dry eye syndrome dry eye syndrome dry eye syndrome, also known as keratoconjunctivitis sicca, is the condition of having dry eyes. symptoms include dryness in the eye, irritation, redness, discharge, blurred vision, and easily fatigued eyes. symptoms range from mild and occasional to severe and continuous. dry eye syndrome can lead to blurred vision, instability of the tear film, increased risk of damage to the ocular surface such as scaring of the cornea, and changes in the eye including the neurosensory system. dry eye syndromeother namesdry eye, keratoconjunctivitis sicca, dry eye disease (ded), keratitis siccadiffuse lissamine green staining in a person with severe dry eye.specialtyophthalmology, optometrysymptomsdry eyes, irritation, redness, discharge, blurred visioncomplicationscorneal scarringcausescontact lenses, meibomian gland dysfunction, pregnancy, sjögren syndrome, vitamin a deficiency, lasik surgery, antihistamines, hormone replacement therapy, antidepressantstreatmentartificial tears, wrap around glasses, changing certain medicationsmedicationciclosporin, steroid eye dropsfrequency~20% dry eye occurs when either the eye does not produce enough tears or when the tears evaporate too quickly. this can be caused by age, contact lens use, meibomian gland dysfunction, pregnancy, sjögren syndrome, vitamin a deficiency, omega-3 fatty acid deficiency, lasik surgery, and certain medications such as antihistamines, some blood pressure medication, hormone replacement therapy, and antidepressants. chronic conjunctivitis such as from tobacco smoke exposure or infection may also lead to the condition. diagnosis is mostly based on the symptoms, though a number of other tests may be used. dry eye syndrome occasionally makes wearing contact lenses impossible. treatment depends on the underlying cause. artificial tears are usually the first line of treatment. wrap-around glasses that fit close to the face may decrease tear evaporation. looking carefully at the medications a person is taking and, if safe, altering the medications may also improve symptoms if these medications are the cause. some topical medications may be suggested to help treat the condition. the immunosuppressant cyclosporine (ciclosporin) may be recommended to increase tear production and, for short term use, topical corticosteroid medications are also sometimes helpful to reduce inflammation. another treatment that is sometimes suggested is lacrimal plugs that prevent tears from draining from the surface of the eye. dry eye syndrome is a common eye disease. it affects 5–34% of people to some degree depending on the population looked at. among older people it affects up to 70%. in china it affects about 17% of people. the phrase "keratoconjunctivitis sicca" means "dryness of the cornea and conjunctiva" in latin signs and symptoms typical symptoms of dry eye syndrome are dryness, burning and a sandy-gritty eye irritation that gets worse as the day goes on. symptoms may also be described as itchy, stinging or tired eyes. other symptoms are pain, redness, a pulling sensation, and pressure behind the eye. there may be a feeling that something, such as a speck of dirt, is in the eye. the resultant damage to the eye's surface increases discomfort and sensitivity to bright light. both eyes usually are affected. there may also be a stringy discharge from the eyes. although it may seem contradictory, dry eye can cause the eyes to water due to irritation. one may experience excessive tearing such as if something got into the eye. these reflex tears will not necessarily make the eyes feel better since they are the watery tears that are produced in response to injury, irritation, or emotion which lack the lubricating qualities necessary to prevent dry eye. because blinking coats the eye with tears, symptoms are worsened by activities in which the rate of blinking is reduced due to prolonged use of the eyes. these activities include prolonged reading, computer usage (computer vision syndrome), driving, or watching television. symptoms increase in windy, dusty or smoky (including cigarette smoke) areas, in dry environments high altitudes including airplanes, on days with low humidity, and in areas where an air conditioner (especially in a car), fan, heater, or even a hair dryer is being used. symptoms reduce during cool, rainy, or foggy weather and in humid places, such as in the shower. most people who have dry eyes experience mild irritation with no long-term effects. however, if the condition is left untreated or becomes severe, it can produce complications that can cause eye damage, instability of the tear film, neurosensory changes, impaired vision, or (rarely) in the loss of vision. causes any abnormality of any one of the three layers of tears produces an unstable tear film, resulting in symptoms of dry eyes. increased evaporation the most common cause of dry eye is increased evaporation of the tear film, typically as a result of meibomian gland dysfunction. the meibomian glands are two sets of oil glands that line the upper and lower eyelids and secrete the oily outer layer of the tear film—the lipid layer. these glands often become clogged due to inflammation caused by blepharitis and/or rosacea, preventing an even distribution of oil. the result is an unstable lipid layer that leads to increased evaporation of the tear film. in severe cases of mgd, the meibomiam glands can atrophy and cease producing oil entirely. low humidity low humidity may cause dry eye syndrome. decreased tear production keratoconjunctivitis sicca can be caused by inadequate tear production from lacrimal hyposecretion. the aqueous tear layer is affected, resulting in aqueous tear deficiency (atd). the lacrimal gland does not produce sufficient tears to keep the entire conjunctiva and cornea covered by a complete layer. this usually occurs in people who are otherwise healthy. increased age is associated with decreased tearing. this is the most common type found in postmenopausal women. in many cases, aqueous deficient dry eye may have no apparent cause (idiopathic). other causes include congenital alacrima, xerophthalmia, lacrimal gland ablation, and sensory denervation. in rare cases, it may be a symptom of collagen vascular diseases, including relapsing polychondritis, rheumatoid arthritis, granulomatosis with polyangiitis, and systemic lupus erythematosus. sjögren syndrome and other autoimmune diseases are associated with aqueous tear deficiency. drugs such as isotretinoin, sedatives, diuretics, tricyclic antidepressants, antihypertensives, oral contraceptives, antihistamines, nasal decongestants, beta-blockers, phenothiazines, atropine, and pain relieving opiates such as morphine can cause or worsen this condition. infiltration of the lacrimal glands by sarcoidosis or tumors, or postradiation fibrosis of the lacrimal glands can also cause this condition. recent attention has been paid to the composition of tears in normal or dry eye individuals. only a small fraction of the estimated 1543 proteins in tears are differentially deficient or upregulated in dry eye, one of which is lacritin. topical lacritin promotes tearing in rabbit preclinical studies. also, topical treatment of eyes of dry eye mice (aire knockout mouse model of dry eye) restored tearing, and suppressed both corneal staining and the size of inflammatory foci in lacrimal glands. additional causes excess screen time on computers, smartphones, tablets, or other digital devices can cause dry eye. "humans normally blink about 15 times in one minute. however, studies show that we only blink about 5 to 7 times in a minute while using computers and other digital screen devices. blinking is the eye’s way of getting the moisture it needs on its surface." aging is one of the most common causes of dry eyes because tear production decreases with age. several classes of medications (both prescription and otc) have been hypothesized as a major cause of dry eye, especially in the elderly. particularly, anticholinergic medications that also cause dry mouth are believed to promote dry eye. dry eye may also be caused by thermal or chemical burns, or (in epidemic cases) by adenoviruses. a number of studies have found that people with diabetes have an increased risk for the condition. about half of all people who wear contact lenses complain of dry eyes. there are two potential connections between contact usage and dry eye. traditionally, it was believed that soft contact lenses, which float on the tear film that covers the cornea, absorb the tears in the eyes. the connection between a loss in nerve sensitivity and tear production is also the subject of current research. dry eye also occurs or becomes worse after lasik and other refractive surgeries, in which the corneal nerves which stimulate tear secretion are cut during the creation of a corneal flap. dry eye caused by these procedures usually resolves after several months, but it can be permanent. persons who are thinking about refractive surgery should consider this. an eye injury or other problem with the eyes or eyelids, such as bulging eyes or a drooping eyelid can cause keratoconjunctivitis sicca. disorders of the eyelid can impair the complex blinking motion required to spread tears. abnormalities of the mucin tear layer caused by vitamin a deficiency, trachoma, diphtheric keratoconjunctivitis, mucocutaneous disorders, and certain topical medications are also causes of keratoconjunctivitis sicca. persons with keratoconjunctivitis sicca have elevated levels of tear nerve growth factor (ngf). it is possible that this eye's surface ngf plays an important role in ocular surface inflammation associated with dry eyes. pathophysiology having dry eyes for a while can lead to tiny abrasions on the surface of the eyes. in advanced cases, the epithelium undergoes pathologic changes, namely squamous metaplasia and loss of goblet cells. some severe cases result in thickening of the corneal surface, corneal erosion, punctate keratopathy, epithelial defects, corneal ulceration (sterile and infected), corneal neovascularization, corneal scarring, corneal thinning, and even corneal perforation. another contributing factor may be lacritin monomer deficiency. lacritin monomer, active form of lacritin, is selectively decreased in aqueous deficient dry eye, sjögren syndrome dry eye, contact lens-related dry eye and in blepharitis. diagnosis symptom assessment is a key component of dry eye diagnosis – to the extent that many believe dry eye syndrome to be a symptom-based disease. several questionnaires have been developed to determine a score that would allow for a diagnosis. the mcmonnies & ho dry eye questionnaire is often used in clinical studies of dry eyes. some tests allow patients to be classified into one of two categories, “aqueous-deficient” or “hyperevaporative.” diagnostic guidelines were published in 2007 by the dry eye workshop. a slit lamp examination can be performed to diagnose dry eyes and to document any damage to the eye. when realizing this test, the practitioner is testing the eyelid margin. a schirmer's test can measure the amount of moisture bathing the eye. this test is useful for determining the severity of the condition. a five-minute schirmer's test with and without anesthesia using a whatman #41 filter paper 5 mm wide by 35 mm long is performed. for this test, wetting under 5 mm with or without anesthesia is considered diagnostic for dry eyes. if the results for the schirmer's test are abnormal, a schirmer ii test can be performed to measure reflex secretion. in this test, the nasal mucosa is irritated with a cotton-tipped applicator, after which tear production is measured with a whatman #41 filter paper. for this test, wetting under 15 mm after five minutes is considered abnormal. a tear breakup time (tbut) test measures the time it takes for tears to break up in the eye. the tear breakup time can be determined after placing a drop of fluorescein in the cul-de-sac. a tear protein analysis test measures the lysozyme contained within tears. in tears, lysozyme accounts for approximately 20 to 40 percent of total protein content. a lactoferrin analysis test provides good correlation with other tests. the presence of the recently described molecule ap4a, naturally occurring in tears, is abnormally high in different states of ocular dryness. this molecule can be quantified biochemically simply by taking a tear sample with a plain schirmer test. utilizing this technique it is possible to determine the concentrations of ap4a in the tears of patients and in such way diagnose objectively if the samples are indicative of dry eye. the tear osmolarity test has been proposed as a test for dry eye disease. tear osmolarity may be a more sensitive method of diagnosing and grading the severity of dry eye compared to corneal and conjunctival staining, tear break-up time, schirmer test, and meibomian gland grading. others have recently questioned the utility of tear osmolarity in monitoring dry eye treatment. prevention avoiding refractive surgery (lasik & prk), limiting contact lens use, limiting computer screen use, avoiding environmental conditions can decrease symptoms. complications can be prevented by use of wetting and lubricating drops and ointments. treatment a variety of approaches can