Herpes

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Herpes simplex keratitis

  • Herpes simplex virus (HSV).
    • It is a DNA virus.
    • Its only natural host is man
    • HSV is epitheliotropic but may become neurotropic.
    • HSV type I typically causes infection above the waist
    • HSV type II below the waist (herpes genitalis)
  • Mode of Infection
    • HSV-1 infection
      • It is acquired by kissing or coming in close contact with a patient suffering from herpes labialis.
    • HSV-II infection.
      • It is transmitted to eyes of neonates through infected genitalia of the mother(MCQ)
  • Ocular lesions of herpes simplex
    • Primary herpes
      • Skin lesions
      • Conjunctiva-acute follicular conjunctivitis
      • Cornea
        • Fine epithelial punctate keratitis
        • Coarse epithelial punctate keratitis
        • Dendritic ulcer
    • Recurrent herpes
      • Active epithelial keratitis
        • Punctate epthelial keratitis
        • Dendritic ulcer
        • Geographical ulcer
      • Stromal keratitis
        • Disciform keratitis
        • Diffuse stromal necrotic keratitis
      • Trophic keratitis (meta-herpetic)
      • Herpetic iridocyclitis
  • Primary ocular herpes
    • Primary infection (first attack) involves a nonimmune person.
    • It typically occurs in children between 6 months and 5 years of age and in teenagers.
    • Primary infection is usually self-limiting but the virus travels up to the trigeminal ganglion and establishes the latent infection
  • Recurrent ocular herpes
    • The virus which lies dormant in the trigeminal ganglion
    • periodically reactivates and causes recurrent infection.
    • Predisposing stress stimuli which trigger an attack of herpetic keratitis include
      • fever such as malaria, flu
      • exposure to ultraviolet rays
      • general ill- health,
      • emotional or physical exhaustion,
      • mild trauma,
      • menstrual stress,
      • following administration of topical or systemic steroids and immunosuppressive agents.
  • Dendritic ulcer (MCQ)
    • typical lesion of recurrent epithelial keratitis.
    • The ulcer is of an irregular, zigzag linear branching shape.
    • The branches are generally knobbed at the ends.
    • Floor of the ulcer stains with fluorescein
    • virus-laden cells at the margin take up rose bengal.
    • There is an associated marked diminution of corneal sensations
  • Geographical ulcer (MCQ)
    • branches of dendritic ulcer enlarge and coalesce to form a large epithelial ulcer with a ‘geographical’ or ‘amoeboid’ configuration
    • The use of steroids in dendritic ulcer hastens the formation of geographical ulcer. (MCQ)
  • Symptoms of epithelial keratitis are: photophobia lacrimation, pain.
  • Treatment of epithelial keratitis
    • Antiviral drugs are the first choice presently.
      • Acycloguanosine (Aciclovir) 3 percent ointment:(MCQ)
        • It is least toxic and most commonly used antiviral drug.
        • It penetrates intact corneal epithelium and stroma
        • achieves therapeutic levels in aqueous humour
        • used to treat herpetic keratitis.
      • Ganciclovir (0.15% gel)
      • Triflurothymidine 1 percent
      • Adenine arabinoside (Vidarabine) 3 percent ointment
    • Mechanical debridement of the involved area along with a rim of surrounding healthy epithelium
      • helps by removing the virus-laden cells.
      • it is reserved for: resistant cases
    • Disciform keratitis (MCQ)
      • It is due to delayed hypersensitivity reaction to the HSV antigen (MCQ)
      • There occurs low grade stromal inflammation and damage to the underlying endothelium.
      • Endothelial damage results in corneal oedema due to imbibation of aqueous humour.
      • Disciform keratitis is characterized by
      • Focal disc-shaped patch of stromal oedema without necrosis
      • Folds in Descemet’s membrane,
    • Keratic precipitates,
      • Ring of stromal infilterate (Wessley immune ring) (MCQ)
      • may be present surrounding the stromal oedema
      • It signifies the junction between viral antigen and host antibody.
      • Corneal sensations are diminished.
      • Intraocular pressure (IOP) may be raised despite only mild anterior uveitis.
        • During active stage diminished corneal sensations and keratic precipitates are the differentiating points from other causes of stromal oedema.
    • Treatment
      • consists of diluted steroid eye drops instilled 4-5 times a day with an antiviral cover (aciclovir 3%) twice a day.
      • When disciform keratitis is present with an infected epithelial ulcer, antiviral drugs should be started 5-7 days before the steroids.

HERPES ZOSTER OPHTHALMICUS

  • an acute infection of Gasserian ganglion of the fifth cranial nerve by the varicella-zoster virus (VZV)
  • Varicella -zoster virus.
    • It is a DNA virus
    • produces acidophilic intranuclear inclusion bodies.
    • It is neurotropic in nature.
  • Mode of infection.
    • The infection is contracted in childhood, which manifests as chickenpox
    • virus then remains dormant in the sensory ganglion of trigeminal nerve.
    • in elderly people with depressed cellular immunity, the virus reactivates, replicates and travels down along one or more of the branches of the ophthalmic division of the fifth nerve.
  • Clinical features
    •  In herpes zoster ophthalmicus, frontal nerve is more frequently affected than the lacrimal and nasociliary nerves.(MCQ)
    •  The Hutchinson’s rule
      • ocular involvement is frequent if the side or tip of nose presents vesicles (cutaneous involvement of nasociliary nerve)
      •  Lesions of herpes zoster are strictly limited to one side of the midline of head.
    • Cutaneous lesions.
      • appear usually after 3-4 days of onset of the disease.
      • To begin with, the skin of lids and other affected areas become red and oedematous (mimicking erysipelas), followed by vesicle formation.
      • In due course of time vesicles are converted into pustules, which subsequently burst to become crusting ulcers.
      • When crusts are shed, permanent pitted scars are left.
      • The active eruptive phase lasts for about 3 weeks.
      • Main symptom is severe neuralgic pain
      • anaesthesia dolorosa
        • There occurs some anaesthesia of the affected skin associated with continued post-herpetic neuralgia
    • Ocular lesions.
      • usually appear at the subsidence of skin eruptions
      • Conjunctivitis
        • one of the most common complication of herpes zoster.
      • Zoster keratitis
        • Fine or coarse punctate epithelial keratitis.
        • Microdendritic epithelial ulcers.
          • These unlike dendritic ulcers of herpes simplex are usually peripheral and stellate rather than exactly dendritic in shape.
          • It contrast to Herpes simplex dendrites, they have tapered ends which lack bulbs.
        •  Nummular keratitis
          • is seen in about one-third number of total cases.
          • It typically occurs as multiple tiny granular deposits surrounded by a halo of stromal haze.
        •  Disciform keratitis
          • occurs in about 50 percent of cases
          • is always preceded by nummular keratitis.
      • Neuroparalytic ulceration may occur as a sequelae of acute infection and Gasserian ganglion destruction.
      • Exposure keratitis due to associated facial palsy.
      • Mucous plaque keratitis develops
        • Occurs between 3rd and 5th months
        • characterised by sudden development of elevated mucous plaque with stain brilliantly with rose Bengal
      • Episcleritis and scleritis.
      • Iridocyclitis
      • Acute retinal necrosis
      • Anterior segment necrosis and phthisis bulbi
      • Secondary glaucoma.
  • Treatment
    • Oral antiviral drugs.
      • These significantly decrease pain, curtail vesiculation, stop viral progression and reduce the incidence as well as severity of keratitis and iritis.
      • In order to be effective, the treatment should be started immediately after the onset of rash.
      • It has no effect on post herpetic neuralgia(MCQ)
      • Acyclovir , Valaciclovir are used
    • Systemic steroids.
      • They appear to inhibit development of post-herpetic neuralgia when given in high doses.
      • Steroids are commonly recommended in cases developing neurological complications such as third nerve palsy and optic neuritis.
    • Amitriptyline should be used to relieve the accompanying depression in acute phase.
    • No calamine lotion.
      • Cool zinc calamine application, as advocated earlier, is better avoided
      • it promotes crust formation.

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