Eye prosthetic consideration / cosmetic dentistry courses

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Eye –Anatomy, visual
perception and prosthetic
rehabilitation
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

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The management of an anoptholmic
socket requires the combined effort of
ophthalmologist and maxillofacial
Prosthodontist. The surgeon provide the
basis for successful rehabilitation. The
maxillofacial Prosthodontist provide prosthetic
treatment to the best of his ability. A through
knowledge of the anatomy is necessary for
successful treatment. The goal of any
prosthetic treatment is to return the patient to
society with a normal appearance.

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The orbits are pyramidal cavities, situated
one on each side of the root of the nose. They
provide sockets for rotatory movements of the
eyeball. The long axis of the each orbit passes
backwards and medially. The medial walls are
parallel to each other. But the lateral walls are
set at right angles to each other. The contents of
the orbit are as follows

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1. Eyeball
2. Fascia: Orbital and bulbar.
3. Muscles: Extraocular muscles
4. Vessels: Ophthalmic artery, superior
and inferior ophthalmic Veins and
lymphatics.
5. Nerves: Optic, oculomotor, trochlear,
abducent, branches of ophthalmic
nerve and sympathetic nerves.
6. Lacrimal gland
7. Orbital fat.

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A. ORBITAL FASCIA (PERIORBITA)
It forms the periosteum of the bony orbit.
Due to the loose connection to bone, it can be
easily stripped. Posteriorly, it is continuous with
the dura mater and with the sheath of the optic
nerve. Anteriorly, it is continuous with the
periosteum lining the bones around the orbital
margin.

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Facial sheath of Eyeball (bulbar fascia)
Tenon’s capsule: It forms a thin loose,
membranous sheath around the eyeball,
extending from the optic nerve to the
sclerocorneal junction. The eye can freely
move within this sheath
The sheath is pierced:
(a) extraocular muscles
(b) by the ciliary vessels and nerves around the
entrance of the optic nerve.

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The sheath gives off a number of expansions.
(a) A tubular sheath covers each orbital muscle
(b) The medial check ligament is a strong
triangular expansion from the sheath of the
medial rectus muscle: it is attached to the
lacrimal bone
(c) The lateral check ligament is a strong
triangular expansion from the sheath of the
lateral rectus muscle: It is attached to the
zygomatic bone.

The lower part of the tenon’s capsule is
thickened and is named the suspensory ligament
of the eye or the suspensory ligament of
Lockwood. It is slung like a hammock below the
eyeball. It is formed by union of the margins of the
sheaths of the inferior rectus and the inferior
oblique muscles with the medial and lateral check
ligaments.
8www.indiandentalacademy.com

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EXTRAOCULAR MUSCLES
Voluntary muscles
1. Four recti: (a) Superior rectus
(b) Inferior rectus
(c) Medial rectus
(d) Lateral rectus.
2. Two obliqui: (a) Superior oblique and
(b) Inferior oblique
3. Levator palpebrae superioris

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Involuntary muscles
1. superior tarsal muscle
2. Inferior tarsal muscle
3. orbitalis

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RECTI
origin
The four recti arise from a common annular
ring (tendinous ring). This ring is attached to the
orbital surface of the apex of the orbit. It
encloses the optic canal and the middle part of
the superior orbital fissure. The lateral rectus
has an additional small tendinous head which
arises from the orbital surface of the greater
wing of the sphenoid bone lateral to the
tendinous ring.

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Insertion
The recti are inserted into the sclera, a little
posterior to the limbus. The average distances
of the insertions from the cornea is :
superior 7.7 mm
inferior 6.5 mm
medial 5.5 mm
lateral 6.9 mm

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Nerve supply
The lateral rectus is supplied by the 6th
cranial (abducent) nerve.
superior recti, inferior recti, and medial recti
are supplied by 3th
cranial (oculomotor) nerve
Action
Superior rectus: upward rotation,
Medial rotation.

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Inferior rectus: Downward rotation,
Medial rotation.
Medial rectus: Medial rotation.
Lateral rectus: Lateral rotation

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OBLIQUE MUSCLE
Origin
The superior oblique arises from the body
of the sphenoid, superomedial to the optic canal
The inferior oblique arises from the orbital
surface of the maxilla, lateral to the lacrimal
groove. The muscle is situated near the anterior
margin of the orbit.

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Insertion
superior oblique is inserted into the sclera
behind the equator of the eyeball, between
the superior rectus and lateral rectus
Inferior oblique is inserted close to the superior
oblique a little below and posterior to the
superior oblique

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Nerve supply
Superior oblique is supplied by the 4th
cranial
(trochlear) nerve
Inferior oblique is supplied by the 3rd cranial
(oculomotor) nerve
Action
Superior oblique: downward rotation,
Lateral rotation.
Inferior oblique: Upward rotation,
Lateral rotation.

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LEVATOR PALPEBRAE SUPERIORIS
Origin
The levator palpebrae superioris arises from
the orbital surface of the lesser wing of the
sphenoid bone, anterosuperior to the optic canal
and to the origin of the superior rectus
Insertion
it is inserted into superior tarsus and into the
skin of the upper eyelid

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Nerve supply
Supplied by the 3th
cranial (oculomotor)
nerve
Action
Elevation of the upper eyelid

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Movements are produced by combined
actions of muscles. Similar actions get added
together, while opposing actions cancel each
other
Normally, movements of the two eyes are
harmoniously coordinated. Such coordinated
movement of the both eye are called conjugate
ocular movements. These are usually horizontal
or vertical, but oblique movement also occur

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SQUINT Weakness or paralysis of a muscle
causes squint or strabismus. The two eyes
appear to look in different direction. when the
movement is attempted in a direction
produced by the paralysed muscle, one eye
moves normally, but the other eye is unable
to keep up with it. Hence the two eyes are
directed differently
NYSTAGMUS –is characterized by involuntary
rhythmical oscillatory movements of the eyes,
due to in coordination of the ocular muscle
APPLIED ANATOMY

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THE EYEBALL
The eyeball is the origin of sight. It closely
resembles a camera in its structure. It is almost
spherical in shape and has a diameter of about
2.5cm.It is made up of three concentric coats. The
outer or fibrous coat comprises the sclera and the
cornea. The middle or vascular coat (also called
the uveal tract) consists of the choroid, the ciliary
body and the iris. The inner or nervous coat is the
retina. Light entering the eyeball passes through
several refracting media. From before backwards
these are the cornea, the aqueous humour, the
lens and the vitreous body

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The Sclera
The sclera is opaque and forms the posterior
five sixths of the eyeball. It is composed of
dense fibrous tissue which is firm and maintains
the shape of the eyeball. The outer surface of
the sclera is white and smooth. Its anterior part
is covered by conjunctiva through which it can
be seen as the white of the eye. The sclera is
continuous anteriorly with the cornea at the
sclerocorneal junction or limbus. Posteriorly it is
fused with the dural sheath of the optic nerve.
The sclera is almost avascular ,however the
loose connective tissue between the conjunctiva
and sclera is vascularwww.indiandentalacademy.com

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CORNEA
The cornea is transparent. It replaces the
sclera over the anterior one sixth of the
eyeball. Its junction with the sclera is called
the sclerocorneal junction or limbus. The
cornea is more convex, than the sclera, but
the curvature diminishes with age. It is
separated from the iris by a space called the
anterior chamber of the eye. The cornea is
avascular and is nourished by lymph which
circulates in the numerous corneal, spaces.

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CHOROID
It is a thin pigmented layer which
separates the posterior part of the sclera from
the retina. Anteriorly it ends at the ora serrata
by merging with the ciliary body. Posteriorly it
is perforated by the optic nerve to which it is
firmly attached. The attachment to the sclera
is loose, so that it can be easily stripped. The
inner layer is firmly united to the retina

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CILIARY BODY
This is a thickened part of the vascular
tract lying just posterior to the corneal limbus.
It is continuous anteriorly with the iris and
posteriorly with the choroid. It suspends the
lens and helps it in accommodation for near
vision. The ciliary body is triangular in cross
section. It is thick in front and thin behind.
The scleral surface of this body contains the
ciliary muscle.

The ciliary muscle is a ring of (radial and circular
muscle). The radial fibres arise from a projection
of sclera (scleral spur) near the limbus. The
circular fibres lie within the anterior part of the
radial fibres. Their contraction relaxes the
suspensory ligament so that the lens becomes
more convex for near vision.

IRIS___________________
This is the anterior part
of the vascular tract. It forms
a circular curtain with an
opening in the centre, called
the pupil. By adjusting the
size of the pupil it controls
the amount of light entering
the eye, and thus behaves
like an adjustable diaphragm.It is placed vertically between the cornea and the
lens, and divides the anterior segment of the eye
into anterior and posterior chambers, both
containing aqueous humour 31www.indiandentalacademy.com

Its peripheral margin is attached to the
middle of the anterior surface of the ciliary
body. The centre free margin rest against
the lens. The colour of the iris determined
by the number of pigment cells in its
connective tissue. If the pigment cells are
absent, the iris is blue in colour due to the
diffusion of light in front of the black
posterior surface.

Iris contains two sets of smooth muscles are seen:
One set of well developed smooth muscles, called
the constrictor pupillae is a circular band of smooth
muscles surrounding the pupil. when contract,
cause constriction of the pupil. The other set of
smooth muscles, arranged radially are supplied by
sympathetic fibers.
When these muscles
contract, dilatation of
the pupil occurs and
hence these fibers are
called dilator pupillae

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AQUEOUS HUMOUR
This is a clear fluid which fills the space
between the cornea in front and the lens
behind (anterior segment). This space is
divided by the iris into anterior and posterior
chambers which freely communicate with
each other through the pupil. Interference
with the drainage of the aqueous humour
results in an increase of intraocular pressure
(glaucoma). This produces cupping of the
optic disc and pressure atrophy of the retina
causing blindnesswww.indiandentalacademy.com

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LENS
The lens is a transparent bi-convex
structure which is placed between the anterior
and posterior segment of the eye. It is circular
in outline and has a diameter of one cm.
The central points of the anterior and
posterior surfaces are called the anterior and
posterior poles. The line connecting the pole
constitutes the axis of the lens, while the
marginal circumference is termed the equator

The posterior surface of the lens is
more convex than the anterior. The
anterior surface is kept flattened by the
tension of the suspensory ligament. When
the ligament is relaxed (by contraction of
the ciliary muscle) the anterior surface
becomes more convex due to elasticity of
the lens substance. The suspensory
ligament of the lens retains the lens In
position and its tension keeps the anterior
surface of the lens flattened.

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VITREOUS BODY
It is a colorless, jelly-like transparent
mass which fills the posterior segment
(posterior 4/5) of the eyeball. It is
enclosed in a delicate homogeneous
hyaloid membrane. The anterior surface
of the vitreous body is indented by the
lens and the ciliary processes

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RETINA
This is the thin, delicate inner layer of the
eyeball. It is continuous posteriorly with the optic
nerve. The outer surface of the retina is attached to
the choroid, while the inner surface is in contact
with the hyaloid membrane (of the vitreous).
Opposite the entrance of the optic nerve there is a
circular area known as the optic disc. It is 1.5 mm
in diameter. The optic part of the retina contains
nervous tissue and is sensitive to light. It extends
from the optic disc to the posterior end of the ciliary
body. The anterior margin of the optic part of the
retina forms a wavy line called the ora serrata

The depressed area of the optic disc is
called the physiological cup. It contains no
rods or cones and is therefore insensitive to
light physiological blind spot. At the posterior
pole of the eye (3 mm lateral to the optic
disc) there is another depression of similar
size, called the macula lutea. It is avascular
and yellow in colour. The centre of the
macula is further depressed to form the
fovea centralis. This is the thinnest part of
the retina. It contains cones only, and is the
site of maximum acuity of vision. 41www.indiandentalacademy.com

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1) Pigment layer
2) Layer of rods and cones projecting into the
pigment
3) Outer limiting membrane
4) Outer nuclear layer containing the cell bodies of
the rods and cones
5) Outer plexiform layer
6) Inner nuclear layer
7) Inner plexiform layer
8) Ganglionic layer
9) Layer of optic nerve fibers
10)Inner limiting membrane
LAYERS OF THE RETINA
The functional components of the retina arranged in
layers from the outside to the inside as follows:

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OPTICS OF THE EYE
Refractive index
Refractive index of a transparent substance is
the ratio of the velocity of light in air to the
velocity of light while traveling through the
substance. The refractive index of air is
presumed as 1.

FOCAL LENGTH OF A LENS
When light rays pass from one medium to another
medium it bends or refracts. When parallel light rays
passes through each point of a convex lens it will
converge to a single point which is called the Focal
Point.
The distance beyond a convex lens at which parallel
light ray converge to a common focal point is called
the Focal Length of the Lens
Focal Point

ACCOMODATION
If while looking at an object, situated at infinity,
the gaze be transferred to an object near at hand,
some readjustment of the power of the crystalline lens
will have to occur, otherwise the image will fall behind
the retina. This readjustment of the power of the
crystalline lens are called accomodation. During
accomodation, the ciliary muscles contract, this cause
relaxation of the suspensory ligament and as a result
of this relaxation, the anterior surface of the lens
bulges and its power increases. By this mechanism,
the image is focused nearer so that it is on the retina
now.

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FORMATION OF AN IMAGE
When a light ray passes through the center of a
convex lens, it will not be refracted in either
direction. Any object in front of the lens is in reality
a mosaic of point source of light. Each point source
of light come to a point focus on the opposite side
of the lens directly in line with point source and the
center of the lens. This image is upside down with
respect to the original object and the two lateral
sides of the image are reversed. This is the method
by which the lens focuses images on to the retina.

POINT SOURCE FOCAL POINTS

After light passes through the lens system of
the eye and then through the vitreous humor, it
enters the retina from the inside that is, it passes
first through the ganglion cells and then through
the plexiform layers, nuclear layer, and limiting
membranes before it finally reaches the layer of
rods and cones located all the way on the outer
side of the retina. This distance is a thickness of
several hundred micrometers. visual acuity is
decreased by this passage through such
nonhomogeneous tissue. However, in the central
region of the retina, the inside layers are pulled
aside for prevention of this loss of acuity.

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There are about 120 million rods and 6
million cones in each eye. The rods and cones
are the light receptors of the eye. The rods
contain a pigment called visual purple. They can
respond to dim light (scotopic vision). The
periphery of the retina contains only rods, but
the fovea has none at all. The cones respond
only to bright light (photopic vision) and are
sensitive to colour. The fovea centralis has only
cones. Their number diminishes towards the
periphery of the retina.
RODS AND CONES

Functional segment of rods and cones
(1) the outer segment,
(2) the inner segment,
(3) the nucleus; and
(4) the synaptic body.
In the outer segment, the light-sensitive
photochemical is found. In the case of the
rods, this is rhodopsin, and in the cones, it is
one of three "color" photochemicals, usually
called color pigments. In the cones, each of
the discs is actually an infolded shelf of cell
membrane.

Functional segment
of rods and cones
(1) the outer segment,
(2) the inner segment,
(3) the nucleus; and
(4) the synaptic body.

However, In the rod, the discs separate from the
membrane and are flat sacs lying totally inside the
cell. There are as many as 1000 discs in each rod or
cone. Color pigments are incorporated into the
membrane of the discs in the form of transmembrane
proteins. The concentrations of these photosensitive
pigments in the discs constitute about 40 per cent of
the entire mass of the outer segment.
The inner segment contains the cytoplasm of the
cell with the cytoplasmic organelles and the
mitochondria, which provide the energy for the
function of the photoreceptors. The synaptic body is
the portion of the rod or cone that connect with the
neuronal cells 53www.indiandentalacademy.com

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RHODOPSIN AND ITS DECOMPOSITION BY
LIGHT ENERGY
Rhodopsin is a combination of the
protein scotopsin and the carotenoid pigment
retinal . The retinal is a particular type called
11-cis retinal. This cis form of the retinal is
important because only this form can bind
with scotopsin to synthesize rhodopsin.
When light energy is absorbed by
rhodopsin, the rhodopsin begins within
trillionths of a second to decompose to

bathorhodopsin, which is a partially split
combination of the all-trans retinal and scotopsin.
Bathorhodopsin itself is an extremely unstable
compound and decays in nanoseconds to
lumirhodopsin. This then decays in microseconds
to metarhodopsin I, then in about a millisecond to
metarhodopsin II, and finally, much more slowly (in
seconds) into the completely split products:
scotopsin and all-trans retinal. It is the
metarhodopsin II, also called activated rhodopsin,
that excites electrical changes in the rods that then
transmit the visual image into the central nervous
system

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PHOTOCHEMISTRY OF CONES
Cones have almost exactly the same
chemical composition as that of rhodopsin in
the rods. The only difference is that the
protein portions, the opsins, called photopsins
in the cones. The retinal portion of all the
visual pigments is exactly the same in the
cones as in the rods. The color-sensitive
pigments of the cones, therefore, are
combinations of retinal and photopsins. The
color pigments are called blue-sensitive
pigment, green-sensitive pigment, and red-
sensitive pigment.

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COLOR VISION
Color vision is possible because of the presence
of cones, a normal person can see all wave
lengths between violet to red. There are three
types of cones, (i) red sensitive, (ii) green sensitive
and (iii) blue sensitive cones. Proper admixture of
the three primary colors can produce all varieties of
color. When they are of equal proportion, the
mixture has a white color. Black color means
absence of color.

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An orange monochromatic light with a
wavelength of 580 nanometers stimulates the
red cones to a stimulus value of about 99 (99
per cent of the peak stimulation at optimum
wavelength) It stimulates the green cones to
a stimulus value of about 42 but the blue
cones not at all. Thus, the ratios of
stimulation of the three types of cones in this
instance are 99: 42: O. The nervous system
interprets this set of ratios as the sensation of
orange. www.indiandentalacademy.com

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Dark Adaptation
When someone enters a dark room from a
brightly lit outdoor, at first he sees almost nothing
but gradually the person begins to see more, ie,
he becomes adapted to the dark. This is dark
adaptation . As soon as one enters a dark room
from the bright outdoor visibility is very poor and
the threshold of stimulation of the photoreceptors
is very high. The low intensity light that is
available in the dark room fails to stimulate the
photo receptors. At around 40th minute, the dark
adaptation is almost complete

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Light Adaptation
When someone is exposed to a very
strong light then he, (specially if he was in dark
room immediately before) cannot see anything.
Thereafter, the ability to see increases and the
person is stated to be developing light
adaptation. Light adaptation is complete within
about 5 minutes. During light adaptation the
threshold rises rapidly.

VISUAL PATHWAY___________________________
The impulses from the axons of the ganglion
cells are collected by the optic nerve, and they
make exit from the eye through the optic disc and
continue to proceed to their destination as optic
nerve. Fibers of the each optic nerve partially
decussate at optic chiasm; the fibers from the
nasal half of each retina cross to the opposite side
but those of the temporal halves do not cross.
After decussation, what is formed is called optic
tract. Each optic tract contains fibers from nasal
half of the opposite side and fibers from the
temporal half of the same side. 64www.indiandentalacademy.com

The fibers of each optic tract synapse
in the dorsal lateral geniculate nucleus, and
from here, the geniculocalcarine fibers pass
by way of the optic radiation (or
geniculocalcarine tract) to the primary visual
cortex in the calcarine area of the occipital
lobe called (Brodmann's) area 17). The
neighbouring areas, area 18 and area 19 are
visual association areas. This area is
concerned with understanding and
interpreting what one is seeing

Common Defects of the
Image-Forming Mechanism
Hyperopia
In some individuals, the eyeball is shorter than
normal and the parallel rays of light are brought to a
focus behind the retina. This abnormality is called
hyperopia or farsightedness. The defect can be
corrected by using glasses with convex lenses,
which aid the refractive power of the eye in
shortening the focal distance.

Myopia
In myopia (nearsightedness), the
anteroposterior diameter of the eyeball is too long.
This defect can be corrected by glasses with
biconcave lenses, which make parallel light rays
diverge slightly before they strike the eye

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Astigmatism
Astigmatism is a common condition in
which the curvature of the cornea is not
uniform. When the curvature in one meridian
is different from that in others, light rays in
that meridian are refracted to a different
focus, so that part of the retinal image is
blurred. Astigmatism can usually be corrected
with cylindrical lenses placed in such a way
that they equalize the refraction in all
meridians.

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Presbyopia
Presbyopia is due to increasing
hardness of the lens, with a resulting loss of
accommodation. The nearest point to the eye
at which an object can be brought into clear
focus by accommodation is called the near
point of vision. The near point recedes
throughout life, slowly at first and then rapidly
with advancing age, from approximately 9 cm
at age 10 to approximately 83 cm at age 60.

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CATARACTS
A cataract is a cloudy or opaque area or
areas in the lens. In cataract formation, the
protein in some of the lens fibres become
denatured. Later these proteins coagulate to
form opaque areas in the place of normal
transparent protein fibres. If there is complete
impairment of vision, the condition can be
corrected by surgical removal of lens.

Prosthetic rehabilitation
The fabrication of eyes is not limited to this
modern age. They have been used for centuries, with
the earliest know examples found in mummies dating
back to the fourth dynasty in Egypt (1613-2494 BC).
Ambrose pare, a French dentist, is
considered to be the pioneer of modern artificial
eyes. He fabricated eye made of glasses and
porcelain.
Naval dental school (1940), tested the use of
acrylic resin in fabricating a custom ocular prosthesis.
Unlike a glass eye, an acrylic eye was easy to fit and
adjust, unbreakable, inert to ocular fluids, esthetical
good, longer lasting and easier to fabricate

Surgical procedures in the removal of an eye
are classified into three categories
Evisceration- Removal of the contents of the
globe, but leaving the sclera and sometimes
the cornea in place. Because the extra-ocular
muscles are left intact, good mobility of the
prosthesis is usually possible
Enucleation- Removal of the eyeball itself
Exenteration- Removal of the entire contents
of the orbit, including the extraocular muscles

Ocular implants are classified as
1. Integrated
2. Semi - integrated
3. Non-integrated
and
1. Buried or
2. Non-buried
Integrated implants are designed to improve
prosthesis motility by coupling to the overlying
prosthesis. Implants is exposed through the
conjunctiva to be directly coupled to the
prosthesis with a peg, pin, screw or other
method.

Semi-integrated ocular implants consist of an
acrylic resin implant with 4 protruding mounds on
the anterior surface. These acrylic resin mounds
on the implant protrude against the encapsulating
tissue. When an ocular prosthesis is made, a
counter contour to the implant is formed on the
posterior surface of the prosthesis.
Nonintegrated implant This is done by placing a
hollow or solid acrylic resin sphere ranging from
10 to 22mm in diameter.

Stock tray impression technique
An impression is made of the ocular defect
using a disposable syringe, stock ocular trays and
irreversible hydrocolloid. During the procedure ,the
patient should be seated in an upright position with
the head supported by the headrest. This position
allows the natural positioning of the palpebrae and
surrounding tissue relative to the force of gravity.
The tray should be placed into the defect to
determine the proper orientation and fit without
overextension. The tray is then removed and the
impression material is loaded in the syringe and
sufficient material is ejected to fill the concavity of
the tray. The tray is reinserted and sufficient 77www.indiandentalacademy.com

material is injected to elevate the lid contours
similar to the normal side. once filled the patient is
directed to move their eyes both up and done. After
the impression sets the assembly is removed and
examined for defects and voids.

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External tray impression technique
Alginate impression material is
expressed into the defect using a disposable
syringe. Next a perforated acrylic resin tray is
loaded and placed over the defect. The
impression is first recovered from the lower,
shallower sulcus first, then rotated out of the
deeper, upper sulcus. The impression is
boxed and poured in the dental stone up to
the height of contour of the impression. A
separating agent is placed and the reminder
of the impression is poured

wax pattern
The melted wax is then poured through the funnel
shaped hole and into the assembled mold. Soaking
the mold in water for a few minutes prior to filling it
with molten wax will prevent the wax from adhering
to the stone. After the wax has cooled, the wax
pattern is recovered. Once the wax pattern has been
smoothed and polished, it is ready to be tried in the
eye socket. To insert the wax pattern, the upper lid is
lifted, and the superior edge of the pattern is placed
behind the lid and gently pushed upward. While
drawing the lower lid down, the inferior border of the
pattern is seated in the inferior fornix, and then the
lower lid is released. The eye contours are checked.
Custom Ocular Prosthesis Fabrication

Paper Iris Disk Technique
When the wax pattern is determined to
be appropriate, it is flasked and processed in
scleral resin. The scleral blank is then
finished, and it is polished using pumice and
acrylic resin polish

The scleral blank is tried in and the
middle of the pupil is marked while the patient
gazes directly at the clinician. The size of the
iris is measured using a millimeter
measurement gauge or optical scale. The
outline of the iris is then marked on the
scleral blank using Carmen red ink.

This ink will transfer to the investing stone,
facilitating the appropriate placement of the
corneal prominence. The blank is tried in again to
verify the location and size of the iris. The location
of the iris will transfer to the investment and a
scraper can then be used to create the corneal
prominence of the prosthesis in the investment.

A disk of ordinary artist's watercolor paper
is punched out using a die. The size selected
should be 1 mm smaller than the measured size
of the iris. This will allow the iris to appear to be
the appropriate size because the corneal
prominence will cause a slight magnification of the
iris disk. A good selection of colors for this
purpose includes ultramarine blue, yellow ochre,
burnt sienna, burnt umber, yellow oxide, titanium
white. Colors should be mixed and reapplied in a
layering fashion to mimic the colored striations in
the patient's iris.

Limbus
Medial canthus
Pupil
IRIS ANATOMY

Begin by painting the darkest color, the area
toward the outer edge of the iris ring (limbus). The
color of the limbus varies from eye to eye, but it
usually is a combination of gray and iris body color. In
the natural eye, it can appear as a shadow from the
overlapping sclera, covering the edge of the cornea.
Next the collarette is painted.
It is usually a lighter
color than the body
of the iris A black
spot should be
painted in the
center of the disk to
represent the pupil.

The diameter should mimic the natural pupil
under indoor light conditions. This will make size
appear relatively appropriate under most
conditions. After the paint has dried, a drop of water
is applied to create the magnification of the corneal
prominence and the color matched

Using a flatend bur, a flat surface is
prepared in the scleral blank for the iris painting. A
sprue wax is luted to the prepared flat surface and
tried in. The orientation of the surface is adjusted until
the sprue points directly at the observer while the
patient looks directly into the observer's eye. This will
ensure that the prosthesis and the natural eye will
have the same gaze

Using a large abrasive stone, the entire anterior surface
of the scleral blank is reduced at least 1 mm. The
remainder of the prosthesis is then painted to match the
sclera of the natural eye. Fine red embroidery threads
are placed on the scleral painting to mimic the blood
vessels of the patient's natural eye. The entire scleral
portion is then coated with monomer polymer syrup to
keep the bloodvessel fibers in place and allowed to set.

Once the monomerpolymer syrup has set, the
scleral blank is replaced into the flask, and the iris
painting is placed on the flat section. Clear ocular
acrylic resin is mixed and placed into the mold
space and the flask trial packed. Once trial packed,
the flash is removed and the location of the painting
verified to ensure that it has not moved during trial
packing.

93
Black Iris Disk Technique
The natural eye is observed closely and
the diameter of the iris is estimated using a
millimeter measurement gauge or optical
scale. Ocular discs, which are used in the
iris painting, are available in half mm sized
increments, ranging from 11 mm to 13 mm.
They come in black or clear, and either with
or without pupil apertures. Clear corneal
buttons are available in the same sizes as
the discs. The buttons can also be purchased
with pupils of various sizes already in place.

The technique employed in painting the
disk produces a threedimensional effect. oil
pigments are employed in this technique but are
mixed with a monomerpolymer syrup during the
painting process. This mixing procedure provides
some degree of translucency in the iris painting
and permits rapid drying of the pigments. The
basic eye color or background color is observed
along with the limbus color. The background color
is applied to the disk first, using brush strokes
from the center toward the periphery.

After the background color is applied and
dried, a coat of the clear syrup is applied and
allowed to dry. Characteristic striations are
applied over the clear layer and allowed to
dry. A second clear layer is then applied and
further characterization accomplished. After
the second layer is dried, the limbus color is
matched around the periphery of the disk and
a third clear layer applied. The color around
the pupil is applied over the last clear layer
and the final color evaluated with the water
interface. After a satisfactory color match has
been obtained, a final clear layer is applied
and allowed to stand for 15 minutes. 95www.indiandentalacademy.com

A single droplet of the monomerpolymer
syrup is then placed in the center of the iris
disk and the lens button is gently placed and
centered. The positioning of the irislens
assembly on the wax scleral pattern is the
most important phase in fabrication of the
prosthesis. Fix the lens button to the scleral
pattern in a manner such that the apparent
gaze of both natural and artificial eyes is on
the same object, or parallel to one another and
in the same plane.

The size of the lens assembly selected
should be large enough to include the limbus.
The lens assembly is placed in a slight
depression in the scleral pattern, and a thin
layer of wax should be brought up over the
curvature of the lens assembly. This thin
layer of wax will allow the opaque white
scleral acrylic resin to flow up over the edge
curvature of the lens assembly during the
packing procedure, forming a very thin,
translucent layer. The finished pattern is then
invested in a small twopiece brass flask. The
resulting scleral blank is deflasked, trimmed,
and polished

The position and gaze of the artificial eye
is again observed. The sclera is slightly
roughened using sandpaper disks in
preparation for adding the simulated
vasculature. Rayonthread fibrils are placed
onto the surface of the sclera using the
monomer polymer syrup. The pattern and
type of vessels ( tortuous, straight, branched)
of the opposite eye are reproduced. The
colors found in the sclera are usually yellow
and blue, or combinations of these. Greens
and browns can also be present. The scleral
painting begins with the application of a wash
of yellow comparable to that found on the
patient's natural eye.

Next, blue is added, which is usually located
inferior and superior to the iris. Finally, any
characteristic details present in the natural eye are
added. Once complete, a coat of monomer and
polymer is applied to the sclera. The eye is now
ready for the final processing, the application of a
layer of clear acrylic resin

The prosthesis is cleaned and placed in socket.
The fit of the artificial eye are evaluated and
adjustments are made as necessary.

COMPLICATIONS IN FITTNG
ANOPHTHALMIC SOCKET
Ptosis: Superior eyelid ptosis is a frequent problem
in the restoration of an anophthalmic patient.
Pseudoptosis is due to the loss of volume between
the implant and the lids after removal of the eye. If
the physiological function of the eyelids is intact,
correction of Pseudoptosis is achieved by
increasing the volume of the prosthesis in the
socket. This condition usually occurs whenever a
small, poorly fitted prostheses is used. A simple
technique of correcting Pseudoptosis is to make a
larger prosthesis that will thrust forward and
separate the eyelids 102www.indiandentalacademy.com

Persistent ptosis requires modification of the
ocular prosthesis to correct for a deficient levator
muscle, which causes the upper eyelid to droop.
Attempts aimed at increasing the size of the
ocular prosthesis, as seen in Pseudoptosis, will
not correct the problem in persistent ptosis. The
tension on the superior lid forces the larger
prosthesis downward, thus depressing the lower
eyelid, deflecting the gaze downward and
creating patient discomfort.

A thin transparent shelf can be made across
the front surface of the eye to hold the upper
eyelid at the desired open position. The shelf is 3
to 4 mm wide and is placed along the upper
limbus. This modification of the prosthesis works
well for ptosis caused by a superiorly migrated,
large, spherical implant with limited socket space
between the implant and the upper eyelid.The
major drawback to the shelf is that eye cannot
blink or close. The weight of the upper eyelid and
the action of the orbicularis muscle may press the
eye downward.

This may be corrected by adding material to the
inferior tissue surface of the prosthesis to contour it
backward and upward. The surface above the shelf
can be reduced to decrease the weight of the
prosthesis and to create space for a tight upper
eyelid.

Ectropion: Inferior displacement of the implant
can lead to the loss of the inferior fornix and
cause ectropion of the lower lid. Patients have
difficulty with retention of the prosthesis, since it
has a tendency to slip down and out over the
everted lower lid. This is rectified by extending a
thin lower edge that will press downward upon
the tarsus, and rotate it into a more vertical plane,
thus creating a lower fornix. The lower edge
should be rounded and at least 1 mm in thickness
so it will not cut into the socket. The lower fornix
will deepen within minutes of modification, and
insertion of the prosthesis and retention will
improve 106www.indiandentalacademy.com

Sagging lower eyelid: The weight of the
prosthesis, and the contraction force of the upper
eyelid on the prosthesis can cause a downward
displacement of the lower eyelid, causing it to
droop.

Degenerative disease may also weaken the lower
eyelid, causing it to droop. By removing resin from
the mid inferior margin of the prosthesis, downward
pressure against the middle of the lower fornix is
relieved. Wax is added to extend the nasal and
temporal aspects of the inferior margin to create
pressure in the medial and lateral areas of the lid.
This directs the weight of the prosthesis where the
lower eyelid is strongest, near the palpebral
ligaments. These modifications tilt the tarsus of the
lower eyelid favorably so that the eyelid margin is
elevated.

conclusion
The goal of any prosthetic treatment is to return
the patient to society with a normal appearance and
reasonable motility of the prosthetic eye. The
disfigurement resulting from loss of eye can cause
significant psychological, as well as social
consequences. However with the advancement in
ophthalmic surgery and ocular prosthesis, patient
can be rehabilitated very effectively.
The maxillofacial Prosthodontist should provide
prosthetic treatment to the best of his ability and
should also consider psychological aspects and if
necessary the help of other specialist should be
taken into consideration.

1. Textbook of Medical Physiology –
GUYTON AND HALL
2. Review of Medical Physiology
WILLAM F. GANONG
3. Medical Physiology –
CHAUDHARY
4. Clinical Maxillofacial Prosthetics
THOMAS D. TAYLOR
5. Maxillo Facial Rehabilitation – Prosthodontic and
surgical consideration
JOHN BEUMER

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