TUNNEL CONSTRUCTION IN SICS
Dr. Navin Gupta
IOL Fellow
Introduction


Wound- not just a portal of entry into the
anterior segment
Cataract surgery -now become a form of
refractive surgery offering improvements in
‘best corrected’ and ‘uncorrected’ visual
acuity.
Principles of Wound Construction

Basic Objective

Astigmatism
- neutrality
- Stability
Variables of Incision
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Location
Extent
Form
Closure
Evolution of Modern Scleral Tunnel
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Dr. Richard Kratz – Scleral pocket incision
Michael Mc Farland (1990 ) – First to perform
sutureless closure of scleral tunnel wound
Paul Ernest – scleral tunnel with internal corneal
lip. It is a modification of Mc Farland’s wound
technique by carrying forward the tunnel into
clear cornea
Koch’s Incisional Funnel
Scleral Tunnel

3 components

External scleral incision

Sclerocorneal tunnel

Internal corneal incision
Components of Scleral Tunnel
width
length
Ideal Incision – External Scleral
Groove



Location : 2.5 to 3 mm from anterior border
of limbus
Depth : 1/3 to ½ thickness of sclera
1.5mm internal corneal lip
Shape of the Incision
Length of External Incision

Manual SICS
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
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Inverted trapezoid shape
According to the size and density of nucleus 66.5mm (7-7.5mm)
Phaco



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4mm square wound
Extend according to size of IOL
5-5.5mm all PMMA IOL
3.5-4mm for foldable
Instrumentation



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Caliper
Razor blade/Guarded diamond
Crescent knife
3.2mm broad keratome
15 no. super blade
Beveling of Blades
Beveled Down
Beveling of Blades
Technique – Scleral Tunnel
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
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External Scleral Groove
Tunneling with creation of 1-1.5mm internal
corneal lip of uniform thickness
Bevel up crescent blade preferred
Side port entry
Anterior chamber entry
Extension of the internal lip of the tunnel
Avoid button holing of scleral flap and premature
entry into anterior chamber
Side Port Entry


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At 9 ‘0’ clock in clear cornea
1.5mm from the limbus
2mm in width
Uses


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For doing capsulorrhexis
12 ‘0’ clock cortex aspiration
Formation of anterior chamber at the end of
surgery
Anterior chamber entry

Done with 3.2mm angled keratome

Dimple down technique

Be cautious not to damage anterior capsule
or corneal endothelium
Dimple Down Technique
Extension of Anterior Chamber Entry

Done with keratome

Length of internal corneal incision should
be more than external scleral groove
Wound Construction
Beveling of Keratome & Internal
Corneal Incision
Advantages of Scleral Tunnel

Surgical

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Less incidence of iris prolapse
Water tight – Decreased incidence of
expulsive haemorrhage
Advantages to the patient


Stronger wound permitting greater range in
postoperative activities
No suture induced FB sensation / astigmatism
Complications of Tunnel

Anterior Incision – Poor self sealing effect

Wound leak
ATR Astigmatism
Management - Suture
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Posterior Incision
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Risk of Bleeding / Premature entry
Difficulty in nucleus delivery and instrument
manipulation
Management – Suture for premature entry
Complications – Incision Length

Short Incision
Difficult nucleus delivery
Endothelial damage
Iris damage
Management – Enlarge the incision with keratome

Long Incision – Poor Approximation
Wound leak
ATR Astigmatism
Management - Suture
Complication – Incision Depth

Button holing

Premature entry

Scleral Disinsertion
Management –
Button Holing
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
Button holing or cut through the scleral roof
 Abandon the original dissection
 Start at the opposite end
 Deeper dissection and sweep laterally
Avoid bunching of advancing scleral tissue as the
crescent blade advances towards surgical limbus
Management of Premature Entry


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Start fresh with less
depth of dissection into
sclera
Avoid aggressive
angling of keratome
blade
Increase the dissection
into clear cornea
Suture the tunnel
Management of Scleral Disinsertion


Occurs when initial
scleral groove is full
thickness or deep
Radial suture should
be used to appose the
edges of scleral
groove
Suturing of Scleral Tunnel

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Indicated in premature entry and weak tunnels
Radial sutures having a vertical component will
cause post operative with the rule astigmatism
Horizontal suture is more physiological to the
scleral tunnel and causes less with the rule
astigmatism
Infinity Suture Technique
Infinity Suture Completed
Tunnel Complication - Descemet’s Stripping


Caused by cannula tip in the corneal canal
causing intralamellar hydrodissection
(saline / viscoelastic injection
During tunnel construction
MANAGEMENT OF DESCEMET’S
STRIPPING

Management



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Careful instrumentation
Injection of air bubble beyond the point of
detachment
Inferior ½ of cornea – reposit with viscoelastics
Large DM stripping – Full thickness corneal
suturing
Complications - Paracentesis


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Too far into cornea / Too small- DM
Stripping
Too periphery into sclera- bleeding
Too large – Leakage
Not parallel to iris – Injury to lens capsule /
Iris
Temporal Scleral Tunnel

Indications

High ATR astigmatism cases

Presence of superior filtering bleb
Temporal Scleral Tunnel

Advantages



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Less induced astigmatism as compared to
superior incision
No brow effect
Good red glow
Disadvantages

Orientation for surgeon
Comparison – Phaco / SICS Tunnel

Length of external Incision


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Phaco – 3 - 5 mm
Manual SICS – 6 - 7 mm
Width of tunnel

Manual SICS – dissection is more posterior
in sclera and more anterior in cornea

Internal opening

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Phaco –equal to external opening
Manual SICS is larger than external
Paracentesis

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Instrumental – 2 and 10 ‘ 0’ clock
Manual SICS – 9 ‘0‘ clock
Concepts of Corneal Incisions


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Single plane - Dr. I. Howard Fine
Two plane or groove incision - Harry B.
Garbow
Three plane - Richard A. Fichman
I
hear…I forget
 I see……I Remember
 I do …..I understand
Confucius