1. Retrospective Study of 4 Cases That Developed Ectasia After LASIK (Intralase flaps) with Low-Risk Based on Ectasia Risk Score System
Allan Luz, MD
Colin Chan, MD; Michael Lawless, MD; Claudia Francesconi, MD, PhD; Frederico Guerra, MD; Renato Ambrósio Jr., MD, PhD
Purpose: To evaluate the preoperative corneal thickness profiles (CTP) and vertical assymetry pachymetry (VAP) of patients who developed unexplained ectasia after LASIK based on traditional corneal topography and pachymetry screening.
Financial Disclosure:
Authors do not have financial or commercial interest in mentioned equipments
Dr. Ambrosio is a consultant to Oculus Gmb
Dra. Francesconi is a consultant to B&L

2. The need for enhanced methods for screenning
One of the most serious complication of LASIK is progressive thinning and ectasia of the laser-ablated corneal tissue
The factors thought to be responsible are preexisting corneal pathology primarily in the form of keratoconus (forme fruste keratoconus) or mechanical instability produced by weakening the residual stromal bed due to excessive tissue removal
Factors that have been report to identify an increased risk for developing corneal ectasia after laser in situ keratomileusis (LASIK) include preoperative topographic abnormality , low residual stroma bed (RSB) thickness, young age, thin cornea and high myopia
Mysteries of Iatrogenic Keratoectasia
There are important mysteries related to ectasia after refractive corneal procedures. There are cases with no risk factors that develop ectasia and there are cases with risk factors that are stable with good results
RAO_ectasia
Binder OS. Ectasia after laser in situ keratomileusis. J Cataract Refract Surg 2003; 29:
Randlemann_risk score
Comprehensive corneal thickness evaluation_ref.36-40
The need for enhanced methods for screenning
The identification of ectatic corneas is critical because this is the most important risk factor for iatrogenic ectasia

3. Ectasia Risk Score System
The following variables determine the risk score:
Topographic pattern, predicted residual stromal bed (RSB) thickness, age, preoperative corneal thickness (CT) and manifest refraction spherical equivalent (MRSE)

4. Corneal Thickness Profile and Vertical Assymetry Pachymetry
Corneal Thickness Profile (CTP): Percentage of increase of average of the thickness values along seven circles centered on the thinnest point
Vertical Assymetry Pachmetry (VAP): Differences among superior and inferior pachymetry values on vertical axis through the thinnest point

5. Methods Vertical Assimetry Pachmetry Corneal Thickness profile
Corneal Thickness profile

6. Results: Ectasia Risk Score System
Case 01 OD
24 years with preoperative pachymetry 527µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 352.6µm
Risk score: low risk
Developed Ectasia
Case 01 OS
24 years with preoperative pachymetry 523µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 315.9µm
Risk score: low risk
Developed Ectasia
Randlemann_risk score

7. Results: Ectasia Risk Score System
Case 02 OD
39 years with preoperative pachymetry 528µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 338.1µm
Risk score: low risk
Developed Ectasia
Case 02 OS
39 years with preoperative pachymetry 525µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 343.6µm
Risk score: low risk
Developed Ectasia

8. Results: Corneal Thickness Profile - CTP
24 years with preoperative pachymetry 527µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 352.6µm
Risk score: low risk Developed Ectasia
In Case 01 OD, the curve is on the superior limit of normal curve, but between points 6-7 there is an abrupt decrease of the curve which suggests CTP’s morfology alteration.
In Case 01 OS, the CTP curve is an abnormal curve since the fifth point of CTP’s analysis, which suggests CTP’s morfology alteration.
24 years with preoperative pachymetry 523µm
MRSE Underwent LASIK with femtosecond
Laser to perform flap. RSB was 315.9µm
Risk score: low risk Developed Ectasia

9. Results: Vertical Assymetry Pachymetry- VAP
24 years with preoperative pachymetry 527µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 352.6µm
Risk score: low risk Developed Ectasia
There is an ascendant curve in VAP which suggests more flexible cornea.
24 years with preoperative pachymetry 523µm
MRSE Underwent LASIK with femtosecond
Laser to perform flap. RSB was 315.9µm
Risk score: low risk Developed Ectasia
There is a descendant curve in VAP with suggests rigid cornea.

10. Results: Corneal Thickness Profile - CTP
39 years with preoperative pachymetry 528µm
MRSE Underwent LASIK with femtosecond laser to perform flap. RSB was 338.1µm
Risk score: low risk Developed Ectasia
In Case 02 OD there is a normal curve in CTP.
39 years with preoperative pachymetry 528µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 338.1µm
Risk score: low risk Developed Ectasia
In Case 02 OS there is an abnormal curve in CTP since the first point, which suggests CTP’s morfology alteration .

11. Results: Vertical Assymetry Pachymetry - VAP
39 years with preoperative pachymetry 528µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 338.1µm
Risk score: low risk Developed Ectasia
There is an ascendant curve in VAP which suggests
flexible cornea.
There is an ascendant curve in VAP with suggests
flexible cornea.
39 years with preoperative pachymetry 528µm
MRSE Underwent LASIK with femtosecond
laser to perform flap. RSB was 338.1µm
Risk score: low risk Developed Ectasia

12. Enhanced Pachymetric analysis ( Corneal Thickness Profile and
Vertical Assymetry Pachymetry )
helps identyfing Ectasia suscetibility
Discussion
This study shows that indices generated from corneal thickness meansurement over the entire cornea can identify ectasia suscetibility
Thereby increases the safety for screening
refractive surgery candidates