Conjunctivitis

Epidemiology and Etiology

Epidemiology

• Most common non-traumatic eye complaint
• Estimated incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency in the United States is 6 million people per year 
• Most frequently found in infants, school-age children, and the elderly

Etiology

Infectious conjunctivitis

• Viral
  • Adenoviruses (most common cause, 65%–90% of cases)
  • Herpes simplex virus Simplex Virus A genus of the family herpesviridae, subfamily alphaherpesvirinae, consisting of herpes simplex-like viruses. The type species is herpesvirus 1, human. Herpes Simplex Virus 1 and 2 (most commonly seen in children and infants)
  • Varicella zoster virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology (most common in the elderly)
  • Picornavirus ( enterovirus Enterovirus A genus of the family picornaviridae whose members preferentially inhabit the intestinal tract of a variety of hosts. The genus contains many species. Newly described members of human enteroviruses are assigned continuous numbers with the species designated ‘human enterovirus’. Coxsackievirus and coxsackievirus Coxsackievirus Coxsackievirus is a member of a family of viruses called Picornaviridae and the genus Enterovirus. Coxsackieviruses are single-stranded, positive-sense RNA viruses, and are divided into coxsackie group A and B viruses. Both groups of viruses cause upper respiratory infections, rashes, aseptic meningitis, or encephalitis. Coxsackievirus cause acute hemorrhagic conjunctivitis)
  • Molluscum contagiosum Molluscum contagiosum Molluscum contagiosum is a viral infection limited to the epidermis and is common in children below 5 years of age. Lesions appear as grouped, flesh-colored, dome-shaped papules with central umbilication. Molluscum Contagiosum (causes chronic follicular conjunctivitis)
  • HIV HIV Anti-HIV Drugs (usually affects posterior segment of the eye)
• Bacterial
  • Staphylococcus Staphylococcus Staphylococcus is a medically important genera of Gram-positive, aerobic cocci. These bacteria form clusters resembling grapes on culture plates. Staphylococci are ubiquitous for humans, and many strains compose the normal skin flora. Staphylococcus aureus (most common cause in adults)
  • Streptococcus Streptococcus Streptococcus is one of the two medically important genera of gram-positive cocci, the other being Staphylococcus. Streptococci are identified as different species on blood agar on the basis of their hemolytic pattern and sensitivity to optochin and bacitracin. There are many pathogenic species of streptococci, including S. pyogenes, S. agalactiae, S. pneumoniae, and the viridans streptococci. Streptococcus pneumoniae
  • Haemophilus Haemophilus Haemophilus is a genus of Gram-negative coccobacilli, all of whose strains require at least 1 of 2 factors for growth (factor V [NAD] and factor X [heme]); therefore, it is most often isolated on chocolate agar, which can supply both factors. The pathogenic species are H. influenzae and H. ducreyi. Haemophilus influenzae (most common cause in children)
  • Moraxella Moraxella Moraxella is a genus of gram-negative diplococci, with M. catarrhalis being the most clinically relevant species. M. catarrhalis is part of the normal flora of the upper respiratory tract, but it can cause infection in susceptible individuals. The infection is transmitted through respiratory droplets and can lead to chronic obstructive pulmonary disease (COPD) exacerbations in adults and otitis media in children. Moraxella catarrhalis
  • Neisseria gonorrhoeae Neisseria gonorrhoeae A species of gram-negative, aerobic bacteria primarily found in purulent venereal discharges. It is the causative agent of gonorrhea. Neisseria (more common in newborns) or Neisseria meningitidis Neisseria meningitidis A species of gram-negative, aerobic bacteria. It is a commensal and pathogen only of humans, and can be carried asymptomatically in the nasopharynx. When found in cerebrospinal fluid it is the causative agent of cerebrospinal meningitis. It is also found in venereal discharges and blood. There are at least 13 serogroups based on antigenic differences in the capsular polysaccharides; the ones causing most meningitis infections being a, b, c, y, and w-135. Each serogroup can be further classified by serotype, serosubtype, and immunotype. Neisseria 
  • Chlamydia trachomatis Chlamydia trachomatis Type species of Chlamydia causing a variety of ocular and urogenital diseases. Chlamydia
  • Gram-negative enteric flora

Noninfectious conjunctivitis

• Allergic (e.g., from airborne allergens)
• Nonallergic (e.g., “dry eye syndrome,” associated with blepharitis Blepharitis Blepharitis is an ocular condition characterized by eyelid inflammation. Anterior blepharitis involves the eyelid skin and eyelashes, while the posterior type affects the meibomian glands. Often, these conditions overlap. Blepharitis, Sjögren’s syndrome, reactive arthritis Reactive arthritis Reactive arthritis is a seronegative autoimmune spondyloarthropathy that occurs in response to a previous gastrointestinal (GI) or genitourinary (GU) infection. The disease manifests as asymmetric oligoarthritis (particularly of large joints in the lower extremities), enthesopathy, dactylitis, and/or sacroiliitis. Reactive Arthritis)

Clinical Presentation

Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship can present with some or all of the following symptoms:

• Hyperemia of the conjunctiva Conjunctiva The mucous membrane that covers the posterior surface of the eyelids and the anterior pericorneal surface of the eyeball. Eye: Anatomy with injection of blood vessels (classic “pink eye” appearance)
• Watery eyes or excessive tearing
• Swelling Swelling Inflammation of the eyelids Eyelids Each of the upper and lower folds of skin which cover the eye when closed. Blepharitis and conjunctiva Conjunctiva The mucous membrane that covers the posterior surface of the eyelids and the anterior pericorneal surface of the eyeball. Eye: Anatomy (chemosis)
• Discharge and crust Crust Dried exudate of body fluids (blood, pus, or sebum) on an area of damaged skin Secondary Skin Lesions formation (varies depending on etiology)
• Itching, burning, or foreign-body sensation in the eye
• Photophobia Photophobia Abnormal sensitivity to light. This may occur as a manifestation of eye diseases; migraine; subarachnoid hemorrhage; meningitis; and other disorders. Photophobia may also occur in association with depression and other mental disorders. Migraine Headache 
• Normally reactive pupils with normal visual acuity Visual Acuity Clarity or sharpness of ocular vision or the ability of the eye to see fine details. Visual acuity depends on the functions of retina, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast. Ophthalmic Exam (important for differential diagnoses!)

Diagnosis

The diagnosis is mainly clinical.

• Viral conjunctivitis: 
  • History of recent viral infection (not mandatory)
    • If symptoms are recurrent/chronic →  conjunctival smear, cultures, or viral isolation required 
    • Mononuclear cells and lymphocytes Lymphocytes Lymphocytes are heterogeneous WBCs involved in immune response. Lymphocytes develop from the bone marrow, starting from hematopoietic stem cells (HSCs) and progressing to common lymphoid progenitors (CLPs). B and T lymphocytes and natural killer (NK) cells arise from the lineage. Lymphocytes: Histology are seen on Giemsa stain Giemsa stain Borrelia of conjunctival scrapings.
• Bacterial conjunctivitis:
  • If persistent or severe disease, diagnosis is uncertain, and in newborn Newborn An infant during the first 28 days after birth. Physical Examination of the Newborn conjunctivitis →  conjunctival scrapings, culture, or PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) required
  • Findings for various bacterial infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease:
    • Bacterial conjunctivitis shows a predominance of neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation on Giemsa staining.
    • In gonococcal ophthalmia neonatorum Ophthalmia Neonatorum Acute conjunctival inflammation in the newborn, usually caused by maternal gonococcal infection. The causative agent is Neisseria gonorrhoeae. The baby’s eyes are contaminated during passage through the birth canal. Gonorrhea, Gram stain Gram stain Klebsiella of exudate Exudate Exudates are fluids, cells, or other cellular substances that are slowly discharged from blood vessels usually from inflamed tissues. Pleural Effusion shows gram-negative intracellular diplococci; culture in modified Thayer-Martin medium Thayer-Martin Medium Brucella/Brucellosis grows N. gonorrhoeae N. gonorrhoeae A species of gram-negative, aerobic bacteria primarily found in purulent venereal discharges. It is the causative agent of gonorrhea. Neisseria.
    • In chlamydial conjunctivitis, Giemsa stain Giemsa stain Borrelia shows neutrophils Neutrophils Granular leukocytes having a nucleus with three to five lobes connected by slender threads of chromatin, and cytoplasm containing fine inconspicuous granules and stainable by neutral dyes. Innate Immunity: Phagocytes and Antigen Presentation with inclusion bodies and plasma cells Plasma cells Specialized forms of antibody-producing B-lymphocytes. They synthesize and secrete immunoglobulin. They are found only in lymphoid organs and at sites of immune responses and normally do not circulate in the blood or lymph. Humoral Adaptive Immunity.
• Allergic conjunctivitis:
  • Clinical history, signs, and symptoms are usually sufficient.
  • Eye pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways is not characteristic of allergic conjunctivitis, and more serious disorders must be ruled out, including angle-closure glaucoma Glaucoma Glaucoma is an optic neuropathy characterized by typical visual field defects and optic nerve atrophy seen as optic disc cupping on examination. The acute form of glaucoma is a medical emergency. Glaucoma is often, but not always, caused by increased intraocular pressure (IOP). Glaucoma, scleritis Scleritis Refers to any inflammation of the sclera including episcleritis, a benign condition affecting only the episclera, which is generally short-lived and easily treated. Classic scleritis, on the other hand, affects deeper tissue and is characterized by higher rates of visual acuity loss and even mortality, particularly in necrotizing form. Crohn’s Disease, or episcleritis.
  • If patient does not respond to therapy, referral to an ophthalmologist is indicated, who may refer to an allergist for possible skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions testing to detect the causative allergen(s).
• In cases of visual impairment, significantly increased photophobia Photophobia Abnormal sensitivity to light. This may occur as a manifestation of eye diseases; migraine; subarachnoid hemorrhage; meningitis; and other disorders. Photophobia may also occur in association with depression and other mental disorders. Migraine Headache, inability to keep the eye open, abnormal pupil Pupil The pupil is the space within the eye that permits light to project onto the retina. Anatomically located in front of the lens, the pupil’s size is controlled by the surrounding iris. The pupil provides insight into the function of the central and autonomic nervous systems. Pupil: Physiology and Abnormalities reaction to light, or severe headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess with nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics, other diagnoses must be ruled out (and specialist referrals are indicated):
  • Glaucoma Glaucoma Glaucoma is an optic neuropathy characterized by typical visual field defects and optic nerve atrophy seen as optic disc cupping on examination. The acute form of glaucoma is a medical emergency. Glaucoma is often, but not always, caused by increased intraocular pressure (IOP). Glaucoma
  • Uveitis Uveitis Uveitis is the inflammation of the uvea, the pigmented middle layer of the eye, which comprises the iris, ciliary body, and choroid. The condition is categorized based on the site of disease; anterior uveitis is the most common. Diseases of the Uvea
  • Keratitis Keratitis Inflammation of the cornea. Herpes Simplex Virus 1 and 2
  • Meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis (especially in infants)

Management

Viral conjunctivitis

• Uncomplicated viral conjunctivitis is treated symptomatically. 
• Antihistamine drops/artificial tears
• Herpes simplex Herpes Simplex A group of acute infections caused by herpes simplex virus type 1 or type 2 that is characterized by the development of one or more small fluid-filled vesicles with a raised erythematous base on the skin or mucous membrane. It occurs as a primary infection or recurs due to a reactivation of a latent infection. Congenital TORCH Infections infection is treated with a topical antiviral Antiviral Antivirals for Hepatitis B (e.g., ganciclovir Ganciclovir An acyclovir analog that is a potent inhibitor of the herpesvirus family including cytomegalovirus. Ganciclovir is used to treat complications from aids-associated cytomegalovirus infections. Antivirals for Herpes Virus).

Bacterial conjunctivitis

• Topical broad-spectrum Broad-Spectrum Fluoroquinolones antibiotics (e.g., erythromycin Erythromycin A bacteriostatic antibiotic macrolide produced by streptomyces erythreus. Erythromycin a is considered its major active component. In sensitive organisms, it inhibits protein synthesis by binding to 50s ribosomal subunits. This binding process inhibits peptidyl transferase activity and interferes with translocation of amino acids during translation and assembly of proteins. Macrolides and Ketolides, trimethoprim-polymyxin B) 
• Neisserial and chlamydial infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease require systemic treatment
  • For gonococcal conjunctivitis:
    • Single dose of intramuscular ceftriaxone Ceftriaxone A broad-spectrum cephalosporin antibiotic and cefotaxime derivative with a very long half-life and high penetrability to meninges, eyes and inner ears. Cephalosporins plus oral doxycycline or azithromycin Azithromycin A semi-synthetic macrolide antibiotic structurally related to erythromycin. It has been used in the treatment of Mycobacterium avium intracellulare infections, toxoplasmosis, and cryptosporidiosis. Macrolides and Ketolides
    • Alternative agents: cefotaxime Cefotaxime Semisynthetic broad-spectrum cephalosporin. Cephalosporins or ceftazidime Ceftazidime Semisynthetic, broad-spectrum antibacterial derived from cephaloridine and used especially for pseudomonas and other gram-negative infections in debilitated patients. Cephalosporins
  • For chlamydial neonatal conjunctivitis, oral erythromycin Erythromycin A bacteriostatic antibiotic macrolide produced by streptomyces erythreus. Erythromycin a is considered its major active component. In sensitive organisms, it inhibits protein synthesis by binding to 50s ribosomal subunits. This binding process inhibits peptidyl transferase activity and interferes with translocation of amino acids during translation and assembly of proteins. Macrolides and Ketolides is preferred.
• Prevention of ophthalmia neonatorum Ophthalmia Neonatorum Acute conjunctival inflammation in the newborn, usually caused by maternal gonococcal infection. The causative agent is Neisseria gonorrhoeae. The baby’s eyes are contaminated during passage through the birth canal. Gonorrhea: prenatal maternal screening Screening Preoperative Care, systemic antibiotic treatment, and prophylaxis Prophylaxis Cephalosporins for newborns

Allergic conjunctivitis

• Antihistamine drops/artificial tears
• Oral antihistamines Antihistamines Antihistamines are drugs that target histamine receptors, particularly H1 and H2 receptors. H1 antagonists are competitive and reversible inhibitors of H1 receptors. First-generation antihistamines cross the blood-brain barrier and can cause sedation. Antihistamines and mast-cell stabilizers (e.g., ketotifen Ketotifen A cycloheptathiophene blocker of histamine h1 receptors and release of inflammatory mediators. It has been proposed for the treatment of asthma, rhinitis, skin allergies, and anaphylaxis. Antihistamines)
• Cold compresses
• Nonsteroidal anti-inflammatory drugs (e.g., ketorolac)
• Corticosteroids Corticosteroids Chorioretinitis (e.g., fluorometholone)

Differential Diagnosis

The following conditions enter into the differential diagnoses of conjunctivitis:

• Glaucoma Glaucoma Glaucoma is an optic neuropathy characterized by typical visual field defects and optic nerve atrophy seen as optic disc cupping on examination. The acute form of glaucoma is a medical emergency. Glaucoma is often, but not always, caused by increased intraocular pressure (IOP). Glaucoma: a condition caused by acutely or chronically increased intraocular pressure Increased intraocular pressure An ocular disease, occurring in many forms, having as its primary characteristics an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function. The consequences of the increased pressure may be manifested in a variety of symptoms, depending upon type and severity, such as excavation of the optic disk, hardness of the eyeball, corneal anesthesia, reduced visual acuity, seeing of colored halos around lights, disturbed dark adaptation, visual field defects, and headaches. Osmotic Diuretics or — since up to 40% of those affected do not have increased IOP — there may be heightened ganglion susceptibility to normal pressure, problems with the microcirculation or extracellular matrix Extracellular matrix A meshwork-like substance found within the extracellular space and in association with the basement membrane of the cell surface. It promotes cellular proliferation and provides a supporting structure to which cells or cell lysates in culture dishes adhere. Hypertrophic and Keloid Scars in the optic nerve Optic nerve The 2nd cranial nerve which conveys visual information from the retina to the brain. The nerve carries the axons of the retinal ganglion cells which sort at the optic chiasm and continue via the optic tracts to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the superior colliculi and the suprachiasmatic nuclei. Though known as the second cranial nerve, it is considered part of the central nervous system. The 12 Cranial Nerves: Overview and Functions. Treatment includes surgery plus topical beta-blockers Beta-blockers Drugs that bind to but do not activate beta-adrenergic receptors thereby blocking the actions of beta-adrenergic agonists. Adrenergic beta-antagonists are used for treatment of hypertension, cardiac arrhythmias, angina pectoris, glaucoma, migraine headaches, and anxiety. Class 2 Antiarrhythmic Drugs (Beta Blockers) and prostaglandins Prostaglandins A group of compounds derived from unsaturated 20-carbon fatty acids, primarily arachidonic acid, via the cyclooxygenase pathway. They are extremely potent mediators of a diverse group of physiological processes. Eicosanoids. If left untreated, both the common open-angle and the less common angle-closure glaucoma Glaucoma Glaucoma is an optic neuropathy characterized by typical visual field defects and optic nerve atrophy seen as optic disc cupping on examination. The acute form of glaucoma is a medical emergency. Glaucoma is often, but not always, caused by increased intraocular pressure (IOP). Glaucoma can lead to blindness Blindness The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of eye diseases; optic nerve diseases; optic chiasm diseases; or brain diseases affecting the visual pathways or occipital lobe. Retinopathy of Prematurity.
• Uveitis Uveitis Uveitis is the inflammation of the uvea, the pigmented middle layer of the eye, which comprises the iris, ciliary body, and choroid. The condition is categorized based on the site of disease; anterior uveitis is the most common. Diseases of the Uvea: an ophthalmic emergency caused by the inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the uvea Uvea The pigmented vascular coat of the eyeball, consisting of the choroid; ciliary body; and iris, which are continuous with each other. Eye: Anatomy, which includes the iris and ciliary body Ciliary body A ring of tissue extending from the scleral spur to the ora serrata of the retina. It consists of the uveal portion and the epithelial portion. The ciliary muscle is in the uveal portion and the ciliary processes are in the epithelial portion. Eye: Anatomy, the choroid Choroid The thin, highly vascular membrane covering most of the posterior of the eye between the retina and sclera. Eye: Anatomy. The cause can be either infectious (mostly viral) or noninfectious. Common symptoms include burning of the eye, redness Redness Inflammation, blurry vision Vision Ophthalmic Exam, photophobia Photophobia Abnormal sensitivity to light. This may occur as a manifestation of eye diseases; migraine; subarachnoid hemorrhage; meningitis; and other disorders. Photophobia may also occur in association with depression and other mental disorders. Migraine Headache, floaters Floaters Chorioretinitis, and irregular pupils. Treatment includes topical or systemic steroids Steroids A group of polycyclic compounds closely related biochemically to terpenes. They include cholesterol, numerous hormones, precursors of certain vitamins, bile acids, alcohols (sterols), and certain natural drugs and poisons. Steroids have a common nucleus, a fused, reduced 17-carbon atom ring system, cyclopentanoperhydrophenanthrene. Most steroids also have two methyl groups and an aliphatic side-chain attached to the nucleus. Benign Liver Tumors, antivirals, and topical atropine Atropine An alkaloid, originally from atropa belladonna, but found in other plants, mainly solanaceae. Hyoscyamine is the 3(s)-endo isomer of atropine. Anticholinergic Drugs.
• Keratitis Keratitis Inflammation of the cornea. Herpes Simplex Virus 1 and 2: a mostly infectious acute or chronic inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the cornea Cornea The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous corneal epithelium; bowman membrane; corneal stroma; descemet membrane; and mesenchymal corneal endothelium. It serves as the first refracting medium of the eye. Eye: Anatomy. Other causes include allergy Allergy An abnormal adaptive immune response that may or may not involve antigen-specific IgE Type I Hypersensitivity Reaction and trauma. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship commonly present with a red, teary painful eye, impaired vision Vision Ophthalmic Exam, and photophobia Photophobia Abnormal sensitivity to light. This may occur as a manifestation of eye diseases; migraine; subarachnoid hemorrhage; meningitis; and other disorders. Photophobia may also occur in association with depression and other mental disorders. Migraine Headache. Treatment depends on the underlying condition and includes topical antivirals, antibiotics, and antifungals.
• Meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis (especially in infants): a potentially life-threatening inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the leptomeninges Leptomeninges Meninges: Anatomy, mostly due to viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology or bacteria Bacteria Bacteria are prokaryotic single-celled microorganisms that are metabolically active and divide by binary fission. Some of these organisms play a significant role in the pathogenesis of diseases. Bacteriology. Common symptoms include headaches, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, a stiff neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, altered mental status Altered Mental Status Sepsis in Children, photophobia Photophobia Abnormal sensitivity to light. This may occur as a manifestation of eye diseases; migraine; subarachnoid hemorrhage; meningitis; and other disorders. Photophobia may also occur in association with depression and other mental disorders. Migraine Headache, and phonophobia Phonophobia Specific Phobias. Young children often present with nonspecific symptoms. Treatment consists of antibiotics, antivirals, and corticosteroids Corticosteroids Chorioretinitis. 
• Subconjunctival hemorrhage: This condition is usually asymptomatic. The clinical appearance, with demarcated areas of extravasated blood just beneath the surface of the eye, is generally both obvious and diagnostic. It may occur spontaneously or with Valsalva-associated mechanisms (e.g., coughing, sneezing Sneezing The sudden, forceful, involuntary expulsion of air from the nose and mouth caused by irritation to the mucous membranes of the upper respiratory tract. Rhinovirus, or vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia). The diagnosis is confirmed by normal acuity and the absence of discharge, photophobia Photophobia Abnormal sensitivity to light. This may occur as a manifestation of eye diseases; migraine; subarachnoid hemorrhage; meningitis; and other disorders. Photophobia may also occur in association with depression and other mental disorders. Migraine Headache, or foreign body Foreign Body Foreign Body Aspiration sensation. It typically resolves within 1 to 2 weeks.
• Chalazion Chalazion A chalazion is one of the most common inflammatory lesions of the eyelid. It is caused by obstruction of the Meibomian or Zeis glands, leading to granulomatous inflammation and resulting in a firm, rubbery, slow-growing nodule that is typically non-tender. Chalazion: presents as painless localized eyelid swelling Swelling Inflammation and firm rubbery nodule Nodule Chalazion. It is caused by the obstruction of Zeis or Meibomian glands.
• Dry eye syndrome: a multifactorial disease of the ocular surface with loss of tear film and ocular symptoms, also known as keratoconjunctivitis sicca Keratoconjunctivitis Sicca Rheumatoid Arthritis. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship present with dryness and redness Redness Inflammation of the eye, general irritation, gritty/burning sensation, foreign body Foreign Body Foreign Body Aspiration sensation, paradoxical excessive tearing, photophobia Photophobia Abnormal sensitivity to light. This may occur as a manifestation of eye diseases; migraine; subarachnoid hemorrhage; meningitis; and other disorders. Photophobia may also occur in association with depression and other mental disorders. Migraine Headache, or blurred vision Vision Ophthalmic Exam. 
• Blepharitis Blepharitis Blepharitis is an ocular condition characterized by eyelid inflammation. Anterior blepharitis involves the eyelid skin and eyelashes, while the posterior type affects the meibomian glands. Often, these conditions overlap. Blepharitis: an inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the eyelid margin with eye irritation. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship usually present with red, swollen, or itchy eyelids Eyelids Each of the upper and lower folds of skin which cover the eye when closed. Blepharitis, a gritty burning sensation, conjunctival injection, crusting and matting of the eyelashes in the morning, photophobia Photophobia Abnormal sensitivity to light. This may occur as a manifestation of eye diseases; migraine; subarachnoid hemorrhage; meningitis; and other disorders. Photophobia may also occur in association with depression and other mental disorders. Migraine Headache, and blurred vision Vision Ophthalmic Exam.