Pathological classification
Divided into four categories:
(1) dry eye caused by lack of water sample;
(2) dry eye caused by mucin deficiency;
(3) dry eye caused by lipid deficiency;
(4) Dry eye caused by abnormal tear dynamics (distribution).
1995 classification proposed by American dry eye research group, ***2 categories:
(1) Partial deficiency of tear production: dry eye caused by lacrimal gland diseases or dysfunction, that is, the above ATD, can be further divided into dry eye and non-SS-ATD. SS, namely conjunctival Sjogren's syndrome, is a chronic autoimmune disease, which can be divided into primary disease and secondary disease. It is characterized by the infiltration of a large number of lymphocytes in lacrimal gland and the destruction of tear secretion function.
(2) Excessive evaporation type: dry eye caused by normal tear secretion and excessive evaporation. The classification of dry eye is not completely independent of each other. In fact, classification often exists at the same time, and rarely appears alone.
The cause of disease
Recently, it is considered that ocular surface changes, immune-based inflammatory response, apoptosis and changes in sex hormone levels are related factors for the occurrence and development of dry eye, but the relationship between these factors is still unclear. Etiology can be divided into the following four categories:
1. Lacrimal secretion of lacrimal gland in aqueous humor is insufficient.
Xerophthalmia
It is the most common cause of dry eye angle; Congenital absence of lacrimal gland, senile hypofunction of lacrimal gland or some autoimmune diseases cause lacrimal gland inflammation, trauma, infection and autonomic nerve disorder. Long-term use of some eye drops or taking some drugs will cause insufficient tear secretion. People who wear contact lenses for a long time.
2. Insufficient oil layer secretion
Dysfunction of meibomian gland caused by eyelid diseases.
3. Insufficient secretion of mucin layer
Vitamin A 1 deficiency, chronic conjunctivitis, chemical burns, etc.
4. Excessive evaporation of tears and uneven distribution of tear film.
Eyelid diseases lead to poor eyelid closure, reduced blinking times, and long-term stay in air-conditioned rooms or outdoor strong winds and hot environments.
clinical picture
Xerophthalmia
The most common symptoms of keratoconjunctivitis dryness are eye fatigue, foreign body sensation and dryness. Other symptoms include burning sensation, eye swelling, eye pain, photophobia and jealousy.
The signs of dry eye include vasodilation of bulbar conjunctiva, loss of luster of bulbar conjunctiva, thickening, edema, wrinkles, narrowing or interruption of lacrimal river, sometimes yellowish mucus secretion in the lower fornix, punctate shedding of corneal epithelium in the palpebral fissure area to varying degrees, and positive staining of 1% tiger red. Fluorescein staining of corneal epithelial defect area. Dry eye slightly affects vision in the early stage. After the disease develops, filamentous keratitis may appear and the symptoms may become unbearable. Corneal ulcer, corneal thinning, perforation and occasional secondary bacterial infection may occur in the late stage. After corneal scar formation, it seriously affects vision.
In addition to the above symptoms of dry eye, patients with meibomian gland dysfunction can also have meibomian gland cysts repeatedly, and the posterior lip of meibomian margin can have permanent vasodilation from back to front. The opening of meibomian gland is often blocked by white keratin and bulges and deforms. When the lesion progresses, the meibomian gland will have yellow mucus-like secretion. After repeated inflammation of meibomian gland, most glands atrophy, and no secretion overflows after extrusion. Meibomian gland atrophy can be observed by infrared photography.
Keratitis of palpebral fissure. The tear film rupture time of this disease is shortened, which can cause filamentous keratitis and keratoconjunctivitis xerosis, which is characterized by the decrease of tears at the eyelid margin. Schirmer's experiment shows that the decrease of tears is often a disease peculiar to the elderly, but most of them are common in some manifestations of Sjogren's syndrome in the eyes. Sjogren syndrome includes dry mouth, dry eyes and arthritis. It can also occur in many autoimmune diseases and systemic diseases, such as sarcoma and Waldenstroms macroglobulinemia. The treatment is to replace it with artificial tears. In severe cases, you can wear protective glasses or block the lacrimal punctum.
cause of a disease
Normally, there are two kinds of tears: basic and reflective. The basic components of tears include water, grease, protein, electrolyte, antibody, mucus and so on. Its function is to nourish the eyes and absorb oxygen from the atmosphere for the cornea. And make the eyeball surface smooth, so that light can enter the eye better. When the basic tears are insufficient or the ingredients are not good, it will cause dry eye.
There are many reasons for dry eye, some of which are congenital and lack of vitamins; It is more common to wear contact lenses for too long; There is also insufficient lacrimal gland secretion caused by inflammation or injury. Physical problems can also lead to dry eye, including thyroid diseases and immune system diseases, such as rheumatoid arthritis, Sjogren's syndrome, lupus erythematosus and so on. Others are also affected by drugs, such as some antihypertensive drugs, psychotropic drugs, birth control pills, and even some eye drops are improperly used.
Once the symptoms of dry eye are found, you should go to the hospital for treatment in time, find out the cause and prescribe the right medicine.