Ambrósio et al e-POSTER San Diego 2007 Corneal Biomechanics, Pachymetric Progression Profile and...
-
date post
15-Jan-2016 -
Category
Documents
-
view
218 -
download
0
Transcript of Ambrósio et al e-POSTER San Diego 2007 Corneal Biomechanics, Pachymetric Progression Profile and...
Ambrósio Ambrósio et alet al
e-POSTER e-POSTER
San Diego San Diego 20072007
Corneal Biomechanics, Corneal Biomechanics, Pachymetric Progression Pachymetric Progression
Profile and Corneal Volume: Profile and Corneal Volume: Indices for Detecting Ectasia Indices for Detecting Ectasia
and Screening Refractive and Screening Refractive
CandidatesCandidates Renato Ambrósio Jr., MD, PhDRenato Ambrósio Jr., MD, PhD
Ruiz Alonso, MD; Allan Luz, MD; Daniela Jardim, Ruiz Alonso, MD; Allan Luz, MD; Daniela Jardim, MD; MD;
Marcella Salomão, MD; Simone Boghossian, MD; Marcella Salomão, MD; Simone Boghossian, MD; Bruno Fontes, MDBruno Fontes, MD
Rio de Janeiro - Brazil
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
IntroductionIntroductionUltrasonic Pachymetry (US-CCT) and Ultrasonic Pachymetry (US-CCT) and
Corneal Topography are considered the Corneal Topography are considered the “gold standard”“gold standard” for screening refractive candidates
Corneal Tomography (CTm) and Corneal Tomography (CTm) and Biomechanical Measurements provide Biomechanical Measurements provide further characterization of the cornea further characterization of the cornea beyond surface maps and single point beyond surface maps and single point thicknessthickness
PurposePurposeTo describe novel parameters, based on To describe novel parameters, based on
corneal geometry or architecture corneal geometry or architecture (tomography - CTm) and biomechanical (tomography - CTm) and biomechanical properties, for diagnosing corneal ectasia properties, for diagnosing corneal ectasia and ectasia risk (susceptibility)and ectasia risk (susceptibility)
Describe examples in which these data Describe examples in which these data had enhanced the screening process for had enhanced the screening process for refractive candidatesrefractive candidates
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
Pentacam exam, taking Pentacam exam, taking 25 rotating 25 rotating 360° Scheimpflug images, was used to 360° Scheimpflug images, was used to compute Corneal Tomography (CTm) compute Corneal Tomography (CTm) and extract architecture parameters and extract architecture parameters using using custom software from corneal custom software from corneal thickness and calculated corneal thickness and calculated corneal volume:volume:
Methods Methods
Thinnest Point (TP) Value & PositionThinnest Point (TP) Value & PositionCorneal Thickness Spatial Profile (CTSP) Corneal Thickness Spatial Profile (CTSP) Percentage of Increase of Thickness (PIT)Percentage of Increase of Thickness (PIT)Corneal Volume Distribution (CVD)Corneal Volume Distribution (CVD)Percentage of Increase in Volume (PIV)Percentage of Increase in Volume (PIV)
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
““TRUE” Thinnest Point (TP) TRUE” Thinnest Point (TP) DataData
OD OS
OD: x is positive towards nasalOS: x is positive towards temporal
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
Corneal Thickness Spatial Profile Corneal Thickness Spatial Profile (CTSP) and Percentage of (CTSP) and Percentage of
Increase of Thickness (PIT)Increase of Thickness (PIT)
Average of the thickness Average of the thickness values along twenty-two values along twenty-two imaginary circles imaginary circles centered on the thinnest centered on the thinnest point TP with increased point TP with increased diameters at 0,4mm-diameters at 0,4mm-stepssteps
Percentage of increase from the thinnest Percentage of increase from the thinnest point of each of the averages of twenty-two point of each of the averages of twenty-two imaginary circles centered on the TP using a imaginary circles centered on the TP using a simple formula:simple formula:
(CT(CT@@xx - TP) / TP - TP) / TP((x x representes the diameter of the imaginary representes the diameter of the imaginary circle)circle)
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
Corneal volume was calculated with diameters Corneal volume was calculated with diameters from 1,0 to 7,0mm with 0,5mm-steps from 1,0 to 7,0mm with 0,5mm-steps
centered on the TP to create the Corneal centered on the TP to create the Corneal Volume Distribution (CVD)Volume Distribution (CVD)
The percentage of increase of volume from the The percentage of increase of volume from the 1,0mm volume (PIV) was calculated for each 1,0mm volume (PIV) was calculated for each
position using a simple formula:position using a simple formula:
(CV (CV @@ y y - CV - CV @@ 1mm 1mm) / CV ) / CV @@ 1mm1mm
where ywhere y represents the diameter (from represents the diameter (from 1,0 to 7,0mm) from which corneal volume 1,0 to 7,0mm) from which corneal volume
was calculatedwas calculated
Corneal Volume Distribution Corneal Volume Distribution (CVD) and Percentage of (CVD) and Percentage of Increase in Volume (PIV)Increase in Volume (PIV)
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
Importance of the Pachymetric Importance of the Pachymetric Map to Map to detect the TRUE Thinnest detect the TRUE Thinnest
point point
34 years old patient, scheduled for LASIK34 years old patient, scheduled for LASIK(-5.75 -1.00 x 79)(-5.75 -1.00 x 79)
Normal Topography; US-CCT: 512 Normal Topography; US-CCT: 512 μμm m (Ave. of 5 measurements with St. Dev <3)(Ave. of 5 measurements with St. Dev <3)
Corneal Thickness Map (Pentacam): Thinnest Corneal Thickness Map (Pentacam): Thinnest Point located inferiorly to the geometrical Point located inferiorly to the geometrical center with 493 center with 493 μμm; careful regional US m; careful regional US
performed inferiorly and confirmed (495performed inferiorly and confirmed (495μμm)m)Decided to change for Surface AblationDecided to change for Surface Ablation
Error in determining the Thinnest Point by measuring US-CCT might be one Error in determining the Thinnest Point by measuring US-CCT might be one of the most important causes of “non explained” ectasia after LASIK of the most important causes of “non explained” ectasia after LASIK
(when no risk factors are detected)(when no risk factors are detected)
12% of normal patients 12% of normal patients have more than 10μm of have more than 10μm of
difference between central difference between central & thinnest points; & thinnest points;
Correlation between Correlation between Distance from central & Distance from central &
thinnest points & thinnest points & Difference (rDifference (r22 0.61) 0.61)
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
CTSP CTSP –– Spatial Distribution of Thickness Spatial Distribution of Thickness Values for Values for NormalsNormalsand and KeratoconusKeratoconus
PIT PIT –– Percentage of Increase of Thickness from Percentage of Increase of Thickness from the Thinnest Point for the Thinnest Point for NormalsNormalsand and KeratoconusKeratoconus
Corneal Thickness Spatial Profile Corneal Thickness Spatial Profile (CTSP) and Corneal Volume (CTSP) and Corneal Volume
Distribution (CVD): Study Distribution (CVD): Study ResultsResults
Ambrósio R Jr, Alonso RS, Luz A, Coca Velarde LG. Corneal-thickness spatial profile and corneal-volume distribution: tomographic indices to detect keratoconus. J Cataract Refract
Surg. 2006 Nov;32(11):1851-9.
46 eyes with mild to moderate 46 eyes with mild to moderate keratoconus and from 364 normal eyes keratoconus and from 364 normal eyes
Statistically significant differences Statistically significant differences were observed among the groups were observed among the groups (p<0.05) for all positions of CTSP, CVD (p<0.05) for all positions of CTSP, CVD and for PIT.and for PIT.
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
MethodsMethodsCorneal biomechanical properties Corneal biomechanical properties measurement was obtained using the measurement was obtained using the ORA (Ocular Response Analyzer – ORA (Ocular Response Analyzer – Reichert) which Reichert) which monitors corneal response monitors corneal response to a precise “Gaussian” air pulse, providing to a precise “Gaussian” air pulse, providing two variables:two variables:
Corneal Hysteresis (CH = p1 – p2)Corneal Hysteresis (CH = p1 – p2)Corneal Resistance Factor (CRF = p1 –Corneal Resistance Factor (CRF = p1 –[k]*p2 )[k]*p2 )
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
ORA Biomechanical ORA Biomechanical Measurements: Study ResultsMeasurements: Study Results
82 eyes with forme fruste to moderate 82 eyes with forme fruste to moderate keratoconus and from 322 normal eyes keratoconus and from 322 normal eyes
CH and CRF are statistically lower in CH and CRF are statistically lower in keratoconus than normals (p<0.05).keratoconus than normals (p<0.05).
Mean – mmHg (+/-
SD) CH CRFKeratoconus 7.81 (+/-2.25) 7.2 (+/- 2.23)
Normal 10.1 (+/-1.8) 10.0 (+/- 1.9)
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
CTSP, PIT and CH / CRF help explain CTSP, PIT and CH / CRF help explain “ectasia susceptibility” in “ectasia susceptibility” in mysteriousmysterious
casescases28 yo with progressive ectasia after LASIK in OS (1999) with 28 yo with progressive ectasia after LASIK in OS (1999) with no identifiable risk factorsno identifiable risk factors; c; central flap thickness: 159 µm entral flap thickness: 159 µm and residual stromal bed: 270 µm and residual stromal bed: 270 µm
OD remained stable over 7 years would still OD remained stable over 7 years would still be considered a good LASIK candidate be considered a good LASIK candidate based on topography and US-CCT.based on topography and US-CCT.
Normal Pre Op TopographyNormal Pre Op TopographyMRx: -6.00 = -1.00 x 180MRx: -6.00 = -1.00 x 180oo, 20/15 - OD , 20/15 - OD -5.75 = -1.25 x 10-5.75 = -1.25 x 10oo, 20/15 - , 20/15 - OSOSUS-CCT: 528µm OUUS-CCT: 528µm OU
These parameters have been critical for clinical decison for borderline These parameters have been critical for clinical decison for borderline LASIK candidatesLASIK candidates
OD (non operated eye)OD (non operated eye) Borderline CTSP and PIT & Borderline CTSP and PIT & low CH (9.8) and CRF (8.1) low CH (9.8) and CRF (8.1)
High “ectasia High “ectasia susceptibility”susceptibility”
Progressive Ectasia OSProgressive Ectasia OS
Ambrósio et alAmbrósio et al
e-POSTER e-POSTER
San DiegoSan Diego
20072007
Novel Parameters can also Novel Parameters can also increase specificity for LASIK increase specificity for LASIK
screening! screening! 23 yo LASIK candidate, mild asymmetry on the axial maps23 yo LASIK candidate, mild asymmetry on the axial maps
Normal CTSP and PIT and above average CRF (13.1/12.2 mmHg) and CH Normal CTSP and PIT and above average CRF (13.1/12.2 mmHg) and CH (12.1/12.0 mmHg ) help us to decide doing LASIK, with excellent and stable results (12.1/12.0 mmHg ) help us to decide doing LASIK, with excellent and stable results in both eyes (FU > 1year). in both eyes (FU > 1year).
MRx: - 9.50 -1.75 x 3º OD – MRx: - 9.50 -1.75 x 3º OD – 20/60 20/60 - 7.25 -1.25 x 179º - 7.25 -1.25 x 179º
OS – 20/20OS – 20/20
US-CCT: 565 / 545 US-CCT: 565 / 545 µm (OD / µm (OD / OS)OS)
ODODUCVA: 20/50UCVA: 20/50
OSOSUCVA: 20/20UCVA: 20/20
ODOD OSOS
Pre Op. CTSP and PIT OD / OSPre Op. CTSP and PIT OD / OS Dif. Axial Maps OD / OSDif. Axial Maps OD / OS
Pre Op. ORAPre Op. ORA normal OUnormal OU