Focus on dry eye

Dry eye syndrome: what it is, who it affects and why

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Monday, 21 May 2018

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Dry Eye

The components of the ocular surface (cornea, conjunctiva, eyelids and tear film), together with the lacrimal glands, are essential for maintaining proper vision. When these components fail to preserve the integrity of the ocular surface, various problems can arise, including the dry eye syndrome (dry eye disease - DED). DED is a complex disease in which multiple risk factors such as genetic factors, age, gender, nutrition, environmental conditions, lifestyle, work characteristics, immune status, hormonal status and medications contribute to changes in the morphology and function of the ocular surface components we listed above.

Currently, two main types of DED have been identified, a clinical form resulting from the dysfunction of the lacrimal gland and is defined as 'reduced tear production'. and another defined "from evaporation"induced, instead, by a defect in the functioning of the Meibomian glands, the sebaceous glands present on the eyelids and responsible for producing the oily component of tears. Affected patients commonly manifest a mix of both types of DED, regardless of aetiology.

Indeed, while the poor quality and/or reduced flow of fluid from the Meibomian gland may cause a reduced production of the lipid layer of the tear film and thus an 'evaporative' dry eye, in parallel, a chronic 'reduced tear production' state may induce an increased presence of proinflammatory cytokines and cause damage to the ductal orifices of the Meibomian gland.

I symptoms most frequent of DED are dryness, burning, irritation and/or foreign body sensation usually accompanied by visual changes and general deterioration of quality of life.

Dry eye syndrome: does it affect women more and more severely?

For both ocular surface conditions that we have illustrated above, it is considered that the peri- and post-menopausal women are one of the categories most at risk.

This higher prevalence of the disease in this segment of the female population is probably due to Hormonal factors: hormones, and thus hormonal dysregulation during this period of life, play an important role in regulating the ocular surface and adnexa.

It would appear that both androgens and oestrogens have an effect on the components of the tear film. I sex hormone receptors are present on the meibomian glands: androgen binding would result in increased lipid secretion, while oestrogen would cause a decrease in lipid production.

For this reason, it is believed that increased levels of estradiol are a risk factor for the onset of dry eye syndrome. However, the exact relationship between serum levels of sex hormones and clinical symptoms of dry eye remains unclear and controversial.

Gender, however, also plays an important role on the symptoms of dry eye disease and their impact on vision quality. In fact, a recent study showed in a total of 755 patients that women, on average, scored higher on their symptoms and signs in most of the tests performed.

Sleep, depression and dry eye: related disorders in women?

Recent studies have reported that individuals with DED may suffer from depression more frequently than the healthy population, this problem would particularly affect peri-menopausal women who also have sleep disorders. During the peri-menopausal period, in fact, hormonal changes have marked effects on women's health, especially on the endocrine and circulatory systems, which is why hormone replacement therapy may be proposed for the treatment of disorders associated with the approach of the menopause, including DED.

Several studies also indicate that eye conditions can affect sleep by causing pain and discomfort, particularly in individuals with DED who also suffer from lagophthalmos night (i.e., incomplete closure of the eyelid rhyme). In turn, sleep deprivation may reduce tear secretion, leading to a vicious circle that needs to be addressed with the help of a specialist.

Possible role of omega-3 for the prevention of dry eye disease?

An increasing number of studies aim to investigate the effects of omega-3 fatty acid supplementation on the prevention of ocular surface disease. Although the mechanism has not been fully elucidated, some data have been produced supporting the mitigation of DED following omega-3 supplementation due to their anti-inflammatory properties. Indeed, a diet rich in polyunsaturated fatty acids could potentially improve meibum flow, decreasing its viscosity while reducing ductal obstruction, a key mechanism in the onset of dry eye syndrome.

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