Ambrósio et al
e-POSTER
Enhanced Screening for Refractive
Candidates based on Corneal
Tomography and Biomechanics
Renato Ambrósio Jr., MD, PhD
Ruiz Alonso, MD; Daniela Jardim, MD; Frederico xxx, MD
Marcella Salomão, MD; Simone Boghossian, MD; Bruno Fontes, MD
Rio de Janeiro - Brazil
Ambrósio et al
e-POSTER
Screening Refractive Candidates
Ultrasonic Pachymetry (US-CCT) and Placido
Corneal Topography have been considered the
“gold standard”
Unexplained ectasia may occur in cases
considered as good candidates based on CCT and
Placido´s topography
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
Enhanced screening with corneal tomography and
biomechanics provides more sensitivity and
specificity for determining candidacy for LASIK
Clinical Example 1: LASIK Candidate?
Ambrósio et al
e-POSTER
32 years old, female
MRx OD:
-6.00 = -1.00 x 180º, 20/15
US-CCT: 528 µm
Clinical Example 2: LASIK Candidate?
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
21 years old, male
MRx OS:
-1,00 - 0,50 x 126, 20/15
US- CCT: 531 µm
Example 1: “unexplained” ectasia after LASIK OS
Ambrósio et al
e-POSTER
Example 2: “unilateral” keratoconus OD
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
Screening Refractive Candidates
Ambrósio et al
e-POSTER
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
US-CCT and Placido Corneal Topography would
qualify cases 1 (OD) and 2 (OS) for LASIK
Case 1 had similar condition in OD when presented
for LASIK, which resulted in “unexplained” ectasia
Either cases would not be considered as a good
candidates for LASIK if considering topography
from the contra-lateral eye
But a bilateral presentation as in the “normal” eyes
may be the reason for many cases with ectasia after
LASIK with no identifiable risk factors
Purpose: To present novel criteria based on corneal
tomography (CTm) and biomechanical measurements
to screen for ectasia (and for ectasia susceptibility)
Ambrósio et al
e-POSTER
Ectasia Susceptibility:
Conreal Tomography and Biomechanics
Example 1: “unexplained” ectasia after LASIK OS
CTSP and PIT: Abnormal S shape
CRF: 8.1 mmHg
Example 2: “unilateral” keratoconus OD
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
CTSP and PIT: Tangent to 95% CI
Ave PI=1.2
CRF: 7.1 mmHg
Corneal Tomography: Corneal Thickness Profiles
Ambrósio et al
e-POSTER
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
Average of the thickness values along
twenty-two imaginary circles centered on
the thinnest point TP with increased
diameters at 0,4mm-steps - CTSP
PTI - Percentage of increase from the
thinnest point of each of the circles
(CT@x - TP) / TP
Data is presented in a Graph with
95%CI from a normal population
Progression Index: average, min and max
Thinnest Point Value, Position and
Distance from the Apex
Corneal Tomography: Enhanced Elevation (Belin)
Ambrósio et al
e-POSTER
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
New reference sphere (new-BFS)
that best fits to the peripheral corneal
area excluding the central area with
New-BFS enhances the cone
4mm in diameter centered on the
thinnest point
The elevation map considering the
new-BFS was subtracted from the
Standard-BFS may “hide” the cone
elevation map with the standard BFS
that best fits the total corneal area.
The highest difference between the
elevation maps in the central 4mm
area was noted for anterior and
posterior cornea
Anterior - green is below 6
yellow is between 6 - 12, red is > 12
Posterior: green is < 8
yellow is between 8 - 20, red is > 20
Belin-Ambrósio Enhanced Ectasia Display
Ambrósio et al
e-POSTER
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
Enhanced Elevation and Pachymetric Profiles are
complementary to increase sensitivity and specificity!
Asymmetric Keratoconus Study
Ambrósio et al
e-POSTER
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
Patients with keratoconus in one eye and normal axial
(surface) topography in the contra-lateral eye were
collected from different centers
All cases: 25 patients (20 ♂) had Pentacam exam
12 patients (8 ♂) had additional biomechanical
measureemnts (ORA - Reichert)
Average age: 30.2 (From 16 to 58)
88% had at least one abnormal finding on the
Belin/Ambrósio Enhanced Ectasia]
CRF (ORA) was lower than 8.5 mmHg in 84% of
cases
Hysteresis (ORA) was lower than 8.8 mmHg in 75% of
cases
Newer metrics from the ORA are under study
Ambrósio et al
e-POSTER
Rio de Janeiro
Corneal
Tomograhy
and
Biomechanics
Study Group
Enhanced Elevation and Pachy Profiles
are Complementary
Combination of Enhanced Elevation and Pachymetric Profiles add
to each other in sensitivity and specificity
Ambrósio et al
e-POSTER
Conclusions: Enhanced Screening for
Refractive Candidates
New diagnostic parameters based on Corneal
Tomography (Enhanced Elevation and Pachy
Profiles) and Corneal Biomechanics (Hysteresis, CRF
and new metrics from ORA signals) add to Ultrasonic
Pachymetry (US-CCT) and Placido Corneal
Topography to enhance screening for refractive
candidates
Rio de Janeiro
Corneal
Rio
de Janeiro
Tomograhy
Corneal
and
Tomograhy
Biomechanics
andGroup
Study
Biomechanics
Study Group
These new parameters increase sensitivity and
specificity for the screening process and should be
considered