Almost all diseases of the cornea have some form or degree of
inflammation. =Keratitis= is the word generally used for inflammation
of the cornea. In order to aid clearness in discussion there are
various subdivisions of keratitis made by different writers.
Suppurative and non-suppurative are the principal types. In
=suppurative keratitis= there is always some destruction of corneal
tissue which on healing leaves an opacity with partial loss of vision.
Germs gain entrance into the tissues usually from the exterior and some
form of ulceration results.
The following classification is taken from Fuchs:
=Suppurative Keratitis.=—(1) Ulcer of the cornea; (2) Serpiginous
ulcer; (3) Keratomalacia or Xerosis; (4) Keratitis neuroparalytica.
=Non-suppurative Keratitis.=—(A) SUPERFICIAL: (1) Pannus, or keratitis
with blood vessels; (2) Phlyctenular, or keratitis with vesicles. (B)
DEEP: (1) Parenchymatous or interstitial.
In keratitis there is first an infiltration or the increase of cells
in the substantia propria or the parenchyma of the cornea. This is
the exudate of the inflammation. It causes the cornea to look more
or less dull or cloudy. The disease may clear up at this point or
go on to suppuration. If it clears up it is known as =resorption=.
If the lamellæ of the substantia propria are not destroyed by the
process, resorption takes place with no loss of substance. The exudate
disappears and there is perfect transparency of the cornea again. There
may be slight damage of the stroma preventing perfect transparency.
Resorption of the exudate may not be quite complete which may
become partly organized and left permanently fixed in the cornea.
Cases resorbing without destruction of the stroma are forms of the
non-suppurative keratitis group.
If the stroma breaks, suppuration occurs. This is the second stage and
is associated with a localized destruction of the cornea. These cases
are known as =suppurative keratitis= or =ulceration of the cornea=.
The disintegration begins in the most anterior layers of the cornea.
A slight depression in the cornea can be noticed. The infiltration is
all about the ulcer, getting less as it is more remote from it. If the
floor and walls of the ulcer are foul with the infiltrate it is known
as a =progressive= ulcer. =Sloughing= may continue to spread the ulcer.
If the cloudiness around it disappears and the ulcer acquires a smooth
transparent base and edges it is known as a =retrogressive= or clean
ulcer.
The disintegrated areas of the cornea may be replaced by newly formed
tissue. This is the third stage or that of =cicatrization=. This new
tissue is connective tissue. It is opaque, leaving a permanent opacity.
=Stages of keratitis=:
=Suppurative.=—(1) Infiltration; (2) Suppuration and (3) Cicatrization
or Reparation. The suppuration is progressive or retrogressive.
=Non-suppurative.=—(1) Infiltration; (2) Resorption.
In the diagnosis of a keratitis one should look at it very carefully. A
loupe which has thick plus sphere lenses will magnify the field and may
be of great assistance in observing closely the condition.
If the cornea is clouded and dull the trouble is recent and if there
is no loss of substance it is an infiltrate (first stage). If there is
loss of substance it is a progressive ulcer (second stage.)
If the surface is lustrous but cloudy the trouble is an old one and if
there is loss of substance it is a retrogressive ulcer; if no loss of
substance it is a cicatrix.
Frequently blood vessels grow in from the margin in ulcerations of the
cornea. This is usually a process of healing of the corneal ulcer.
The advent of the blood vessels is favorable. After healing the blood
vessels gradually disappear. They never entirely disappear from large
cicatrices.
In some cases new vessels accompany the inflammatory process and like
the exudate are a part of the clinical picture of the disease as in
parenchymatous or interstitial keratitis. Pannus also has vessels. They
are not in the cornea but are in new tissue deposited upon it.
=Symptoms appearing in keratitis=:
1. =Ciliary injection= or a red area encircling the cornea. If the
keratitis is severe there will be considerable inflammation of the
conjunctiva which may hide to some extent the ciliary injection.
2. =Iritis or iridocyclitis= may set in. The iris and ciliary body are
in such intimate relation with the cornea that these structures are
very subject to involvement in any severe keratitis. With iritis would
come danger of =synechiae= or adherence of the iris to the anterior
surface of the lens.
3. =Hypopyon.=—In suppurative keratitis there is some exudate into the
anterior chamber of the eye. This exudate drops to the bottom of the
chamber and looks like pus had gathered in the bottom of the aqueous.
This condition is called hypopyon.
4. Other symptoms which are frequently prominent are =diminished
vision=, =pain=, =photophobia=, excessive =lachrymation= and
=blepharospasm=. Edema of the lids and conjunctiva may occur.
Intelligent treatment of keratitis of course is based upon the exact
conditions present. Great care in diagnosis and treatment should be
exercised.