Femtosecond Lasers in LASIK Surgery

Dr Chan Tat Keong

Senior Consultant

Refractive Surgery Service

Singapore National Eye Centre

Disclosure

• Speaker has no financial interest in the products

to be discussed in this presentation

• Travel funding from Alcon, Santen & Carl Zeiss

Modern LASIK Surgery Today

• Better excimer laser design, optics & algorithms

• Tissue saving

• Customised treatments

• Aspheric (for spherical aberration)

• Wavefront-guided (for higher order aberrations)

• Better eye trackers

• Bladeless corneal flap creation: Femtosecond laser technology

Why use femtosecond laser technology during the first step of LASIK?

• Provides a 100% blade-free LASIK procedure

• Enables more people to achieve 20/20 (6/6) vision or better

• Fewer flap related complications

• Incomplete flaps

• Free flaps

• Button holes in flaps

• Recurrent erosions in the cornea

Bladed Microkeratome: Source of Serious Complications

• A focusable infrared laser that uses ultra-short pulses in the hundred-femtosecond (100x10-15 seconds) (1052nm) duration (600-800 fs) range.

The Femtosecond Laser

7

Photoablation:Excimer

Precise Surface EffectsPrecise Sub-Surface Effects

Photodisruption:

Femtosecond

Laser-Tissue Interactions

Nd:Yag1064 nmNd:Yag1064 nm

Argon488-514 nm

Green HeNe543 nm

CO2

10,600 nm

Diode680 nm

ArF193 nm

ArF193 nm

KrF248 nm

KrF248 nm

XeCl308 nm

XeCl308 nm

XeF351nm

XeF351nm

HeNe632 nm

Ultraviolet InfraredVisible

750 nm400 nm

Not to Scale

• The laser-induced vaporized tissue forms a cavitation gas

bubble that consists of CO2, N2 H2O, will diffuse through

cornea.

Femtosecond Laser Technology in LASIK

Mehta JS et al. Femtosecond Laser-Assisted Endothelial Keratoplasty A

Laboratory Model. Cornea In Press.

Femtosecond Laser Flap Creation

• The laser spots are either fired in a spiral or zigzag (raster) pattern

• Raster – IntraLase

– Spiral – FEMTEC, (Visumax) Zeiss

Femtosecond Lasers

Femtosecond Lasers in Refractive Surgery Today

• Intralase FS (60 & 150) (AMO)

• Femtec (Technolas)

• Femto LDV Laser (Ziemer)

• VisuMax (Carl Zeiss Meditech)

• FS 2000 Laser (Wavelight, Alcon)

Two Femtosecond Lasers for Refractive Surgery Service in SNEC

IntraLase FS LaserVisuMax

History

• 1998: First clinical Femtosecond Laser in cornea

• 2000: Initial U.S. use of Femtosecond Laser keratome for LASIK

• 2001: Commercial launch of IntraLase FS (1st generation)

• 2003: 2nd generation IntraLase FS Laser (15 kHz)

• 2005: 3rd generation IntraLase FS Laser (30 kHz)

• 2006: 4th generation IntraLase FS Laser (60 kHz)

• 2008: 5th generation IntraLase FS Laser (150 kHz)

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Properties of IntraLase FS Laser4th Generation 60kHz

• Designed to enable surgeons to:

• Program all surgical parameters for personalized flaps

• Predict the precision of uniformly planar flaps

• Create the LASIK flap in under 30 secs

• Structure of the Intralase flap

• Smooth, precise & uniform

• Adjustable dimensions

• Sharp edge

• Dry corneal bed

Programmable Parameters

• Flap thickness

• Diameter

• Centration

• Hinge angle

• Side cut angle

LASIK procedure with IntraLase FS laser

Corneal Bed Surface Comparison

9x 30x 135x 300x

IntraLase FS Laser

Microkeratome

Precise Thin Uniform Flap

Attempted = 90 um

Achieved = 89 – 90 um

VisuMaxFemtosecond Laser System by

Carl Zeiss Meditec

• Designed for corneal laser surgery

• Workstation concept

• Ergonomic workplace

• High quality surgical microscope for surgery

• Short laser start-up time

• Integrated high resolution video camera

VisuMax Femtosecond System

• Touch-screen user interface for surgical procedure

• Separate screen for treatment planning

• Interactive guidance

• Voice messages

• Full visual microscope control over entire procedure

• Integrated slit lamp for immediate evaluation

• Patient comfort

• Easy entry

• Automatic adjustment

• Adjustable headrest

• Flexible joystick position

VisuMax Femtosecond Laser System

Patient Bed

VisuMax : Innovative Corneal Interface

• Gentle corneal interface concept

• Suction applied only during laser procedure

• Patient fixation considered for optimum flap positioning

• Minimal ocular discomfort, low suction

• Suitable for small Asian eyes

VisuMaxflap cut

Flat PI (same eye)

Comparison of Corneal Interface Designs

Normal EyeNormal Eye

Curved PI (same eye)

VisuMax

IntraLase

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Visumax Femtosecond System

OCT flap imaging

•• Homogeneous flap thicknessHomogeneous flap thickness

•• Regular interfaceRegular interface

HighPulse Rate

Precise Focusing

Low Spot Energy

High pulse repetition rate

• Short procedure time

• Easy flap lift / tissue

separation

• Extended 3D shapes

Low & very stable laser energy

• Excellent cut quality

• No adverse side effects (DLK)

Precise focussing/small spot:

• Well defined incisions

• Flaps & Femtosecond

lenticule extraction (FLEx)

Triangle of treatment parameters

typical: <300 nJ (<0.3 µJ)

3 … 6 µm500 kHz

Femto Systems Overview

IntraLase VisuMax

Laser Concept Amplifier Amplifier

Wavelength 1053 nm 1043 nm

Patient Interface Flat Curved

Interface Pressure Floating Lens Computer-controlled

Suction Scleral (manual) Corneal (computer controlled)

Loss of vision Yes No

Flap Creation Speed Around 15 - 18 seconds Around 18 seconds

Size, Mobility Bulky, fixed Bulky, fixed

Femtosecond lenticule extraction (FLEx)

No Yes

Summary

• Femtosecond lasers produce stronger flap adhesion postoperatively

• Vertical edge flap architecture provides optimal profile for wound healing

• Improved epithelial preservation a significant safety advantage

• VisuMax & IntraLase capable of creating flaps in a very short time

• The VisuMax patient interface appears more gentle with less likelihood of subconjunctival haemorrhage

• Corneal suction of the VisuMax ideal for small Asian eyes

Thank you!