Herpes Simplex Keratitis (HSV keratitis)
1. Definition
- Corneal
infection จาก Herpes simplex virus (HSV-1)
- เป็นสาเหตุสำคัญของ corneal blindness จาก
scarring
2. Pathophysiology
Key concept
- primary
infection → latency ที่ trigeminal ganglion
- reactivation
→ corneal infection
3 mechanisms หลัก
1.
active viral infection (epithelium)
2.
immune-mediated inflammation (stroma)
3.
post-infectious neurotrophic damage
3. Epidemiology / Risk
- infection
พบได้มาก (seropositive >90%)
- ocular
disease ส่วนใหญ่ = reactivation
Risk factors (recurrence)
- UV
exposure
- stress
/ trauma
- ocular
surgery
- topical
steroid
- immunosuppression
👉 recurrence สูงมาก (up to 67% ใน 10 ปี)
4. Clinical Presentation
4.1 Symptoms
- pain
- photophobia
- blurred
vision
- tearing
- red
eye
👉 มัก unilateral
5. Classification (สำคัญมากทางคลินิก)
5.1 Epithelial keratitis (most common)
- hallmark:
dendritic ulcer
- ↓ corneal sensation
👉 เกิดจาก active
viral replication
5.2 Stromal keratitis (vision-threatening)
- immune-mediated
(most common)
- stromal
opacity / haze
- neovascularization
👉 เสี่ยง corneal
scarring
5.3 Necrotizing keratitis (severe)
- stromal
infiltrate + ulcer
- อาจ perforate
5.4 Endotheliitis (disciform)
- stromal
edema (disc-shaped)
- keratic
precipitates
5.5 Neurotrophic keratopathy
- ↓ corneal sensation
- non-healing
epithelial defect
6. Diagnosis
6.1 Clinical diagnosis (ส่วนใหญ่)
- dendritic
lesion = pathognomonic
6.2 Investigations
- slit
lamp + fluorescein
- PCR
(กรณี atypical/severe)
7. Differential Diagnosis
- Herpes
zoster (pseudodendrite)
- corneal
abrasion
- Acanthamoeba
keratitis
- bacterial
keratitis
8. Management
🚨 Key rule
❗ ห้ามใช้ topical
steroid เดี่ยวใน epithelial disease
8.1 Epithelial keratitis
First-line
- Oral
antiviral (preferred)
- acyclovir
400 mg 5x/day
- valacyclovir
500 mg TID
OR
- topical
antiviral (ganciclovir gel)
⏱ duration ~10–14 วัน
👉 healing เร็วขึ้น
(1–2 สัปดาห์)
8.2 Stromal keratitis / Endotheliitis
standard
- topical
steroid + antiviral
👉 steroid ลด
inflammation
👉
antiviral ป้องกัน viral reactivation
8.3 Adjunct
- epithelial
debridement (บาง case)
8.4 Follow-up
- epithelial
→ review 1 week
- stromal
→ close follow-up
9. Indications for Referral
- ทุก case ควร follow กับ ophthalmology
- urgent
ถ้า
- stromal
involvement
- severe
pain / ↓ vision
- diagnostic
uncertainty
10. Complications
- corneal
scarring
- vision
loss
- perforation
(severe case)
- recurrent
disease
11. Recurrence Prevention
- suppressive
antiviral
- acyclovir
400 mg BID
- valacyclovir
500 mg daily
👉 ลด recurrence
(~50%)
12. Clinical Pearls
- dendritic
ulcer = HSV until proven otherwise
- unilateral
+ recurrent same eye →
clue
- ↓ corneal sensation → helpful sign
- steroid
alone → ทำให้แย่ลง
- stromal
disease = immune → ต้อง steroid
13. Practical Approach (ER/OPD)
Step 1: suspect
- unilateral
red eye + pain + photophobia
Step 2: exam
- fluorescein
→ dendritic?
Step 3: treat
- epithelial
→ antiviral
- stromal
→ steroid + antiviral
Step 4: refer
- ophthalmology
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