Upload
dr-dean-dornic
View
1.023
Download
1
Embed Size (px)
DESCRIPTION
A lecture describing the evolution of LASIK and differences in LASIK technology.
Citation preview
The Science of Vision Correction
Dean Dornic, MD
(Mr. Science)
Laser Eye Center of Carolina
A 60 Year History of LASIK
1949 Columbian Ophthalmologist Barraquer describes a lamellar corneal procedure to correct refractive error
ALK the Predecessor to LASIK
A microkeratome is used to create a flap and to remove a disc of corneal tissue
Birth of LASIK: Introduction of Excimer Laser Results in Name
Change
1983: First journal article describing the use of the Excimer laser to treat refractive error
1989: First patent for the LASIK procedure
Improvements in Technology Have Resulted in Improvements
in Outcomes
Lower risk of complications (decentered ablations, asymmetric ablations, quality of vision issues)
Higher likelihood of spectacle independence
Higher Order Aberrations
Introduction of aberrations reduce visual quality and decrease patient satisfaction
Spherical aberration a result of oblate cornea
Significant Refinements: Ablation
Wider treatment zones
Flying spot
Pupil tracker
Wavefront-guided and optimized treatments
Iris registration
Wavefront Technology
Wavefront-guided procedures utilize a wavefront analyzer to correct higher order aberrations
No analyzer necessary for wavefront-optimized procedures
Wavefront Technology Benefits are More than Just Theoretical
Wavefront-guided procedures have greatest rates of 20/20 or better
WFG procedures have lowest enhancement and night-vision problems
Night Vision Satisfaction after CustomVue
Patient satisfaction with night vision increases after WFG procedures
Ratio of improved vs worsened night vision is 4:1
Important Points for Patients
Wavefront Guided is not equivalent to Wavefront OptimizedWFG Procedures can correct HOAs
WFO Procedures strive to limit new HOAsYou can achieve good results with conventional LASIKWFG need not be reserved for patients with high HOAs
WFG Procedures give the Opportunity for Improved BVAWFG Procedures Give the Best Night VisionWhy would you not want a WFG procedure?
The LASIK Flap
Serves to speed recovery
Lessens likelihood of haze, regression and infection
Most common source of complication
Significant Refinements in Flap Creation/ Improved Safety
Elimination of perforation riskElimination of exposed gears
Elimination of on-eye assemblyVacuum meters/ audible tones
Increased customizationFemtosecond laser flap creation
Sidecuts
Cornea Flap Creation with Microkeratome
Suction ring exposes cornea.
Oscillating blade a set distance below metal plate creates flap
Variability in amount of exposed cornea results in variability of flap parameters
Flap Creation with IntraLase Femtosecond Laser
Cleavage plane created by photodisruption and resultant gas bubbles released a set distance below cornea surface applanated by glass plate
Downside of IntraLase (FS30)
Increased ExpenseIncreased Time
Flaps More Difficult to LiftRisk of Flap Tears
Transient Light Sensitivity Syndrome
Ziemer LDV
PortableFamiliar Technique
FastAble to Create Thin Flaps
Ziemer Complications
Free FlapsSmall Irregular Flaps
Result of Ziemer Complications
Small Irregular Flaps Managed with Immediate PRK
Both Cases Required Enhancements For Quality of Vision Issues
IntraLase FS60
Less OBL DelayFaster Procedure Time
No Free FlapsNo Small Irregular Flaps
Head to Head Comparison of Complications: First 150 Cases
Most Previous Papers Attempt to Compare Complication Rates Utilized Different Surgeons
Same Surgeon
98 cases IntraLase FS30
150 cases Ziemer LDV
52 Cases IntraLase FS60 added to IntraLase Group for Equal Sample Size
Comparison of ComplicationsFirst 150 Cases
IntraLase
1 incomplete flap
1 slipped flap
Ziemer
2 free flaps
2 small irregular flaps
1 slipped flap
My Ziemer Complication Rate vs Pietela et al J Ref Surg
My Results (150 cases)
2 Free Flaps 1.3%
2 Irregular Flaps 1.3%
1 Flap Displacement 0.7%
Pietela (787 cases)
21 Free Flaps 2.7%
16 Decentered 2.0%
10 Pseudobuttonholes 1.3%
2 Split Flaps 0.3%
3 Flap Displacements 0.4%
IntraLase Flap Creation
3-Dimensional flap
2-steps with side cut added last
Flap creation visible throughout
IntraLase Flap Creation
Diameter and location of flap can be altered before proceeding
Side cut is created last as a seperate stage
IntraLase Control Panel
Allows for perfectly centered flap
True customization
Unlimited flap diameters and flap thicknesses
Last minute adjustments
IntraLase Flap
Flap creation visible throughout procedure
Because surface not affected, flap can still be salvaged if there is interruption
Ziemer Flap Creation
Single Plane “Cut” Similar to Microkeratome
Initial Applanation and Alignment Visible
Creation of Flap Not Visible to Surgeon
Ziemer Flap Creation
Diameter of Ziemer flap dependent on area applanated
Diameter affected by corneal curvature
Sidecut performed simultaneously with the rest of the flap
Loss of Suction with IntraLase
Loss of suction visible. Procedure can be halted and resumed.
Loss of Suction with Ziemer
Loss of full applanation before flap creation is initiated results in a free flap
Loss of full applanation after flap initiation results in smaller, irregular flap
Suction Loss is Not Rare
The Consequences of Suction Loss is Different for 2 Reasons:
1. Surgeon is “Blind” to Flap Creation When the Ziemer Laser is Used: Loss of Full Applanation May not Be Apparent
2. The Side Cut is a Second Seperate Stage When the IntraLase Laser is Used: This Allows for Recovery/Salvage of the Case When Suction is Lost
Prevention of Complications
Proper and Adequate Suction/Applanation
Separate Side-Cut With “Manhole” Configuration Should Reduce Slipped Flaps
Separate Side Cut Allows for Salvage/Resumation When Suction Lost
Full Visualization/Proper Intervention Should Limit Incomplete or Free Flaps
Ziemer Pros and Cons
Pros
Portable
No OBL
Technique Familiar
Fast
Flaps Easy to Lift
Cons
Limited Customization
Diameter Influenced by Corneal Shape
Single Plane Flaps
Unable to Visualize
Interuption of Case Usually Results in Cancellation
Higher Complication Rate
IntraLase Pros and Cons
Pros
Customization
Better “Fine Tuning”
Manhole Configuration
Full Visualization
Free and Irregular Flaps are Rare
Interruption Rarely Results in Cancellation
Cons
More Cumbersome
OBL Can Slow Down Case
Not as Portable
More Uncomfortable For Patient
Higher Rate of Subconjunctival Hemorrhage
Summary
Femtosecond Laser Technology Can Produce Thinner, More Consistent Flaps
The IntraLase Laser Allows for Better Surgeon Control and Is Much Less Likely to Result in Complications, Postponement or Conversion to PRK than the Ziemer LDV Laser
Z-LASIK Flap Architecture
Single plane, exactly as that created by a microkeratome
All complications seen with microkeratome can be seen with Z-LASIK
IntraLase Flap Architecure
Manhole configuration
No free flaps
No Small/ irregular flaps
Second chance possible
More secure
Electron Micrograph Comparison
IntraLase Flap
Z-LASIK Flap
Bonus Advantage
Stromal bed smoother with IntraLase
IntraLase Flap Creation
Monitor View
Conclusion
Safest way to make a flap is IntraLase
Best vision achievable is with CustomVue
Chief advantage of Z-LASIK is cost
Military does not perform Z-LASIK. Statements such as “technology approved by the military” are, at the very least, misleading
All “custom procedures” are not equivalent
All “all-laser” procedures are not equivalent
Need for New Terminology
The precedence for a change in terminology is evidenced by change from ALK to LASIK
There is a need to differentiate iLASIK and similar technologies from LASIK and Z-LASIK
Side effect / complication statistics from earlier technologies are not applicable to iLASIK
Consumers need to be able to compare “apples to apples”