CORNEAL OEDEMA

The water content of normal cornea is 78 percent. It
is kept constant by a balance of factors which draw
water in the cornea (e.g., intraocular pressure and
swelling pressure of the stromal matrix = 60 mm of
Hg) and the factors which draw water out of cornea
(viz. the active pumping action of corneal
endothelium, and the mechanical barrier action of
epithelium and endothelium).
Disturbance of any of the above factors leads to
corneal oedema, wherein its hydration becomes above
78 percent, central thickness increases and
transparency reduces.
Causes of corneal oedema
1. Raised intraocular pressure
2. Endothelial damage
i. Due to injuries, such as birth trauma (forceps
delivery), surgical trauma during intraocular
operation, contusion injuries and penetrating
injuries.
ii. Endothelial damage associated with corneal
dystrophies such as, Fuchs dystrophy,
congenital hereditary endothelial dystrophy
and posterior polymorphous dystrophy.
iii. Endothelial damage secondary to inflammations
such as uveitis, endophthalmitis and corneal
graft infection.
3. Epithelial damage due to :
i. mechanical injuries
ii. chemical burns
iii. radiational injuries
Clinical features
Initially there occurs stromal haze with reduced vision.
In long-standing cases with chronic endothelial
failure (e.g., in Fuch's dystrophy) there occurs
permanent oedema with epithelial vesicles and bullae
formation (bullous keratopathy). This is associated
with marked loss of vision, pain, discomfort and
photophobia, due to periodic rupture of bullae.
Treatment
1. Treat the cause wherever possible, e.g., raised
IOP and ocular inflammations.
2. Dehydration of cornea may be tried by use of:
i. Hypertonic agents e.g., 5 percent sodium
chloride drops or ointments or anhydrous
glycerine may provide sufficient dehydrating
effect.
ii. Hot forced air from hair dryer may be useful.
3. Therapeutic soft contact lenses may be used to
get relief from discomfort of bullous keratopathy.
4. Penetrating keratoplasty is required for longstanding
cases of corneal oedema, non-responsive
to conservative therapy.