First, the protective mechanism and destructive factors of the normal conjunctiva Conjunctiva (conjunctiva) is a layer of translucent mucous membrane tissue that covers the back of the eyelid and the front of the eyeball, starting from the end of the eyelid margin between the eyelid margins and consisting of the bulbar conjunctiva, lid conjunctiva and the vault conjunctiva, the lid conjunctiva is tightly bound to the eyelid plate, while the bulbar conjunctiva outside the corneoconjunctival rim and the vault conjunctiva are loosely bound to the eyeball. The conjunctiva is histologically divided into an epithelium and a submucosal stroma. The cellular morphology of the conjunctival epithelium is highly variable, with the bulbar conjunctiva dominated by a complex squamous epithelium, the lid conjunctival epithelium being stratified and cuboidal with a gradual transition to columnar epithelium toward the dome, and the number of cup-shaped cells accounting for about 10% of the number of conjunctival epithelial cells in the basal cell mass, which is mostly found in the lid conjunctiva and the bulbar conjunctiva in the subnasal region. The parenchymal layer of the conjunctiva consists of loose connective tissue and contains conjunctiva-associated lymphoid tissue composed of lymphocytes and other leukocytes. The conjunctiva is rich in nerves and blood vessels. The conjunctiva shares a common blood supply with the eyelids, and the bulbar conjunctiva derives its blood supply from the anterior ciliary artery, a branch of the ophthalmic artery. Conjunctival sensation is innervated by branches of the lacrimal, supraorbital, supratrochlear, and infraorbital nerves of the ophthalmic branch of the V cranial nerve. The conjunctiva not only functions as an ocular surface barrier, but also contains associated lymphoid tissue containing immunoglobulins, neutrophils and lymphocytes (100,000/mm2), mast cells (5,000/mm2), and plasma cells. In addition to this, the conjunctival stroma layer itself contains antigen-presenting cells. Physiologically the conjunctival tissue does not contain basophils and eosinophils. The conjunctiva serves as mucosa-associated lymphoid tissue (MALT), and the interaction between lymphocytes and mucosal epithelial cells promotes a regulatory immune response through growth factor, cytokine, and neuropeptide-mediated regulatory signaling. The conjunctival epithelium continues in close relationship with the corneal epithelium, the mucosal epithelium of the lacrimal duct and the epithelium of the lacrimal gland openings, and therefore diseases of these sites tend to interact with each other. Most of the surface of the conjunctiva is exposed to the outside world and is susceptible to disease from irritants and microbial infections in the external environment; the most common disease is conjunctivitis, followed by degenerative diseases. Conjunctival epithelial cell healing is similar to that of other mucosal cells, and epithelial cell injury is usually repaired within 1 to 2 days. In contrast, repair of the conjunctival stroma is accompanied by neovascularization, and the repair process is influenced by the amount of angiogenesis, the degree of inflammatory response, and the rate of tissue renewal. The superficial layer of the conjunctiva is usually composed of loose tissue, which cannot be restored to exactly the same tissue as the original after injury. After repair of the deeper tissue (fibrous tissue layer) damage, the fibroblasts overproliferate and secrete collagen so that the conjunctival tissue adheres to the sclera, which is the reason for the formation of conjunctival scar tissue after inner eye surgery. Second, the etiology of conjunctivitis conjunctiva and a variety of microorganisms and the external environment contact, but the eye surface of the specific and non-specific protective mechanisms so that it has a certain degree of prevention of infection and the ability to make the infection limited, but when these defenses are weakened or external disease-causing factors to enhance the occurrence of conjunctival tissue inflammation, which is characterized by vasodilatation, oozing and cellular infiltration, the inflammation is collectively referred to as conjunctivitis. Conjunctivitis is one of the most common diseases in ophthalmology, and its causes can be divided into microbial and non-microbial categories, depending on the source of exogenous or endogenous, but also due to the spread of inflammation in neighboring tissues. The most common is microbial infection, and the causative microorganisms can be bacteria (e.g., pneumococcus, Haemophilus influenzae, Staphylococcus aureus, meningococcus, gonococcus, etc.), viruses (e.g., human adenovirus strains, herpes simplex viruses type I and II, and micro ribonucleic acid viruses), or chlamydia. Occasionally, fungal, rickettsial, and parasitic infections are seen. Conjunctivitis can also be caused by physical irritation (e.g., sand, smoke, ultraviolet light, etc.) and chemical damage (e.g., medical drugs, acids, alkalis, or toxic gases). Some conjunctivitis is also caused by immune lesions (allergic), internal causes related to systemic conditions (tuberculosis, syphilis, thyroid disease, etc.), and the spread of inflammation in neighboring tissues (cornea, sclera, eyelids, orbit, lacrimal apparatus, nasal cavity and paranasal sinuses, etc.). Third, the classification of conjunctivitis according to the rapidity of the onset of conjunctivitis can be divided into hyperacute, acute or subacute, chronic conjunctivitis. Generally speaking, the duration of the disease is less than three weeks for acute conjunctivitis, and more than three weeks for chronic conjunctivitis. Conjunctivitis can be classified according to etiology as infectious, immunologic, chemical or irritant, systemic disease-related, secondary, and unexplained. According to the main form of conjunctival response to the lesion can be divided into papillary, follicular, membranous/pseudomembranous, scarring and granulomatous conjunctivitis. Fourth, common signs of conjunctivitis Conjunctivitis symptoms include foreign body sensation, burning sensation, itching, photophobia, and tearing. Important signs include conjunctival congestion, edema, exudate, papillary hyperplasia, follicles, pseudomembranes and true membranes, granulomas, pseudo ptosis, and enlarged lymph nodes in front of the ear. 1.Conjunctival congestion can be caused by a variety of factors stimulation, including infection, chemical smoke, wind, ultraviolet radiation and long-term topical medication, etc. It is the most common sign of acute conjunctivitis. Conjunctival congestion is characterized by superficial vascular congestion to the fornix obvious, to the corneal edge of the direction of congestion to reduce, these superficial blood vessels can move with the mechanical movement of the conjunctiva, and local point of use of epinephrine after the disappearance of congestion. 2.Conjunctival secretion A common sign of acute conjunctivitis, the secretion can be purulent, mucopurulent or plasma. Bacterial invasion of the conjunctiva can cause polymorphonuclear leukocyte reaction, at first the secretion was dilute plasma, with the secretion of mucus from the cup cells and the increase of inflammatory cells and necrotic epithelial cells, the secretion becomes mucous and purulent. The pathogens that most commonly cause purulent secretions are gonococci and meningococci, while other pathogenic bacteria usually cause mucopurulent secretions. Because the mucopurulent discharge can cling to the eyelashes, thereby causing the lid margins to stick together, patients may wake up in the morning with difficulty opening their eyes, suggesting a possible bacterial infection or chlamydial infection. Allergic conjunctivitis secretions are sticky and filmy. Viral conjunctivitis secretion is watery or plasma. 3.Papillary hyperplasia A non-specific sign of conjunctival inflammation. Mostly seen in the lid conjunctiva, the appearance of flat, small papillae, presenting a velvety appearance, the corneoconjunctival margin of the more dome-shaped. In the physiologic state, some large papillae are visible at the upper edge of the lid conjunctiva after turning the upper eyelid, which may be related to fewer diaphragm-like fixed structures in this area. The papillae are made up of hyperplastic epithelial folds or bulges, with dilated capillaries in the center reaching the tip and spreading out in a spoke-like pattern under slit lamp. Red papillary conjunctivitis is mostly bacterial or chlamydial conjunctivitis. Conjunctival papillae on the upper lid are seen mainly in springtime conjunctivitis and conjunctival irritation in response to foreign bodies (e.g., sutures, corneal contact lenses, artificial corneas, etc.), and in allergic conjunctivitis when also present on the lower lid. Hyperplastic papillae larger than 1 mm in diameter, called macropapillae, occur when the diaphragm-like fixation structure attached to the conjunctival epithelium to the lid plate disintegrates, causing the papillae to fuse. Macropapillae can be seen in a number of different etiologies, such as vernal keratoconjunctivitis, atopic keratoconjunctivitis, caused by contact lenses, prosthetic eyes, or sutures. Giant papillae in blepharoconjunctival vernal conjunctivitis are polygonal and have a flattened surface, whereas giant papillae in keratoconjunctival limbal vernal conjunctivitis have a smooth, rounded surface and are often accompanied by Horner-Trantas dots. Contact lens-induced macropapillae mostly occur in the upper lid conjunctiva, mildly elevated, asymmetric, pale surface, easily confused with early follicles on the upper lid margin, after the contact lens is removed, the patient’s symptoms gradually subside, but macropapillae signs will still persist for several months. Follicle formation is caused by lymphocyte reaction, presenting a smooth appearance, translucent elevated conjunctival changes (Figure 7-3). Follicles are scattered, often occurring in the upper lid conjunctiva and lower dome conjunctiva, but can also be seen in the corneal conjunctival rim conjunctiva. The diameter of the follicles is usually 0.5 to 2.0 mm, with some exceeding 2.0 mm, and, unlike the papillae, there is no vascularity in the center of the follicle, with the vascularity gradually disappearing from the peripheral base to the top. Follicles are important to identify and are relatively specific signs of inflammatory response in some conjunctivitis. Most viral conjunctivitis, chlamydial conjunctivitis (with the exception of neonatal inclusion body conjunctivitis), conjunctivitis caused by some parasites, and conjunctivitis caused by medications (iodoside, diphenhydramine, and pupil-contracting agents) result in follicle formation. Moraxella catarrhalis conjunctivitis and meningococcal conjunctivitis have also been reported. Follicles located on the margins of the lower fornix palpebral plate are of little diagnostic value, and if they are located on the upper palpebral plate, the possibility of chlamydial, viral, or drug-induced conjunctivitis should be considered. Follicular proliferation in children and adolescents does not always imply pathologic changes, and small follicles are sometimes seen in the temporal conjunctiva of normal young people, often evident in the fornix and disappearing near the margins of the lids, which is a physiologic alteration known as benign lymphoid follicular proliferation. 5, the true membrane and pseudomembrane Some pathogenic infections can cause the true membrane or pseudomembrane, formed by the shedding of conjunctival epithelial cells, leukocytes, pathogens, and exudate rich in cellulose mixed. True membranes are condensation of exudate on the conjunctival surface from a severe inflammatory response, involve the entire epithelium, and are rough and bleed easily when forcibly removed (Fig. 7-4). Pseudomembranes are condensations on the epithelial surface that remain intact after removal. In the past, Corynebacterium diphtheriae conjunctivitis and β-hemolytic streptococcal conjunctivitis were thought to be the main causes of membrane formation, but in recent years, adenoviral conjunctivitis has become the most common cause, followed by primary herpes simplex viral conjunctivitis, with others including spring conjunctivitis, inclusion body conjunctivitis, and Candida infective conjunctivitis. Erythema multiforme or Stevens-Johnson syndrome often involves the mucous membranes and skin, leading to bilateral pseudomembrane formation and ultimately severe conjunctival scarring, loss of cupped cells, lid entropion, impaction, and corneal limbal stem cell failure. 6.Globe conjunctival edema The exudate from vasodilatation enters the loose subconjunctival tissue, leading to conjunctival edema, and when the edema is severe, the globe conjunctiva may protrude beyond the lid fissure. Acute allergic conjunctivitis, gonococcal or meningococcal conjunctivitis, and adenoviral conjunctivitis all have significant conjunctival edema. Conjunctival edema can precede physical signs such as cellular infiltration and secretions. In addition to inflammation, damage to the orbital veins or obstruction of lymphatic reflux, low intravascular osmotic pressure can cause conjunctival edema. 7.Subconjunctival hemorrhage Severe conjunctivitis such as adenovirus and enterovirus caused by epidemic conjunctivitis and acute conjunctivitis caused by Kochweeks bacillus, etc., in addition to conjunctival congestion, can also appear point or piece of subconjunctival hemorrhage, the color is bright red, and when the amount is dark red. 8, conjunctival granuloma granuloma is generally composed of proliferation of fibrovascular tissue and monocytes, macrophages. Commonly, blepharocysts, and some endogenous diseases such as syphilis, cat-scratch disease, sarcoidosis, Parinaud’s oculoglandular syndrome, etc. Parinaud’s oculoglandular syndrome is manifested as monocular granulomatous conjunctivitis and localized follicular proliferation, which is often accompanied by enlargement of the lymph nodes in front of the ear or submandibular lymph nodes, fever and other systemic manifestations. Tissue biopsy is helpful in the diagnosis of these diseases. Conjunctival scarring Simple conjunctival epithelial injury does not lead to scarring, and scarring occurs only when the damage involves the stroma. Early manifestations of scarring are shallow conjunctival domes and linear or stellate, lace-like epithelial fibrosis. Prolonged subconjunctival scarring can cause complications such as lid entropion and impaction. As the disease progresses, the damage to the shallowed conjunctival vault worsens. Severe end-stage scarring manifests as loss of the conjunctival vault, epithelial keratinization, and lid adhesions, as in ocular pemphigoid disease. Late stages of membranous conjunctivitis can lead to subepithelial fibrosis and lid bulb adhesions, and this scarring can occur anywhere in the conjunctiva. Complicated scarring in the later stages of idiopathic conjunctivitis is often focal and centrally located in the macroglossia, and can eventually lead to extensive constriction of the subconjunctival vault, but lid entropion and impaction are not usually present. The specific pathology of the scar in trachoma is a follicular rim surrounding the scar, called the “Herbert’s notch”. Subconjunctival fibrosis in trachoma can occur near the upper border of the upper eyelid plate, called Arlt’s line. Pseudo ptosis is caused by cellular infiltration or scar formation, which results in hypertrophy of the upper eyelid tissues and increased weight, mostly seen in trachoma, plasmacytoma, etc. Mild ptosis can also occur. Mild ptosis can also be caused by inflammatory cells infiltrating Muller’s muscle. 11, pre-auricular lymph node enlargement An important sign of viral conjunctivitis, and other types of conjunctivitis is an important point of differentiation, the early stage of the disease or mild symptoms do not have this performance. It can also be seen in chlamydial, gonococcal, and various diseases that can cause granulomatous conjunctivitis and dacryoadenitis. It should be noted that children with blepharospasmal infections may also have enlarged lymph nodes in front of the ear. Fifth, the common diagnostic methods of conjunctivitis can be clinically based on the basic signs and symptoms of conjunctivitis, such as conjunctival congestion, increased secretion, eyelid swelling, etc., to make a diagnosis, but to confirm the diagnosis of conjunctivitis due to what causes still need to rely on laboratory tests. Laboratory tests include cytology, culture and identification of pathogens, and immunologic and serologic tests. The history is very important in making the diagnosis. Infectious conjunctivitis tends to develop in both eyes and is often transmitted to family members or community members. Patients with acute viral conjunctivitis most often present with onset in one eye early in the course of the disease, with the contralateral eye also being involved a few days later. Uniocular onset is common in conjunctivitis caused by toxicity, drugs, or trauma. The duration of the disease is helpful in making the diagnosis and is a commonly used criterion for classifying conjunctivitis. Generally, a duration of less than three weeks is considered acute conjunctivitis, while more than three weeks is considered chronic conjunctivitis. In addition, the type of exudate and the site of inflammation are also important bases for definitive diagnosis. 1, clinical examination, clinical symptoms and main signs appear in different parts of the conjunctivitis can help differential diagnosis. Conjunctival follicles and papillae are important diagnostic and differential diagnostic basis of the location, shape, size, for example, trachoma inflammation of the upper eyelid conjunctiva than the lower eyelid, follicles often appear in the upper eyelid conjunctiva edge, while inclusion body conjunctivitis follicular proliferative changes are more common in the lower eyelid conjunctiva. In addition, the amount and nature of secretion, true/pseudomembrane, ulceration, herpes, keratitis, and the presence of angular opacities, and the presence of enlarged lymph nodes in front of the ear can help in the diagnosis, and the clinical features and diagnostic points of the different conjunctivitis will be described in detail in the individual papers. Pathologic examination is sometimes necessary for etiologic diagnosis and correct treatment. Conjunctival secretion smear can help to diagnose the presence of bacterial infection, such as gonococcal conjunctival infection caused by gonococcus, in the conjunctival epithelium and neutrophil cells can be found in pairs of gonococcus. Cultures of bacteria and fungi, drug sensitivity tests, etc. can be done if necessary. If there is no bacterial growth, the possibility of chlamydia or viruses should be considered, and isolation and characterization is required. Isolation and culture of viruses are not often performed in the clinic because they are technically complex, expensive and time-consuming. In addition, immunofluorescence, enzyme-linked immunoassay, and polymerase chain reaction (PCR) can be applied to detect antigens of pathogens. Checking the potency of serum antibodies in the patient’s serum during the acute and recovery phases is also helpful in the diagnosis of viral conjunctivitis, especially herpes simplex virus conjunctivitis, in which the titer of serum antibodies in the peripheral blood during the acute phase can be elevated by four times or more. 3, cytologic examination Different types of conjunctivitis, its cellular response is not the same, conjunctival secretion smear examination Gram stain (identify bacterial species), Giemsa stain (distinguish cell morphology, type) to help clinical diagnosis. Conjunctival smear should be taken from the most obvious area of inflammation to improve the detection rate. If the lesion spreads to the lid conjunctiva, the upper lid conjunctiva is the ideal site for conjunctival smear. Bacterial conjunctivitis smears are predominantly polymorphonuclear leukocytes. In viral conjunctivitis, mononuclear cells, especially lymphocytes, predominate. Pseudomembrane formation (epidemic keratoconjunctivitis) is characterized by an increase in neutrophils, suggesting conjunctival necrosis. Chlamydial conjunctivitis smears are 50/50 neutrophils and lymphocytes. Eosinophils and basophils are seen in biopsy specimens of allergic conjunctivitis, but in low numbers in conjunctival smears. Eosinophilic granules were seen in large numbers in epithelial cells of vernal conjunctivitis. Protein products secreted by eosinophils can be detected in the tear fluid of patients with vernal conjunctivitis, hereditary allergic conjunctivitis, and allergic conjunctivitis. All types of conjunctivitis are infiltrated by plasma cells in the stroma, usually they do not pass through the epithelial cell layer, but only if the epithelial layer is necrotic can the plasma cells reach the conjunctival surface to be detected, for example, after rupture of the trachoma follicle, the conjunctival secretion is positive for plasma cells in smears and scrapings. Conjunctival scraping to find inclusion bodies also help to confirm the diagnosis of trachoma six, the principle of treatment of conjunctivitis for the treatment of the cause, the local administration of the main drug, if necessary, systemic medication. Acute phase avoid bandaging the affected eye. Eye drops: the most basic route of administration for the treatment of conjunctivitis. For microbial conjunctivitis, sensitive antibacterial drugs or/and antiviral eye drops should be used. Effective drugs may be selected on the basis of pathogen culture and drug sensitivity testing, if necessary. In severe cases, a mixture of several antibiotic eye drops may be used until drug sensitivity testing is performed. In the acute stage, eye drops should be applied frequently, every 1 to 2 hours. The frequency of eye drops can be reduced when the disease improves. Eye ointment applied to the eyes: eye ointment stays in the conjunctival sac for a long time, and it is advisable to use it before going to bed for a sustained therapeutic effect. Flushing the conjunctival sac: When the conjunctival sac has more secretions, use a non-irritating rinsing solution (physiologic eye drops or 3% boric acid water) to rinse the conjunctival sac 1 to 2 times a day to remove the secretions in the conjunctival sac. The rinsing solution should not flow into the healthy eye, causing cross-infection. Systemic treatment: severe conjunctivitis such as gonococcal conjunctivitis and chlamydial conjunctivitis, in addition to topical medication also requires systemic use of antibiotics or sulfonamides. Prognosis and prevention of conjunctivitis Most types of conjunctivitis heal without complications, but a few can be complicated by inflammation of the cornea and thus impair vision. Severe or chronic conjunctival inflammation may result in permanent changes, such as lid adhesions due to conjunctival scarring, eyelid deformity, or secondary dry eye. Infectious conjunctivitis can cause epidemic infections and therefore must be prevented. Conjunctivitis is mostly a contact infection, so it is recommended to wash hands and face frequently, and not to wipe the eyes with hands and sleeves. Patients with infectious conjunctivitis should be isolated, and toiletries used by patients must be isolated and disinfected. Medical personnel should wash and disinfect their hands after examining patients to prevent cross-infection. Hygiene promotion, regular inspections and strengthened management should be carried out in places with a high concentration of people, such as barber stores, restaurants, factories, schools, nurseries and swimming pools.