The term coloboma representing merely a hiatus or deficiency is
applied to different parts of the eye according as there may be a lack
of substance of the part in question:—=Coloboma palpebrarum=
(deficiency of the palpebræ or lids), =C. iridis= (perforation of the
iris), and =C. choroideæ= (partial absence of the choroid).
=Coloboma palpebrarum= is usually congenital and takes the form of a
vertical notch on the upper lid, separating its two lateral parts into
independent flaps. According to the breadth and depth of the notch are
the extent of the exposure of the bulbar conjunctiva and the liability
to irritation and infection by foreign bodies. The same condition of
things will occur traumatically and require identical measures of
repair. These consist in paring the edges of the notch and bringing them
accurately together with catgut, silk or quilled suture, the
approximation being rendered more perfect by the application of
collodion, shellac or gelatine mixture (see wounds of eyelids). The
vascularity and extensibility of the tissues of the lids greatly favor a
kindly healing. Rubbing of the eye must be guarded against as advised
under wounds of the eyelids.
ORGANIC UNION OF THE EYELIDS. ANKYLOBLEPHARON. NARROWED FISSURE BETWEEN
THE LIDS. BLEPHAROPHYMOSIS.
Complete closure of the palpebral fissure has been seen as a congenital
infirmity in sheep, dogs and cats, while the partial closure has been
found in all classes of animals as the result of chronic conjunctivitis
and contraction of the exudation in undergoing organization. Narrowing
of the fissure gives the appearance of a small eye, so that a
progressive diminution is usually supposed to come from a reduction in
size of the bulb, though no actual atrophy of that organ has taken
place. In drooping of the upper lid (ptosis) too, the fissure is reduced
and the illusion of an atrophy of the eyeball is induced. The closure of
the fissure may come from _blepharospasm_, as the result of irritants in
the eye, or even of nervous disorder.
_Treatment._ In case of complete closure of the palpebral fissure, the
skin is picked up with forceps and an incision is made between the two
tarsi into the conjunctival sac. Then with probe pointed scissors, or a
grooved director and bistuory the incision is carried between the tarsi
to the proper position for the internal and external canthi. During
healing the lids should be frequently bathed with a boric acid solution,
and an ointment of the same with vaseline should be applied to prevent
adhesion.
When the trouble consists in a drawing together of the skin at the outer
canthus, the result of inflammation, the adhesions are separated by a
horizontal incision leading outward from the line of the angle. The
edges of the conjunctiva and skin are then sutured together, so as to
prevent further adhesion and the part treated as an ordinary wound. This
is known as _canthoplasty_.
Ptosis coming from tumors on the lid, or excess of fat in its substance,
or from oculo-motor disease must be treated according to indications.
The same remark applies to _spasm_ of the orbicular muscle
(_blepharospasm_), whether clonic or tonic. In domestic animals the
removal of the cause (foreign body, eyelash), will usually succeed.