Allergic conjunctivitis, also known as allergic conjunctivitis, is a hypersensitivity reaction of the conjunctiva to external allergens. It mainly includes type I allergic reaction and type IV allergic reaction, among which type I allergic conjunctivitis is the most common. Type I allergic conjunctivitis is rapid and mainly refers to allergic conjunctivitis including seasonal allergic conjunctivitis, perennial allergic conjunctivitis, giant papillary conjunctivitis, springtime keratoconjunctivitis, ectopic keratoconjunctivitis, etc.; Type IV allergic conjunctivitis is delayed and mainly includes vesicular conjunctivitis.
Etiology
Both seasonal and perennial allergens can trigger allergic immune responses. Seasonal allergens include: tree pollen, grasses, weed pollen and outdoor fungi. Perennial allergens include dust mites, indoor fungi, and animal dander (mostly cats and dogs).
Clinical presentation
The most common symptom of allergic conjunctivitis is itchy eyes, which can occur in almost all patients with allergic conjunctivitis, with springtime keratoconjunctivitis usually being the most pronounced. Other symptoms include tearing, burning sensation, photophobia and increased secretions. The secretions are mostly mucus-based. Some of the more severe forms of allergic conjunctivitis, such as springtime keratoconjunctivitis and atopic keratoconjunctivitis, can sometimes present with vision loss.
The most common sign of allergic conjunctivitis is conjunctival congestion. Conjunctival papillomegaly is another common sign, with papillae mostly found on the upper lid conjunctiva. Macropapillary conjunctivitis and springtime keratoconjunctivitis have specific morphologic features of the hyperplastic papillae. Ectopic keratoconjunctivitis often presents with conjunctival fibrosis (scarring) changes. Conjunctival edema may also occur during episodes of seasonal allergic conjunctivitis and is particularly common in children. Corneal damage is most common in springtime keratoconjunctivitis and atopic keratoconjunctivitis.
Examination
1. Conjunctival secretion smear and conjunctival scraping examination
In seasonal allergic conjunctivitis, perennial allergic conjunctivitis and spring keratoconjunctivitis about half of the patients can find degenerated epithelial cells and eosinophils, while in giant papillary conjunctivitis and ectopic keratoconjunctivitis the positive rate is very low.
2.Quantitative analysis of IgE in tears
The quantification of IgE by aspiration of tear fluid from the inferior vault through nitrocellulose acetate filter paper is a semi-quantitative method. This method is simple to operate, but its sensitivity and specificity are not high. The presence of IgE in tears supports the diagnosis of allergic conjunctivitis to some extent, but IgE deficiency does not exclude the diagnosis.
3. Skin test and conjunctival allergen provocation test
It 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 effect of anti-allergic treatment, and this test is often used to clarify allergens before desensitization treatment. 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.Blot cell test
This is a non-invasive test. Patients with allergic conjunctivitis are often found to have an increase in degenerated epithelial cells and eosinophils.
5. Conjunctival biopsy
Conjunctival biopsy is used only when other methods fail to confirm the diagnosis and is mainly used for the diagnosis of patients with suspected atopic keratitis (AKC).
6.Conjunctival scraping
In allergic conjunctivitis, eosinophils are present in 20% to 80% of conjunctival scrapings. A negative eosinophil scraping test does not exclude the diagnosis of allergic conjunctivitis.
7. Skin tests
It is of diagnostic value to confirm whether a reaction to a suspected allergen has occurred. The test can be performed on the surface of the skin and, if necessary, intradermal testing. Usually the allergens to be tested include: tree grass, pollen mites and animal dander.
8.Radioallergen adsorption test (RAST)
The RAST is less sensitive than the skin test and more expensive, so it should only be used when skin testing is not possible or other in vitro methods, such as the presence of severe rash and the inability to discontinue antihistamines in patients.
9. Trypsin-like assay
Using a sensitive immunoassay, an increase in tear trypsin-like levels can be detected in allergic conjunctivitis. Because trypsin-like enzymes are released from mast cells, elevations are limited to early reactions. Measurement of trypsin-like levels is valuable for assessing the therapeutic effect of mast cell stabilizers.
10. Histological testing.
Allergic conjunctivitis is difficult to cure by medication because it is an individual decision. It tends to be most severe during the child’s adolescence. This is because the most common allergens are dust mites, molds, and pollen. They can be detected by allergy tests, but these are all in life, and will be encountered every day, it is difficult to completely avoid contact, so families with allergic people should often open the windows to ventilate, dry bedding, avoid the spring to the place where there are too many flowers and plants, but sometimes the allergens can not be prevented, it is necessary to avoid contact, while the drug control symptoms.
The principle of medication is to use it when there are symptoms, and stop when there are no symptoms. Anti-allergy eye medications alone are not toxic, such as Rimadyl, Emadyl, Alamax, Pantanello and so on. If the symptoms are more severe, you can use oral anti-allergy medication, or topical short-term application of hormones. Of course, you should be aware of the side effects of hormones. To tell you a good prevention method, if your child has an attack in April every year, you can use Alamax eye drops half a month earlier in mid-March for the purpose of stabilizing the mast cells and reducing the symptoms during the attack. However, if an attack has already occurred it needs to be combined with the histamine antagonist Emetine for better results.