John M'Lachlan.

Applied anatomy: surgical, medical and operative online

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anterior and lower part of which the levator palpebrse is inserted ;



Surgical, Medical, and Operative.



521



(6) palpebral ligament, (7) Meibomian glands, (8) conjunctiva, the
mucous membrane of tbe eye, which lines the inner surface of the
eyelids, and is reiiected from them over the fore part of the sclerotic
and cornea (Fig. 114). In the palpebral part of the conjunctiva
there are many nodules of adenoid tissue, also mucous follicles
and papillsa ; in the condition known as granular lids, or Trachoma,
these structures are much hypertrophied, and cause great irritation
of the upper half of the ocular conjunctiva, leading directly to



Fig. 114.
The Eyelids.



Tendon of Levator ,

Palpebraj

Orbicularis Palpe-
brarum -,

Tbe Skin /

Tarsal Cartilage — - ^ -



The Eyelashes



/^^ ^ Palpebral Ligament.
y^ j/^^r\ Conjunctiva.

' -^ ^ ■'^^^^ir. Meibomian Glands.

. , „ ^ S Sclerotic.

C Cornea.




L6v,ator
Palpebrse
Muscle.



pannus, and, after cicatrisation, to inversion of the eyelashes and
entropion. The common tarsal cyst is a retention cyst developed
in one of the Meibomian glands, and should be removed from,
the inside by everting the lid, cutting through the conjunctiva,
and shelling it out. A dermoid cyst is often met with at the
upper and outer angle of the orbit, under the orbicularis muscle j



522 Applied Anatomy :

it is very thin walled, and contains epithelial cells and fine hairs.
It is attached to the periosteum, and very often causes a depression
in the bone as well, but the superficial structures move freely over
it. The wall of the sac is usually very thin, and a very careful
and tedious dissection is required to remove it; occasionally, it is
connected with the dura mater. These cysts are developed in the
situation of the inner end of the embryonic fronto-orbital fissure.
Dermoids are also met with occasionally at the inner and lower
angle of the orbit, in the situation of the upper end of the
embryonic naso - maxillary fissure ; the nasal duct represents a
persistent portion of the same cleft or fissure. One must be very
careful not to confound a meningocele, in this situation, with a
dermoid cyst.

The Eyeball (Fig. 115). — The eyeball consists of three coats and
the refracting media. The outer COat is formed by the sclerotic
and cornea, (a) The sclerotic forms five-sixths of the circumference
of the globe, and is composed of strong fibrous tissue, being thicker
behind than in front ; its weakest part is about a quarter-of-an-
inch behind the cornea. (6) The cornea forms the anterior sixth
of the circumference of the globe, forming a small projection in
front, being the segment of a smaller sphere than the sclerotic. It
consists of five layers — (1) Anterior epithelium — squamous and
stratified, (2) anterior elastic lamina of Bowman, (3) the corneal
tissue proper, (4) posterior elastic lamina of Descemet or Demours,
and (5) the posterior epithelium — a single layer of squamous cells.
The corneal tissue is continuous with the sclerotic, but the opaque
sclerotic overlaps the cornea very much in the same way as a
watch-glass is overlapped by the edge of the groove that receives it.
It is important to remember this in making incisions abouttlie
comeo-sclerotic junction.

The middle coat consists of the choroid, ciliary body, and iris,
(a) The Choroid is the vascular and pigmented coat of the eyeball,
and is often the seat of melanotic sarcoma. It consists of— (1) The
lamina supra-choroidea and the lamina fusca, which connect it with
the sclerotic, and between which is found a lymph space. (2) The
venae Torticosse, which end in the ophthalmic vein and return the
blood from the globe; in cases of increased intra-ocular tension,
as in glaucoma, pressure on these veins is indicated by the dilated



Surgical, Medical, and Operative.



523



and enlarged veins observed on the surface, of the sclerotic. (3) A
closely-set capillary plexus, formed by the short ciliary vessels,
known as the tunica Eusychiana. (4) The lamina vitrea, and
(5) the layer of hexagonal pigment cells, which may be regarded as
belonging either to this coat or, more properly, to the retina. The
choroid is the nutritive tunic of the eyeball, having an especial



Fig. 115,
Antero-Posterior Section of Eyeball.

(From Okay's "Anatomy.")

TENDON OF RECTUS



SCLEROTIC'
CHOROID'
RETINA




CILIARY MUSCLE
K LIGAMENT



CILIARY PROCESS
CIRCULAR SINU

CANAL OF PETIT



relation to the vitreous humour. Disease of the choroid may be
primary, that is, beginning in the choroid (choroiditis), or secondary
to iritis, the mischief spreading backwards and involving the choroid
(irido-choroiditis). There are two clinical signs that point very
strongly to choroidal disease, the first is diminished tension of the
globe, and the second is the presence of floating opacities in the
vitreous, (6) The Ciliary body consists of the ciliary processes and



524 Applied Anatomy:

the ciliary muscle — the muscle of accommodation ^ it arises from
the posterior surface of the cornea and sclerotic junction close to
the canal of Schlemm and the spaces of Fontana, and is inserted
into the choroid, opposite the ciliary processes. The vascular supply,
like that of the choroid, is derived from the short ciliary arteries,
(c) The iris — this is also a muscular structure, and forms a self-
acting diaphragm, excluding or. admitting light as required, like
the diaphragm of a microscope, becoming narrower during active
accommodation (equal to high 'power of microscope) and widening
during passive accommodation (low pmeerj. It consists of the
following structures : — (1) In front, a layer of epithelial cells, con-
tinuous with those on the posterior surface of the cornea. (2) A
stroma, formed of cells and connective tissue bundles arranged in
a radiating manner towards the pupil, and which gives the iris a
striated, fibrous look; when the iris is inflamed this fibrous look is
lost, and the iris seems smooth and dull in appearance. (3) Non-
striped muscular fibres arranged in a circular and radiating manner;
the circular fibres form the sphincter pupillm and surround the
margin of the pupil, the radiating form the dilator pupillm. (4) The
posterior surface is covered with pigment of a deep purple tint,
known as the uvea. The vascular supply of the iris is derived,
for the most part, from the two long ciliary arteries which form
the greater and the lesser arterial circles of the iris; it also receives
blood from the anterior ciliary arteries, which are derived from the
muscular branches, and which join the great arterial circle. The
iris is very vascular, almost resembling erectile tissue, and it often
affords important information as to the state of the cerebral circu-
lation ; thus, when the brain is ansemic, as in typhoid fever, the
pupil is dilated, but when the brain is engorged, as in typhus fever,
the pupil is contracted. For the same reason it is also slightly
contracted in iritis. The circular fibres are supplied by the third
nerve, and the radiating by the sympathetic. In the foetus the
pupil is closed by a delicate vascular membrane, which thus divides
the chamber of the aqueous into two separate compartments — ^the
menibrana pupillaris; it begins to disappear about the seventh
month, and has usually quite disappeared, vessels and all, before
birth. Occasionally traces of it remain after birth, and occasionally
it is permanent, causing blindness. In some animals it remains



Surgical, Medical, and Operative. 525

apparent for a few days after birth, such heing said, in popular
parlance, to he horn hlind, hut to compensate for this few days'
hlindness, it is said they see in the dart ever afterwards. Its
remains in the human eye are apt to he mistaken for old iritic
adhesions; they form thin shreds of the same colour as the iris,
and are attached to its anterior surface close to its pupillary border.
They are longer and more slender than posterior synechise, and are
not attached to the lens capsule. The entire membrane is the
anterior portion of the capsulo -pupillary memhrane, which at one
time forms a complete fibro - vascular ' covering of the lens; the
capsulo-pupillary membrane is developed from the enclosed meso-
blast, and is supplied by a branch of the central artery of the
retina, which passes forward in the axis of the globe in a canal in
the vitreous humour (Canal of Stilling), and breaks up at the
back of the lens into a brush of capillaries.

At its circumference the iris is connected to the cornea by the
ligamentum pectinatum iridis, which is derived from the posterior
elastic lamina of that tunic. Passing through this ligament are
a number of cavernous spaces, known as the spaces of Fontana ;
these communicate with the canal of Schlemm, a sinus tunnelling
the choroid near its corneal junction. This sinus is either a vein
or a lymph canal, having a very intimate relation with the veins
of the globe, and in this way, therefore, the aqueous humour is
brought into very direct relation with the venous system. The
pupillary margin of the iris is free, and floats in the aqueous
humour ; in cases, therefore, of penetrating wounds of the cornea,
the iris is apt to prolapse, being carried out with the gush of the
aqueous fluid. This is an exceedingly troublesome and serious
complication, and unless reduced, may give rise later to recurrent
attacks of iritis, or even to sympathetic ophthalmia, from the
irritation caused by the adhesion of the iris to the corneal cicatrix.
Sometimes prolapse occurs in the case of wounds, made by the
Surgeon, in the ciliary region for the puri^ose of removing an
opaque lens (cataract); to avoid this as far as possible, a small
bit of the iris is removed opposite the wound, but, even with
this, one must be careful to see that no part of the iris is included
in the wound, as this will delay healing very much. The iris is a
muscular structure, and, therefore, may be made to contract or dilate



526 Applied Anatomy:

like other muscles; this fact is made use of in corneal wounds to
prevent prolapse : for example, in wounds situated near the circum-
ference of the cornea, whether the result of accident or made by
the Surgeon, a solution of Calabar bean (eserine) is dropped into
the eye, since this causes contraction of the iris, and will, therefore,
draw it away from the wound; whereas in wounds near the centre
of the cornea, a solution of atropine is used to dilate the pupil, and .
thus again carry the iris away from the wound.

The inner coat consists Tif the retina, which is formed by the
expansion of the optic nerve, and is the seeing part of the eye.
It is thickest behind, and becomes gradually thinner as it passes
forwards ; it ends by a jagged margin, the era serrata, just behind
the ciliary body. From within outwards it consists of the following
layers : — (1) Internal limiting membrane, next the vitreous humour;

(2) layer of nerve fibres; (3) layer of nerve cells; (4) inner mole-
cular layer; (5) inner nuclear layer; (6) outer molecular layer;
(7) outer nuclear layer; (8) external limiting membrane; (9) layer
of rods and cones; and (10) layer of hexagonal pigment cells. At
the yellow spot, however, the structure is a little different — the layer
of nerve fibres is absent, but the layer of nerve cells consists of -
several strata; the rods are few, and absent altogether in its centre,
but the cones are many and large. All the other layers are thinner,
and there are scarcely any blood-vessels, only a few capillaries.
When looked at, by the aid of the opthalmoscope, the following
parts may be recognised : — (1) The optic disc or blind spot, one-
tenth of an inch to the inner side of the axis of the eye; (2) the
macvla lutea or yellow spot, as nearly as possible in the axis of the
eyeball : in its centre is a slight depression — the fovea centralis ;

(3) the arteria centralis retime, which enters through the optic
disc and divides into four or five branches, which pass over the
retina in various directions, but seem to avoid the macula lutea ;
and (4) sometimes the vessels of the choroid may be seen.

The fundus itself is bright ferrety red, the depth of the colour
depending on the complexion of the individual ; this red appear-
ance does not come from the retina — which is invisible except
under rare conditions — but from the choroid. When the lens is
opaque, as in cataract, this redness is obscured more or less, and
when it cannot be seen at all the cataract is said to be "ripe."



Surgical, Medical, and Operative. 527

The optic disc is of a lighter pink than the rest of the fundus,
and is circular or slightly oval, and very markedly so, should the
patient be astigmatic ; the centre of the disc is still paler, and into
this the greater number of the blood-vessels dip. This central
white spot represents a hollow cup — the physiological cup — left
by the optic nerve fibres as they radiate from the centre of the
disc towards the periphery. Compare this with the large, deep
pathological cup seen in glaucoma ; in health the cup does not
extend to the edge of the disc, whereas in glaucoma it does, and is
also very deep. In atrophy of the optic nerve, the cup though
wide is very shallow. In health the edge of the optic disc is
sharply defined, and it is often surrounded by a white ring — the
scleral ring — which corresponds to the edge of the sclerotic. In
cases of myopia a greyish white crescentic patch is often seen on
the apparent inner side of the optic disc, in indirect examination
{i.e., next the yellow spot). This is known as the "myopic
crescent," and is due to atrophy of the choroid ; it is also known
as a "■posterior staphyloma." In some cases the lamina cribrosa
may be distinguished like a number" of dots at the bottom of the
physiological cup. The veins of the retina are easily distinguished
from the arteries by their larger size, deeper colour, and single
outline; the arteries have a double outline and pursue a straighter
course. The visible retinal vessels are few in number, widely
spread, and are what are known as terminal vessels, as the arteries
do not anastomose with each other, while the choroidal vessels, if
seen, branch and anastomose freely, forming a closely set network ;
in embolism, therefore, of the retinal vessels, an infarct is produced.
In cases of glaucoma and aortic regurgitation one may sometimes
be able to see the vessels pulsating.

As the optic disc lies to the nasal side of the posterior pole
of the eye, in the indirect method of ophthalmoscopic examination,
the cornea must be turned a little inwards, towards the patient's
nose, to bring the disc opposite the pupil ; in this movement, of
course, the back of the eye is carried outwards, and the patient
must be directed to turn his eye, not his head.

Advantage is taken of the red reflection of the fundus, but
especially of the pale disc, in examining for floating opacities in
the vitreous. The Surgeon sits about twelve to eighteen inches in



528 Applied Anatomy :

front of the patient's eye, and directs him to move his eye sharply
and freely from side to side, and up and down, and then quickly
to fix it so that the disc will he opposite the pupil, when the
floating particles will be seen passing across the optic disc, like
figures in a magic lantern, as they continue to move through the
vitreous from their inertia, after the eye has come to rest. In
this way, too, they are distinguished from opacities in the cornea
and lens, or pigment spots on the fundus, which come at once to
rest when the eye stops.

Anatomically, the Refracting Media of the eye are— (1) The
Cornea. (2) The Aqueous Humour, which fills the space between
the cornea in front, and the lens with its suspensory ligament
behind j this space is partially subdivided into two by the iris —
the anterior and posterior chambers of anatomists. It should be
noted, however, that oculists call the whole cavity the anterior
chamber — their posterior chamber being the cavity containing the
vitreous humour. In infants, the anterior chamber is very shallow,
the lens being close behind the cornea; this probably explains
the occurrence of anterior polar or pyramidal cataract, which is
caused by a localised inflammation of the lens capsule and the
layers immediately below it, and is usually the result of ophthalmia
neonatorum, which has probably caused a central perforating ulcer
of the cornea. (3) The Lens with its Capsule, which are held in
position by the suspensory ligament. (4) The Vitreous Humour
with its Hyaloid Membrane.

Physiologically, however, refraction only takes place at three
surfaces — the anterior surface of the cornea, the anterior surface
of the lens, and the posterior surface of the lens.

The eyeball lies in the orbital cavity, and is surrounded by
much fine;ly granular fat, which forms a soft elastic packing for it.
Coursing through this fat are many arteries and veins, going to
and returning from the globe, and it occasionally happens that we
find here some one of the many forms of aneurism.

The conditions giving rise to "orbital aneurism" are very
numerous and of a most varied character, and extremely difficult
to diagnose with certainty; and sometimes, even at the post-
mortem, nothing abnormal is found to account for the symptoms
during life.



Surgical, Medical, and Operative. -529

Symptoms. — Pulsation, displacement of the eyeball, and some-
times loss of sight, from pressure optic neuritis; in .the arterio-
venous forms we have the iisual thrill and bruits. Conditions
present in some cases — Cirsoid aneurism, aneurism by anastomoses,
arterio-venous aneurism of the orbit, pulsatile dilatation of the
vessels of the orbit — as in exophthalmic goitre, communication
between the internal carotid artery and the cavernous sinus,
aneurism of the internal carotid, tumours pressing upon the
termination of the ophthalmic vein, thrombosis of the cavernous
sinus, dilatation of the carotid artery, aneurism of the ophthalmic
in the cranium, and occasionally true aneurism. As regards the
diagnosis^note (1) that ordinary aneurism and varicose aneurism
tend to grow larger, so also would pulsating malignant tumours;
and (2) that aneurismal varix does not tend to increase in size.

The arterio-venous varieties are caused by wounds implicating
simultaneously an artery and vein ; the author has seen two such
cases, one caused by a knitting-needle, the other by an umbrella
wire. This fat in the orbit is often the seat of abscess, due either
to a primary septic cellulitis, or from disease of the neighbouring
bones, especially . strumous caries of the lachrymal or ethmoid ; in
this condition there may be no redness of the skin as the abscess
is so deep, but there is usually oedema of the lid. At the inner
angle of the orbit the facial and ophthalmic veins communicate,
and in cases of malignant facial carbuncle, the septic thrombosis
readily extends along the facial veia and through the ophthalmic
to the cavernous and other sinuses, speedily setting up a condition
of septic embolism and pyaemia. In young people also, soft
rapidly growing sarcomatous tumours may start in the cellular
tissue round about and behind the globe, from an injury, as a
blow with a snowball. Ivory exostosis, and enostosis growing in
the frontal sinus, are also sometimes found in the inner wall of
the orbit, displacing the eyeball. Tumours of purely local origin,
pressing upon the optic nerve and displacing the eyeball, will cause
uni-lateral optic neuritis {" eholced disc"), followed by atrophy of
the nerve pressed upon ; in tumours of cerebral origin, the same
appearances are usually found in hoth eyes. Between the packing
of the cavity and the globe itself, however, we find a membranous
sac, which is known as the capsule of Tenon or the tunica vaginalis

2l



530 Applied Anatomy.

ocuU. It is regarded as a distinct serous sac, ■with, a parietal layer
covering the fatty tissue, and a visceral layer enclosing about three-
fourths of the entire globe, extending from the base of the orbit to
the optic nerve, with the sheath of which it blends. Just as in the
case of the peritoneum, lymphatic vessels begin on the epithelial-
lined surface- by stomata. The ocular muscles pierce this capsule
as they pass to their insertion into the choroid y in operations there-
fore for strabismus, this capsule must be opened before the tendon
is thoroughlyexposed ; and since a serous cavity is thus opened, the
necessity for strict antiseptic precautions is very evident.

THE LACHRYMAL APPARATUS.

This consists of — (1) The lachrymal gland and its ducts opening
around the outer canthus, especially on the upper lid ; (2) puncta
lachrymalia, which are the openings into (3) the canaliculi, which
lead into (4) the lachrymal sac, from which (5) the nasal duct
descends to open into the inferior meatus of the nose (Fig. 116).

Puncta Lachrymalia and Canaliculi.— The puncta are two
small apertures, situated one on the free margin of each lid,
about- one quarter of an inch from the inner canthus j they are
the openings of two small ducts — the canaliculi. Each canaliculus
takes a curved course inwards — the upper first passing upwards and
then curving downwards ; the lower first passing downwards and
inwards, and then curving upwards and inwards; and therefore,
in introducing a probe, or in slitting open the canaliculus, the
lid should be drawn outwards, to make it as straight as possible.
The lower canaliculus is shorter, wider, and not so much arched
as the upper, and is the one usually opened, both because it is
easier, and also because it carries off most of the fluid. In doing
this the edge of the knife is directed inwards, and passed first a
little downwards and a little inwards, and then inwards and very
slightly upwards, tUl it touches the lachrymal bone.

Lachrymal Sac. — If from any cause this sac requires to be
opened {e.g., when suppuration has occurred in it), it should he
opened from the outer side,' because the angular artery (the
termination of the facial) and the large angular vein are on its
inner or nasal side. The sac is placed in the inner angle of the
orbit, and crossed in front by the tendo-oculi and some of the



Surgical, Medical, and Operative.



531



inner fibres of the orbicularis muscle, a little above its niiddlo :
while on its orbital surface is the tensor tarsi mu^scle. If the
finger be placed on the inner edge of the orbit, this little tendon
wiU be felt to tighten every time the eye is closed, and still more
so if the eyelid be drawn outwards. In this way the tendon
serves a most important purpose in helping to drain away the
tears, as its pressure empties the lachrymal sac, and then, when
it relaxes, the sac sucks up the tears through the canaliculi^ —
resembling, in fact, an ordinary injection syringe. In opening
an abscess of the lachrymal sac, the knife must be entered just
below this tendon, and towards the outer side, to avoid the angular
vessels.

Fig. 116.
The Lachrymal Apparatus.

(From Gra'y's "Anatomy.")
f /




Nasal Duct. — This duct leads from the lachrymal sac to the
inferior meatus of the nose. The edges of the canal through
which it passes may be felt on one's own person, by pressing the
finger on the inner edge of the orbit on its lower aspect. To pass
a probe through it, it should be directed downwards, outwards,
and a little backwards (the direction of the duct). Obstruction
of this duct leads to distension, and consequently to irritation



532 Applied Anatomy :

and disease of the lachrymal sac, and, unless properly treated,
inflammation and suppuration follow, which may end in fistula
lachrymalis. It is also a cause of "Epiphora" or " Stillicidiura
Lachrymarum," trickling of tears over the cheek, or "Watery Eye."
Each duct opens into the anterior part of the inferior meatus of
the nose, immediately below, and about a quarter of an inch
behind, the anterior end of the inferior turbinated bone, or an
inch behind the orifice of the nostril, and about three-quarters
of an inch above the floor of the nose ; they are about half-an-inch
long, and they are narrowest about the middle.

"Watery Eye." — This condition may be due to excessive
secretion of fluid, when it is known as "Epiphora;" or to some
obstruction preventing the proper drainage of a normal quantity
of fluid, and it is then called " Stilliaidium Lachrymarum."

Causes of Watery Eye. — (1) Obstruction of the nasal duct from
chronic thickening of the mucous and submucous tissue, tumours



Online LibraryJohn M'LachlanApplied anatomy: surgical, medical and operative → online text (page 46 of 54)