Photokeratitis (UV keratitis / snow blindness / welder’s eye)
1. Definition
- Acute
corneal injury จาก ultraviolet (UV) radiation
- เกิด epithelial damage →
pain มาก
- self-limited
disease
2. Pathophysiology
- Cornea
absorb UV (especially UV-B, UV-C)
- → epithelial cell death +
desquamation
- → expose nerve endings → severe pain
timeline
- onset:
30 min – หลายชั่วโมงหลัง exposure
- recovery:
24–72 hr (re-epithelialization)
3. Common Causes
Recreational
- snow
/ skiing (snow blindness)
- beach
/ water reflection
Occupational
- welding
(arc eye)
- UV
lamp / germicidal lamp
- tanning
bed
4. Clinical Presentation
4.1 Symptoms (สำคัญ)
- severe
eye pain
- foreign
body sensation
- photophobia
- tearing
- ↓ vision (mild)
👉 มัก bilateral
4.2 Key clue
- history
UV exposure + delayed onset
5. Physical Examination
- conjunctival
injection
- tearing
- eyelid
erythema (sunburn)
- fluorescein
→ diffuse
punctate epithelial erosions
👉 visual acuity: mild ↓ (not severe)
6. Diagnosis
clinical diagnosis
- UV
exposure history + typical exam
👉 สำคัญมาก:
- ต้อง exclude infectious keratitis
7. Differential Diagnosis
|
Disease |
Key difference |
|
Corneal abrasion |
unilateral, focal stain |
|
Infectious keratitis |
severe vision loss + infiltrate |
|
Conjunctivitis |
discharge / itching |
|
Dry eye |
chronic |
|
Exposure keratopathy |
inferior cornea involvement |
8. Management (supportive)
8.1 First-line treatment
- artificial
tears (frequent)
- topical
antibiotic (prophylaxis)
- moxifloxacin
/ ofloxacin / erythromycin
- oral
NSAIDs
👉 severe pain → short course opioid
8.2 Additional care
- หยุด contact lens
- follow-up
2–3 วัน
8.3 Do NOT do
❌ topical anesthetic (ใช้เฉพาะตรวจ)
→ risk corneal ulcer /
blindness
❌ eye patch
❌ routine cycloplegic
9. Indications for Referral
- severe
↓ vision
- unilateral
atypical
- contact
lens user (สงสัย infectious keratitis)
- no
improvement in 48–72 hr
10. Prognosis
- recovery
ภายใน 3–7 วัน
- ไม่มี long-term sequelae ใน acute case
11. Prevention
- UV-block
sunglasses (UV-A + UV-B)
- protective
goggles (welding / UV lamp)
12. Clinical Pearls
- pain
มาก แต่ exam mild →
นึกถึง photokeratitis
- bilateral
+ delayed onset = key clue
- fluorescein
= diffuse pattern
- ห้ามให้ topical anesthetic กลับบ้าน
13. Practical ER Approach
Step 1: history
- UV
exposure? (welding / snow / UV lamp)
Step 2: exam
- VA +
fluorescein
- exclude
ulcer / infiltrate
Step 3: treat
- lubricant
+ topical ATB + analgesia
Step 4: follow-up
- 48–72
hr
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