Dry eye disease (also known as keratoconjunctivitis sicca) is a multifactorial disease of the tear film and ocular surface. It results in various symptoms of discomfort such as pain, tearing, fatigue, and headache. Visual function can also deteriorate, and quality of life is negatively affected. Tear film instability which may lead to damage to the ocular surface with an inflammatory reaction is key to the pathogenesis of dry eye disease. This review discussed the classification, pathogenesis, diagnostic approaches, and treatment options of dry eye disease.
Dry Eye Syndromes ; Fatigue ; Headache ; Inflammation ; Keratoconjunctivitis Sicca ; Quality of Life ; Tears

Allergic conjunctivitis is characterized by specific immunologic responses known as type 1 hypersensitivity, resulting in corneal and conjunctival inflammation. Histamine plays an important role in the pathophysiologic mechanism of allergic conjunctivitis. Five subtypes of allergic conjunctivitis have been defined according to specific signs and symptoms: seasonal allergic conjunctivitis, perennial allergic conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis and giant papillary conjunctivitis. Above all, avoidance of the offending antigen is the primary behavioral modification used to treat all types of allergic conjunctivitis. However, this may be difficult for practical reasons; therefore, a range of medical treatment options, such as topical antihistamines, mast cell stabilizers, non-steroidal anti-inflammatory drugs, and corticosteroids are prescribed in clinical practice.
Adrenal Cortex Hormones ; Conjunctivitis, Allergic* ; Histamine ; Histamine Antagonists ; Hypersensitivity ; Inflammation ; Keratoconjunctivitis ; Mast Cells ; Seasons

Purpose: In the present study, we determined the prevalence of obstructive meibomian gland dysfunction (MGD), hyposecretory MGD, grossly normal MG, and hypersecretory MGD in patients with dry eye syndrome using lipid layer thickness (LLT) and MG dropout. Methods: Eighty-eight patients with dry eye syndrome were included in the study. Patients were categorized into four groups according to the LLT and weighted total meiboscore. The proportion of patients in each group was calculated. The age, sex, Ocular Surface Disease Index, LLT, Schirmer, tear film breakup time, cornea stain, weighted total meiboscore, expressibility, and quality of meibum were compared between the four groups. Results: Fifteen eyes (17.0%) had obstructive MGD, two eyes (2.3%) had hyposecretory MGD, 40 eyes (45.5%) had grossly normal MG, and 17 eyes (19.3%) had hypersecretory MGD. The obstructive MGD group was younger than the grossly normal MG group. In obstructive MGD, the ratio of men to women was higher than that of the other groups. However, Ocular Surface Disease Index, Schirmer, tear film breakup time, and corneal stain did not show statistically significant differences between the four groups. The meibum expressibility of the hyposecretoy MGD group was worse than those of the other groups. The meibum expressibility of the hyposecretoy MGD group was poor than those of the obstructive and hypersecretory MGD group. Conclusions This categorization was expected to help determine the best treatment method for dry eye syndrome, according to the MG status.