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

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; 29:2419-2429 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

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)

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 Vertical Assimetry Pachmetry Corneal Thickness profile http://ascrs2008.conferencefilms.com/atables.wcs?entryid=414765 Corneal Thickness profile

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 Randlemann_risk score

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 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 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 - 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 - 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

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