enhanced screening for refractive candidates based on corneal tomography and biomechanics

$: Enhanced Screening for Refractive Candidates based on Corneal Tomography and Biomechanics$
Ambrósio et Ambrósio et alal

e-POSTER e-POSTER Enhanced Screening for Enhanced Screening for Refractive Candidates Refractive Candidates

based on Corneal based on Corneal Tomography and Tomography and

BiomechanicsBiomechanicsRenato Ambrósio Jr., MD, PhDRenato Ambrósio Jr., MD, PhD

Ruiz Alonso, MD; Daniela Jardim, MD; Frederico xxx, Ruiz Alonso, MD; Daniela Jardim, MD; Frederico xxx, MDMD

Marcella Salomão, MD; Simone Boghossian, MD; Marcella Salomão, MD; Simone Boghossian, MD; Bruno Fontes, MDBruno Fontes, MD

Rio de Janeiro - Brazil


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Rio de JaneiroRio de JaneiroCornealCorneal

TomograhyTomograhyandand

BiomechanicsBiomechanics Study Group Study Group

Screening Refractive Screening Refractive CandidatesCandidates

Ultrasonic Pachymetry (US-CCT) and Ultrasonic Pachymetry (US-CCT) and Placido CPlacido Corneal Topography orneal Topography have beenhave been considered the considered the “gold standard”“gold standard”

Unexplained ectasia may occur in cases considered as good candidates based on CCT and Placido´s topography

Enhanced screening with corneal Enhanced screening with corneal tomography and biomechanics provides tomography and biomechanics provides more sensitivity and specificity for more sensitivity and specificity for determining candidacy for LASIKdetermining candidacy for LASIK


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Clinical Example 1: LASIK CandidateClinical Example 1: LASIK Candidate??

32 years old, 32 years old, femalefemale

MRx OD: MRx OD: -6.00 = -1.00 x 180º, -6.00 = -1.00 x 180º, 20/15 20/15

US-CCT: 528 µmUS-CCT: 528 µm

Clinical Example 2: LASIK CandidateClinical Example 2: LASIK Candidate??

21 years old, 21 years old, malemale

MRx OS:MRx OS:-1,00 - 0,50 x 126, -1,00 - 0,50 x 126, 20/1520/15

US- CCT: 531 µmUS- CCT: 531 µm


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Example 1: “unexplained” ectasia after Example 1: “unexplained” ectasia after LASIK OSLASIK OS

Example 2: “unilateral” keratoconus ODExample 2: “unilateral” keratoconus OD


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Screening Refractive Screening Refractive CandidatesCandidates

US-CCT and US-CCT and Placido CPlacido Corneal Topography orneal Topography would would qualify cases 1 (OD) and 2 (OS) for LASIKqualify cases 1 (OD) and 2 (OS) for LASIKCase 1 had similar condition in OD when presented for LASIK, which resulted in “unexplained” ectasiaEither cases would not be considered as a good candidates for LASIK if considering topography from the contra-lateral eyeBut a bilateral presentation as in the “normalBut a bilateral presentation as in the “normal”” eyes may be the reason for many cases with eyes may be the reason for many cases with ectasia after LASIK with no identifiable risk ectasia after LASIK with no identifiable risk factors factors Purpose:Purpose: To present novel criteria To present novel criteria based on corneal tomography (CTm) and based on corneal tomography (CTm) and biomechanical measurements to screen biomechanical measurements to screen for ectasia (and for ectasia for ectasia (and for ectasia susceptibility)susceptibility)


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Ectasia SusceptibilityEctasia Susceptibility: : Conreal Tomography and BiomechanicsConreal Tomography and Biomechanics

Example 1: “unexplained” ectasia after LASIK Example 1: “unexplained” ectasia after LASIK OSOS

Example 2: “unilateral” keratoconus ODExample 2: “unilateral” keratoconus OD

CTSP and PIT: Abnormal CTSP and PIT: Abnormal SS shape shape

CRF: 8.1 mmHgCRF: 8.1 mmHg

CTSP and PIT: Tangent to 95% CI CTSP and PIT: Tangent to 95% CI Ave PI=1.2Ave PI=1.2 CRF: 7.1 mmHgCRF: 7.1 mmHg


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Corneal Tomography: Corneal Thickness Corneal Tomography: Corneal Thickness ProfilesProfiles

Average of the thickness Average of the thickness values along twenty-two values along twenty-two imaginary circles centered on imaginary circles centered on the thinnest point TP with the thinnest point TP with increased diameters at 0,4mm-increased diameters at 0,4mm-stepssteps - CTSP - CTSP

PTI - PTI - Percentage of increase Percentage of increase from the thinnest point of each from the thinnest point of each of the circles of the circles

(CT(CT@@x - TP) / TPx - TP) / TP Data is presented in a Graph Data is presented in a Graph

with 95%CI from a normal with 95%CI from a normal populationpopulation

Progression Index: average, Progression Index: average, min and maxmin and max

Thinnest Point Value, Position Thinnest Point Value, Position and Distance from the Apexand Distance from the Apex


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Corneal Tomography: Enhanced Elevation Corneal Tomography: Enhanced Elevation (Belin)(Belin)

New reference sphere New reference sphere (new-BFS) that best fits to (new-BFS) that best fits to the peripheral corneal area the peripheral corneal area excluding the central area excluding the central area with 4mm in diameter with 4mm in diameter centered on the thinnest centered on the thinnest pointpoint

The elevation map The elevation map considering the new-BFS considering the new-BFS was subtracted from the was subtracted from the elevation map with the elevation map with the standard BFS that best fits standard BFS that best fits the total corneal area. the total corneal area.

The highest difference The highest difference between the elevation maps between the elevation maps in the central 4mm area was in the central 4mm area was noted for anterior and noted for anterior and posterior corneaposterior cornea

Anterior - green is below 6 yellow is between 6 -

12, red is > 12Posterior: green is < 8 yellow is between 8 - 20, red is > 20

New-BFS enhances the cone

Standard-BFS may “hide” the cone


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Belin-Ambrósio Enhanced Ectasia Display Belin-Ambrósio Enhanced Ectasia Display

Enhanced Elevation and Pachymetric Profiles Enhanced Elevation and Pachymetric Profiles are complementary to increase sensitivity and are complementary to increase sensitivity and specificity!specificity!


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Asymmetric Keratoconus Asymmetric Keratoconus StudyStudy

Patients with keratoconus in one eye and Patients with keratoconus in one eye and normal axial (surface) topography in the contra-normal axial (surface) topography in the contra-lateral eye were collected from different centerslateral eye were collected from different centersAll cases: 25 patients (20 ♂) had Pentacam All cases: 25 patients (20 ♂) had Pentacam examexam12 patients (8 ♂) had additional biomechanical 12 patients (8 ♂) had additional biomechanical measureemnts (ORA - Reichert)measureemnts (ORA - Reichert)Average age: 30.2 (From 16 to 58) Average age: 30.2 (From 16 to 58) 88% had at least one abnormal finding on the 88% had at least one abnormal finding on the Belin/Ambrósio Enhanced Ectasia]Belin/Ambrósio Enhanced Ectasia]CRF (ORA) was lower than 8.5 mmHg in 84% of CRF (ORA) was lower than 8.5 mmHg in 84% of cases cases Hysteresis (ORA) was lower than 8.8 mmHg in Hysteresis (ORA) was lower than 8.8 mmHg in 75% of cases75% of casesNewer metrics from the ORA are under studyNewer metrics from the ORA are under study


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Enhanced Elevation and Pachy Profiles Enhanced Elevation and Pachy Profiles are Complementary are Complementary

Combination of Enhanced Elevation and Combination of Enhanced Elevation and Pachymetric Profiles add to each other in sensitivity Pachymetric Profiles add to each other in sensitivity and specificity and specificity


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Conclusions: Conclusions: Enhanced Screening Enhanced Screening for Refractive Candidates for Refractive Candidates

New diagnostic parameters based on New diagnostic parameters based on Corneal Tomography (Enhanced Corneal Tomography (Enhanced Elevation and Pachy Profiles) and Elevation and Pachy Profiles) and Corneal Biomechanics (Hysteresis, CRF Corneal Biomechanics (Hysteresis, CRF and new metrics from ORA signals) add and new metrics from ORA signals) add to to Ultrasonic Pachymetry (US-CCT) and Ultrasonic Pachymetry (US-CCT) and Placido CPlacido Corneal Topography orneal Topography to enhance to enhance screening for refractive candidatesscreening for refractive candidates

These new parameters increase These new parameters increase sensitivity and specificity for the sensitivity and specificity for the screening process and should be screening process and should be considered considered

enhanced screening for refractive candidates based on corneal tomography and biomechanics

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