Retrospective Study of 4 Cases That Developed Ectasia After LASIK (Intralase flaps) with Low-Risk Ba...
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Retrospective Study of 4 Cases That Developed Ectasia After LASIK (Intralase flaps) with Low-Risk Based on Ectasia Risk Score System.

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Allan Luz, MD

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Allan luz md

Retrospective Study of 4 Cases That Developed Ectasia After LASIK (Intralase flaps) with Low-Risk Based on Ectasia Risk Score System

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.

Allan Luz, MD

Colin Chan, MD; Michael Lawless, MD; Claudia Francesconi, MD, PhD; Frederico Guerra, MD; Renato Ambrósio Jr., MD, PhD

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


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 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

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


Ectasia risk score system

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)


Allan luz md

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


Methods

Methods

Vertical Assimetry Pachmetry

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

Corneal Thickness profile


Results ectasia risk score system

Results: Ectasia Risk Score System

Case 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 risk

Developed Ectasia

Case 01 OS

24 years with preoperative pachymetry 523µm

MRSE -6.625. Underwent LASIK with femtosecond

laser to perform flap. RSB was 315.9µm

Risk score: low risk

Developed Ectasia


Results ectasia risk score system1

Results: Ectasia Risk Score System

Case 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 risk

Developed Ectasia

Case 02 OS

39 years with preoperative pachymetry 525µm

MRSE -2.875. Underwent LASIK with femtosecond

laser to perform flap. RSB was 343.6µm

Risk score: low risk

Developed Ectasia


Results corneal thickness profile ctp

Results: Corneal Thickness Profile - CTP

24 years with preoperative pachymetry 527µm

MRSE -4.625. 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 -6.625. Underwent LASIK with femtosecond

Laser to perform flap. RSB was 315.9µm

Risk score: low risk Developed Ectasia


Results vertical assymetry pachymetry vap

Results: Vertical Assymetry Pachymetry- VAP

24 years with preoperative pachymetry 527µm

MRSE -4.625. 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 -6.625. 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.


Results corneal thickness profile ctp1

Results: Corneal Thickness Profile - CTP

39 years with preoperative pachymetry 528µm

MRSE -4.0. 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 -4.0. 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 .


Results vertical assymetry pachymetry vap1

Results: Vertical Assymetry Pachymetry - VAP

39 years with preoperative pachymetry 528µm

MRSE -4.0. 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 -4.0. Underwent LASIK with femtosecond

laser to perform flap. RSB was 338.1µm

Risk score: low risk Developed Ectasia


Discussion

Discussion

Enhanced Pachymetric analysis ( Corneal Thickness Profile and

Vertical Assymetry Pachymetry )

helps identyfing Ectasia suscetibility

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


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