46-overview-of-Phaco - M.M.Joshi Eye Institute

Report
Overview of Phaco
Dr. Anil Kulkarni, M.S.
Miraj
Phacodynamics
Common Terms
USG power
Irrigation
Aspiration/ Flow
Vacuum
ACOUSTIC VIBRATOR
Two Types
Magneto-restrictivePiezoelectric – electrical energy is used to
reorient piezoelectric crystal which in turn
is translated in to linear movement.
ULTRASONIC POWER
Vibration of tip – Energy release
Jackhammer effect
Cavitation :
when tip retreats fluid cannot follow,
void created produce tiny bubbles
Bubbles implode amongst themselves creating
shock waves.
Heat (By product)
ULTRASONIC POWER
Phaco Power : Power depends on –
Amplitude (stroke length) of phaco tip
Continuous Power
Pulse Power
Burst Power
ULTRASONIC POWER
Linear – On pressing the foot pedal there is gradual
rise of parameters from “O” to preset values with a
linear relation to foot pedal control.
Panel – On pressing foot pedal, the parameters
reach to the preset panel values.
ULTRASONIC POWER
Constant Mode –
Power is delivered continuously.
It can be linear or panel controlled.
Pulse mode –
Phaco power is delivered at preset intervals.
It can be varied.
It gives relative intervals, where there is absence of
tip movement.
ULTRASONIC POWER
Effective Phaco time –
It is the total phaco time at 100% phaco power.
It can be less than total foot pedal time.
Less EPT indicates less energy delivered to the eye.
Irrigation
Gravity driven
IOP > 10 mm Hg
wound leak reduces
pressure spikes
Bottle height 30-75 cm
double irrigation for
high vacuum
ASPIRATION SYSTEM
Aspiration – Evacuation of fluid through a closed
system.
Flow Rate – Quantity of fluid pulled from the eye per
minute through the instrument tip
Measured in CC/Min.
PERISTALTIC PUMP
Principle – A pressure differential is created by
compression of the aspiration tubing in a rotating
motion.
•
Aspiration tube passes over the knobs.
•
When the drum rotates aspiration tube is successively
compressed by the knobs over the drum to produce
vacuum in the tubing.
VENTURI PUMP
This uses compressed gas
to create inverse pressure.
Vacuum generated is
related to gas flow which is
regulated by a valve.
The vacuum build up is
almost instantaneous on
pressing the foot pedal.
Surge
Sudden increase in
outflow
uncompensated =
A/C collapse
High IOP and
negative pressure in
aspiration tubing
Surge Prevention
Decrease vacuum
decrease flow rate
non compliant tubes
tighter wound
raise bottle height
microprocessor
venting
Venting
Safety mechanism to limit
the vacuum to
predetermined maximum
level
bleeding air or fluid in
aspiration line.
Balance IOP and negative
pressure in aspiration line
Rise time
SUPERIOR INCISION
BETWEEN 11 & 1 O’CLOCK
Advantages :
a. Maximum protection against infection
b. Easy for beginners
Disadvantages :
a. Difficult to construct & work in deep seated eyes
b. Poor visibility - corneal folds
c. Less Red Glow
d. Difficult in cases of filtering surgery
e. Maximum ATR
TEMPORAL INCISION
BETWEEN 8 & 10 O’ Clock.
Advantages :
a. Easy to make/manipulate in deep seated eyes
b. Good tissue visibility
c. Maximum red glow
d. All types of cases
e. Less foreign body sensation
Disadvantages :
a. More chances of infection
b. Sitting position difficult.
CLEAR CORNEAL INCISION
SIMPLE & FAST
Diamond Blades
Single plane incision - single blade
(No groove/No cautery/ No scleral
tunnel)
Easy for topical anesthesia
DISADVANTAGES :
a. More chances of Infection
b. More endothelial damage
c. Increased astigmatism (if >5 mm)
ASTIGMATIC CONSIDERATIONS
Incision funnel : Bonded by two curved lines.
Incisions made with in the funnel :
Curvilinear incision - Maximum ATR
Straight line incision - Less ATR
Frown /Cheveron incision - Least ATR
SITE OF INCISION
Superior incision - More ATR
Supero-temporal Incision - Moderate ATR
Temporal Incision - Least ATR
Methods To Enlarge Pupil
A) Sphincter sparing
1. Synechiolysis –
Old uveitis,
Prior surgery,
prolonged miotics
2. Membranectomy
3. Visco elastic – Cohesive
eg. Na,Hyaluronate
Methods To Enlarge Pupil
B) Involving the sphincter
1.
Pupil Stretching
: By two instruments
: By Prongs
Methods To Enlarge Pupil
2. Mini sphincterotomies
3. Grieshaber Iris hooks
4. Pupil ring expanders
5. Iridotomy
Gradual Enlargement of the Pupil is
preferred over rapid, sudden tugging.
Stretching always performed under visco
elastic
Intra cameral Lidocaine may be necessary
Aim for adequate pupil (Not very large)
Undesirable effects
Large sphincter tears
Atonic pupil,
photophobia
Iris damage
– Mechanical,
-- Thermal
Cost involvement
Deformed pupil /
Aesthetic change
Iris haematoma
Post operative
inflammation
Capsulorhexis
Posterior Zonular Fibres are inserted 1 to 1.5
mm. and Anterior Zonular Fibres about 2 mm.
From Equator.
Central 6 mm. is Zonule free area of the
anterior Capsule.
Krag by computer simulation showed that
C.C.C. diameter needs only to be 1/2 to 2/3
diameter of IOL Optic diameter.
Anterior chamber maintained
: Visco elastic
: Air
: A/C maintainer.
Bent needle of 26 No.
Or Forceps can be used.
Shearing
Ripping
While tearing, always catch the
cutting edge.
CCC Advantages
In the Bag Phaco emulsification is possible.
Centering of IOL is possible.
In case of PCR, IOL can be implanted over the
capsular rim.
Chances of posterior synechiae are reduced.
Complications
Shrinkage of anterior capsular opening.
Capsular bag hyperdistension.
Epithelial cell hyperproliferation on the
posterior capsule.
Hydrodissection
Through side port :
No escape of fluid & hence
post capsular rupture
(Always use main incision)
Large Volume Fluid Trapped
[ to avoid – ½ ml. at a time,
at 2-3 places, after lifting the
anterior capsule]
Nucleus Management
Soft cataract/ posterior subcapsular cataract
SPRING Technique
Hard Cataract :
Cracking operations.
1. Divide & Conquer
2. Stop & Chop
3. Quick Chop.
SPRING TECHNIQUE
Sequential Pulsed Removal of Inner Nuclear Girdle.
Central Sculpting - Broad & Deep
Relaxing Nucleotomies 7.30, 4.30, Center.
Aspiration of the collapsed wings.
Spring with crack hybrid technique.
SPRING
DIVIDE & CONQUER
4 Basic steps :
1. Sculpting to a very thin posterior nuclear Plate.
2. Fracturing nuclear rim and posterior plate.
3. Fracturing again to break wedge shaped Section.
4. Rotating the nucleus, further fracturing followed by
emulsification.
TRENCH, DIVIDE & CONQUER
Trench should be small, central &
vertical to leave enough firm nucleus for
applying force of two instruments.
More nuclear density fuller length of trenching.
Crack starts at the posterior pole
and then extends to 6 & 12 o’clock.
Hemisections are then further divided.
CRATER, DIVIDE & CONQUER
Deep Central Sculpting to produce
large crater leaving dense
peripheral rim, for fracturing.
Harder the nucleus –
smaller the wedge shaped sections.
All sections are left in the bag:
To keep it distended ;
To keep ultrasonic turbulence in
bag.
Nagahara Chop
Advantage : Least phaco time.
Disadvantage:
Pieces rejoin and prevent their removal
Threat to the integrity of anterior capsule by
chopper
Stop & chop
Koch’s modification :
Trench sculpted & nucleus
is halved,
then stop and start chop.
PHACO QUICK CHOP (PFIFER)
Main difference is placement of chopper.
It is placed on top of the buried phaco tip near
centre of lens- away from anterior capsular rim.
PHACO QUICK CHOP (PFIFER)
near vertical chopping.
Chopper pushed down, phaco tip moves
up and then both are laterally separated.
Prepare all fragments before emulsifying
to enable endo capsular phaco.
2mm exposure of phaco tip.
Coaxial MICS
Use of micro tip
Nano sleeves
Incision 2 – 2.2 mm
No change in surgeon’s technique
IOLs available for insertion
High vacuum and phaco aspiration possible
P.C. Rent (INTRA-OP FACTORS)
Peripheral escape of rhexis
forceful hydrodissection
high vacuum and high power settings
one handed technique-chasing the fragments
sculpting too deep / too peripheral
POSTERIOR CAPSULAR RENT
signs
Sudden deepening of the AC.
New found difficulty in emulsifying the nucleus…
mydriasis / pupil distortion
Visible vitreous in AC!!..
STOP!! EVALUATE…PLAN..!!
RENT CONTROL ACTS..!!!
The 10 commandments..
1.
FREEZE movements,reduce bottle height
2.
inject visco from side port
3.
stop irrigation
4.
press reflux
5.
withdraw phaco tip from AC
Assess damage-site , extent of rent.
Rent control acts..!! Contd..
6. Mechanized bimanual vitrectomy
7. Removal of residual nuclear fragments
8. Dry cortex aspiration
9. Re-assess capsular support
and insert IOL …PC / AC
10.Secure wound closure
Post op care-antibiotics, steroids, NSAIDs

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