Application of Quantitative Method for Prospectively Identifying

Risk for Ectasia After LASIK in Normal, Suspect,

and Ectatic Eyes Mujtaba A. Qazi, MD

Pepose Vision Institute and Department of Ophthalmology Washington University School of

MedicineSt. Louis, Missouri

Co-INVESTIGATORS:Pete Kollbaum, OD, PhD,1 Ashraf M. Mahmoud,2

Michael Twa, OD, PhD,3 & Cynthia J. Roberts, PhD,2,5

Mohinder M. Merchea, OD, PhD,6 Jay S. Pepose, MD, PhD7,8

1. Indiana University, School of Optometry

2. The Ohio State University, Department of Ophthalmology

3. University of Houston, College of Optometry

4. The Ohio State University, Department of Biomedical Engineering

5. Bausch & Lomb 6. Pepose Vision Institute 7. Washington University School

of Medicine, Department of Ophthalmology and Visual Sciences

Financial disclosures: Qazi: Alcon B; Allergan B Roberts: Reichert D,E; Ziemer A, D, E, P

Merchea: Bausch & Lomb Y Pepose: Bausch & Lomb A, D; Visiogen A

Purpose:

To compare the Randleman Ectasia Risk Factor (ERF)

Score in populations with a clinical diagnosis of

normal, suspect keratoconus, and kerectasia,

including keratoconus and post-LASIK ectasia.

Design:

Retrospective: chart review Keratoconus (KCN, n=36)

CLEK Study Criteria: Irregular Mires or Reflex; Vogt’s Striae or Fleisher ring or

Apical scar Fellow eye of Keratoconus (KCF, n=10)

No definite slit-lamp findings in study eye, with (+) CLEK criteria in contralateral eye

Keratoconus Suspect (KCS, n=44) Topographic irregularity but no slit-lamp findings in either

eye Normal (n=32) Post-LASIK Ectasia (n=9)

Design:

Ectasia Risk Score Parameters Age Central Pachymetry (CCT) Spherical Equivalent (SE) Calculated Residual Stromal Bed (RSB)

120 micron flap for all eyes

14 microns/D of SE calculated for ablation (AD)

RSB = CCT - (120 + AD) Topography

Methods: Randleman Ectasia Risk Factor (ERF) Scoring System

Age

Anterior & Posterior Elevation

Curvature (Axial, Mean, Tangential)

Pachymetry

Topography Grading System 1. Normal/symmetrical; includes round, oval, or symmetric bowtie patterns. 2. Suspicious; includes the following asymmetric patterns:

a. Asymmetric bowtie i. Asymmetric steepening in any direction less than 1.0 D ii. No skewed radial axis

b. Inferior steep/skewed radial axis i. Significant skewed radial axis with or without inferior steepening, or ii. One diopter or more of inferior steepening in some areas but an I-S value of less than 1.4.

3. Abnormal; includes keratoconus, pellucid marginal corneal degeneration, or forme fruste keratoconus with an I-S value of 1.4 or more.

Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery.. Ophthalmology. 2008 Jan;115(1):37-50.

Randleman ERF Score

Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery.. Ophthalmology. 2008 Jan;115(1):37-50.

ERF Scores

MEAN SD RANGE MEDIANP VALUE comparing

study group to NORMAL

NORMAL 1.67 1.76 0 - 6 1

Keratoconus Sustpect (no slit lamp lsigns in

either eye but)3.91 2.25 1 -9 4.0 <0.01

Keratoconus Fellow(slit lamp signs in comtralateral eye

only)

4.50 2.51 1 – 8 4.5 <0.01

Keratoconus(slit lamp signs in

study eye)9.08 4.29 3 – 16 8 <0.01

Preop parameters of Post-LASIK Ectasia

2.33 1.00 1 - 3 4.5 0.23

RESULTS In the KCNfellow (mean 2.60±1.43, range 1-4,

median 3) and PLE (2.33±1.00, 1-3, 3) groups, only the topography score was statistically significantly higher (p<0.001) than in NRM (0.39±0.50, 0-1, 0).

In PLE, 66% of eyes had skewed asymmetry and 33% had an asymmetric bowtie.

Irregular topography (1.82±1.87, 0-4, 1, p<0.001) and younger age (p=0.01) scores were statistically higher in the KCS group compared to NRM.

SUMMARY Application of the Randleman Ectasia after

LASIK Risk Score in ectatic and suspicious eyes highlights the importance of topographic analysis in the preoperative assessment of the keratorefractive surgery candidate.

Differential weighting of the topography score may enhance the efficacy of ectasia risk analysis.

The relative risk of specific topographic features should be further quantified.