Download Orbital Implants

Orbital
Implants
• Prior to 1885 orbital implants were not used. The eye
was removed by enucleation or evisceration and the
socket was left to heal in its own. The result was an
unsightly sunken depression of the eyelids into the eye
socket. The use of an orbital implant was a major
breakthrough in anophthalmic socket surgery. The
implant improved postoperative cosmetic by filling
orbital volume and also reducing the chance of socket
contractions due to scar tissue formation.
• Over the last 100 years a variety of materials have been
used for the orbital implant including: gold, silver,
cartilage, bone, fat, cork, sponge, rubber, paraffin, wool,
asbestos, as well as a variety of others in an attempt to
find the most biocompatible implant .
• A variety of shapes and sizes have also been tried in an
attempt to promote some motility to the socket. In 1985 a
new concept in eye socket implants began to evolve when
a researcher (Dr. Arthur Perry, San Diego, CA) began to
study sea coral as an ocular implant. Through a patented
hydrothermal process the calcium carbonate component
of sea coral was turned into calcium phosphate and a
substance known as hydroxyapatite was made.
Hydroxyapatite has the same chemical structure and
porous structure as human body tissue .
• Hydroxyapatite orbital implant
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• The implant material (corralline hydroxyapatite) is
biocompatible, non-toxic and non-allergenic. The body’s tissue
recognizes the material as similar and because of the porous
nature, tissue will grow into it. The implant becomes more
fixed and therefore resists migration. The implant allows
attachment of the extraocular muscles which in turn leads to
improved orbital implant motility. The orbital implant can also
be directly attached to the prosthesis through a peg, protruding
from the implant (Figure 4b) allowing a wide range of
prosthetic movement as well as the darting eye movements
commonly seen when people are engaged in conversation. The
increased range and fine darting movements allow a more lifelike quality to the prosthetic eye.
• The hydroxyapatite implant, also known as the Bio-Eye™
(integrated Orbital implants, San Diego) is called a “porous
implant.” Since its introduction, a number of other “porous
implants” have been introduced.
• Another synthetic porous implant that has become increasingly
popular is a type of porous plastic known as Porous
Polyethylene (Medpor™ - Porex Surgical Inc, Cooledge Park,
GA). This material is a synthetic man-made material that
previously has been used in a wide range of cranio-facial
reconstructive procedures and facial fractures, with few
problems. Its properties demonstrate high tensile strength,
malleability, biocompatibility and fibrovascular ingrowth. The
porous polyethylene orbital implants are also cheaper than the
original Bio-Eye™, and are available in spherical, egg, conical
or mounded shapes
• -Aluminum oxide (Al2O3) another man-made biomaterial that
has been in use for more than 30 years as an implant in
orthopedics and dentistry has also been studied extensively
(Dr. D.R. Jordan - University of Ottawa Eye Institute, Ottawa,
Ontario, Canada) and is emerging as an orbital implant in
Canada, Europe and several other parts of the world.
The aluminum oxide implant, also known as the •
Bioceramic Implant (FCI, Issy-Les-Moulineaux, Cedex,
France) looks identical to the Bio-Eye™ hydroxyapatite
with multiple interconnected pores. Like the synthetic HA
and porous polyethylene, it is less expensive than the
Bio-Eye™. There is evidence that human osteoblasts and
fibroblasts appear to grow better on aluminum oxide than
hydroxyapatite, suggesting it may be more biocompatible
than hydroxyapatite and better tolerated in the eye socket.
Spherical porous
polyethylene.
Drawing of hydroxyapatite
implant with muscles attached
and a peg in position .
Synthetic hydroxyapatite
implant.
Orbital Implant
Complications
• Complications associated with hydroxyapatite that also
apply to other porous orbital implants have gradually
come to light since the introduction and widespread use
of hydroxyapatite in the early 1990’s. Reported
complications include: implant exposure, conjunctival
thinning, discharge, pyogenic granuloma formation
(excess healing tissue formation), and rarely persistent
pain or discomfort. The complication discussed most
often is implant exposure with exposure rates ranging
from 0 to 22%
• Predisposing factors to exposure include: wound closure under
tension, inadequate or poor wound closure technique,
infection, mechanical or inflammatory irritation from the
speculated surface of the HA implant and delayed ingrowth of
fibrovascular tissue with subsequent tissue breakdown.
• The most feared complication of porous orbital implants is
infection within the implant. Porous orbital implants have
multiple interconnected pores that fill with fibrovascular tissue
over the first 6-12 months which theoretically should help
resist infection. Prior to this time implant exposure can
predispose the implant to entry of bacterial contamination and
implant infection. Once an implant infection does occur, it
may not be easy to recognize or treat. Hallmarks of implant
infection are, recurrent discharge resistant to multiple drops,
implant discomfort (to touch), and recurrent pyogenic
granuloma (excess healing tissue) on the surface of the
implant .
Orbital implant infection - the eye
socket is very inflamed, there is
lots of discharge and a recurrent
pyogenic granuloma (black
arrows).
Exposure of a hydroxyapatite
implant.
• Implant infection does not respond to oral, intravenous
and/or topical antibiotics and generally the implant has to
be removed. Removal of an infected implant requires
general anaesthesia and is traumatic to the eye socket as
the implant has been partially integrated with the socket
tissue. Following removal of the porous orbital implant it
is not advisable to have another porous implant until a
sufficient length of time (at least 6 months) has past to
ensure tissue healing. A plastic nonporous sphere can be
put in to maintain volume while waiting out the 6-month
period and contemplating another porous implant.
Artificial Eye Motility :
Implant Pegging
Procedures
• a) To peg or not to peg? One of the many advantages of
porous implants (hydroxyapatite, porous polyethylene,
aluminum oxide) is the ability to integrate them with the
overlying artificial eye through a peg system. By coupling the
orbital implant to the artificial eye a wide range of prosthetic
eye movements as well as darting eye movements commonly
seen in conversational speech can occur. These movements
impart a more life-like quality to the prosthetic eye. To peg or
not to peg, is up to the surgeon and patient. They are certainly
not for everyone and with all due respect, not all eye socket
surgeons are equally skilled at putting them in. Before
considering a peg the implant has to be fully vascularized
(minimum of 6 months, in some this may take a year or more)
and, the socket has to be a healthy one. Patients with diabetes,
previous radiation, systemic disease such as Systemic Lupus
Erythematosis (SLE) or, individuals on medications such as
steroids, are not good candidates for pegging, because their
socket tissue simply does not have good blood flow.
• Pegs are not fool proof and do have their own inherent set
of problems above and beyond those of the implant. A
meticulous peg placement technique is required to obtain
excellent results; a fact not appreciated by many. The
pegs must be central and straight. They must also be flush
with the implant with no exposed portion to ensure a
good result. Once pegged, the individuals do require
regular follow up initially to be sure the peg is sitting
well. With time the follow-ups can decrease (yearly) if all
is well. The most worrisome problem associated with
pegging is introduction of infection to the implant,
requiring implant removal.
• Other potential peg problems include discharge, pyogenic
granuloma (excess healing tissue) around the peg, peg
falling out, poor transfer of movement, clicking,
conjunctival overgrowth, poor fitting or loose sleeve, part
of sleeve shaft visible, peg drilled on an angle, peg drilled
of center, HA visible around peg hole, and excess
movement of peg.
• Thus, although pegs allow a more lifelike quality to the
artificial eye, they are not for everyone.
• b) Peg Variations
the original peg was made of plastic (polycarbonate). A hole
was drilled into the implant and a standard peg was put in
place. To obtain a more secure fit between the orbital implant
and peg, a peg and sleeve system was designed. Following
drilling of a hole into the implant, a sleeve is screwed into the
implant until it is tight and flush with the implant surface. A
peg is then placed into the center of the sleeve. In more recent
years titanium has replaced polycarbonate as a peg and sleeve
material since it is better tolerated in the socket tissue `(more
biocompatible).
• Some companies produce pure titanium peg systems whereas
others produce hydroxyapatite-coated titanium
• The hydroxyapatite coating results in significantly greater
interface strength than uncoated titanium.
Figure 1: Polycarbonate
peg system - original
standard peg is to the
right (black arrow); the
peg and sleeve system to
the left with screwdriver
for sleeve below.
Figure 2: Pure titanium
peg and sleeve system.
Figure
3: Hydroxyapatitecoated titanium sleeve
with several titanium
pegs.
Socket Reconstructive
Procedures
• a) Volume Augmentation - some degree of sunkenness is
common in artificial eye patients. The appropriate selection of
an adequate implant size at the time of enucleation or
evisceration is the first step in decreasing the sunken
appearance of the artificial eye patient. However, if there
remains some sunkenness, techniques are available to decrease
it. One option is to undergo a second surgical procedure to
implant a second implant (sled or floor implant) into the eye
socket, underneath and behind the first. A general anaesthetic
is required to put these volume augmentation implants into
position. They are designed to slip in underneath and posterior
to the first implant. They can be secured in position by glue,
wire or a mini plate system used in facial reconstruction. The
surgery is short (45 minutes) and patients are discharged with a
patch in place on the day of surgery or the following morning.
The artificial eye remains in position but may require an
adjustment in the first few weeks. Pain is not a big factor as
there is very little disruption to the socket tissues
• Another technique to decrease a sunken appearance involves the use
of “dermal fat” grafts. A graft of fat just beneath the skin (“dermal
fat”) can be harvested from the hip of the patient. This fat is then
implanted into the sunken appearing upper lid (sulcus). The hip
incision lies beneath the underwear or bathing suit area. The fat is
trimmed and implanted into the sunken appearing upper lid (sulcus)
making a 1-inch long eyelid skin crease incision. A pocket is made
for the fat graft, which is then implanted followed by skin closure.
This procedure is routinely done under local or local stand-by
anaesthesia (twilight anaesthesia) as a day patient. It is not painful
and has good to excellent results. Over correction is required as some
fat atrophy does occur in the first 3 months.
• Lastly, to balance the sunken appearance of the artificial eye, removal
of a small amount of skin and fat from the upper lid of the opposite
seeing eye can be performed. This is a very simple and quick
procedure that is routinely done as an outpatient. Sometimes it can be
performed with nice results even prior to consideration of the “floor
implants” or “fat graft technique” described.
Figure 1: Sunken socket
appearance.
Figure 2: 3 months following
an orbital floor implant - the
sunken appearance is gone.
• b) Fornix Reconstruction - After many years of wearing
an artificial eye, recurring socket infection and/or scarring
secondary to trauma, the pocket behind the lower lid
where the artificial eye sits (“inferior fornix”) can become
shallow. This may be associated with a retracted
appearing lower lid (a lower lid that looks too low) as
well as artificial eye fitting problems with the artificial
eye recurrently falling out
• To correct this, an initial assessment by the ocularist can
be performed to determine if a modified custom made
prosthesis might be of some benefit. If not, a fornix
deepening surgical procedure is required. One such
surgery involves borrowing some of the lining from the
inside of the mouth (mucous membrane) and using it to
create a deeper lower lid pocket. Hard palate mucosa
(from the palate of the mouth) can also be used as well as
ear cartilage or donor sclera. These surgeries are done
under local stand-by anaesthesia (twilight anaesthesia) or
general anaesthesia. They generally take 1-1½ hours and
are very well tolerated. If hard palate mucosa is used, hot
foods and liquids may be difficult to tolerate for a few
weeks.
With a shallow inferior fornix the lower
lid appears pushed down and the lashes
are rolled upward toward the
prosthesis.
Concluding Remarks
About Artificial Eyes
• the artificial eye patient to maintain a natural, normalappearing prosthetic eye. In recent years major developments
have taken place in reconstruction of an eye socket following
enucleation/evisceration or secondary implant surgery. The
ideal orbital implant has been sought for more than a century.
Porous materials (hydroxyapatite, porous polyethylene and
aluminum oxide) are currently the preferred orbital implants
primarily because of the vascularization and tissue integration
that can occur. These implants are less likely to migrate than
previously used plastic implant and are associated with a
higher degree of motility especially when coupled to the
overlying artificial eye through a peg system. Which implant is
best is currently a matter of debate. The ideal porous implant is
one that is biocompatible, bioinert, non-toxic, non-allergenic,
inexpensive and stable over time.
• By : Aisha Lubbad .
Montaha Ali .
Maryam Alsarraj .
Doaa Tayeb .
For : Dr . Khaled Awad .
2013 – 2014