the evolution of lasik by j. alberto martinez md cope id 31538-rs

The evolution of lasik

From freezing to photoablation

J. Alberto Martinez, M.D. Visionary OphthalmologyMay 12, 2011

OUTLINEIncisional refractive surgery

Lamellar refractive surgery

Non-excimer laser lamellar refractive surgery

Excimer assisted lamellar refractive surgery

LASIK in the US

Femptosecond role in LASIK

Future of Refractive surgery

Martinez’ classification of refractive surgery Corneal procedures

Conjuntival procedures

Scleral procedures

Anterior chamber procedures

Iris/pupil procedures?

Sulcus procedures

Crystalline lens procedures

Globe shortening procedures

Corneal procedures

Incisional procedures: RK, AK, LRI

Surface reshaping: PRK ( PTK), CK orthokeratology

Stromal reshaping: LASIK, Intralase stromal ablation

Augmentation procedures: Corneal inlays, Intacts

Radial Keratotomy

Tsutomu Sato of Japan, 1933: 40-45 endothelial side cuts: Corneal edema

Cornea: RK, AK/LRI

RK reshapes the cornea by relaxing steep meridians

Advantages: Quick, inexpensive

Disadvantages: Inaccurate, variable

Radial KeratotomyEarly 1970s, Dr. Yenaliev,

Durnev and Fyodorov: External

incisions only

Dr Fyodorov And Dr. Leo Boris introduced RK in the United States in 1978

Incisional refractive surgery still plays a role in some procedures, mostly LRI’s or limbal relaxing incisions for astigmatic correction after cataract surgery

Incisional refractive surgery (IRS)

Outdated because:

Unpredictability

Limited range of effect (minor myopia, up to four diopters)

Better options (lamellar)

Still however used today as LRI, limbal relaxing incisions for multifocal IOLs

Dr. Luis Ruiz, RK innovator

CK®

Thermokeratoplasty: technique that uses RF energy to heat and reshape the cornea

Lamellar Refractive surgery

Conceived and developed By Dr. Jose Barraquer Bogota, Colombia.Voted as the most influential ophthalmologist of the 20th century

Ley de Espesores – Law of Thicknes

Keratomilieusis

The Microkeratome

Automated Lamellar Keratoplasty, ALK

Excimer Laser

Developed at IBM in 1976 to etch microchips

First introduced by Stephen Trokel in 1983

LASIK was essentially a procedure already performed in Bogota

by Dr. Barraquer.

Excimer laser only

made it more accurate

EXCIMER LASER

Excimer Laser in ALK

1990 LASIK was born as the “flap and Zap” Dr.

Steven Slade

1995 LASIK approved by the FDA for commercial

use

1999 use of wavefront technology

2008 LASIK approved for Navy Pilots and

astronauts

ALK + Excimer = LASIK

First Generation Excimer lasers

Second Generation Excimer Lasers

Wavescan: Wavefront scan

Customized Ablations

WAVEFRONT GUIDED

VS.

WAVEFRONT OPTIMIZED

Wavefront GUIDED Treatment

Wavefront measurement ( lower order aberrations:

Defocus (sphere) and Astigmatism (cylinder)

To measure Higher order aberrrations

Need Dilated pupils ( correspond to 6-7mmOZ)

Wavefront GUIDED Treatment

A wavefront refration with small pupils

Plus larger diameter treatments=

High technology autorefraction followed by standard excimer laser treatment

Optical aberrations increase with age, mostly associated with lenticular changes, thus not stable over time.

ALLEGRETTO WAVE® LASER FEATURES

Wavefront Optimized excimer lasers: Latest generation of lasers

Wavefront Optimized

Latest lasers: Smaller scanning spots

But smaller: more rapid repetition rate to achieve a given amount of tissue removal

Increased rate of laser firing causes higher temperature at treatment site.

Optimized shot distribution ensure that only every 5th pulse is allowed to overlap the first. This helps minimize thermal build up and provides adequate time for plume evacuation.

1

3 4

2

5

• Due to the high pulse frequency, there is a theoretical risk of thermal effects1.

• ALLEGRETTO WAVE® Eye-Q laser prevents this by only allowing every fifth pulse to overlap with a previous one.

• Optimal temporal and spacial shot distribution is required to minimize potential thermal load

1. Mrochen M et al. J Cataract Refract Surg. 2009;35:363-373.

Thermal Optimized Shot Distribution

Eye tracking

Must have PRECISE eye tracking to follow eye during abaltion

Precision limited by LATENCY

Time between eye recognition of movement and redirection of scanning spot

With smaller spots LATENCY must be minimized

Eye tracking is an integral feature that helps assure that each laser pulse is placed where planned1.

The 400-Hz eye tracking system verifies the eye position and automatically

corrects shot placement for natural eye movement.

• Natural eye movements range from 20 Hz

to 60 Hz• The ALLEGRETTO WAVE® Eye-Q laser

tracker can: – Center on natural pupils from 1.5 mm to

8 mm diameter – Track pupil movements at 400 Hz – Acquires the image, processes it and

verifies the position of eye before releasing the pulse.

1. Chalita MR, Krueger RR. In: Albert & Jakobiec’s Principles and Practices in Ophthalmology. 3rd ed. Philadelphia, PA: Saunders W B Co; 2008:1041-1049.

Active, High-speed Eye Tracking

Wavefront Optimized

Designed to avoid induction of spherical aberration

Earlier lasers and techniques less predictable with spherical aberration

Goal is to reshape cornea to a theoretically superior profile

Translate clinical data to precise tissue removal

Peripheral Pulse ControlTo compensate for energy loss in the cornea periphery,

the number of laser shots are increased

Normal Ablation

When beam shape broadens in the periphery, fluency can fall below the ablation threshold (≈45 uJ/cm2).

Energy loss is attributed to1:• The cosine effect and beam

ovalization which decrease energy• The angle of incidence approaches

the critical angle in the periphery and becomes partially absorbed

• The result is less fluence and thus sub-optimal ablation

Wavefront Optimized ® algorithms maintain the natural pre-op

corneal curvature by compensating for this effect. The algorithm delivers more shots to the periphery, to produce a refractive

treatment with minimal increases in spherical aberration.1. Seiler T, Koller T. In: Albert & Jakobiec’s Principles and Practices in Ophthalmology. 3rd ed. Philadelphia, PA: Saunders W B Co; 2008:981-985.

The Femtosecond laser

Corneal reshaping: Intralase

PresbyLASIK: Ablation within the stroma without disrupting the surface. Great promise . Developed by Dr. Luis A. Ruiz of Bogota, Colombia

IDEAL IOL

Contact information:J. Alberto Martinez MDwww.myeyesurgeon.comjalbertom@comcast.net

Thank you for your attention!