Keratoconjunctivitis sicca (KCS), also called keratitis sicca,[1] sicca syndrome,[1] xerophthalmia,[1] dry eye syndrome (DES),[1] or simply dry eyes,[1] is an eye disease caused by decreased tear production or increased tear film evaporation commonly found in humans and some animals[2]. Keratoconjunctivitis sicca is Latin and its literal translation is “dryness of the cornea and conjunctiva”. It may be helpful to know that “sicca” is part of the English word “desiccate.”

Typical symptoms of keratoconjunctivitis are dryness, burning[3] and a sandy-gritty eye irritation that gets worse as the day goes on.[1] Symptoms may also be described as itchy,[3] scratchy,[4] stingy[3] or tired[3] eyes. Other symptoms are pain,[5] redness,[5] a pulling sensation,[3] and pressure behind the eye[3]. There may be a feeling that something,[3] such as a speck of dirt,[5] is in the eye. The resultant damage to the eye surface increases discomfort and sensitivity to bright light.[3] Both eyes usually are affected.[6]

There may also be a stringy discharge from the eyes.[5] Although it may seem strange, dry eye can cause the eyes to water.[5] This can happen because the eyes are irritated.[5] One may experience excessive tearing in the same way as one would if something got into the eye.[5] These reflex tears will not necessarily make the eyes feel better.[5] This is because they are the watery type that are produced in response to injury, irritation, or emotion.[5] They do not have the lubricating qualities necessary to prevent dry eye.[5]

Because blinking coats the eye with tears,[5] symptoms are worsened by activities in which the rate of blinking is reduced due to prolonged use of the eyes[3]. These activities include prolonged reading,[1] computer usage,[1][5][3] driving,[3] or watching television[5][3]. Symptoms increase in windy,[5] dusty[5][3] or smoky (including cigarette smoke[5]) areas,[1][3] in dry environments[1][3], high altitudes including airplanes,[6] on days with low humidity,[3] and in areas where an air conditioner[5] (especially in a car[3]), fan,[3] heater,[3] or even a hair dryer[5] is being used. Symptoms reduce during cool, rainy, or foggy weather and in humid places, such as in the shower.[3]

Most people who have dry eyes experience mild irritation with no long-term effects.[5] However, if the condition is left untreated or becomes severe, it can produce complications that can cause eye damage,[5] resulting in impaired vision or (rarely[3]) in the loss of vision[5].

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 dry eye diagnosis. McMonnies & Ho dry eye questionnaire is the one that is often used in clinical studies of dry eyes. There are 14 questions that can give a score from 0 to 45. Scores above 14.5 are consistent with dry eye diagnosis.