Jun 02, 2015
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Outdated because: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 [email protected]
Thank you for your attention!