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Surgical limbus can be divided into two zones by three lines (Figure 1) 1 Anterior limbal border: corresponds to termination of Bowman's membrane and is marked externally by insertion of Tenon's capsule and conjunctiva that forms a prominent ridge. Middle limbal border: when conjunctiva and Tenon's capsule is dissected there is a bluish zone visible followed by a white zone of sclera. The junction between these two is known as middle limbal border. This is the termination of Descemet's membrane and overlies the Schwalbe's line. Posterior limbal border: lies over the scleral spur and can be seen only with sclerotic scatter. It is 1 mm behind the middle limbal border. Astigmatic Neutral Funnel The concept has been derived from two important mathematical equations: • Surgically induced astigmatism (SIA) α length of incision 2 • SIA α1/distance of incision from corneal centre Therefore, it was found that incision of 3-3.5 mm at the limbus results in minimal astigmatism of 0.25 – 0.50 D and it can be considered astigmatically neutral for all practical purposes. The funnel's base is at the limbus and as it moves away it widens (Figure2). The incision which is made within this funnel is astigmatically neutral. A self sealing incision is characterized by a corneal valve and square incisions. When IOP of the eye rises it causes corneal valve to close against the pressure of aqueous so that it is pushed up against the dome of cornea. The smoother and larger is corneal lip, better is the sealing action. A 4 mm width with 1.75 mm length is sufficient to create a self sealing incision 3 .
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The trend in the cataract surgery has been towards smaller
incision, moving from superior scleral incision to temporal
clear corneal incision, in an attempt to reduce post operative
astigmatism.
Anatomy of Limbus
Surgical limbus can be divided into two zones by three lines
(Figure 1)1
Anterior limbal border: corresponds to termination of Bowmans
membrane and is marked externally by insertion of Tenon’s capsule
and conjunctiva that forms a prominent ridge.
Middle limbal border: when conjunctiva and Tenons capsule is
dissected there is a bluish zone visible followed by a white zone of
sclera. The junction between these two is known as middle limbal
border. This is the termination of Descemet’s membrane and
overlies the Schwalbes line.
Posterior limbal border: lies over the scleral spur and can be seen
only with sclerotic scatter. It is 1 mm behind the middle limbal
border.
Astigmatic Neutral Funnel
The concept has been derived from two important mathematical
equations:
Surgically induced astigmatism (SIA) α length of incision2
SIA α1/distance of incision from corneal centre
Therefore, it was found that incision of 3-3.5 mm at the limbus
results in minimal astigmatism of 0.25 – 0.50 D and it can be
considered astigmatically neutral for all practical purposes. The
funnel’s base is at the limbus and as it moves away it widens
(Figure2). The incision which is made within this funnel is
astigmatically neutral.
Self Sealing Incision
A self sealing incision is characterized by a corneal valve and square
incisions. When IOP of the eye rises it causes corneal valve to
close against the pressure of aqueous so that it is pushed up
against the dome of cornea. The smoother and larger is corneal
lip, better is the sealing action. A 4 mm width with 1.75 mm length
is sufficient to create a self sealing incision3.
Classification of Small Incision
Small incision means any incision having a size of 5mm or less.
These can be classified into following categories:
•Site
• Position
•Size
• Shape
Depending on the Site
Incision can be of following types on the basis of the site.
•Temporal
•Superior
Oblique: superotemporal / inferotemporal
In correspondence to axis of greater curvature.
The site of incision depends on induced astigmatism and
ergonomics of the surgery.
The temporal approach provides the surgeon easiest access to the
surgical zone because it is not obstructed by the orbital edge of
frontal bone and minimizes the effect of Bell’s phenomenon. The
horizontal meridian of cornea is more than the vertical meridian.
Therefore, the distance from periphery to visual axis is longer in
this position and it is also less flattening. More over there is no
role of bridle suture in such cases. There is also marked increase in
the red reflex because the iris is perpendicular to the light of
microscope. It also facilitates drainage of fluid through lateral
canthus and thus prevents fluid accumulation. Therefore, the most
Wound Construction
Shalini Mohan MS, Sudarshan Khokhar MD, Anand Aggarwal MD, Anita Panda MD, FRCS
Cataract
Dr. Rajendra Prasad Centre for Ophthalmic Sciences,
All India Institute of Medical Sciences,
New Delhi-110029 Figure 2. Astigmatic neutral funnel
Figure 1. Surgical limbus
14 DOS Times - Vol. 13, No.1, July 2007
popular incision these days is temporal approach as it also produces
excellent results in terms of astigmatism, both immediate and
long term3.
The superior approach was popular few years ago but now it is
preferred only in the cases of the sclero corneal tunnel. It can be
used to reduce with the rule astigmatism. It is found that induced
astigmatism from temporal versus superior incisions is 0.6D versus
0.9D3. This is due to effect of flattening which is less in the temporal
approach than the superior.
The oblique incisions are made for better ergonomics but only
provide partial benefit of temporal incisions.
The incisions on the steepest meridian (on-axis) can be made to
reduce mild pre operative astigmatism of 1 D or less as it causes
flattening of the meridian in which incision is given with increase
in curvature of the opposite meridian2. A latest study done by
making ‘on axis’ incision, in various locations to correct
preoperative astigmatism showed that nasal incision increased
preoperative cylinder from 1.13 D to 1.83 D 6 months after
surgery.4
Depending on the Position
Depending on the position incision can be of following types:
• Corneal
Limbal (near corneal)
•Scleral
• Sclero-corneal
For the obvious reasons the astigmatism decreases as the incision
moves from the clear cornea to the sclera.
Corneal Incisions
The incisions are known as clear corneal when the anterior limit is
positioned anterior to the limbal vascular arches.
Advantages
The surgery can be performed under topical anaesthesia
Obviates the need for manipulation of conjunctiva and
therefore reduced scarring which offers futures advantages
of filtering surgery, if required
Esthetically satisfactory result
Facilitates intraoperative visibility as the tunnel is shorter and
hence less intra operative stria formation
Total surgical time is less
Fewer instruments are required
There is no bleeding except in cases of vascularised corneas.
Therefore, there is lower incidence of hyphemas and so no
contraindication to anticoagulants
Decreased incidence of iris prolapse
The eye is protected from epithelial in growth
A shallow anterior chamber is extremely rare
Less chances of formation of peripheral anterior synechia,
because the internal aspect of the wound is further forward
than the cornea /scleral and well away from iris.
Less chances of expulsive choroidal hemorrhage
In cases of expulsive choroidal hemorrhage, merely taking
the instruments out results into the immediate closure of the
eye.
Similarly in the patients with cardiac / respiratory arrest the
instruments can be withdrawn followed by resuscitation.
Disadvantages
There is poor wound stability and therefore it can lead to leakage
causing:
•Hypotony
• Endophthalmitis
Relatively high astigmatism
Early high rise of IOP
Slower healing
Contraindications
Preoperative radial keratotomy where the incisions extend as
far as limbus (Figure 3)
Peripheral corneal degenerations
Limbal Incisions
When the external incision is made 0.5 mm posterior to the external
arcades then it is known as limbal incision.
Advantages
Besides the advantages of the clear corneal incisions they have
additional benefits like:
They induce less astigmatism as they are away from the visual
axis
Heal more rapidly
Figure 3. Phacoemulcification in operated Radial Keratotomy eye.
Ballooning of conjunctiva is seen.
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Cause less discomfort
Offer greater resistance to pressure with respect to clear
corneal incisions.5,6
Disadvantages
The main disadvantage is ballooning of conjunctiva (Figure 3)
which can lead to poor visibility during surgery.
The bleeding from the limbal vessels can track into corneal
tunnel and can cause staining of the tunnel which can persist
postoperatively.
Increased risk of sub conjunctival hemorrhage, which can be
of prime psychological concern for the patient.
Relative Contraindications
The indications of the limbal incision are gradually expanding but
in certain situations corneal incisions are to be preferred over limbal
incisions. These are patients with increased tendency for bleeding3:
Diabetic patients
Patients on anticoagulant therapy
Patients with blood dyscrasias
Patients with history of alcohol abuse
Sclero Corneal Incision
These incisions are made electively when a larger incision of
5 mm or more is needed to implant an IOL. These are sometimes
also used in pediatric cataract surgery cases for implanting rigid
IOLs. These incisions have got better sealing properties. Thses are
made 1.5-2.0 mm posterior to the limbus (Figure 4). They can be
sutureless if a tunnel is created with an internal corneal lip.
Otherwise the incision can be closed with a single 10-0
monofilament nylon infinity suture.
The scleral flap incision has three dimensions (Figure 5):
• Depth
•Width
• Length
Depth
The sclera is 0.6 mm thick, 2 mm posterior to limbus. So the
incision depth ranges from 0.1 mm to 0.5mm. Flap depth can be
determined accurately with a guarded calibrated diamond knife.
Width
The distance between the external groove and the internal entry
into the anterior chamber is the width of the incision (Figure5).
For production of an astigmatically neutral incision the external
incision should be as far as possible to minimize the effect of the
suture. More over wider the flap, lesser is the astigmatism as it
provides the pillar which supports the existing shape of the eye.
But one can not move too far off as it is limited by the amount of
the bleeding and difficult manipulation in the anterior chamber.
Advantages
Minimal astigmatism induction
Better resistance to both internal and external pressure.
Disadvantages
The conjunctival aperture must be large. Otherwise there is a
need to put in the superior rectus bridle suture or clear corneal
Figure 4. Scleral incision
Figure 5. Scleral flap incision
Figure 6a. Stab (uniplanar) incision
16 DOS Times - Vol. 13, No.1, July 2007
traction suture.
Diathermy is necessary
Greater time is required for wound construction
Greater discomfort for the patient if surgery is being
performed under topical anesthesia. In such cases, a
subconjunctival anesthesia is usually required.
The manipulation of the instruments inside the eye is difficult
because of frequent corneal distortion.
Depending on the Shape
When examined in longitudinal section, the incisions can be of
following types:
Single plane, one step stab incision (Figure 6a)- it was
proposed by Fine7 and is prototype of a clear corneal incision.
The blade is driven into the eye upto 2 mm (Figure 6b). Then
the blade is dipped to nick Descemet’s membrane and the
blade is driven upto its hub.
The Biplanar (Figure 7) was introduced by Williamson2,7 and
is characterized by a groove of 300-400 µm perpendicular to
the corneal surface and is arc shaped. The tunnel starts from
the deepest part of the groove. This shape creates a thicker
corneal flap which is more resistant when caught with forceps
or when sutured.
Triplanar incision (Figure 8): after making a groove, blade is
made to travel parallel in cornea and then dips down into the
anterior chamber.
The hinged incision (Figure 9): was proposed by Langerman.8
It is known that when properly performed the corneal
incisions do not leak when ever pressure is applied to the dome
of cornea. But it does leak when the pressure is applied to the
posterior lip of the incision7. This incision is characterized by
a hinge perpendicular to the corneal surface and 0.75 mm
deep. The corneal tunnel is constructed at a depth of about
500 µm, a depth superior than the hinge. This consists of
marking of a groove that is deeper than the plane of the
tunnel. The hinge physically separates the floor of the tunnel
from the posterior wall of the groove. In this way when
pressure is applied onto the posterior lip of the incision, the
groove and the external part of the tunnel open but the internal
part of the tunnel seals. There may be small amount of leakage
in the initial post operative period but this may cause the
inferior part of the corneal lip to become flaccid as it is thinner
than the superior part, therefore it seals the incision.9
Hayashi et al also did a study to correlate between incision sizes
and change in the corneal shape in suture less surgery using corneal
topography. They found that 3.2 mm incision did not induce any
significant corneal shape changes in comparison to 4 mm and 5mm
incisions.10
The shape of the sclero corneal incisions can also be classified in
terms of the initial cut. 7 (Figure 10)
Parallel to limbus – convex
Antiparallel- frown incision
• Straight
Arrow like- chevron incision
Figure 6b. Stab incision being made with MVR knife.
Creation of side port 1.4mm MVR blade.
Figure 7. Biplanar (grooved) incision Figure 8. Triplanar incision
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“J’ shaped
•Trapezoid shaped
When the incision is made in the astigmatically neutral funnel
then with same chord length and with equal distance from the
limbus, a convex incision will extend slightly outside the funnel
followed by straight and then the concave incision having the least
part outside the funnel (Figure 2) . Therefore, astigmatism will
also be maximum with convex incision. Sagging of the incision
leading to wound gape is also maximum with convex incision.
The last of the above two incisions have been made to reduce
astigmatism as they remain entirely inside the funnel but are not
very popular.
Depending on Size (Length)
The size of the incision can vary from 1 mm to 6.5 mm depending
upon the IOL to be implanted. The insertion with forceps or an
injector tends to widen the incision by 10%7. The recently
developed rollable IOLs can be implanted through an incision size
of 1.1 mm. The studies clearly demonstrate that increase in length
of incision increases the degree of SIA. In cases of sclero corneal
incision, the size of the astigmatically neutral incision can be upto
4.5 mm & in cases operated through corneal or near corneal
incisions the size is 4 mm.
In an experimental study it was found that microincision coaxial
phacoemulsification (2.2mm size) and standard coaxial
phacoemulsification (2.75mm) induce less wound stress and
alteration of wound morphology leading to less wound leakage
than microincision bimanual phacoemulsification (1.2mm)11.
Surgical Technique
Construction of Scleral Tunnel Incision
Wound Architect ure:
The important step in this procedure is creation of a tunnel which
is joined by (Figure 11)
External incision: it is the scleral groove and the types have
already been described above.
Internal incision: the entry into the eye
Surgical Steps
Conjunctival flap is made precisely as the width of the scleral
tunnel followed by vertical releasing incisions in the
conjunctiva and Tenon’s capsule extending approximately 5
mm.
Mild bipolar cautery is performed. However, the larger vessels
are to be directly and adequately cauterized so that the tunnel
remains dry during the entire procedure.
Following this a caliper is taken and a 5mm mark is given 1 -
2mm behind the limbus.
The sclera is cut perpendicularly which should be atleast 50 %
Figure 9. Hinged incision
Figure 10a. Scleral Incisions: parallel Figure 10b. Scleral Incisions: Straight
Figure 10c. Scleral Incisions: Antiparallel Figure 10d. Scleral Incisions: Cheveron
18 DOS Times - Vol. 13, No.1, July 2007
scleral depth (Figure 11) so that the surgeon can look down
the groove and pick the depth within the sclera and dissect
the scleral tunnel.9 A crescent knife is used to dissect the tunnel.
The leading edge of the knife should be down while cutting
anteriorly or sideways (Figure 11).
Now, viscoelastic is injected into the anterior chamber after
making a side port. This results in a very stiff and stable anterior
chamber.
A 3.2 mm keratome is brought into the tunnel and at the
anterior edge of the vascular arcade; it is depressed lightly
resulting in a dimple formation on the anterior corneal surface.
The dimple is frequently outlined by a semi circular light
reflex with the tip of keratome at the centre.
Now, the keratome is advanced horizontally parallel to the
iris which results in a linear horizontal cut through the
Descemet’s membrane into the anterior chamber. A straight
cut in the descemet’s membrane is necessary for the correct
architecture of the incision.
The important thing to note is that forceps is used to elevate the
tunnel roof while placing the keratome inside the tunnel but
counter traction is placed on the posterior lip of the groove rather
than anterior lip during cutting of the Descemet’s membrane with
a keratome. The use of chilled Balanced Salt Solution (BSS)
maximizes cooling of the phaco tip, thus minimizing tunnel
shrinkage and consequent irregular astigmatism.
Internal incision: can be of two varieties –
Corneal lip incisions – it is created by a 3 step procedure.
Here an external incision is made followed by creation of a
tunnel through the sclera which enters about 2 mm into the
clear cornea. This is followed by entry into the anterior
chamber. This creates the corneal flap/lip which acts as a self
sealing incision. The wound seals when the eye is closed under
normal IOP by injecting saline into the anterior chamber. The
posterior corneal lip is pushed up through pressure of the
fluid into the anterior chamber and closes the wound.
Non corneal lip incisions – It is directly beveled into the anterior
chamber from external incision in a two step fashion. The
anterior chamber entry is just anterior to the Schwalbe’s
line so that only a small ledge of the descemet’s
membrane is there. It is non self sealing and requires
other associated manuever Suturing lite for sealing to take
place.
Construction of Clear Corneal Incision
A fine Thornton 13 mm fixation ring can be used to allow the
globe stabilization and manipulations without creating conjunctival
tears, sub conjunctival hemorrhage or corneal abrasion. This is
especially true for cases taken up under topical anesthesia. A
sideport is created with a MVR knife. After staining the anterior
capsule with trypan blue, the anterior chamber is pressurized with
a viscoelastic. Now, a 300 µm groove is placed at the anterior edge
of the vascular arcade. Then, an incision is made by depressing the
posterior edge of the groove with a 3.2 mm or 2.75 mm keratome
flattening the blade against the surface of the eye (Figure 12).
Now, the blade is moved in the plane of the cornea until the
shoulders which are 2 mm posterior to the point of the knife
touch the external edge of the incision and following this, a dimpled
down technique as described previously, is utilized to initiate the
cut through the Descemet’s membrane. After phacoemulsification
and cortical clean up, the incision in the Descemet’s membrane is
widened with a blunt tipped keratome depending upon the IOL to
be implanted (Figure 13).
After the anterior chamber is pressurized by BSS through the side
port, the lips of the wound is tested by applying pressure with a
sponge against the posterior lip of the wound. If the incision leaks,
Figure 11. Scleral incision construction
Initial Curvilinear Incision Scleral tunnel central with
crescent blade
Side pocket creation of
scleral tunnel
Figure 12. Clear corneal temporal incision being made
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a single 10-0 nylon monofilament suture is placed. Following
completion of the phacoemulsification procedure, stromal
hydration of the clear corneal incision can be performed in order
to seal the incision.
The rationale for grooved clear corneal incision was to make a
thicker external edge to the roof of the tunnel and less likelihood
of tearing or cheese wiring. Langermans single hinged incision
had minimal differences in surgically induced astigmatism from
grooved incision.8
Complications
Intra Operative
Complications can be seen in all types of incisions but clear corneal
incisions by the nature of their architecture and location have some
unique complications associated with them.
Ballooning of conjunctiva (Figure 3): This complication may be
seen if one incidentally incises the conjunctiva. This may hamper
the subsequent visualization due to fluid accumulation and
seriously increases the rate of intraoperative complications
including posterior capsular rent. This can be relieved by making
multiple nicks in conjunctiva to drain the fluid.
Staining of tunnel: Use of crescent blade to make corneal tunnel
can cause blood to track down the incision causing staining of
tunnel (Figure-15).
Premature entry: This common complication especially in
learning curve, can lead to intra operative iris prolapse besides
making the incision non self-sealing and shallowing of anterior
chamber. The options available to deal with this complication are
following:-
If iris prolapses, it should be reposited back and another tunnel
made underneath the original incision, this time making sure
that the internal entry is more than the original width. The
original incision gets sealed by the roof of the new tunnel
when the pressure is exerted from the fluid entering from the
phaco probe.
Alternately, the iris is reposited back, the wound secured with
one 10-0 nylon suture, and the surgeon should shift to another
position (if temporal originally, then shifting to a superior
position is appropriate with fresh incision construction).
A calibrated angled diamond knife or a disc knife is also available
for proper tunnel construction. The surgeon should enter the
anterior chamber after injecting sufficient viscoelastic and the blade
should be angled upwards while making the tunnel.
A long entry may result into compromised visualization due to
striae formation in the cornea and make subsequent steps difficult.
Tearing of roof of the tunnel can result especia lly at the edges because
of discrepancy in the size of the incision and phaco handpiece
(Figure 15).
Tearing of the internal lip can also occur causing the incision to
lose its self sealing character or rarely a small Descemet’s membrane
detachment or scrolling of descemet membrane in anterior edge
of the incision.
Incisional burns leading to incision thermal contraction can
develop in clear corneal incisions. They cause compromised self
sealability, corneal edema and severe induced astigmatism. A study
done on 76,581 procedures found incidence of wound burn as
0.98/1000 procedures. Twenty eight percent occurred during early
sculpting, and 71% occurred during fragment removal.12
A extremly narrow tunnel may obstruct the irrigation portion of
the phaco sleeve and compromises inflow which can lead to corneal
burn. This is especially true in cases operated via Micro incision
cataract surgery (MICS). This complication has now been reduced
through various phaco power modulations now available, with
the newer generation phaco machines. Customizable power
Figure 13. Enlargement of incision for implantation of rigid IOL.
5.2mm Keratome for wound enlargement for
PMMA IOL insertion.
Figure 15. Tear of anterior lip due to thin anterior tunnel.
Figure 14. Blood staining of the tunnel.
20 DOS Times - Vol. 13, No.1, July 2007
modulation with microburst and hyperpulse technology13 further
reduces wound temperature during bimanual sleeveless
phacoemulsification. Studies done to compare the thermal effect
of the three recent machines Alcon Legacy AdvanTec, Bausch &
Lomb Millennium, and AMO Sovereign WhiteStar showed that
under a variety of power, load, and duty-cycle settings, the
Millennium and the Sovereign WhiteStar, operating in both pulse
and continuous modes, generated higher peak temperatures than
the Legacy AdvanTec.14
Recently Aqualase emulsification technology is fast gaining
popularity especially in cases of refractive lens exchange. This
technology is supposed to cause minimal heat generation as
microfluid pulses are being employed for nuclear disassembly in
place of ultrasound.
Post Operative Complications
Post operative hypotony may be seen in cases of poor sealability of
incision.
Wound leak and iris prolapse can occur in infrequent case especial ly
if the wound size is more than 3.5 mm width.
Increased risk of endophthalmitis has been noted in a large meta
analysis15 in case operated via clear corneal incision of more than
4 mm size in comparison to sclero corneal incision.
Clinical Course and Outcome
Comparison of temporal clear corneal incision size of 3.5 mm,
4 mm and 5 mm found a mean induced astigmatism of 0.37D,
0.56 D and 0.70 D respectively after 6 months.16
A study done to evaluate the surgically induced astigmatism in the
eyes operated via temporal clear corneal incision versus ‘on axis’
corneal incision showed that the surgical induced astigmatism (SIA)
was less in eyes operated via clear corneal temporal incision.
However, the drawback of the study was a relatively short duration
of follow up before astigmatism analysis (done at 7 weeks).17
A RPC study evaluated paired 3.2 mm
opposite clear corneal incisions made in the
steep axis in one group with single clear
corneal incisions in the other group. Mean
SIA was 1.66 +/- 0.50 D and 0.85 +/- 0.75 D
in Group 1 and Group 2, respectively (P =
.00). They concluded that paired opposite
clear corneal incisions were predictable and
effective in providing an enhanced effect
for correcting preexisting corneal
astigmatism in cataract surgery18.
Table 1 shows various studies comparing
superior with temporal incision. The range
is 0.41D – 0.69 D for temporal clear corneal
in comparison to 0.61D- 0.98D in superior
scleral incision19,20,21,22 .
The effect of 2.75 mm clear corneal incision
on SIA was also reported. The study
revealed that there was little difference in
the SIA of 2.75 mm incision regardless of
the incision site.23
Table 2 20,24,25 shows the range of
astigmatism induced in various studies. Similarly sized incisions
larger than 2.75 mm, when compared in regards to wound location
(temporal versus superior clear corneal incision) have
demonstrated more flattening in the superior axis. The oblique
supero lateral clear corneal incision has also demonstrated more
flattening with the passage of time. That’s why the current trend is
moving towards temporal approach phacoemulsification when
astigmatic neutral incision is desired.
Now it is being emphasized that corneal topography guided
incisions can yield better visual acuity by reducing the pre-existing
astigmatism and inducing less corneal aberrations than
conventional temporal corneal tunnel phacoemulsification.26
A study done to compare the astigmatism and high order
aberrations of the cornea after microincision versus small incision
cataract surgery found that Microincision cataract surgery
generates statistically significantly less corneal astigmatism and
better optical quality of the cornea compared with small incision
cataract surgery. However, microincision cataract surgery showed
no significant advantage in reducing corneal high order
aberrations27. Similarly, corneal and sclero corneal incisions can
also be considered equivalent in terms of inducing higher order
aberrations.
Conclusions
It is a common dictum that ‘well begun is half the work done. The
incision used for cataract surgery has to serve 3 purposes- the
ease of performance of phacoemulsification, minimum
astigmatism induction, safety and self sealability of the incision.
Smaller size of incision and proper wound construction has
transformed cataract surgery. With clear corneal incisions coming
into vogue, the surgery can be done under topical anesthesia with
relative astigmatic neutrality and almost instant visual
rehabilitation. With increasing expectations of patients following
cataract surgery, it is becoming more and more imperative on part
of the surgeon, not only to give good best corrected visual acuity
Table 1. Studies comparing Astigmatism in scleral tunnel superior and clear corneal
temporal approach phacoemulsification
Author Incision Astigmatism Astigmatism Duration
size (Superior (Temporal of study
approach) approach)
Lyhne 200119 4.0mm 0.61D 0.41D 12 months
Roman et al 199820 4.0mm 0.69D 0.69D 12 months
Oshima et al199721 3.0mm 0.65D 0.56D 3 months
Roman et al199722 4.0mm 0.98D 0.58D 1 months
Table 2. Studies comparing Astigmatism in clear corneal superior and clear corneal
temporal approach phacoemulsification
Author Incision Astigmatism Astigmatism Follow up
size (Superior (Temporal
approach) approach)
Marek et al 200624 2.8mm 0.96D 0.54D 3 months
Roman et al 199820 4.0mm 1.52D 0.69D 12 months
Simsek et al199825 1.44D 0.62D 3 months
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but also fairly good uncorrected acuity. For the attainment of the
second goal, proper surgical incisions are now being increasingly
combined either with limbal relaxing incisions or phaco being
performed on the steep meridian to correct pre existing corneal
astigmatism, or through the use of opposite clear corneal incisions
at the time of phacoemulsification.18 No doubt, these incisions
have clearly revolutionized the outcomes and acceptance of cataract
surgery. Taking clues from these incisions, the same incisions are
also being increasingly used for undertaking posterior lamellar
corneal procedures like deep lamellar endothelial keratoplasty
(DLEK).
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Author
Sudarshan Khokhar MD
... It has come as a boon to fill the yawning gap between high cost, high tech phaco machine and conventional large incision ECCE. 3 The trend in the cataract surgery has been towards smaller incision, moving from superior scleral incision to temporal approach, in an attempt to reduce post-operative astigmatism. 4 The temporal approach provides the surgeon easiest access to the surgical zone because it is not obstructed by the orbital edge of frontal bone and minimizes the effect of Bell's phenomenon. The horizontal meridian of cornea is more than the vertical meridian. ...
... It also produces excellent results in terms of astigmatism, both immediate and long term. 4 As cataract surgery accounts for the bulk of the surgeries performed in our institute, this study protocol is designed to assess the complications, visual outcome, patient and surgeon comfort and comparison of surgical duration in superior and oblique approaches of MSICS. ...
Article
Full-text available
AIMS: Comparative study of manual SICS technique by superior straight incision and oblique (9-12 O’clock) straight incision in terms of surgical duration, surgeon and patient’s comfort, intraoperative and postoperative complications and visual outcome up to 6 weeks. MATERIALS AND METHODS: 200 eyes of cataract were randomly subjected to cataract surgery by manual SICS technique using superior and oblique incision approach in 100 eyes each. Further grouping was done as Group A: RSS-Right superior straight incision, Group B: RSUT-Right superior upper temporal: Group C: LSS-Left superior straight, Group D: LSUN-Left superior upper nasal: 50 case each. Surgeon comfort was accessed in 5 steps namely tunnel making, capsulorrhexis, nucleus delivery, cortical wash and IOL implantation in both groups and graded as comfortable, convenient and difficult. Patient comfort was accessed as pain felt at 1st postoperative day, taken as P1, P2 and P3 according to increasing pain intensity. Surgical duration in both approaches was studied and compared. Visual outcome and complications were accessed at 2, 4 and 6 weeks. STATISTICAL ANALYSIS: Commercial SPSS 17 was used for statistical analysis. Chi square test and independent t test was used for calculating p value. RESULTS: Visual outcome was comparable in both the groups at 2, 4 and 6 weeks (p>0.05).Mean SIA in superior incision was +0.88D and +0.63D in oblique group (p value=0.00).Mean surgical duration in oblique group was 455.88+14.559 seconds and 541.63+31.699 seconds in superior group. Surgeon was comfortable in all 5 steps in both approaches except tunnel making, being difficult in oblique incision. Patient comfort at 1st postoperative day was insignificant between two groups. Postoperative hyphaema was found in 6 % in superior as compared to 14% in oblique incision group. CONCLUSION: Oblique (9-12 O’clock) incision was associated with less surgically induced astigmatism and surgical duration as compared to Superior incisional approach. Difference in visual outcome, Intra and postoperative complications, surgeon and patient comfort was insignificant between two groups.
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To examine the correlation between incision size and corneal shape changes in sutureless surgery using corneal topography. Two hundred eyes undergoing sutureless cataract surgery were assigned randomly to three groups according to the incision size: group A, 3.2-mm incision; group B, 4.0-mm incision; and group C, 5.0-mm incision. All eyes were examined by corneal topography preoperatively as well as at 1 week and at 1, 3, and 6 months after surgery. In the average of difference maps of eyes in the 3.2-mm incision group, a wound-related flattening in the peripheral cornea occurred 1 week after surgery, but decreased rapidly thereafter. Subsequently, no significant changes were observed in the cornea after 1 month. In the 4.0-mm incision group, with a reduction of the wound-related peripheral flattening, an irregular steepening appeared in the lower central cornea 6 months after surgery. In the 5.0-mm incision group, a similar steepening in the lower cornea occurred just after surgery. This steepening persisted and even extended to the upper central cornea in its later postoperative periods. The 3.2-mm incision hardly produced any irreversible corneal shape changes, whereas both the 4.0- and 5.0-mm incisions caused a persistent irregular steepening in the central cornea.
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This report describes a corneal tunnel incision that is self-sealing and does not leak when pressure is applied to the posterior lip of the wound. The success of the incision is in the construction of a single hinge. Results in patients who had the procedure are discussed.
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A prospective, randomized study compared the surgically induced astigmatism after 3.5 mm, 4.0 mm, and 5.0 mm temporal corneal tunnel incisions over six months. We studied 60 eyes of 60 patients who had phacoemulsification through a two-step clear corneal tunnel incision and implantation of one of three posterior chamber intraocular lenses (IOLs). Patients were divided into three groups of 20 each: Group A, cartridge injection of a foldable plate-haptic silicone IOL through a 3.5 mm self-sealing incision; Group B, cartridge injection of a disc silicone IOL through a 4.0 mm self-sealing incision; Group C, 5.0 mm optic poly(methyl methacrylate) IOL through a 5.0 mm incision with one radial suture. Corneal topography data were obtained using a computerized videokeratographic analysis system preoperatively and one week and six months postoperatively. Vector analysis was performed to calculate the surgically induced astigmatism. After the first postoperative week, mean induced astigmatism was 0.63 diopters (D) (+/- 0.41) in Group A, 0.64 D (+/- 0.35) in Group B, and 0.91 D (+/- 0.77) in Group C. After six months, it was 0.37 D (+/- 0.14) in Group A, 0.56 D (+/- 0.34) in Group B, and 0.70 D (+/- 0.50) in Group C. Surgically induced astigmatism was significantly lower in Group A than in Group B (P < .05) and Group C (P < .005) after six months. Vector analysis demonstrated that temporal corneal tunnel incisions induced clinically minimal astigmatism over six months postoperatively depending on incision size.
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Sutureless cataract incisions should ideally remain sealed with increased intraocular pressure and be able to withstand increased external pressure to the posterior aspect. Cadaver eye studies have shown that meeting these criteria requires an internal corneal lip of at least 1.5 mm and a square wound. Scleral incisions can meet these criteria but sacrifice aesthetics and surgical efficiency. Clear corneal incisions provide aesthetics and surgical efficiency but not wound stability. An ideal incision would combined stability with aesthetics and efficiency. We tested a posterior limbal incision to assess its stability, aesthetics, and efficiency. The incision originated at the posterior limbus within the conjunctiva, gaining about 1.0 mm in tunnel length over a clear corneal incision. This was enough to obtain a square profile for 3.0 x 3.0 mm wide incisions, while providing the aesthetics and surgical efficiency of a clear corneal incision. We compared a 3.0 x 2.0 mm posterior limbal with a 3.0 x 2.0 mm clear corneal incision. Each was tested in stepped, paracentesis, and hinged profiles. When compared with the clear corneal incision, the posterior limbal incision is equal in aesthetics and surgical efficiency, slightly superior in patient comfort, and far more stable.
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To compare the clinical outcome of phacoemulsification and foldable silicone intraocular lens (IOL) implantation through a 3.0 mm temporal clear corneal incision and 3.0 mm superior scleral tunnel incision. Department of Ophthalmology, Yodogawa Christian Hospital, Osaka, Japan. Eighty cataractous eyes of 78 patients with pre-existing against-the-rule (ATR) astigmatism were recruited for this prospective, randomized study. The patients were assigned to one of the two groups. Data on uncorrected and corrected visual acuities, keratometry, flare intensity measurement, and central cornea endothelial cell count were evaluated preoperatively and at 2 days, 1 week, and 1 and 3 months postoperatively. Although the pre-existing keratometric cylinder decreased in the temporal clear corneal incision group and increased in the superior scleral tunnel incision group, the amount of cylinder shift was not significantly different. Mean scalar shift of keratometric cylinder in the corneal incision group was 1.19 diopters (D) at 2 days postoperatively, 0.86 D at 1 week, and 0.56 D at 3 months and in the scleral incision group, 1.09 D at 2 days, 0.76 D at 1 week, and 0.65 D at 3 months. Eighty percent of the eyes in each group achieved an uncorrected visual acuity of 20/40 or better from the second day postoperatively. No statistically significant difference in visual rehabilitation or other parameters was noted between the groups throughout the study. Complications including corneal endothelial cell loss and wound incompetence requiring suturing were observed in the temporal clear corneal incision group. Both incisions offered satisfactory clinical results, but the superior scleral tunnel incision resulted in fewer complications. Minimal corneal keratometric change induced by a 3.0 mm incision was not related to uncorrected visual rehabilitation.
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To evaluate the effect of superior and temporal clear corneal incisions on astigmatism after sutureless, small incision phacoemulsification. World Eye Hospital, Istanbul, Turkey. This prospective study evaluated 40 eyes of 20 patients with cataract having bilateral, sutureless, small incision phacoemulsification by the same surgeon. A superior clear corneal incision was used in all right eyes and a temporal clear corneal incision in all left eyes. Mean preoperative astigmatism was 0.63 diopter (D) +/- 0.21 (SD) and 0.65 +/- 0.20 D, respectively. Mean patient age was 66.45 years. Patients were examined preoperatively and 1 day, 1 week, and 1 and 3 months postoperatively. Three months postoperatively, mean astigmatism was 1.60 +/- 0.37 D in the superior incision group and 0.83 +/- 0.19 D in the temporal incision group. Induced astigmatism calculated by vector analysis was 1.44 +/- 0.31 D and 0.62 +/- 0.28 D, respectively. The temporal incision group had significantly lower astigmatism at all follow-ups (P = .000). Upper lid pressure on the superior corneal incisions led to fluctuating, against-the-rule astigmatism that was significantly higher than that induced by temporal incisions.
Article
To compare surgically induced astigmatism, postoperative astigmatism and uncorrected visual acuity after cataract surgery depending on the site of a 4 mm sutureless incision (superior scleral or corneal temporal) and on the preoperative astigmatism. According to preoperative astigmatism and to the site of incision 4 groups have been distinguished. Group I: with-the-rule preoperative astigmatism and superior scleral incision, group II: with-the-rule preoperative astigmatism and corneal temporal incision, group III: against-the-rule preoperative astigmatism and superior scleral incision, group IV: against-the-rule preoperative astigmatism and temporal incision. The patients had a preoperative and postoperative (Day 1, 8, 30, 180, 360) keratometry. Surgically induced astigmatism, preoperative and postoperative astigmatism have been expressed according to Naeser method. The uncorrected visual acuity at Day 30 has been compared in each group. Preoperative astigmatism was similar in the four groups. Surgically induced astigmatism was -0.18 diopter (D) at day 30 and -0.41 D at day 360 for the scleral incisions and +0.60 D at day 30 and +0.33 D at day 360 for the temporal incisions. The postoperative astigmatism was +0.5 D at day 30 and +0.27 at day 360 for the group I and +1.22 D at day 30 and +0.95 D at day 360 for group II. There was no statistical difference in the uncorrected visual acuity. Postoperative astigmatism was -0.8 D at day 30 and -1.03 D at day 360 in group III and -0.04 D at day 30 and -0.31 D at day 360 in group IV. The visual acuity was significantly better in group IV than in group III. In cases of preoperative with-the-rule astigmatism < or = 0.75 D the two sites of incisions are possible. In cases of WTR astigmatism over 0.75 D we perform a superior scleral approach. In cases of against-the-rule astigmatism the temporal incision is the only one to consider.
Article
To evaluate surgically induced astigmatism (SIA), postoperative astigmatism, and uncorrected visual acuity (UCVA) after cataract surgery with superior corneal, superior scleral, and temporal corneal 4.0 mm sutureless incisions in cases of preoperative with-the-rule (WTR) astigmatism. Hopital des Quinze-Vingts, Paris, France. This prospective evaluation included patients having phacoemulsification with foldable lens implantation through a 4.0 mm incision. Patients with preoperative WTR astigmatism were randomly assigned to 1 of 3 incisions: superior corneal (Group 1), superior scleral (Group 2), or temporal corneal (Group 3). All patients had autokeratometry preoperatively and postoperatively (1 day, 1 week, 1 month, 1 year). Surgically induced astigmatism using the vector method, postoperative astigmatism, and UCVA (patients whose spherical equivalent was with +/- 1 diopter) were evaluated. Ninety patients were included in the study; there were 30 in each incision group. One year postoperatively, Group 1 had 1.52 diopters (D) of SIA and 1.36 D of postoperative astigmatism; 53.5% of patients had a UCVA of 20/32 or better, Group 2 had 0.69 D of SIA (P < .05) and 0.67 D of postoperative astigmatism (P < .05); 82.7% of patients had a UCVA of 20/32 or better (P < .05). Group 3 had 0.69 D (P > .05), 0.98 D (P < .05), and 79.3% (P > .05), respectively. In this study, the superior corneal incision produced significant SIA, leading to high postoperative astigmatism and poor UCVA. The scleral and temporal incisions produced minimal SIA and good UCVA.