1. Differential diagnosis
1.1. Acanthamoeba keratitis
1.2. Herpes zoster keratitis
1.3. Adenoviral keratitis
1.4. Staphylococcal marginal keratitis
1.5. Graft rejection
2. Treatment
2.1. Epithelial keratitis
2.1.1. Topical antiviral
2.1.2. Oral antiviral
2.1.3. +/- epithelial debridement
2.2. Stromal keratitis
2.2.1. Stromal keratitis without ulceration/ Immune stromal keratitis
2.2.1.1. Topical corticosteroid + oral antiviral agent for atleast 10 weeks
2.2.1.2. Balance between antiviral and corticosteroids should be adjusted depending on presence or absence of epithelial defect
2.2.1.3. Oral antiviral preferred in view of better of corneal penetration and safety profile
2.2.2. Stromal keratitis with ulceration/ Necrotising stromal keratitis
2.2.2.1. Therapeutic doses of oral antivirals
2.2.2.2. Judicious use of corticosteroids
2.3. Endothelial keratitis
2.3.1. Topical corticosteroid
2.3.2. Oral antiviral agent
3. Prophylaxis
3.1. When ?
3.1.1. HSV stromal keratitis
3.1.2. After ocular surgery
3.1.3. Recurrent ocular HSV
3.2. What ?
3.2.1. Acyclovir 400 mg BD
3.2.2. Valacyclovir 500 mg OD
4. Antiviral medications
4.1. Topical
4.1.1. Trifluridine solution
4.1.2. Acyclovir ointment
4.1.3. Ganciclovir gel
4.2. Systemic
4.2.1. Acyclovir
4.2.2. Valacyclovir
4.2.3. Famciclovir
4.3. Precautions
4.3.1. Can cause nephrotoxicity
4.3.1.1. Elderly patients
4.3.1.2. Patients with renal impairment
4.3.1.2.1. To administer half dose
4.3.1.2.2. Increase the timing between two doses
4.3.2. Potential to cause neurotoxicity in patients with compromised renal function
5. Special mention
5.1. Acyclovir
5.1.1. Acyclovir resistance
5.1.1.1. when to suspect
5.1.1.1.1. Recurrent HSV infection inspite of prophylaxis
5.1.1.1.2. Immunocompromised host when systemic therapy fails
5.1.1.2. Mechanism
5.1.1.2.1. Complete/partial Thymidine kinase deficiency
5.1.1.2.2. Rarely (5%)-DNA polymerase deficiency
5.1.1.3. Usually cross resistance to valacyclovir, Ganciclovir, Famciclovir
5.1.1.4. Treatment options
5.1.1.4.1. Trifluridine
5.1.1.4.2. Foscarnet
5.1.1.4.3. Cidofovir
6. Epidemiology
6.1. Only natural resorvoirs: Humans
6.2. Transmission: Infected secretions (saliva/tears)
6.3. Seroprevalence higher in socioeconomic class
7. Life cycle of HSV
7.1. Infected secretions
7.1.1. Exposure of skin/mucous memebrane
7.1.1.1. Primary infection
7.1.1.1.1. Blepharitis
7.1.1.1.2. Conjunctivitis
7.1.1.1.3. Keratitis (17%)
7.1.1.2. Asymptomatic carrier
7.1.1.2.1. Retrograde transport through sensory nerves
8. Classification
8.1. Epithelial keratitis
8.1.1. Dendritic epithelial keratitis
8.1.2. Geographic epithelial keratitis
8.2. Stromal keratitis
8.2.1. HSV immune stromal keratitis
8.2.2. HSV necrotising stromal keratitis
8.3. Endothelitis
8.3.1. Disciform
8.3.2. Linear
8.3.3. Diffuse
8.4. Keratouveitis
9. Risk Factors
9.1. Organ transplant recipients
9.2. Diabetes mellitus
9.3. HIV
9.4. Atopy
9.5. Topical medications
9.5.1. Corticosteroids
9.5.2. Prostaglandin analogues
9.5.3. Anti- VEGFs
9.6. Local trauma/surgery
9.6.1. Contact lens use
9.6.2. Refractive surgery
9.6.3. Cataract surgery
9.6.4. Lamellar/penetrating keratoplasty
10. Diagnosis
10.1. Slit lamp biomicroscopy
10.2. Culture
10.2.1. Gold standard in lab diagnosis
10.2.2. Low sensitivity, high specificity
10.2.3. Time consuming : Require 10 days for growth
10.2.4. Avoid use of rose bengal dye during examination : Rose bengal is virucidal when exposed to light
10.3. Direct Fluorescent antibody (DFA)
10.3.1. High sensitivity (87.5%) and high specificity (85.3%)
10.3.2. Rapid test results
10.3.3. Use of topical fluorescein prior to test interferes with results
10.4. Polymerase chain reaction (PCR)
10.4.1. As specific however more sensitive than culture
10.4.2. Detects copies of viral DNA
10.4.3. Rapid test
10.4.4. Unable to differentiate normal virus shedding from infection
10.5. Miscellaneous tests
10.5.1. Tzank smear
10.5.1.1. Giemsa/ Papanicolou stain used
10.5.1.2. Cowdry type A intranuclear inclusions-characteristic
10.5.2. ELISA (Enzyme linked immunosorbent assay)
10.5.2.1. Detection of antigens by specific antibodies against HSV antigens
10.5.3. Serology
10.5.3.1. IgG, IgM titre