Alkali burns

Alkali burns are among the most severe chemical
injuries known to the ophthalmologists. Common
alkalies responsible for burns are: lime, caustic potash
or caustic soda and liquid ammonia (most harmful).
Mechanisms of damage produced by alkalies
includes:
1. Alkalies dissociate and saponify fatty acids of
the cell membrane and, therefore, destroy the
structure of cell membrane of the tissues.
2. Being hygroscopic, they extract water from the
cells, a factor which contributes to the total
necrosis.
3. They combine with lipids of cells to form soluble
compounds, which produce a condition of
softening and gelatinisation.
The above effects result in an increased deep
penetration of the alkalies into the tissues. Alkali
burns, therefore, spread widely, their action continues
for some days and their effects are difficult to
circumscribe. Hence, prognosis in such cases must
always be guarded.
Clinical picture. It can be divided into three stages:
1. Stage of acute ischaemic necrosis. In this stage;
i. Conjunctiva shows marked oedema,
congestion, widespread necrosis and a copious
purulent discharge.
ii. Cornea develops widespread sloughing of the
epithelium, oedema and opalescence of the
stroma.
iii. Iris becomes violently inflamed and in severe
cases both iris and ciliary body are replaced
by granulation tissue.
2. Stage of reparation. In this stage conjunctival
and corneal epithelium regenerate, there occurs
corneal vascularization and inflammation of the
iris subsides.
3. Stage of complications. This is characterised by
development of symblepharon, recurrent corneal
ulceration and development of complicated
cataract and secondary glaucoma.