What is DRY EYE?
Dry eye is a condition in which a person does not have enough quality tears to lubricate and nourish the eye.Tears are necessary to maintain clarity of the cornea and nourishes the front surface of the eye to ensure clear vision.
Any anormaly in the integrity of the eyes tear film,the production or drainage can result in dry eye.This condition is often chronic and mostly affects the older adults.

The  lower and the upper eyelids mechanically spread over the ocular surface through neuronally controlled blinking mechanism to wet the corner and other ocular surfaces and exits through the nasolacrimal drainage system.then into the nose.
Tears provide lubrication,nourish ocular surface to reduce the risk of infections,wash away foreign substances that accidentally fall on the eye,keeps ocular surface smooth to allow clear vision.
What is the differences between dry eye and dry eye syndrome (keratoconjunctivitis sicca )
dry eye is the general condition in which a person does not have enough quality tear to lubricate and nourish the eye.
Dry eye syndrome (keratoconjunctivitis sicca) is when the water layer of the tear film is inadequate.this is the most common form of dry eye.

What Causes Dry Eye?
Dry eyes are part of the natural ageing process.Geriatric clinicians reports its normal for  90% of people older than 65 to experience  some symptoms of dry eye.
Women are more likely to experience dry eye/dry eye syndrome due to some hormonal changes during pregnancy, the use of oral contraceptives and menopause.
Certain meditations such as antihistamines,blood pressure medications,decongestants,and antidepressants can cause reduced tear production.
Medical conditions :
People with medical conditions such as primary Sjogren syndrome (xeropthalmia),secondary Sjogren syndrome such as rheumatoid arthritis,systemic lupus erythematosus,systemic sclerosis,dermatomyositis,thyroid disease and many more.
Conditions due lacrimal gland inflammation (blepharitis,thyroid eye disease and sarcoidosis )
Absence of lacrimal gland following surgical removal,obstruction of the pores of the lacrimal gland,neurological lesions (Riley-Day syndrome ) and the inward(entropion) or outwards ( ectropion) turning of the eye lids.
Environmental conditions 
Evaporative keratoconjunctivitis sicca (DES) is most common due to tear oil difficiency.the tear evaporates faster than normal in hot,dry,windy Environments and sometimes smoke exacerbates the symptoms.A prolonged staring on computer screen with reduced blinking can cause dry eye.
Others :
Long term contact lenses use,irregularities on the ocular surface due to trauma,and refractive surgeries such as LASIK can cause dry eyes.

Foreign body sensation
Eye irritation
Watery eyes
Burning sensation
Stringy mucus discharge
Transient blurring of vision
Surprisingly person rarely complain that their eyes are dry but watery.This sounds paradoxical!!.
REASONS why the eyes profusely tear/water in dry eye is because:The corner is the most sensitive tissue of the body (eye) with majority nerve endings.,therefore,As in dry eye condition,any small change in the tear film integrity that nourishes the cornea will physiologically trigger the brain to automatically trigger a reflex tearing mechanism to wash away and protect the cornea from drying (damage ).

Note: Dry eye predisposes the eye to bacterial keratitis/sterile ulceration which may lead to corneal perforation and later loss of vision.

The main aims of treatment of KCS are to relieve discomfort,provide smooth optical surface and prevent corneal damage.
1.Adding tears
A visit to your ophthalmologist /optometrist for comprehensive examination (tear break-up time,rose bengal test,Schirmer test ) for diagnosis on possible dry eye conditions may cause the need for tear substitutes.example;Eye Drops:
Hypromellose (tears naturale),cool eyes,polyvinyl alcohol(hypotears),sodium hyaluronate(VISMED).,sodium chloride (normosol) and Povidone(Oculet)
 Gels; Viscotears ,Gel tears and many more.   Ointment;lubritears,Lacrilube, only used at bedtime.
2.conserving tears
Room humidifiers,moist chamber googles,UV protective sunglasses,temporary occlusion of the puncta using collagen plugs into the Canaliculi and using Artificial tear supplements.
3.Increasing tear film production
Treatment of underlying anormalies that affects the lacrimal glands and it's adnexae (meibomiam gland topical application of tear supplements improves tear film production in quantity and quality.
4.A Small Lateral tarsorrhaphy :this dercreases the surface area of the interplpebral fissure allowing reduced air cornea contact thereby reducing tear evaporation
5.Other options:
Oral cholinergic agents like Pilcarpine (salagan ) are very effective in the relief of xerostomia and about 40% of patients also obtain relief. 
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