test).
There is also a test to diagnose dry eye by measuring tear osmolarity: an increase in this parameter indicates dry eye.

Treatment

Most forms of dry eye tend to become chronic and recurrent.

Therapy, therefore, must be aimed first and foremost at reducing or eliminating, where possible, the triggering factors of the condition and consequently reducing the discomfort that this condition causes in order to improve the patient's quality of life.

Symptomatic treatment is usually carried out by administering eye drops or gels whose composition is similar to tears, so-called 'artificial tears', with lubricating and moisturising properties.
Recently, the use of artificial tears that also have antioxidant properties is considered important.

Self-prescription of artificial tears is strongly discouraged, and an examination by an ophthalmologist is recommended for a precise diagnostic assessment and prescription of the most appropriate therapy.

In addition, the use of preservative-free artificial tears is preferable, as these could damage the already compromised ocular surface after prolonged use of products containing them.

Dry eye and psychiatric disorders

The association of dry eye syndrome with psychiatric disorders, such as anxiety and depression, has been the subject of numerous epidemiological studies that have attempted to find an explanation for the link between these disorders by examining the prevalence of mental disorders in patients with DED or vice versa.

It turns out that dry eye syndrome and depression are connected by a double thread, which, on the one hand, results in a higher incidence of DED in people suffering from depression, but, on the other hand, causes a higher incidence of depression in people suffering from DED.

The correlation between dry eye syndrome and depression

The studies observed that people with DED have a higher risk of experiencing psychological stress, severe anxiety and depression.

It has been suggested that a predisposition of DED patients to depression exists because symptoms, such as visual difficulties induced by tear film instability, pain and discomfort experienced, may in some way contribute to depressive moods.

Moreover, chronic discomfort and pain due to dry eye symptoms could negatively affect cognitive processes, sleep, mood and mental health. Thus, ocular surface symptoms could adversely affect the performance of daily activities, psychological and emotional well-being and the ability to work.

This, together with the possibility of visual perception disorders, which can be associated with DED, can induce the symptoms of depression or aggravate them if already present.

DED: is it more severe in people suffering from depression?

While DED also seems to underlie depressive disorder, other studies have indicated that patients with depression may experience dry eye syndrome more frequently. This seems to be due to more than one cause.

Possible causes

Some of the drugs prescribed for psychiatric conditions such as depression can worsen dry eyes. Indeed, antidepressants and anxiolytics are associated with DED because of their potential side effects on the state of the tear film.

Furthermore, somatisation is common in depression, and several studies have shown that this may influence the perception of ocular discomfort.

In fact, some research has suggested that people with depression and anxiety may suffer from central sensitisation, which affects pain perception.

In essence, people with these disorders may perceive the sensations of ocular discomfrot differently from healthy people and, conversely, the symptoms of DED may be influenced by their state of mind.

How is it possible to intervene?

Collaboration between ophthalmologists and psychiatrists in the treatment of people with dry eye syndrome can be very helpful.

In fact, therapeutic intervention for DED can help reduce the manifestations of depression, as well as provide appropriate therapy for dry eye symptoms, as these are closely linked to mood and interfere with people's quality of life.

Furthermore, given the link between DED and depression, there is a need to look for new ways to optimise the psychological/psychiatric treatment of patients with ophthalmic diseases, in order to act not only on symptom relief, but also on improving quality of life.

Finally, as far as possible future developments are concerned, studies have suggested that psychological and physical stress may cause a decrease in tear secretion.

Further studies will be useful to evaluate this association and also to understand how the environment, with its cognitive, sensory and social stimuli, may influence eye health and the onset of dry eye syndrome.

1. Galor A. How Depression Might Relate to Dry Eye Disease. JAMA Ophthalmol. 2022 Mar 10. doi: 10.1001/jamaophthalmol.2022.0146. Epub ahead of print. PMID: 35266991.
2. Vieira GCF, Rodrigues BRO, Cunha CEXD, Morais GB, Ferreira LHRM, Ribeiro MVMR. Depression and dry eye: a narrative review. Rev Assoc Med Bras. 2021 Mar;67(3):462-467. 
3. Wan KH, Chen LJ, Young AL. Depression and anxiety in dry eye disease: a systematic review and meta-analysis. Eye (Lond). 2016 Dec;30(12):1558-1567.