What is it?

• Chemical injuries of the eye are ocular emergencies that necessitate urgent clinical attention. 
• Alkali injuries are in general more common and destructive than acidic injuries.
• Alkalis are lipophilic and therefore have greater potential to penetrate tissues by liquefactive necrosis, compared to acidic agents which cause damage by coagulative necrosis and remain on the surface of the eye. 
• Accidental chemical injuries can occur at home or at work. However, it may also be the result of a deliberate assault.

Common Etiological Agents

Alkalis

*Ammonia and lye tend to cause more severe alkali injuries  

Acids

How do they present?  

• Common symptoms include: 
  • Pain/stinging/burning sensation
  • Watery eyes
  • Blurry vision
  • Red eyes 
  • Eyelid swelling
• Patients may also report symptoms from non-chemical injuries e.g. blunt ocular trauma or thermal injuries.
• It is important to determine the duration of contact from the history as this is an important prognostic factor
• Importantly, the severity of the injury does not always correlate with the degree of pain reported by the patient. Patients with alkali eye injuries may not always report serious pain but such cases can lead to serious long-term eye complications if left untreated.

How should you manage in the acute setting?

• IMMEDIATE irrigation – this should be prioritised over history and examination if chemical injury is suspected:
  • Remove any contact lenses if present
  • Measure pH of both eyes using indicator strips or litmus paper (if available)

Figure 1: Litmus paper used to measure pH of the eye. Source: https://go.gale.com/ps/i.do?p=AONE&u=googlescholar&id=GALE|A215061621&v=2.1&it=r&sid=AONE&asid=bf68e18c

• Instil topical anaesthesia (e.g. proxymetacaine)

Figure 2: application of topical anaesthesia. Source: https://go.gale.com/ps/i.do?p=AONE&u=googlescholar&id=GALE|A215061621&v=2.1&it=r&sid=AONE&asid=bf68e18c

• Irrigation with at least 2L of water, normal saline, Diphoterine or Hartmann’s solution via IV tubing. 

Figure 3: Irrigation of the eye using IV giving set. Source: https://go.gale.com/ps/i.do?p=AONE&u=googlescholar&id=GALE|A215061621&v=2.1&it=r&sid=AONE&asid=bf68e18c

• If the fluids above are unavailable, irrigate the eye under a cold-water tap.
  • Irrigation cycle should last at least 20 mins.
• Inspection: 
  • evert the upper and lower lids
  • inspect the upper and lower fornices for retained particulate matter which may perpetuate alkalinity
  • remove any matter with cotton bud
• Measure pH at the end of the irrigation cycle. Repeat irrigation cycle until pH is neutral/near-neutral 
• Once pH is neutral/near-neutral, examine using a slit lamp. In particular, look for fluorescein staining:    
  • Administer one drop of fluorescein 2% and examine the conjunctiva and cornea under the blue light. 
  • Epithelial defects of conjunctiva and/or cornea will highlight green 

Figure 4: corneal epithelial defect noted under blue light after instilling fluorescein 2. Source: https://www.eyenews.uk.com/features/ophthalmology/post/resurfacing-the-ocular-surface

Early review from ophthalmology is imperative to guide further management. This usually involves a thorough examination under the slit lamp. Further treatment includes topical antibiotics, cycloplegia +/- steroids, vitamin C etc

Complications

• Conjunctival and/or corneal epithelial defect – important prognosticator
• Corneal perforation/melt
• Perilimbal ischaemia (loss of corneal stem cells) – important prognosticator
• Intraocular inflammation
• Dry eyes
• Scarring of conjunctiva and/or cornea
• Glaucoma
• Cataract

References

1. https://eyewiki.aao.org/Chemical_(Alkali_and_Acid)_Injury_of_the_Conjunctiva_and_Cornea
2. Singh P, Tyagi M, Kumar Y, Gupta KK, Sharma PD. Ocular chemical injuries and their management. Oman J Ophthalmol. 2013 May;6(2):83-6. doi: 10.4103/0974-620X.116624. PMID: 24082664; PMCID: PMC3779420.
3. Rodrigues Z. Irrigation of the eye after alkaline and acidic burns. Emerg Nurse. 2009 Dec;17(8):26-9. doi: 10.7748/en2009.12.17.8.26.c7431. PMID: 20043429.
4. Denniston, Alastair, and Philip Murray (eds), Oxford Handbook of Ophthalmology, 3 edn, Oxford Medical Handbooks (Oxford, 2014; online edn, Oxford Academic, 1 Oct. 2014), https://doi.org/10.1093/med/9780199679980.001.0001, accessed 21 Dec. 2022.

Written by Mr Felyx Wong (Final Year Medical Student) & reviewed by Dr Byron Lu Morrell (ST3 Ophthalmology)