phacoemulsification some basic ideas…

Phacoemulsification some Basic Ideas…

Khalid M. Al-Arfaj, MDDammam University

3-Vedio …

1-Quiz …

2- lecture …

Case selection … Anesthesia …

Antibiotics

• Control blepharitis well before surgery (endophthalmitis usually results from lid flora)!

• Fluoroquinolones

Povidone-iodine• inexpensive• extremely broad-spectrum• irritating to eye in undiluted (10%)

solution; dilute to 5%• irrigate fornices with solution• paint, do not scrub, eyelashes

when prepping

Pre-operative Eyedrops

History of small incisions

1977: Scleral tunnel1990: Sclerocorneal1991: Clear corneal1991-present: Variations in clear corneal

Conjunctival peritomyDissection through Tenon’s fasciaCauteryScleral groove 1-2 mm posterior to the limbusScleral tunnelKeratome to enter the AC

Advantages:Wound can be safely enlarged for conversion to ECCEConjunctiva covers the woundPotentially less endothelial damageAstigmatically neutral

Disdvantages:Surgical exposure

Sunken eyeballProminent brow

Potential damage to ciliary bodyIris prolapseFiltering blebs and scarring make it difficult

Keratome to tunnel and enter the eye .

Clear cornea

Advantages:Can use topical anesthesiaFasterBetter surgical exposureFiltering blebs and scarring irrelevantNo subconjunctival hemorrhages

Disadvantages:Pre-existing corneal problems a relative contraindication:

FuchsPrevious PK

Possible higher rate of endophthalmitis in unsutured casesBallooning of conjunctiva if incision too posteriorConversion to ECCE more problematic

AstigmatismPre-existing ocular disease:

PterygiaFiltering blebsTubesEndothelial disease

Wound location

Tunnel lengthGoal to be self-sealing“Square” incision

Depends on widthGenerally want at least 2.0-2.5 mm long

Sharp entry through Descemet’s membrane

Wound architecture

External incisionToo anterior or too posterior

Internal incisionToo anterior or too posterior

TunnelToo long or too short

Incision widthToo narrow or too wide

Problems with the wound

Wound Final Thoughts

The wound may be one of the easiest steps of cataract surgery, but it sets the stage for the entire caseEveryone may have a different phaco woundPrinciples the same

Capsulorrhexis

Continuous curvilinear capsulorrhexis (CCC)It is a continuous tear capsulotomy.It can be made in the anterior capsule or both anterior and posterior capsules.It confines the IOL to the capsular bag.It assures long-term centration of the IOL.

TechniqueCompletely fill the anterior chamber with viscoelastic agent.Flatten the dome of the anterior lens capsulePuncture the anterior capsule with a bent 30-gauge needle or sharp-tipped capsulorhexis forceps.Start a flap that flops over toward the incision.

Technique

Grasp the flap with capsulorrhexis forceps (Utrata forceps).Spiral out to the desired diameter.Tear tangentially all the way around (no radial forces).Regrasp the flap as necessary.Keep an equal distance from the pupil margin while tearing.

Hydrodissection & Hydrodelineation

Goals

Nucleus rotationEpinucleus rotationLoosen cortex

Used to separate lens nucleus from surrounding cortex and capsule

Creates a freely mobile nucleusFacilitates nucleus rotation during phacoemulsification

Hydrodissection

Used to separate epinucleus from harder nuclear material

Creates an epinuclear bowl that protects lens capsule during phacoemulsification

Hydrodelineation

Hydrodissection cannula25- to 30- gauge

Flattened tip with angled or curved shaft

Facilitates placement under anterior capsule

J-shaped cannula may be used for sub-incisional area

Background

Technique …

Complete several fluid waves to ensure adhesions to capsule broken

Proceed to hydrodelineationInject fluid into edge of nucleus“Golden ring” sign indicates epinuclear separation

Confirm that nucleus rotates

Lens nucleus occludes capsulorhexis Trapped BSS expands posterior capsule, AC shallowsPosterior capsule may rupture

Intraoperative Capsular Block Syndrome

PHACODYNAMICS

Two Basic Elements

US → Emulsify the CataractFluid circuit → cooling and remove the Emulsified Cataract

Three Main Machine

Functions USFlowIrrigation

Fluidics

IrrigationFlowVacuum

Fluidics

Flow → peristaltic → vacuum only at occlusionVacuum → venture → continuous vacumBOTH → millennium

Flow control mode Vacuum control

mode

Type of Pumps

Irrigation

Amount of fluid that enters the eye Depend on: Bottle

height pressure on

the eye

flow from the eye

Tip diameterWound leak

Flow

Fluid leaving the eye ml/minSpeed with which the material is sucked to the tipControl pump speedNo-occlusion → current and attraction forceWith occlusion → rise time (time for maximum preset vacum)Flow rate

Surge Vacum riseSafety

Vacuum

Holding power With occlusion → No flow

but pump will continue → negative pressure at aspiration line → vacum → Stop pump at maximum preset vacum

Good Fluidics

Irrigation Wound Leak

Aspiration (flow) Vacum

Surge

Sudden ↓ of A/C pressure → collapse

Dynamic ↓ of vacum by surgeon by deocclusion

Bottle height Machine complianceVacum and flow rateTip diameter → resistance

Flow

Flow depends on pump speed

not on bottle height

US Power mode of delivery

USSafest phaco is with appropriate power not with the lower power

Mechanism of Action

Jackhammer → direct contactCavitation → with cavitational bubblesSonic wave

Mode = US Delivery

Continuous Pulse Burst

Pulse

Fixed interval but linear power Fixed duty cycle

Burst Mode

Fixed power of linear intervalVariable duty cycle

Repulsion

Chatter → flaying of peace away from the PHACO tipMode - ↓ by Pulse , Burst and WS