Dry eye has been observed to occur as consequence of disruption of lachrymal functional unit. This lachrymal functional unit consists of lachrymal glands, ocular surface including cornea, conjunctiva, eyelids, meibomian glands, ocular nerves, and goblet cells. There is what is called TEAR FILM; this  tear film is composed of three main layers.

The Innermost Mucin. 

The Middle Aqueous layer and

The Uppermost Lipid Layer. 

The innermost mucin or mucus layer is the thinnest, produced by cells of conjunctiva. The mucus helps the overlying watery layer to spread evenly over the eye. The mucous also reduces the surface tension between the lipid layer of the tear film and the water layer, thus contributing to the stability of the tear film. 

The middle or aqueous layer is the largest, thickest layer produced by the glands of upper lids and the accessory tear glands and contains essentially a very dilute saltwater solution. The aqueous layer keeps the eye moist and helps in the removal of any dust, debris, or foreign particles. Defects of the aqueous layer cause DRY EYES  in most cases. 

The uppermost layer of tear film is a very thin layer of lipids produced by the oil glands in the eyelids. This layer helps to decrease evaporation of the watery layer beneath it. The tear fluid also consists of complex mixture of proteins, immunoglobulins, mucins, electrolytes, cytokines, lysozymes, lactoferrin, and growth factors. Lysozyme may act synergistically with IgA in lysis of bacteria. Tears also contain lactoferrin, which has some antibacterial effect. 

Average glucose concentration of the tears is 2.5 mg/dL and average tear urea level is 0.04 mg/dL. Electrolytes such as K, Na, and Cl occur in higher concentration in the tears than in the blood. Osmolarity of tears is 309 mOsm/liter. Average pH of the tears is 7.25 and refractive index of the tear film is 1.336. The prevalence of dry eye syndrome increases with age.

Causes of Dry Eye Syndrome 

 Decreased tear production, excessive tear evaporation, and abnormality in the production of mucus or lipids of tear layer has been observed to be the main causes of Dry eye Syndrome. Tear deficient dry eye due to poor production of tears by the tear glands is found in older patients, in postmenopausal women, and in patients with autoimmune diseases like primary Sjögren’s syndrome and rheumatoid arthritis. 

Dysfunction of lacrimal functional unit causes changes in composition of the tear fluid and tear film stability. This leads to inflammation of ocular surface. Eye does not produce adequate tears as anti-inflammatory component of eye is lacking and irritation of eye is not controlled. This causes activation of inflammatory cells including T-lymphocytes by immune system of body. T-cells release cytokines which causes inflammation of ocular surface and glands, thereby resulting in abnormal tears and dry eye symptoms. An increase in osmolarity of the aqueous layer is suggested as a global feature of Dry Eye Syndrome and is known to trigger inflammation, damaging the ocular surface. 

Home Management 

The following remedies can always help you handle Dry eyes syndrome DES, cheaper and Temporary in most cases from the comfort of your home. They include but not limited to:

• Warm or code compress on the eye
• Wearing of sunglass
• Clean your eyes area with clean water. 
• Use a humidifier and 
• Always stay hydrated. 

Clinical Management

Most times, the goals of treatment is to relieve the symptoms of a disease or ailment. In the case of Dry Eyes, the treatment goes beyond that to improve the patient comfort, return the ocular surface and tear film to the normal state, and, whenever possible, prevent corneal damage. This treatment ranges from education, environmental or dietary modifications, artificial tear substitutes, punctal plugs, and topical and/or systemic anti-inflammatory medications to surgery in chronic cases.

Have you been diagnosed of Dry Eye Syndrome before? please kindly comment the symptoms you observed and the treatment practice that helped you out.