Grading the Severity of Alkali Burns of the Eye

 

Common alkali chemicals involved in ocular exposure:

(1) sodium hydroxide

(2) lime (calcium hydroxide)

(3) ammonia compounds

 

Phases of alkali injury:

(1) Alkali rapidly penetrates the epithelium of the cornea and conjunctiva after making contact with the eye.

(2) Immediately after the exposure there is pain due to nerve stimulation, followed by anesthesia as the nerve endings are destroyed.

(3) Shortly after the exposure there is lysis of corneal cells with release of chemotactic factors and inactivation of enzymes.

(4) This is followed by a leukocytic infiltration with degranulation and proteolysis.

(5) There is a rapid rise in intraocular pressure.

(6) In more severe injury, the cornea becomes translucent or opaque and the conjunctiva becomes edematous, with involvement of the perilimbal blood vessels resulting in ischemic damage

(7) Ischemic necrosis of conjunctiva or sclera is indicated by blanching, with severe burns resulting in marked whitening of the sclera.

(8) Ongoing injury with recurrent epithelial breakdown and ulceration following the exposure, sometimes occurring months or even years later.

 

Grading Alkali Burns

 

The extent of permanent injury is determined by:

(1) the nature and concentration of the alkali, with the pH critical

(2) the length of time before the eye is irrigated

 

Grading is usually performed about 24 hours after the exposure.

Cornea	Conjunctiva	Grade
no epithelial damage	no ischemia	0
epithelial damage with faint haziness	no ischemia	1
hazy but iris detail seen	ischemia less than one third at limbus	2
total epithelial loss; stromal haze with iris details blurry but still observable	ischemia of one third to one half at limbus	3
opaque with no view of iris or pupil	ischemia affects more than one half at limbus	4

 

where:

• The limbus is point of insertion of the cornea into the sclera.

 

Complications of Alkali Burns

 

Possible complications:

(1) corneal scarring with visual handicap

(2) corneal vascularization with visual handicap

(3) corneal ulceration, which may occur long after the exposure

(4) acute or chronic glaucoma

(5) perforation of the cornea or bulb

(6) hypotonic (phthisis bulbi) because of injury to the aqueous forming structures

(7) symblepharon formation

(8) severe dry eye state due to destruction of the openings from the accessory and main lacrimal glands

 

Grade	Prognosis
1	good
2	good
3	vision reduced, perforation rare
4	poor with prolonged convalescence