e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD Allan Luz MD
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 equipmentsDr. Ambrosio is a consultant to Oculus Gmb
Dra. Francesconi is a consultant to B&L
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
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 removalFactors 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 resultsThe need for enhanced methods for screenning
The identification of ectatic corneas is critical because this is the most important risk factor for iatrogenic ectasia
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
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)
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
Corneal Thickness Profile and Vertical Assymetry
PachymetryCorneal 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
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
Methods
http://ascrs2008.conferencefilms.com/atables.wcs?entryid=414765
Vertical Assimetry Pachmetry
Corneal Thickness profile
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
Results: Ectasia Risk Score SystemCase 01 OD
24 years with preoperative pachymetry 527µm
MRSE -4.625. Underwent LASIK with femtosecond
laser to perform flap. RSB was 352.6µm
Risk score: low riskDeveloped Ectasia
Case 01 OS24 years with preoperative
pachymetry 523µmMRSE -6.625. Underwent LASIK with femtosecond
laser to perform flap. RSB was 315.9µm
Risk score: low riskDeveloped Ectasia
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
Results: Ectasia Risk Score SystemCase 02 OD
39 years with preoperative pachymetry 528µm
MRSE -4.0. Underwent LASIK with femtosecond
laser to perform flap. RSB was 338.1µm
Risk score: low riskDeveloped Ectasia
Case 02 OS39 years with preoperative
pachymetry 525µmMRSE -2.875. Underwent LASIK with femtosecond
laser to perform flap. RSB was 343.6µm
Risk score: low riskDeveloped Ectasia
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
Results: Corneal Thickness Profile - CTP
24 years with preoperative pachymetry 527µmMRSE -4.625. Underwent LASIK with femtosecondlaser to perform flap. RSB was 352.6µmRisk 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.
24 years with preoperative pachymetry 523µmMRSE -6.625. Underwent LASIK with femtosecondLaser to perform flap. RSB was 315.9µmRisk score: low risk Developed Ectasia
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.
1 2 3 4 5 6 70
5
10
15
20
25
CTP Case 01 OD
Circles from thinnest
Thick
ness
Per
cent
age
1 2 3 4 5 6 705
1015202530
CTP Case 01 OS
Cicles from thinnestThick
ness
Per
cent
age
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
Results: Vertical Assymetry Pachymetry- VAP
24 years with preoperative pachymetry 527µmMRSE -4.625. Underwent LASIK with femtosecondlaser to perform flap. RSB was 352.6µmRisk score: low risk Developed Ectasia
24 years with preoperative pachymetry 523µmMRSE -6.625. Underwent LASIK with femtosecondLaser to perform flap. RSB was 315.9µmRisk score: low risk Developed Ectasia
There is an ascendant curve in VAP which suggests more flexible cornea.
There is a descendant curve in VAP with suggests rigid cornea.
1 2 3 4 5 6 7 805
1015202530
VAP Case 01 OD
Vertical axis cross thinnest
Supe
rior i
nfer
ior p
achm
etric
di
ffere
nces
1 2 3 4 5 6 7 80
1020304050
VAP Case 01 OS
Vertical axis cross thinnestSupe
rior i
nfer
ior p
achm
etric
di
ffere
nces
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
Results: Corneal Thickness Profile - CTP
39 years with preoperative pachymetry 528µmMRSE -4.0. Underwent LASIK with femtosecond laser to perform flap. RSB was 338.1µmRisk score: low risk Developed Ectasia
39 years with preoperative pachymetry 528µmMRSE -4.0. Underwent LASIK with femtosecondlaser to perform flap. RSB was 338.1µmRisk score: low risk Developed Ectasia
In Case 02 OD there is a normal curve in CTP.
In Case 02 OS there is an abnormal curve in CTP since the first point, which suggests CTP’s morfology alteration .
1 2 3 4 5 6 70
5
10
15
20
25
CTP Case 02 OD
Circles from thinnest
Thick
ness
Per
cent
age
1 2 3 4 5 6 70
5
10
15
20
25
CTP Case 02 OS
Circles from thinnest
Thick
ness
Per
cent
age
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
Results: Vertical Assymetry Pachymetry - VAP
39 years with preoperative pachymetry 528µmMRSE -4.0. Underwent LASIK with femtosecondlaser to perform flap. RSB was 338.1µmRisk score: low risk Developed Ectasia
39 years with preoperative pachymetry 528µmMRSE -4.0. Underwent LASIK with femtosecondlaser to perform flap. RSB was 338.1µmRisk 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.
1 2 3 4 5 6 7 8 9 10 11 120
5
10
15
20
VAP Case 02 OD
Vertical axis cross thinnestSupe
rior i
nfer
ior p
achm
etric
dif
-fe
renc
es
1 2 3 4 5 6 7 8 9 10 110
10
20
30
40
VAP Case 02 OS
Vertical axis cross thinnest
Supe
rior i
nfer
ior p
achm
etric
di
ffere
nces
e-Poster
Rio de Janeiro Corneal
Tomography andBiomechanicsStudy Group
Allan Luz MD
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
Enhanced Pachymetric analysis
( Corneal Thickness Profile and
Vertical Assymetry Pachymetry )
helps identyfing Ectasia suscetibility
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