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, resulting in impaired vision or (rarely) in the loss of vision.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. 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.
Medical uses
Norethisterone is used as a hormonal contraceptive in combination with an estrogen – usually ethinylestradiol (EE) – in combined oral contraceptive pills and alone in progestogen-only pills. Another medical use of norethisterone is to alleviate endometriosis related pain. In fact, 50% of patients who received medical or surgical treatment for endometriosis-related pelvic pain have benefited from progestin therapy. This could be due to the fact that norethisterone induces endometrial proliferation during secretory phase, which has been shown to alleviate endometrial pain complaints. Another way in which norethisterone may be acting to reduce endometrial pain is via inhibition of ovulation. Endometriosis pain and discomfort is worse during ovulation. Contraindications
High-dose (10 mg/day) norethisterone has been associated with hepatic veno-occlusive disease, and because of this adverse effect, norethisterone should not be given to patients undergoing allogeneic bone marrow transplantation, as it has been associated with substantially lower one-year survival post-transplantation. : 217

Side effects
At contraceptive and hormone replacement dosages (0.35 to 1 mg/day), norethisterone has essentially progestogenic side effects only. In most clinical studies of norethisterone for contraception or menopausal hormone therapy, the drug has been combined with an estrogen, and for this reason, it is difficult to determine which of the side effects were caused by norethisterone and which of them were caused by estrogen in such research. However, NETE, an intramuscularly administered prodrug of norethisterone which is used as a long-acting contraceptive, is used without an estrogen, and hence can be employed as a surrogate for norethisterone in terms of understanding its effects and tolerability.