Keratoplasty update 2016

KERATOPLASTY
UPDATE 2016
PK, DALK, DSEK,DMEK,PDEK
INDOREDRISHTI.WORDPRESS.COM

DR DINESH MITTAL DR SONALEE MITTAL
DRISHTI EYE HOSP VIJAYNAGAR INDORE

From the first
documented
successful corneal
transplant performed
by Eduard Konrad
Zirm in 1906 to
contemporary
femtosecond laser
assisted surgery, the
evolution of
keratoplasty has
been nothing short of
remarkable

THE CORNEA
•The cornea is the refractive surface of
the eye and, with the sclera, forms the
outermost coating of the eyeball. It
constitutes up to one-sixth of the entire
eyeball. The corneal epithelium is
derived from surface ectoderm, and the
mesoderm gives rise to Bowman’s layer,
the stroma, Descemet’s membrane, and
the endothelium.

THE CORNEA
•The average diameter of the cornea
varies from 11 to 12 mm horizontally and
9 to 11 mm vertically. The cornea is
responsible for 48 diopters of the total
power. The posterior surface of the
cornea is more spherical than the
anterior surface, and the central cornea
is thinner (520 μm compared with the
peripheral cornea 650 μm or more).

Precorneal Tear Film
•The tear film is 7 μm thick and has a volume
of 6.5 ± 0.3 μL. The tear film is made up of an
outer lipid layer (0.1 μm), middle aqueous
layer (7 μm), and innermost mucin layer (0.02
to 0.05 μm).The tear film keeps the corneal
surface moist and prevents the adherence of
microbes. More than 98% of the volume of
tears is water. The tear film has many
essential substances, such as electrolytes,
glucose, immunoglobulins, lactoferrin,
lysozyme, albumin, and oxygen.

Anatomy of the Cornea
•The cornea has 5 layers:
•THE EPITHELIUM,
•BOWMAN’S LAYER,
•THE STROMA,
•DESCEMET’S MEMBRANE,
• ENDOTHELIUM

Epithelium
•The corneal epithelium has a thickness of 50
to 90 μm and comprises 5 to 7 layers of
stratified,squamous, and nonkeratinized cells
. The epithelium forms approximately 10% of
the total corneal thickness. cells of corneal
epithelium may be divided into 3 types:
•squamous cells
• middle wing cells
•and deeper basal cells .

Epithelium
• Superficial Layer of Squamous Cells
• The superficial layer, which consists of
squamous cells, forms the outermost 1 to 2
layers of the corneal epithelium. The oldest
epithelial cells disintegrate and shed into
the tear film by process of desquamation.
These superficial cells are composed of
microscopic projections in the form of
microvilli, reticulations, or microplicae .

Epithelium
.
•The fibrillar glycocalyx is present on
these ramifications, which interacts with
the mucinous tear film.
•The epithelial cells are replaced every 7
to 14 days. superficial cells adhere to
each other by presence of desmosomes
and junctional complexes. These
complexes consist of tight junctions that
circumvent entire cell & resist flow of
fluid through epithelial surface.

Epithelium
• . The epithelial cells are replaced every 7 to
14 days. The superficial cells adhere to each
other by the presence of desmosomes and
junctional complexes.
•Middle Layer of Wing Cells
•The middle layer of the corneal epithelium
consists of wing cells, which have lateral,
thin, wing-like projections protruding from a
more rounded cell body.
The wing cells are connected to each other
by desmosomal junctions and gap junctions.

Epithelium
•Deep Layer of Basal Cells
•The deep layer of the corneal epithelium
consists of basal cells, which are cuboidal
to columnar in shape and have a diameter
of 8 to 10 μm. Posteriorly, the cells are flat
and have a basal lamina to which they
anchor with the help of hemidesmosomes.
The basal cells are metabolically active
and are responsible for division, and they
form the wing and the superficial cells.

Epithelium
•The corneal epithelium acts as a tough
protective shield against
microorganisms and foreign bodies;
•however, it is partially permeable to
small molecules such as glucose,
sodium oxygen, and carbon dioxide

Basement Membrane
• The basal cells of corneal epithelium are
anchored with help of hemidesmosomes to
basement membrane, which is located
between corneal epithelium and Bowman’s
membrane.
It is primarily made up of type IV and VII
collagen and glycoproteins and has 2 parts:
the superficial lamina lucida layer and the
deeper lamina densa layer

Bowman’s Layer
•Bowman’s layer is acellular membrane-
like zone with a thickness of 8 to 14 μm.
It has numerous pores for the passage of
corneal nerves into corneal epithelium.
•On examination with electron
microscopy, it is made up of a fine
meshwork of uniform type I and III
collagen fibrils

Corneal Stroma
•The corneal stroma, with a thickness of
approximately 500 μm, is responsible for
90% of the thickness of the cornea. It is
located between Bowman’s layer and
Descemet’s membrane . It is composed of
lamellae, which are formed from flattened
bundles of collagen, stromal keratocytes,
and ground substances like keratan
sulphate. The major structural component
of the corneal stroma is collagen

Corneal Stroma
•There are 200 to 250 bundles of collagen
fibrils, and each bundle has a fibril 2 μm
thick and 9 to 260 μm wide. The collagen
fibers are arranged in a regular manner,
parallel to the corneal surface. Such a
uniform arrangement and equal spacing of
collagen fibers creates a lattice or 3-
dimensional diffraction grating, which is
responsible for the ability of the cornea to
scatter 98% of incoming light rays.

Corneal Stroma
• lamellae in posterior part of stroma have an
orthogonal layering ( the bundles are at right
angles to each other). In anterior one-third of
the stroma, the lamellae have a more oblique
layering. arrangement of ant. and post. lamellar
stromal fibers is different. fibers are more
compact anteriorly so that their compactness
and their oblique arrangement make lamellar
dissection more difficult anteriorly. On the
other hand, the arrangement of the fibers is
less oblique and loose posteriorly .

Corneal Stroma
•On other hand, arrangement of fibers is less
oblique and loose posteriorly so that manual
dissection is simpler in the posterior part.
•The primary glycosaminoglycans of the
stroma are keratin sulfate and chondroitin
sulfate, which occur at a ratio of 3:1. The
lamellar stroma is secreted and maintained by
stromal fibroblasts called keratocytes, which
occupy 3% to 5% of the stromal volume. They
are responsible for the maintenance of
stromal components .

Descemet’s Membrane
•Descemet’s membrane is basement membrane
of corneal endothelium and is synthesized by
endothelium. At birth, the human Descemet’s
membrane is 3 μm wide, but in adulthood,
•the width increases to 12 μm . There are 2
distinct regions in Descemet’s membrane:
•the anterior one-half to one-third, which is
banded; and posterior two-thirds, which are
nonbanded. Recently, another layer of the
cornea, called Dua’s layer, has been
described.

Descemet’s Membrane
•Recently, another layer of the cornea, called
Dua’s layer, has been described. This is a
novel, well-defined, acellular, strong layer in
pre-Descemet’s cornea. It separates along
the last row of keratocytes in most cases with
big bubble technique . Its recognition will have
a considerable impact on posterior corneal
surgery and understanding of corneal
biomechanics and posterior corneal pathology,
such as acute hydrops, descemetocele, and
•pre-Descemet’s dystrophies .

Endothelium
• endothelium is a single-layered, low
cuboidal endothelium. It has 400,000
cells and a thickness of 4 to 6 μm.
endothelial cells have a hexagonal
shape and are 20 μm wide. They
prevent seepage of the aqueous humor
into the stroma..The number of
endothelial cells decreases with age at
the rate of 0.3% to 0.6% per year.

Endothelium
•Unlike the corneal epithelium, endothelial
cells cannot undergo mitosis after birth. At
birth, cell densities range from 3500 to 4000
cells/mm2, whereas an adult’s cell densities
range from 1400 to 2500 cells/mm2. As cells
decrease in number, they become thinner
and attenuated. The cornea loses it clarity
when the endothelial cell densities reach
400 to 700 cells/mm2, below which corneal
edema occurs .

Endothelium
•The endothelial cells are linked to each
other by junctional complexes and gap
junctions, but no desmosomes are present.
The endothelial cells do not replicate in
human beings. They decrease in density with
increasing age, raised IOP , & inflammation
& after intraocular surgery. The endothelium
plays a major role in maintaining stromal
hydration (normally 78%) through the sodium
potassium–activated adenosine triphosphotase
(ATPase) present in basolateral borders of cells.

Endothelium
•Endothelial cell loss varies from 2% to 7%
after anterior lamellar keratoplasty and from
20% to 30% after posterior lamellar keratoplasty
depending on the surgeon’s skill. In cases of
Descemet’s membrane endothelial keratoplasty
(DMEK), endothelial cell loss is higher due to
difficulty in performing this technique.
However, in hands of an experienced Surgeon ,
endothelial cell loss after Descemet’s
stripping endothelial keratoplasty and DMEK
may be similar.

Penetrating Keratoplasty
• PKP is the most common & successful
human transplantation procedure.
•Over 30 000 corneal transplantations are
performed in the United States each year.
•Optical results have improved greatly as a
consequence of advances in tissue selection
and preservation, trephines, & management
of postoperative astigmatism .

Preoperative evaluation and
diagnostic approach
• PKP may be used to provide tectonic support
(such as in corneal thinning and perforation),
& to improve visual outcome (such as in the
replacement of a scarred cornea).
Indications for PK include: keratoconus,
previous graft failure or rejection, full-
thickness or deep corneal scars, Fuchs’
endothelial dystrophy, pseudophakic or
aphakic bullous keratopathy, chemical burns,
corneal ulcers, corneal dystrophies .

diagnostic approach
• Conditions with primarily posterior pathology,
such as Fuchs’ endothelial dystrophy and
pseudophakic or aphakic bullous keratopathy,
are now commonly treated with endothelial
keratoplasty. The rate of success of PK is
often excellent, but the chance of graft
rejection increases significantly with active
or recurrent infection, inflammation, corneal
vascularization, or previous graft rejection.

diagnostic approach
•It is important to perform a careful preop
evaluation & thoroughly discuss with
patient surgery, visual expectation, possible
complications, and, in particular, the long
process of postoperative care. The recipient
must be prepared for lifelong management of
the eye. In general, important considerations
for preoperative evaluation for PK are as
follows

diagnostic approach
• Evaluation of visual potential.
• Ocular surface disease – must be recognized
and treated prior to PK.
• Includes rosacea, dry eyes, blepharitis, trichiasis,
exposure keratopathy, ectropion, and entropion.
• IOP must be controlled prior to surgery.
• Ocular inflammation – must be recognized
and treated.

diagnostic approach
• Prior corneal diseases and vascularization –
a history of herpetic keratitis significantly
reduces the chance of graft success due to
several factors, including recurrent disease
in the graft, vascularization, trabeculitis with
increased IOP, and persistent inflammation
that may induce rejection.
• Peripheral corneal thinning/melting (such as
that associated with rheumatoid arthritis) –
may significantly affect surgical outcome .

Optical:
•A healthy, clear donor cornea is used to
replace an opaque, cloudy, or distorted
cornea in an attempt to improve vision and
hence quality of life
• Pseudophakic bullous keratopathy
•Keratoconus , Regraft secondary to
rejection
• Keratoglobus , Degenerations , Dystrophies
, Scar
• Aphakic bullous keratopathy , Congenital

Tectonic
• A donor cornea is used to restore the
recipient corneal anatomy and globe
integrity
• Descemetocele
• Corneal stromal thinning
• Corneal perforation

Therapeutic
•Surgical intervention is performed
when therapeutic measures have
failed and infection continues to
progress.
• Infection may be due to bacteria,
virus, parasites, or other cause.

Cosmetic
•Corneal transplantation is performed
to improve the appearance of the
patient and has no bearing on the
visual outcome. This could also be
done in a nonseeing eye. An opaque
cornea with a white or blue-gray hue
may be disturbing to the patient, who
may request PK.

Surgical techniques
• decompression of globe is ensured prior to
PK, as excessive preop IOP may increase risk
of expulsive choroidal hemorrhage.
Intravenous mannitol or mechanical ocular
decompression should be considered. Miotics
are placed preoperatively to protect the lens
during surgery. Scleral supporting rings may be
used principally in aphakic eyes or in young
patients. Care is needed when suturing the scleral
fixation rings, as inadvertent misalignment of the
rings may result in irregular trephination

Graft Size Determination
•Before handling the donor cornea, the
recipient graft size should be decided and
both donor and recipient trephine blades
should be examined under the operative
microscope to ascertain the indicated
correct size and quality of the blades.
•Graft size determination is based on three
main factors: the size of the recipient
cornea, the targeted disease, and the known
increased risk of rejection with increasing
graft size.

•Most adult corneas measure slightly greater
in horizontal meridian compared with vertical
meridian because superior limbus descends
slightly superiorly. White-to-white measurements
for an adult cornea in the horizontal meridian
are on average 12.5 mm. A normal-sized cornea
with endothelial disease such as Fuchs'
endothelial dystrophy, iridocorneal
endothelial syndrome, or pseudophakic
bullous keratopathy would typically be
trephinated with a 7.5-mm trephine .

• Although a larger recipient size trephination
would supply a larger quantity of healthy
endothelial cells, larger donor corneal size (>
8 to 8.5 mm) is associated with a higher risk
of rejection . Ectatic corneal pathologic
processes, including keratoconus and PMD ,
require prior recipient donor size measurements at
the slit lamp because the area of corneal thinning
is often larger than that seen under the operating
microscope. It is paramount that the area of
thinning be encompassed in the trephinated tissue
to avoid tissue disparity and wound mismatch .

•Most surgeons use a 0.25-mm
oversize in the donor button to
counteract the 0.2-mm difference
in size produced by endothelial
trephination of the donor cornea.
This essentially counteracts the
disparity to give an equivalent
donor and recipient trephination

TREPHINES USED IN
KERATOPLASTY
Hanna trephine left
Baron hessburg
trephine middle
Open disposable
trephine right

Surgical techniques
•It is customary first to trephinate the donor
cornea before the recipient trephination,
thereby avoiding any error in sizing and an
incomplete or aborted donor cornea
trephination. error in donor cornea trephination
precludes continuing with procedure The AC is
maintained when possible by injection of
balanced salt solution throughout the
procedure, and wound integrity is verified with a
Weck cell sponge at the end of the procedure. All
wound leaks should then be corrected.

Surgical techniques
•The size of the graft is determined based
on location of pathology and clinical
judgment. The donor tissue is typically
sized 0.25 mm larger in diameter than the
recipient tissue. In certain circumstances,
a larger (0.5 mm) donor may be
considered in an aphakic eye to induce
myopia, or a same size donor button,
such as in a recipient with keratoconus,
may be chosen to reduce myopia.

Surgical techniques
•The visual axis of the recipient cornea is
marked with a marking pen. An inked
radial keratotomy marker may be used to
mark the peripheral cornea. If a sclerally-
fixated IOL is planned, the scleral flaps
are made prior to trephination, and the
IOL is prepared before the eye is opened.
A donor corneal button is punched. Today
most commonly used trephine is the Barron
Donor Cornea Punch . donor is cut from
endothelium to epithelium.

Surgical techniques
• donor is cut from endothelium to epithelium.
The donor also may be cut from epithelium to
endothelium using an artificial anterior
chamber, and then a manual trephine as
above, or more recently, the femtosecond
laser may be used.This has the theoretical
advantage that both the donor and recipient
are cut in the same fashion with the same
blade, which reduces donor–recipient
disparity and potentially reduces astigmatism.

Surgical techniques
• The recipient cornea may be cut using a
variety of trephines, such as the Hessburg–
Barron suction trephine , Hanna trephine,
Castroviejo trephine, and now with a
femtosecond laser. The Hessburg– Barron
suction trephine consists of a circular blade
assembly that has a vacuum chamber
attached to a spring-loaded syringe. Excision
of host corneal button may be performed via
a partial-thickness trephination followed by
a controlled entry into anterior chamber.

Surgical techniques
• Excision of host corneal button may be
performed via a partial-thickness
trephination followed by a controlled entry
into anterior chamber using a No. 75 Beaver
blade, or via a continued trephination that is
stopped as soon as aqueous egress shows
anterior chamber has been entered.
recipient button is then excised using
forceps and corneal scissors . edge of
recipient bed is made perpendicular for
optimal graft–host apposition.

Surgical techniques
•Pilocarpine 2% to 4% is typically applied
three times at 5-minute intervals, 1 hour
before surgery. This ensures a constricted
lens-iris diaphragm, therefore reducing
potential damage to the lens, IOL, lens
capsule, and vitreous face.
• Mydriatic agents for pupillary dilation include 1%
tropicamide, 2.5% phenylephrine, and 1%
cyclopentolate. These agents are used when prior
phacoemulsification, open-sky cataract extraction,
or posterior lens repositioning is planned.

Surgical techniques
•If patient requires concurrent cataract
extraction, IOL explantation, anterior
vitrectomy, or the placement of a new IOL,
this may be done prior to trephination, if
visualization allows. Since in many cases
the diseased cornea precludes adequate
visualization, an “open sky” technique is
utilized after trephination Viscoelastic may
be placed in anterior chamber of recipient
and donor button then is placed over
recipient bed and sutured in place with four
cardinal sutures .

Surgical techniques
•Care is taken in placement of the cardinal
sutures, as proper tissue distribution is
paramount. depth of suture is 90% of
corneal thickness. remaining sutures may be a
combination of interrupted and running
sutures or solely interrupted sutures . The
author’s choice is often 8 interrupted sutures
with an additional single 10-0 nylon running
suture that encompasses 360 degrees of
corneal wound. If there is corneal
neovascularization, then interrupted sutures.

Surgical techniques
•Interrupted sutures are suited for vascularized
or thinned cornea, as subsequent selective
removal may be necessary to prevent
advancement of vessels or to control
astigmatism.
•Running sutures have the advantage of speedy
placement intraoperatively and better tension
distribution and healing. Prior to placement of
final sutures, the viscoelastic material in the
anterior chamber is removed.

Surgical techniques
•The running sutures may be adjusted
intraoperatively by using a keratoscope.
•When the suturing is complete, all sutures
are rotated such that the knots are buried
within the stroma, and the security of the
wound is tested.

Four
cardinal
sutures in
place

12
interrupted
sutures in
place

TYPE OF SUTURING
•Four categories of suturing techniques
employed in keratoplasty will be
addressed in subsequent sections:
•1 Interrupted sutures (IS)
•2 Combined continuous and interrupted
sutures (CCIS)
•3 Single continuous suture (SCS)
•4 Double continuous suture (DCS)

Cardinal sutures
The second suture is
180 degrees from the
first suture so that the
donor tissue and
wound are divided
equally into nasal and
temporal halves .
The third and the
fourth sutures also
divide the donor tissue
and wound evenly

Suture Patterns and Suture
Materials
•The suture material of choice for PK is nylon.
corneal suturing techniques ranges from a
combination of interrupted sutures with a
single running suture, to all interrupted
sutures, to double-running sutures. Although
for the most part 10-0 nylon sutures are used,
with double-running sutures, first running
suture may be 10-0, followed by an 11-0 or
10-0 nylon suture for second running suture.

Materials
•The initial step with all grafting techniques is
the fixation of the graft to the donor cornea
with 4 cardinal sutures at the 12-, 6-, 3-, and
9-o’clock positions. The first suture is placed
at the 12-o’clock position. The donor corneal
disc may be held with a double-prong forceps,
such as a Polack forceps (Rumex Inc), for
better donor disc stabilization, and the needle
is passed between the two prongs of the
forceps.

Materials
•For all subsequent sutures, a 0.12 forceps
may be used.
• The second corneal suture is the most
important suture because it determines the
proper seating of the donor graft. This suture
is placed at the 6-o’clock position, and the
graft should have equal corneal tissue on
either side of this suture .

Materials
• last two cardinal sutures are placed at 3- and
9-o’clock positions, and this provides initial
fixation of donor graft to recipient corneal
bed. Whereas the interrupted sutures are
placed deep within corneal stroma of donor
and recipient corneas, the running sutures
are somewhat more superficial. Avoid sutures
passing through the full thickness of the
donor graft. All suture knots are buried within
the cornea to provide patient comfort.

Materials
•Knots may be buried within donor cornea or
the recipient cornea.
•However, some are of the opinion that knots
buried within the host cornea may be more
prone to corneal neovascularization. Use of
intraoperative keratoscopy can provide
optimal suture tension and astigmatism
control.

Five important points regarding suture
adjustment should be emphasized
• 1 Corneal astigmatism is multifactorial and
suture adjustment or removal can only correct
astigmatism that is due to uneven suture
tension in a approximated wound. If wound is
unevenly approximated, adjustment of suture
tension does little to reduce astigmatism.
• If uniform tension in a regular wound is
present and vector forces are even across the
wound, continuous sutures work well.

• However, continuous sutures do not protect a
wound from locally applied forces and they
are poorly suited for irregularly shaped
wounds that require vastly different amounts
of tension at different sites in wound.
Interrupted sutures better serve such
irregularly shaped wounds. astigmatism with all
sutures out postop may reflect poor donor trephination,
uneven use of corneal scissors, and/or improper placement
of the initial interrupted cardinal sutures.

•2 Once the suture has been adjusted or
removed to achieve suitable topography,
remaining sutures should be left in place until
they have to be removed. Patients should be
advised that sutures can be left in place until
there is an indication for removal. Some
fibrosis can be expected around the suture
track, but usually this is not an indication for
removal. most common indication for removal
of single continuous suture is breakage.

•3 After several years, continuous sutures may
be easier to remove than interrupted sutures.
As the suture degrades, knots can become
more difficult to remove. Continuous sutures
may therefore cause less inflammation and
less likelihood of residual buried remnants
than interrupted sutures.

•4 Wound healing can be variable from patient
to patient, and postoperative use of topical
and systemic corticosteroids varies among
surgeons. The decision on when sufficient
wound integrity exists to safely remove a
corneal suture must be made carefully with
these variables in mind, weighing risks and
benefits. timings for suture removal given are
only guidelines & every patient & wound
must be addressed on an individual basis.

•5 The ultimate decision regarding suture
technique comes down to surgeon
preference and individual patient
characteristics.
• All suture techniques can provide excellent
optical results with appropriate surgeon
experience and skill.

Deep Anterior Lamellar
Keratoplasty DALK
•Historically, corneal transplantation has been
performed through full-thickness grafting, also
known as penetrating keratoplasty (PK).
Lamellar keratoplasty (LK) is a more recent
approach to allow for preservation of
unaffected tissue, and specialized procedures
allow for preservation
of either the anterior or posterior corneal
layers. The main determining factor in whether
to use an anterior or posterior approach is

Keratoplasty DALK
• first LK was performed more than 150 years
ago, although historically use of anterior LK
was limited by worse visual outcomes
compared with PK, as well as technical
difficulty of the procedure.In second half of
20th century, PK was largely favored.
However, in 1970s, there was an increased
interest in lamellar procedures. With advances
in technical approach to deep anterior lamellar
keratoplasty (DALK), which involves removal of the

Keratoplasty
•DALK has become an alternative to PK for a
variety of indications . Studies have
demonstrated equivalent best corrected
visual outcomes and superior preservation of
endothelial cell density with DALK compared
with PK. Interest in DALK has been piqued by
its advantages, including enhanced structural
integrity, decreased recovery time, and lower
incidence of rejection and infection.

Surgical Technique
•Depending on patient’s corneal diameter and
disease, the DALK bed is typically measured
with a diameter of 7 to 8.5 mm . A trephine is
used to cut through anterior stromal layer
without entering anterior chamber. depth of
trephination depends on surgeon preference
and depth of disease in stroma. most
surgeons now favoring a Descemet’s–baring
procedure using the big-bubble technique .

Big-Bubble Technique
•1. Trephination
•2. Air injection
•3. Partial keratectomy
•4. Incision into the anterior wall of
big bubble
•5. Severing the stroma with an iris
spatula

Big-Bubble Technique
6. Formation of 2 slits into the anterior wall of
the collapsed bubble
7. Lifting deep stroma and excision with
scissors
8. Moistening Descemet’s membrane
9. Suturing the donor corneal tissue
10. Special situations and complications
• Failure to form big bubble
• Perforation of Descemet’s membrane

Combination Big-
Bubble/Viscoelastic Technique
• We use a combination of steps from the big-
bubble and viscoelastic techniques to
produce successful anatomic and visual
results with the DALK procedure. The steps
of our procedure are as follows :
• 1. Trephination is performed using Hessburg-
Barron trephine to 80% depth (approximately
300 μm) with 4 to 5 quarter turns of handle
(each quarter turn cuts approximately 60 μm).

Combination Big-
2. paracentesis incision is made to decrease
IOP , and 4 to 6 small air bubbles are injected
into the anterior chamber.
3. A bent 27-gauge needle on an air-filled
syringe is used to advance the bevel down into
the deep periphery of the trephined cornea at
the level of the deepest trephination toward
the corneal center;

Combination Big-
this is followed by the Tan cannula on an air-
filled syringe to inject the air with the goal of
dissecting Descemet’s membrane off the
central cornea.
4. Partial keratectomy is performed with a
crescent blade to dissect off the superior
lamellar tissue.

Combination Big-
5. Viscoelastic dissection of Descemet’s
membrane is performed with Healon on a 27-
gauge needle inserted into the corneal center
to dissect off Descemet’s membrane all the
way past the trephine border.
6. The stroma is severed with an iris spatula.
7. Two slits are formed in corneal stroma in a
cruciate pattern with a blade (the viscoelastic
helps protect the underlying Descemet’s membrane
from traumatic damage and performation).

Combination Big-Bubble/Viscoelastic Technique
8. deep stroma is lifted and 4 quadrants are
excised, then Tan DALK scissors are used
to excise these 4 quadrants of tissue and trim
off peripheral rim of the corneal tissue.
9. The donor tissue is cut to the same size.
10. The donor Descemet’s membrane is
stained with trypan blue and subsequently
stripped and removed using a Weck-Cel
sponge and/or smooth tying forceps.
•11. The donor corneal tissue is sutured.

DALK TECHNIQUE
•A POCKET IS
CREATED FOR A
CANNULA TO INJECT
PRE-DESCEMET’S AIR
. THIS POCKET DOES
NOT HAVE TO
COMPLETELY REACH
DESCEMET’S IN
ORDER FOR AN AIR
INJECTION TO
CREATE A CLEVAGE
PLANE.

•Big bubble
formation is
characterized by
a semi-opaque
disk with a near
circular outline.
Air separates
the central
Descemet's
membrane from
the stroma by
forming a large
air bubble

DALK TECHNIQUE
• AIR HAS BEEN
INJECTED TO
SEPARATE DESCEMET
MEMBRANE FROM
STROMA . THE
SUCCESS OF THAT
MANEUVER CANNOT
BE DETERMINED AT
THIS POINT

DALK TECHNIQUE
•AN ANTERIOR
CAP OF
STROMA IS
DISSECTED
AND
REMOVED

DALK TECHNIQUE
• REMOVAL OF NATERIOR
CAP DISCLOSES A DARK
AREA RESULTING FROM
INJECTED AIR .REMOVAL
OF SOME AQUEOUS
HUMOR BY
PARACENTESIS ALLOW
SMALL AIR BUBBLE TO
EXPAND .AIR IS THEN
INJECTED IN ANTERIOR
CHAMBER TO SEE IF
SMALL BUBLE DISPLACES
TI TO PERIPHERY

DALK TECHNIQUE
• A BLUNT 25 CANNULA WITH
A PORT ON POSTERIOR
SURFACE IS USED TO GAIN
ACCESS TO SPACE BETWEEN
STROMA AND DESCEMET
MEMBRANE BY MEANS OF
BLUNT DISSECTION AND
INJECTION OF SODIUM
HYALURONATE .SUCCESS IS
SUGGESTED BY A BILOBED
AIR BUBBLE IN ANTERIOR
CHAMBER

DALK TECHNIQUE
•STROMA IS
BEING
REMOVED

DALK TECHNIQUE
• SMALL AMOUNT OF
PERIPHERAL STROMA
REMAINS . A LARGE
AMOUNT OF CENTRAL
CLEAR DESCMET’S
MEMBRANE IS PRESENT
. IT IS BEST NOT TO
RISK PERFORATION
TRYING TO REMOVE
ALL STROMA .

DALK TECHNIQUE
•DESCEMET’S
MEMBRANE
WITH
ENDOTHELIUM
IS STRIPPED
FROM DONOR

DALK TECHNIQUE
•DONOR IS
SUTURED WITH
EIGHT
CARDINALS AND
A RUNNING
SUTURE .

DALK VS PK
• American Academy of Ophthalmology
DALK/PK studies found visual acuity results
between the 2 procedures to be equivalent,
although there was a trend toward worse
visual outcomes if more than 10% of the
recipient stromal bed was retained. Rates of
both early and late endothelial cell loss are
lower in DALK than in PK, and graft survival
has been shown to be longer in eyes
undergoing DALK with big bubble technique
compared with PK. perience.

DALK VS PK
•In the same study, better visual acuity results
were achieved with the big bubble technique
compared with manual-dissection DALK.
• A recent study focused on outcomes of DALK vs PK
from the patient perspective. Among 20 patients
who had undergone PK in one eye and DALK in
other, there was no significant difference in
objective findings, including visual acuity and
refractive outcomes. However, patientsreported
preferring the PK procedure, although there was no
further detail available on which aspects of
experience were different between 2 procedures.

Conclusion
DALK offers an option for corneal
transplantation in eyes with a healthy corneal
endothelium and is becoming more accessible
to corneal surgeons. This technique is
generally less traumatic, avoids rejection,
provides tectonic support in cases of trauma,
and has advantage of being a largely
extraocular procedure. Although perforation of
Descemet’s membrane may necessitate
conversion to PK, this complication is
increasingly rare.

Conclusion
•DALK should especially be
considered in patients with a high
rejection or infection risk who
require corneal transplantation with
a healthier endothelium due to the
shorter course of topical steroids
required with this technique
compared with PK .

EK TECHNIQUES
•Melles eliminated the challenging
recipient stromal dissection and excision
steps by peeling the Descemet’s
membrane & dysfunctional endothelium
from the recipient cornea before
implanting the donor tissue. This EK
modification became known as
Descemet’s stripping with endothelial
keratoplasty (DSEK).

EK TECHNIQUES
•Use of a microkeratome was introduced
to facilitate the donor lamellar
dissection, and this technique variation
was called either DSEK or Descemet’s
stripping automated endothelial
keratoplasty (DSAEK). In 2005, eye banks
began performing the donor lamellar
dissection with a microkeratome and
providing ‘pre-cut’ tissue to surgeons .

DSEK
•Even though DSEK provides 20/40 or
better vision more reliably than PK, fewer
patients than expected achieve 20/20
vision and variations in the donor stromal
thickness increase the higher order
aberrations of the posterior corneal
surface. Addressing these concerns,
Melles developed a technique for peeling
Descemet’s membrane and healthy
endothelium from a donor cornea.

DMEK
•Melles developed Descemet’s membrane
endothelial keratoplasty (DMEK). The
extremely thin DMEK graft is more
challenging to handle than a thicker DSEK
graft, leading to the development of hybrid
techniques that have a narrow rim of donor
stromal tissue ringing a central area of bare
endothelium without stroma . The hybrid
techniques, known as DMEK-S and DMAEK,
combine excellent visual outcomes with
easier handling.

DMEK
•In 2006, Tappin first performed the true
endothelial cell transplantation of
Descemet’s membrane using a carrier
device. Later, Melles reported the first
clinical results of transplanting isolated
Descemet’s membranes in human eyes
and called the procedure Descemet’s
membrane endothelial keratoplasty
(DMEK). Existence of a distinct pre-
Descemet’s layer (Dua’s layer) of tissue.

PDEK
• evidence of a distinct pre-Descemet’s layer
(Dua’s layer) of tissue was presented by Dua
in 2007. Addition of a 10-μm pre-Descemet’s
layer to the endothelial allow easier handling
and insertion of the tissue because it does
not tend to scroll as much as Descemet’s
membrane, with the pre-Descemet’s layer
splinting Descemet’s membrane. Pre-
Descemet’s endothelial keratoplasty (PDEK)
is term given to this technique in which
additional pre-Descemet’s layer is transplanted.

DSEAK TISSUE PREPARATION
•THE CORNEO
SCLERAL RIM
IS PLACED
OVER THE
ARTIFICIAL
ANTERIOR
CHAMBER

•AN
ALIGNMENT
MARK IS MADE
ON THE
CORNEA

•THE CORNEO
SCLERAL RIM IS
PRESSURISED .
THE
ALIGNMENT
MARK 1 IS SEEN
.

•THE MICRO
KERATOME
HEAD IS
ENGAGED AND
CORNEAL CUT
IS INITIATED

ANTERIOR
STROMAL
CAP 2 IS
CUT

• ANT. STROMAL CAP IS
REMOVED AND
THICKNESS OF POST.
CORNEA CAN BE
MEASURED .A S
SHAPED MARK IS
PLACED OVER
POSTERIOR STROMA
TO HELP WITH
INTRAOCULAR
ORIENTATION

•ANTERIOR STROMAL
CAP IS REPLACED
AND ALIGNMENT
MARK 3 IS
REAPPROXIMATED .
THE S SHAPED
MARK 4 ON
POSTERIOR STROMA
IS VISIBLE

DSEK PROCEDURE
•PREOPERATIVE
APPEARANCE IN A
PATIENT WITH
PSEUDOPHAKIC
BULLOUS
KERATOPATHY

DSEK PROCEDURE
•SURGEON’S VIEW
FROM TEMPORAL
LIMBUS . THE
DESCEMET’S
MEMBRAE IS
BEING STRIPPED
AND FOLDED BACK
UPON ITSELF

DSEK PROCEDURE
•THE
ENDOTHELIUM
DONOR DISC 1
IS LOADED IN
ENDOSERTER .
THE DONOR
STROMA 2 IS
DISCARDED

DSEK PROCEDURE
•THE DONOR
TISSUE IS
RETRACTED
INTO
ENDOSERTER

DSEK PROCEDURE
•THE
ENDOSERTER IS
ROTATED 180
DEGREES AND
THE DONOR DISC
1 IS BEING
DELIVERED IN
ANTERIOR
CHAMBER .

DSEK PROCEDURE
•AIR IS INJECTED
INTO ANTERIOR
CHAMBER
THROUGH A
NEEDLE

DSEK PROCEDURE
•TRANSCORNEAL
VENTING
INCISIONS ARE
MADE WITH A
MYRINGOTOMY
BLADE TO
REMOVE THE
INTERFACE FLUID

DSEK PROCEDURE
•POST OPERATIVE
DAY 1
•CORNEA IS
GETTING CLEAR

INDICATIONS
• EK is an excellent option for any type of
endothelial dysfunction. If anterior stromal
scarring from long-standing corneal edema
is significant, replacement of the full corneal
thickness with a PK may provide better
visual acuity. However, in many cases,
patients who have tolerated long-standing
corneal edema also have other visual
limitations (e.g., retinal problems).In such
cases, EK is an attractive alternative
because it quickly restores vision .

Donor Tissue Preparation and
Insertion
• Donor tissue preparation involves three
steps:
• dissection,
• sizing to the appropriate diameter
with a trephine (usually 8–9 mm),
•and insertion
Preparing the donor tissue before opening the patient’s
eye allows the surgeon to ensure that the tissue will
be suitable for transplantation

DSEK
•The lamellar dissection is usually done with
a microkeratome either at the eye bank or at
the time of surgery . A donor corneal/ scleral
shell is mounted on an artificial anterior
chamber designed to accompany the
microkeratome being used. The artificial
anterior chamber can be filled with
viscoelastic material, balanced salt solution,
or tissue storage solution.

DSEK
•The donor thickness is measured,
and a microkeratome head of
appropriate depth is selected to
provide a posterior donor button of
approximately 0.08−0.20 mm
thickness, according to surgeon
preference.

DSEK
• The donor tissue is carefully transferred from
the artificial anterior chamber and placed
endothelial side up on a standard punch
trephine block, where it is punched to an
diameter, taking into consideration the
horizontal white-to-white dimensions of the
recipient cornea and the anterior chamber
depth. donor tissue is covered with tissue
storage solution while the recipient eye is
prepared.

Insertion techniques
• A variety of insertion techniques are
available, including forceps, glides and
inserters. When using forceps, the posterior
donor button is folded over on itself like a
“taco” with approximately 60% anterior and
40% posterior, and the folded tissue is gently
grasped at the leading edge with forceps that
only compress at the tip as the tissue is
guided into the eye. A disadvantage of this
method is that it can be difficult to unfold the
donor correctly in the eye.

• A disadvantage of this method is that it can
be difficult to unfold the donor correctly in
the eye, especially for surgeons early in the
learning curve. Another method is to fixate
the edge of the donor with a suture, thread
the suture across the anterior chamber & out
through a stab incision nasally, and pull the
tissue into the eye .

• A third method is to place tissue on a glide or
insertion cartridge, insert retina /vitreal
intraocular forceps through a nasal stab
incision, reach across the eye and grasp the
tip of donor through the 5 mm temporal
incision, and pull the tissue into the eye
• Use of a funnel glide or insertion cartridge
helps the donor tissue curl with endothelium
inward for protection as it is inserted. The
tissue can also be inserted with a single-use
cartridge inserter .

Operative steps
•Once donor tissue is in eye & unfolded
stromal side up, anterior chamber is filled
with air to press donor button up against
recipient cornea . Several small incisions can
be made in peripheral recipient cornea down
to graft interface to help drain any fluid .
trapped between donor and recipient tissue
After 8–10 minutes, many surgeons remove
most of the air to prevent pupillary block, and
leave anterior chamber one-third full

Operative steps
•Some surgeons then have the patients lay
face up with a partial air bubble for 30–60
minutes. Other surgeons leave anterior
chamber completely filled for 1–2 hours.
• At completion of surgery, antibiotics,
corticosteroids, dilating drops, and NSAIDs
are applied to the treated eye.

DMEK
•The donor tissue dissection consists of
gently peeling off Descemet’s membrane
(DM) and endothelium First, DM periphery is
scored all the way around. The tissue is
stained with trypan blue to enhance
visualization. The peripheral edge is lifted
all the way around using a microfinger or
hockey stick-shaped instrument.

DMEK DONOR PREPARATION
• MICRODISSECTOR
IS USED TO
ELEVATE THE
SCORED EDGE
OF
DESCEMET’S
MEMBRANE .

DMEK
• With the tissue submerged in tissue storage
solution, an edge of membrane is grasped
with forceps and peeled about halfway to
center, quadrant-by-quadrant, with
replacement of each section on stromal
base . The tissue is partially trephined,
cutting through DM but not completely
through the stroma. An edge is grasped with
nontoothed forceps and the central DM is
gently peeled from the underlying stroma and
replaced in tissue storage solution.

DMEK DONOR PREPARATION
•TUBAGEN
FORCEPS ARE
USED TO PEEL
THE FINAL GRAFT
FROM THE DONOR
RIM AFTER
CENTRAL
TREPHINATION

DMEK
•Immediately before insertion , DM is stained
again with trypan blue to improve
visualization and is placed in a glass pipette
or inserter, such as an intraocular lens
inserter, for placement in the recipient eye.
The donor DM is gently unfolded in the
correct orientation with a combination of
balanced salt solution and air injections.
•Then air is injected beneath the donor tissue
to completely fill the anterior chamber and
press the graft up against the host cornea

DMAEK and DMEK-S
• In the hybrid techniques, the donor preparation
consists of four steps: lamellar dissection, injection
of air to create a big bubble and separate DM from
the central stroma, excision of the stromal tissue
from the central 6–7 mm of the donor graft, and
cutting the tissue to the desired diameter with a
trephine. Although this sequence of donor
preparation steps is more complex than that
required with DMEK, the resulting 1 mm rim of
attached stromal tissue allows the surgeon to
easily insert the hybrid grafts using standard DSEK
techniques, as described above.

OUTCOMES
• EK provides more rapid and predictable visual recovery
than PK, allowing patients to return to work and daily
activities sooner. In large PK series, the rate of 20/40 or
better vision has ranged from 47% to 65% in Fuchs’
dystrophy patients & from 20% to 40% in patients with
pseudophakic or aphakic bullous keratopathy.
Unfortunately, PK can result in significant corneal
distortion, so 10–15% of PK eyes generally require use of a
hard contact lens for best vision, and in some cases vision
can be limited to counting fingers or worse. DSEK is
performed through a small incision and causes little to no
corneal distortion. A mean corrected distance visual
acuity (CDVA) of 20/40 is generally achieved within 3–6
months of DSEK, and over 90% of patients without ocular
co-morbidities achieve 20/40 or better vision.

OUTCOMES
• A small percentage of DSEK patients reach less than 20/40
vision because of irregularities resulting from the lamellar
dissection or from folds that form in the donor tissue as it
conforms to the back of the recipient cornea. With DMEK
and the hybrid techniques, the visual recovery is even
more impressive than it is with DSEK. Over 70% of DMEK
patients without ocular co-morbidities achieve 20/25 or
better vision within 3 months. Overall the visual acuity
achieved with DMEK is comparable to that in normal eyes,
and significantly better than that achieved with DSEK or
PK. One reason for this is that DMEK achieves a more
normal posterior corneal surface with fewer higher-order
aberrations than DSEK or PK.

Refractive Changes
• In contrast to PK, EK causes little to no change in
corneal topography, resulting in far less change in
spherical equivalent or cylinder. Whereas PK
induces 4–5 D of refractive cylinder on average and
may exceed 8 D, DSEK and DMEK cause no
significant increase in mean refractive cylinder.
DSEK generally induces 0.5–2.0 D of hyperopia,
while DMEK causes a smaller mean hyperopic shift
of about 0.25–0.50 D. The expected hyperopic shift
should be factored into intraocular lens
calculations when cataract surgery is staged
before, or combined with, EK.

Graft Survival
• it is not unusual for surgeons who are newly
learning EK to initially have a higher rate of
primary graft failure due to surgical trauma.
However, with experience, the primary graft
failure rate should drop to the low levels
seen with PK.
• In an initial consecutive DSEK series, the 5-
year graft survival rate was similar to that
reported for PK in the large multicenter
Cornea Donor Study

Graft Survival
• In an initial consecutive DSEK series, the 5-
year graft survival rate was similar to that
reported for PK in the large multicenter
Cornea Donor Study (95% vs 93% for Fuchs’
dystrophy & 76% vs 73% for pseudophakic or
aphakic corneal edema). Whereas PK
regrafts generally have a poor 5-year
survival rate of 53% or less, 4-year survival
rate for DSEK under failed PK was 74% in an
initial consecutive series.

Complications
Graft detachment
• Lack of complete adherence between the
donor tissue and host cornea is the most
frequently reported complication with EK.
ranged from 0 to 82%. An EK graft is secured
into position with an air bubble initially,
rather than with sutures, so detachment is
addressed by re-injecting air into eye. Keys
to minimizing the risk of graft detachment
are meticulous wound construction to
preclude postoperative wound leaks ..

Complications
Graft detachment
•Keys to minimizing the risk of graft detachment
are meticulous wound construction to preclude
postoperative wound leaks, complete removal of
fluid from donor/ host interface, achieving a
firm air tamponade, and cautioning patient
not to rub eye in the early postoperative
period. Partially detached DSEK grafts can be
watched as they frequently will seal down
spontaneously over time. With DMEK and hybrid
techniques, partial detachments are more common
and less likely to seal down spontaneously.

Pre-Descemet’s
Endothelial Keratoplasty
PDEK

PDEK
•Addition of a 10-μm pre-Descemet’s layer to
the endothelial graft can generate tissue for
endothelial transplant, allowing easier
handling and insertion of tissue because it
does not tend to scroll as much as
Descemet’s membrane, with pre-Descemet’s
layer splinting Descemet’s membrane. Pre-
Descemet’s endothelial keratoplasty (PDEK)
is the term given to this technique .

Surgical Technique
Donor Preparation
•A corneoscleral disc with an 2-mm scleral rim
is dissected from whole globe or obtained
from an eye bank. A 30-gauge needle
attached to a syringe is inserted from limbus
into midperipheral stroma . Air is slowly
injected into donor stroma until a type 1 big
bubble is formed, which is a well-
circumscribed, central domeshaped elevation
measuring 7 to 8.5 mm in diameter .

Surgical Technique
Donor Preparation
•It starts in center and enlarges centrifugally,
retaining a circular configuration.
Trephination of donor graft is performed
along the margin of big bubble . The bubble
wall is penetrated at the extreme periphery,
and trypan blue is injected into the bubble to
stain the graft, which is then cut all around
the trephine mark with corneoscleral scissors
and covered with the tissue culture medium. graft
is loaded into an injector when ready for insertion.

PDEK donor graft preparation
•A 30 gauge
needle is
inserted at
limbus on
endothelial
side .

•Needle is
advanced into
stroma

•Intra stromal
air injection is
performed

•Central dome
shaped big
bubble is
formed

•Trephination of
endothelial
graft is
performed

•Stained with
tryptan blue
and cut with
corneo scleral
scissors

Recipient Bed Preparation
• After administering peribulbar anesthesia,
the recipient corneal epithelium is debrided
(if grossly edematous) for better
visualization . A trephine mark is made on
the recipient cornea respective to the
diameter of Descemet’s membrane to be
scored on endothelial side . A 2.8-mm tunnel
incision is made at 10-o’clock position near
limbus. The anterior chamber is formed and
maintained with saline injection or infusion.

Recipient Bed Preparation
• margin of Descemet’s membrane to be
removed is scored initially from endothelial
side with a reverse Sinskey hook . Once an
adequate edge is lifted, a nontoothed
forceps is used to gently grab Descemet’s
membrane at its edge, and the graft is
separated from the underlying stroma in a
capsulorrhexis-like circumferential manner.
The peeled Descemet’s membrane is then
removed from the eye.

Donor Lenticule Implantation
•The donor lenticule (endothelium–Descemet’s
membrane–pre-Descemet’s layer) roll is
inserted in the custom-made injector and
slowly pushed up the lumen of the nozzle.
The injector is improvised from an intraocular
lens implant injector by removing the sponge
tire and spring and reattaching the sponge
tire to prevent any back suction and
inadvertent damage to the donor graft.

• Using the injector, the graft roll is injected in
a controlled fashion into the anterior chamber.
The donor graft is oriented endothelial side
down and positioned on the recipient
posterior stroma by careful, indirect
manipulation of the tissue with air and fluid .
• Once the lenticule is unrolled, an air bubble is
injected underneath the donor graft lenticule
to lift it toward the recipient posterior stroma.

• The anterior chamber is completely filled with
air for next 30 minutes, followed by an air-
liquid exchange to pressurize the eye .
• The eye speculum is removed and the anterior
chamber is examined for air position.
• The patient is advised to lie in a strictly
supine position for the next 3 hours

Discussion
•Although DMEK provides a significantly
higher rate of 20/20 and 20/25 vision, with
comparable endothelial cell loss compared
with DSAEK procedure; a 63% air reinjection
rate for partial detachments and 8% rate of
graft failure, which requires a repeat DMEK
or DSAEK, have been reported. It has failed to
gain widespread acceptance mainly because
of difficulty in donor preparation resulting in
a significant loss of donor tissue .

Discussion
•It has failed to gain widespread acceptance
mainly because of difficulty in donor
preparation resulting in a significant loss of
donor tissue, loss of endothelial cells after
Descemet’s membrane removal, and difficulty
in positioning the donor tissue within the eye.
In PDEK, the pre-Descemet’s layer serves as
a splint, which facilitates easy manipulation
of the entire graft.

Discussion
•Because the endothelium–Descemet’s
membrane complex remains adherent to the
underlying pre-Descemet’s layer, tight rolling
of the thin, delicate tissue is prevented. The
splinting effect provided by the additional
layer reduces inadvertent tears or endothelial
damage during tissue harvesting and
intraoperative maneuvers. PDEK donor
membrane complex is thicker than DMEK
donor graft and reduces the likelihood of
upside-down transplantation .

THANK
YOU
DR DINESH
DR SONALEE

Keratoplasty update 2016

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Keratoplasty update 2016