Small incision technique - sutureless, minimizes distortion of the
corneal curvature.
The classical phaco-incision is Z shaped in 3 steps:-
- One limb - vertical gutter
- Second limb - horizontal dissection
- Third limb - entry into the anterior chamber
Vital statistics
- Site of the external incision
- Placement of the incision
- Style of the external incision
- Length of the external incision
- Length of the corneo-scleral tunnel
- Depth of tunnel dissection
- Size of primary incision
- Size of incision for IOL
- Paracentesis opening
Scleral pocket incision
1.5 to 1.75 mm, posterior to limbus, usually at 12'O clock
Clear corneal incision
Just ahead of the limbal vascular arcade
Superior limbus
- Usually anteriorly placed
- Effective corneal valve incision - internal opening too anterior
so more clear corneal. Shifting to temporal cornea.
Clear corneal incision
Incision is placed over the steeper meridian to correct astigmatism
by flattening of the meridian.
Temporal incision - eye does not need to be turned down. It does
not give rise to post operative ptosis and iris plane is parallel
to microscope light, therefore red glow is excellent. This incision
is more stable refractively.
The disadvantage being higher risk of complications and also uncomfortable
position for the surgeon.
External incision - Frown or Straight line incision
Highly recommended incision, leading to less astigmatic shift. Length
of incision is equal to size of IOL although a small entry is made
for phaco.
- Thickness of the roof - about 300 microns, thin roof may lead
to button holing.
- Length of the tunnel 2.5 mm for scleral tunnel, 1.75 mm for clear
corneal incision
- Too long a tunnel causes distortion of corneal dome
- Too short a tunnel - leaking incision
Length of incision for phaco
3 to 3.4 mm, average 3.2 mm
The incision should -
- Allow easy entry of phaco needle
- Allow easy motility of phaco needle
- Minimal incision leak
- Prevent incision burns
Size of opening for IOL
Rigid style PMMA PC IOL - 5.2 mm (should be equal to the size of
the IOL)
Foldable IOL - 2.5 to 3.5 mm
Paracentesis
These are secondary incisions, 0.6 to 1 mm for phaco chopper, lens
hook. A limbal incision just ahead of arcade is preferable.
Comparing Scleral tunnel with Corneal tunnel incisions
| |
Scleral tunnel |
Corneal tunnel |
| Indications & contraindication |
C/I in bleeding disorders, collagen vascular diseases, functioning
blebs. |
Good for blebs, bleeding disorders, conjunctival scarring, scleritis,
dry eye syndrome |
| Construction and tissue trauma |
More difficult, time consuming and more traumatic |
Less so
|
| Astigmatic control |
comparable |
comparable |
| Risk of complications (Endophthalmitis, Iris prolapse, Flat
A/c |
Very rare |
More common |
| Risk of hyphema |
Greater |
Infrequent |
Closure
Clear corneal incision - never let your ego come between the suture
and safety.
A few things need to be avoided to reduce chances of greater astigmatism
-
- Longer incision
- A corneal incision
- Limbus parallel incision
- A uniplanar incision
- A sutured incision
A wound with a "square" configuration (length = breadth)
is considered more stable.
One study suggests that -
- Induced astigmatism was minimal and comparable with both scleral
tunnel and clear corneal incisions.
- Endothelial cell loss was documented to be higher with corneal
incision if it is close to central area.
Achieving emetropia
Temporal clear corneal incision or a frown incision 3 mm behind the
cornea is better.
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Complete Circular Capsulorhexis (CCC)
Developed by Gimbel, Neuhann and Shimizu
Diameter of adult crystalline lens is 9.5 to 10 mm, zonule free area
is 6 mm
Prerequisites -
- Absence of positive pressure with use of viscoelastics, air, irrigation.
- Closed chamber technique
- 26 gauge bent needle
- Special forceps can be used under Healon.
Advantages
- In situ phacoemulsification is facilitated and ultrasonic turbulence
is contained within the new capsule.
- In the bag implantation is possible.
- IOL rotation is possible with no chance of decentering caused
by loops coming out of the bag.
- There is no capsular tag left that can extend up to the posterior
capsule.
- In the event of PC rupture one can implant the lens over rhexis
margin in the sulcus
- Chances of posterior synechiae are less.
Method
Tearing by stretching, tearing and shearing.
Size of CCC is 4-5 mm
One study shows that CCC cases require 0.44 D sph more correction
than those who underwent can opener technique.
Complications
- Shrinkage of anterior capsule opening
- Capsular bag hyperdistension
- Epithelial cell proliferation on posterior capsule
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