Allergic conjunctivitis

Introduction to allergic conjunctivitis Allergic conjunctivitis (allergic conjunctivitis) is a hypersensitivity reaction of the conjunctiva to external allergens. It mainly includes type I allergic reaction (body fluid mediated) and IV allergic reaction (cell mediated), in which type I metamorphosis Allergic conjunctivitis caused by the reaction is most common. basic knowledge The proportion of illness: 0.001% Susceptible people: no specific people Mode of infection: non-infectious Complications: ball adhesion

The cause of allergic conjunctivitis

(1) Causes of the disease

Both seasonal and perennial allergens can trigger allergic immune responses, including seasonal pollen (early spring), grass (May-July), weed pollen (8-October) and Outdoor fungi (such as Phytophthora and Phytophthora), all year rounds of the original dust mites, indoor fungus and animal dander (mostly cats and dogs).

(two) pathogenesis

Allergic conjunctivitis is mainly caused by IgE-mediated type I allergic reaction. When the antigen is in contact with the body, it can bind to the sensitized mast cells and eosinophil surface-specific antigen IgE, causing degranulation of mast cells. On the one hand, the release of mediators such as histamine and kininase in the granules can immediately lead to hypersensitivity reactions, which are the early phases of hypersensitivity reactions, usually occurring after a few seconds of exposure to the antigen, for several 10 minutes to several hours. On the other hand, it can also promote the synthesis of some new media, such as leukotrienes (via the lipoxygenase pathway), prostaglandin D2 (via the cyclooxygenase pathway) and platelet activating factor, etc. Acidic granulocytes can also release histamine, platelet activating factor and other mediators, leading to the occurrence of late phase hypersensitivity reactions, usually occurring after 6 to 12 hours of antigen stimulation, reaching a peak at 48 to 72 hours, which lasts for several days, in allergic rhinitis and Allergic dermatitis, early phase reaction and late phase reaction often have a significant time interval, while in allergic conjunctivitis it usually appears as a continuous process throughout the hypersensitivity process Histamine plays a very important role. According to statistics, more than half of the symptoms and signs of allergic conjunctivitis are related to histamine release. For some severe cases of spring keratoconjunctivitis and atopic keratoconjunctivitis, there are usually T. Participation of lymphocyte-mediated IV allergy.

Allergic conjunctivitis prevention

Look for allergens and avoid contact with allergens.

Allergic conjunctivitis complications Complications

Common corneal damage is diffuse shallow punctate keratitis. In some patients, corneal ulcers and corneal leukoplakia, conjunctival fibrosis and sputum adhesion can also be seen.

Allergic conjunctivitis symptoms Common symptoms Eye swelling, hair dry photophobia, conjunctival nipple hyperplasia, conjunctival hyperemia

The most common symptom of allergic conjunctivitis is itchy eyes. Almost all patients with allergic conjunctivitis can appear, but itching is not a unique symptom. Different subtypes of allergic conjunctivitis have different degrees of itching, including spring keratoconjunctiva. Inflammation usually shows the most obvious symptoms. Other common symptoms include tearing, burning sensation, photophobia and increased secretion. The secretions are mostly mucoid, sticky and silky, and some severe allergic conjunctivitis, such as spring horns. Conjunctivitis and ectopic keratoconjunctivitis can sometimes cause decreased vision.

The most common sign of allergic conjunctivitis is conjunctival hyperemia. The degree of congestion is related to the severity of the disease and the length of the disease. Conjunctival papillary hyperplasia is another common sign. The nipple is more common in the upper conjunctiva, giant papillary conjunctivitis. The nipples with hyperplasia of keratoconjunctivitis in spring have their specific morphological features. Conjunctival fibrosis (scarring) changes often occur in atopic keratoconjunctivitis. Conjunctival edema can also occur in the onset of seasonal allergic conjunctivitis. It is especially common in children. Corneal damage occurs in different subtypes of allergic conjunctivitis. Spring keratoconjunctivitis and atopic keratoconjunctivitis are the most common, while seasonal allergic conjunctivitis, perennial allergic conjunctivitis and giant papillary Conjunctivitis is less common.

Many allergic conjunctivitis lacks characteristic symptoms and signs. You need to carefully ask about the history of the disease, such as family and personal allergy history, medication history, contact lens wear history, the season of onset, the time and speed of onset, the length of the disease, etc. At the same time, closely combined with its clinical performance, if necessary, supplemented by laboratory tests.

Examination of allergic conjunctivitis

1. Conjunctival secretion smear and conjunctival smear examination in seasonal allergic conjunctivitis, perennial allergic conjunctivitis and spring keratoconjunctivitis, about half of patients can find degenerative epithelial cells and eosinophils in the giant nipple The positive rate of conjunctivitis and atopic keratoconjunctivitis is very low.

2. Quantitative analysis of IgE in tears IgE quantitative analysis by extracting tears from the lower iliac crest by acetic acid nitrocellulose membrane paper is a semi-quantitative method. The method is simple, but its sensitivity and specificity are not high, IgE in tears. There is a certain degree of support for the diagnosis of allergic conjunctivitis, but the lack of IgE can not rule out the diagnosis.

3. Skin test and conjunctival allergen challenge test can be used for the diagnosis of allergic diseases, the search for allergens, the observation of clinical manifestations caused by allergens and the evaluation of the effects of anti-allergy treatment, often used before desensitization treatment The test identifies allergens. This test is mostly used for seasonal and perennial allergic conjunctivitis, but the positive rate is not high, and attention should be paid to the occurrence of false positives.

4. Imprinted cell examination This is a non-invasive examination. After topical anesthesia, a cell membrane or a nitrocellulose membrane is applied to the surface of the conjunctiva to obtain cells, followed by cell morphology and some cytokines or Detection of inflammation-related factors, an increase in degenerative epithelial cells and eosinophils is often found in patients with allergic conjunctivitis.

5. Conjunctival biopsy conjunctival biopsy is only used if other methods cannot be diagnosed. It is mainly used for the diagnosis of suspected AKC patients.

6. Conjunctival scraping in allergic conjunctivitis, the incidence of eosinophils in conjunctival scrapings is 20% to 80%, Abelson et al found that about 45% of conjunctival scrapings in patients with hay fever conjunctivitis Eosinophils, this difference may be due to differences in the level and depth of the material taken during the scraping or biopsy. Eosinophils may be located deeper in the level of the conjunctival scraping. Therefore, the eosinophil negative in the scraping test cannot Exclude the diagnosis of allergic conjunctivitis.

7. The skin test has certain diagnostic value for confirming whether it responds to a suspected allergen. It can be tested on the surface of the skin and, if necessary, an intradermal test. The allergens to be tested usually include: trees, grasses. , pollen, alfalfa and animal dander, may have different specific antigens in different regions, so there may be some differences in the allergens used in the trials across the region, in addition to allergens, a positive control should be established [Histamine and/or codeine phosphate] and a negative control (saline), the skin IgE-mediated response is a dermal reaction characterized by a wheeze response, which depends on the degranulation of mast cells after exposure to antigen. The advantages of the above skin tests are simplicity, low cost and high sensitivity.

8. Radioactive allergen adsorption test (radiarergasorbent test (RAST) is one of the in vitro methods for determining the specific IgE level of a specific allergen in vitro. The allergen is covalently bound to the cellulose disk, and the test antibody IgE is added. The cellulose disk is conjugated to the allergen, then the unbound radiolabeled antibody is washed, and the radioactivity of the cellulose disk is determined using a gamma counter. Since the sensitivity of RAST is lower than the skin test and is more expensive, only when This method or other in vitro assays are used in skin tests, such as patients with severe rashes and inability to discontinue antihistamines.

9. Tryptase detection using sensitive immunoassay, the level of tear tryptase can be detected in allergic conjunctivitis, because tryptase is released from mast cells, so the increase is limited to early response, assay class Trypsin levels are of value in assessing the therapeutic effects of mast cell stabilizers.

Diagnosis and identification of allergic conjunctivitis

Seasonal conjunctivitis has its special history and clinical manifestations. The diagnosis is not difficult. For some atypical cases, the pathological biopsy of the conjunctiva or the conjunctival scraping can be done for cytology. In most cases, more eosinophils are common in the attack period. Cells, or eosinophilic particles left behind due to the disappearance of eosinophils and disintegration of the nucleus, are also diagnostic (Fig. 1B). In addition, the IgE content of serum or tears can be measured, which not only assists in diagnosis, but also As an indicator of the course of the disease.

Differential diagnosis

1. Dry eye syndrome Allergic conjunctivitis is particularly difficult to distinguish from dry eye syndrome, because both diseases have intermittent aggravation of mild conjunctival vasodilation and burning sensation, rarely in the symptoms of allergic eye disease Foreign body sensation, but common in dry eye syndrome, dry eye patients have a tendency to develop allergic conjunctivitis, because the dilution of tears on the surface of the conjunctiva and the ability to wash allergens have been destroyed, orbital inflammation, seesaw Gland enlargement and blepharitis may be associated with staphylococcal infection and/or seborrhea, burning symptoms associated with eyelid inflammation, erythema of the eyelids, conjunctival congestion, foamy tear film, eyelids and rim margins Wait.

2. Infectious conjunctivitis has no seasonality. It is heavier when waking up. When getting up in the morning, eyelashes and eyelids often stick together. The secretions are serous and purulent. The pathogens include Neisseria gonorrhoeae and meninges. Neisseria gonorrhoeae, Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus, Moraxella, Chlamydia and virus, conjunctival scrapings show that basophilic inclusion bodies in epithelial cells are characteristic of Chlamydia infection, on the contrary, allergic Conjunctivitis is usually seasonal, and the secretions are mostly sticky or viscous, and the bacterial culture is negative.

3. Spring keratoconjunctivitis is a disease that occurs in a small age group (8-20 years old). It is mainly characterized by severe itching, burning sensation and sticky secretions. There are huge nipples and paving stone nipples in the upper conjunctiva. It may involve the cornea, but shield ulcers are not common.

4. Atopic keratoconjunctivitis can occur in all age groups, often accompanied by serious complications. Clinical signs and symptoms are chronic exudative conjunctivitis with severe itching and burning sensation. Clinical examination revealed: Thick, corneal lesions (including vasospasm, keratitis and ulcers) and chronic red eyes, often accompanied by keratoconus, subcapsular and polar cataracts, as well as susceptible to staphylococcal and herpes simplex virus infections, accompanied by atopic dermatitis, especially It is inflammation of the eyelids and eye appendages.

5. Giant papillary conjunctivitis occurs in people wearing contact lenses or prosthetic eyes. The exposed suture can also induce the disease. Flip the upper eyelid to show the huge follicle corresponding to the contact lens, prosthetic or suture position. Symptoms include congestion, burning sensation, itching and sticky secretions.

6. Contact allergic conjunctivitis The acute phase of contact allergic conjunctivitis is characterized by erythema, conjunctival edema, orbital induration and edema, which is a type IV cell-mediated delayed type hypersensitivity reaction in the chronic phase. For the shelling and lichenization of the eyelids, the affected area is mostly in contact with toxic substances. Sensitization of beauty articles or ophthalmic drugs is a common cause of illness, such as topical neomycin, atropine and preservatives. In some cases, complications such as epithelial defects, corneal opacity and keratitis occur.

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