allan luz, md

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



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



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



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

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Allan Luz MD

Methods

http://ascrs2008.conferencefilms.com/atables.wcs?entryid=414765

Vertical Assimetry Pachmetry

Corneal Thickness profile

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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



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Allan Luz MD

Results: Ectasia Risk Score SystemCase 02 OD

39 years with preoperative pachymetry 528µm

MRSE -4.0. Underwent LASIK with femtosecond



Case 02 OS39 years with preoperative

pachymetry 525µmMRSE -2.875. Underwent LASIK with femtosecond



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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



Allan Luz MD

Results: Vertical Assymetry Pachymetry- VAP


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



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


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


Thick

ness

Per

cent

age

1 2 3 4 5 6 70

5

10

15

20

25

CTP Case 02 OS


Thick

ness

Per

cent

age

e-Poster



Allan Luz MD

Results: Vertical Assymetry Pachymetry - VAP



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



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

allan luz, md

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