AC is a common ocular surface allergic disease. The reported incidence of AC in the general population is 6%-30%[5]. The main ocular symptoms were itching and conjunctival hyperemia, while other symptoms were lack of specificity. The indicators of symptoms and signs selected in this study refer to relevant reports at home and abroad. The most special symptom was abnormal blinking. Some studies have found [6] that the main reason for children to see a doctor is frequent blinking, eye rubbing or photophobia and tears, while the main reason for adults to see a doctor is eye itching, which shows that children are quite different from adults. Considering that this is mainly because children cannot describe the symptoms of eye itching in detail, but show specific signs such as frequent blinking and eye rubbing.
Liu Danning et al.[6] showed that tear IgE was significantly increased in patients with allergic conjunctivitis, but this study showed that there was no statistical differ- ence in total IgE level in tears between patients with allergic conjunctivitis and those without. The relevant factors for this result may as follows:
a.Allergic conjunctivitis is mainly the result of IgE-mediated type I hypersensitivity reaction and CD4 + aggregation Th2-mediated cellular immune response. For children, the immature development of eye tissues and organs, high sensitivity to the out- side world, and strong conjunctival permeability lead to a higher incidence of allergic conjunctivitis in children than in adults[7].
IgE is mainly secreted by plasma cells in the submucosal lymphoid tissues of the nasopharynx, tonsil, trachea and gastrointestinal tract. MMP-9 is mainly found in the basal cells near the corneal epithelium and is regulated by cytokines such as IL-1ß. In this study, the content of total IgE and MMP-9 in tears of children with allergic conjunctivitis was detected. It was found that the changes of tear indexes in children with allergic conjunctivitis were not significant. It is mainly due to the low function of the immune system in early childhood, and the children are easy to express unclear, poor self-care ability, and serious crying when seeing a doctor, which leads to the difficulty of clinical inquiry, easy to misjudge and missed diagnosis. In addition, children are prone to mental stress and other conditions when collecting tears, and relevant studies have shown that stress can lead to the increase and activation of mast cells, and release a variety of bioactive mediators and factors[8], resulting in increased total IgE activity and secretion.
In addition, some studies have shown that the total tear IgE score is related to the severity of allergic conjunctivitis[9]. In clinical practice, children’s cooperation is limited, and some family members do not pay enough attention to the children[10], resulting in inaccurate description of the children’s condition. As the direct guardians of children, parents are responsible for children’s medication related matters at home, and their cognition, attitude and behavior in safe medication are directly related to the safety and rationality of children’s medication[11]. However, the different cognition levels of family members lead to the late discovery or self-medication of some fam- ily members, which leads to different disease development of different children at the time of treatment. There are differences and errors in tear detection indicators. IgE may also be related to climate, allergen retention time, dry eye symptoms and so on. These factors can also stimulate the production of IgE, that is, non-allergic diseases may also lead to the increase of IgE. MMP-9 is related to eye use and video terminals.
b.The inflammatory response of allergic conjunctivitis is mainly divided into early phase reaction (EPR) and late phase reaction (LPR). The early phase reaction is a hypersensitivity reaction mediated by IgE. The combination of allergen and specific IgE leads to the degranulation of mast cells in the conjunctival mucosa, resulting in the increase of histamine and prostaglandin secretion. After 4–6 hours, the late phase reaction occurs, and a variety of inflammatory cells infiltrate, especially eosinophils, which can secrete some proteins such as major basic protein (MBP) and eosinophil cationic protein (ECP) after activation, which are toxic to the corneal epithelium[12]. In the study of Chen Dafu et al.[13], LPR can continue to occur even at low IgE con- centration levels, even undetectable levels, after the second response is initiated. In this study, due to the long course of disease and the fact that most of the patients were return visit patients, multiple responses often occurred in the body, therefore, the return visit patients could still develop LPR and show the related symptoms of allergic conjunctivitis under low IgE levels. At this stage, the total IgE concentration of tears of allergic conjunctivitis patients in the experimental group was mostly low. Total tear IgE did not change significantly.
c.Detection methods are not precise enough. ”Human tears are limited (under 15 microliters, normal secretion < 2 microliters/minute).” Many tear proteins are low abundance proteins, and conventional methods (such as ELISA) can only detect one tear protein at a time. Highly sensitive and high-throughput tear protein analysis techniques are indispensable for clinical research. At present, a variety of methods have been proposed for tear protein detection, among which liquid phase multiplex bead array, solid phase chip membrane microarray, isobar-labeled relative and abso- lute quantification are commonly used. It should be pointed out that at present, there is no large-scale detection of tear immune components in normal people at home and abroad, so there is no recognized reference standard for the normal range of tear immune components[14]. In addition, tear or blood IgE antibody detection is not com- monly used in clinical practice in our country[15].The protein content in human tears is very low, and the IgE content is even lower. This experiment uses the immunochro- matography test reagent, and the possible problems are as follows: First, the presence of some non-specific components in the sample with similar antigenic determinants may lead to inaccurate test results. Second, in order to ensure the reliability of the test results, international agreed standards could be used, but they were not obtained in the experiment, and no quality control was carried out. According to the above, the IgE content in tears is low, and the use of this reagent to carry out experiments may cause large experimental errors, and the detection of IgE is not accurate enough.