1. BY- DR N KThakur
Associate Professor
Department of Ophthalmology
SMCH
CORNEAL EDEMA
2. Cornea
It is a transparent ,avascular structure
It forms anterior one sixth of the outer fibrous coat of the
eyeball
The anterior surface of cornea is elliptical with an average
horizontal diameter of 11.7 mm and vertical diameter of 11
mm.
The posterior surface of cornea is circular with an average
diameter of 11.5 mm.
Thickness of cornea in the centre is about 0.52 mm while at
the periphery it is 0.7 mm.
3. Radius of curvature.The central 5 mm area of the cornea
forms the powerful refracting surface of the eye.
The anterior and posterior radii of curvature of this central
part of cornea are 7.8 mm and 6.5 mm, respectively.
Refractive power of the cornea is about 45 dioptres, which is
roughly three-fourth of the total refractive power of the eye
(60 dioptres)
4. Histology
Cornea consists of five distinct layers. From anterior to
posterior these are:
Epithelium
Bowman’s membrane
Substantia propria (corneal stroma)
Descemet’s membrane
Endothelium
6. FUNCTION
The primary physiological functions of the cornea are
To act as a major refracting medium
To protect the intraocular contents.
To maintain the transparency
7. CORNEAL TRANSPARENCY
The transparency is the result of :
Peculiar arrangement of corneal lamellae (lattice theory of
Maurice)
Avascularity
Relative state of dehydration(78%WATER CONTENT), which is
maintained by barrier effects of epithelium and endothelium and
the active sodium potassiumATPase pump of the endothelium.
Swelling pressure of stroma which encounters the imbibition
effect of IOP
Corneal crystalline ,water soluble protiens of keratocytes
contribute in corneal transparency
9. Corneal Edema
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 ofHg) 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
its hydration becomes above 78 percent, central thickness
increases and transparency reduces
11. Causes of corneal edema
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.
12. ii. Endothelial damage associated with corneal
dystrophies such as
Fuchs dystrophy,
congenital hereditary endothelial dystrophy
posterior polymorphous dystrophy.
iii. Endothelial damage secondary to inflammations
uveitis,
endophthalmitis
corneal graft infection.
13. 3. Epithelial damage due to :
i. mechanical injuries
ii. chemical burns
iii. radiational injuries
14. 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.
15. Treatment
Treat the cause wherever possible, e.g., raised IOP and
ocular inflammations.
Dehydration of cornea may be tried by use of:
1. . Hypertonic agents e.g., 5 percent sodiumchloride drops
or ointments or anhydrous glycerine may provide sufficient
dehydrating effect.
2. Hot forced air from hair dryer may be useful.
16. 3.Therapeutic soft contact lenses may be used to get relief from
discomfort of bullous keratopathy.
4. Penetrating keratoplasty is required for long-
standing cases of corneal oedema, non responsive to
conservative therapy.
