Transcript Pentacam Evaluation Of Corneal Parameters After Descemet

Evaluation of Corneal Parameters and
Spherical Aberration After DSAEK
Measured with Pentacam System
Orkun Muftuoglu, Pawan Prasher,
R. Wayne Bowman, Steven M. Verity, H.
Dwight Cavanagh, James P. McCulley
V .Vinod Mootha MD
University of Texas Southwestern Medical Center at Dallas, Texas
Financial Disclosure
UT Southwestern Medical Center & Aston
Ophthalmology Clinic, Dallas, TX.
► Drs. Bowman, Verity, and McCulley receive consultant
reimbursement from Alcon Inc.
► Dr. Cavanagh receives research reimbursements from
Ciba Inc and Menion Inc.
► None of the authors have financial interest in the
subject matter of this poster.
► Acknowledgements: Supported in part by an
unrestricted research grant from Research to Prevent
Blindness, Inc., New York, New York.
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Introduction
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DSAEK is a technique for selective replacement of dysfunctional
endothelium
 Rapid recovery of vision
 Minimal induced astigmatism and anisometropia
 Enhanced resistance to trauma
 Less risk of expulsive choroidal hemorrhage
 Fewer ocular surface problems
Despite favorable visual outcomes, fewer patients than expected
achieve BCVA of 20/20.
Probable limiting factors: subepithelial scarring, interface changes,
increased corneal thickness and increased higher order aberrations
Hyperopic shift- Anatomical changes induced to posterior corneal
surface???
Purpose
► Compare
corneal parameters of the eyes that
underwent DSAEK with age-matched controls
using rotating Scheimpflug imaging system
Materials and Methods
32 eyes (28 patients) who underwent DSAEK
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32 eyes (32 patients) age-matched controls (no previous ocular surgery)
Pentacam
 Study group had Scheimpflug images (Pentacam, Oculus, Germany) taken after 3 months
post-operatively
 Scheimpflug camera and a monochromatic light source
 The system rotates 180 degrees and takes 25-50 images of the anterior segment in about 2
seconds
 Calculates a 3-dimensional model of the anterior eye segment from as many as 25,000 true
elevation points
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Paremeters evaluated
 Mean anterior keratometry (Ka)
 Mean posterior keratometry (Kp)
 Mean anterior radius of curvature (Ra)
 Mean posterior radius of curvature (Rp)
 True net power (TNP)
 Central corneal thickness (CCT)
 Corneal volume (CV)
 Keratometric Power Deviation (KPD)
 Mean anterior and posterior astigmatism
 Equivalent K Readings (EKR) in 2, 4 and 6mm zone
 HOAs data up to 6th order from anterior and posterior surface in the central 6.0 mm zone
 Corneal densitometry
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DSAEK- 16 eyes
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Phacoemulsification with DSAEK- 14 eyes
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DSAEK with IOL exchange- 2 eyes
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17 clear corneal and 15 scleral tunnel
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Graft size was 8.0mm or larger in all cases
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Results
Visual Acuity
logmar (Snellen)
N
Minimum
Maximum
Mean
Std.
Deviation
32
0
(20/20)
0.60
(20/80)
0.23
(20/30)
0.14
Mean Age
Male
Female
DSAEK
70.1 ± 10.2 years
(49 to 87)
17
15
Controls
69 ± 7 years
(58 to 83)
16
16
Comparison between DSAEK and controls
DSAEK
Control
p
Ra
7.93±0.3
7.73±0.27
0.11
Rp
5.91±0.47
6.45±0.31
0
Ka
42.53±1.52
43.6±1.62
0.009
Kp
6.8±0.55
6.2±0.31
0
True net power
40.55±1.79
42.49±1.57
0
Pachymetry
627.75±46.41
552.53±34.54
0
Volume
72.9±7.77
58.2±4.42
0
KPD
1.89±0.78
1.23±0.27
0
EKR-2mm
41.64±1.89
43.39±1.52
0
EKR-4mm
42.1±1.73
43.77±1.52
0
EKR-6mm
43.03±1.72
44.29±1.44
0.003
Ant astigmatism
0.13±1.77
0.1±0.87
0.717
Post astigmatism
(-1.25±1.4)
0.26±0.28
0.016
P* = Mann-Whitney U test
Cornea HOAs 6mm
Anterior cornea
DSAEK
CONTROL
Total HOA
3.165 ± 1.354
2.15 ± 0.65
Z31
0.590 ± 0.426
Z33
Z40
Difference
% Difference
P*
1.01
47
0.001
0.409 ± 0.223
0.181
44
0.045
0.313 ± 0.323
0.154 ± 0.103
0.158
102
0.01
0.730 ± 0.264
0.667 ± 0.326
0.063
9
0.398
*Mann-whitney U test
All data are mean ± SD (range)
Posterior cornea DSAEK
CONTROL
Difference
% Difference
P*
Total HOA
19.284 ± 8.413
4.414 ± 0.788
14.874
338
<0.001
Z31
3.419 ± 1.875
0.739 ± 0.424
2.679
362
<0.001
Z33
2.719 ± 1.765
0.375 ± 0.232
2.344
625
<0.001
Z40
1.763 ± 1.430
0.823 ± 0.296
0.94
114
<0.001
Anterior
Control
Posterior
DSAEK
VA : 20 / 25
Corneal Densitometry
DSAEK
Control
p
Anterior
48.07±15.9
27.58±2.73
<0.001
Posterior
30.08±7
19.86±2.9
<0.001
P* = Mann-Whitney U test
Discussion
DSAEK surgery► Creation of a new steeper endothelial surface
► Meniscus shaped endothelial graft
► Alteration of physiological relationship between anterior and posterior surface
► Placido based imaging systems could produce erroneous measurements of corneal power
► Measures both anterior and posterior surface
► Calculates true net power based on thick lens formula
► Incorporates refractive indices at each interface along with anterior and posterior curvature and
corneal thickness
► Has been shown to be useful in studying changes in posterior curvature and give repeatable
measurements of corneal thickness- the parameters most affected in DSAEK
Changes induced by DSAEK
► Increased corneal thickness and volume
 additional stromal tissue
► Lower radius of curvature of posterior surface (relative steepening)
 Meniscus shaped graft thicker in the periphery
► Higher radius of curvature of anterior surface (relative flattening)
 Wound related?
 Alteration of curvature on resolution of bullous changes??
► Lower true net power in DSAEK corneas
Conclusions
► Pentacam
measurements show lower true
net power in DSAEK as compared to
controls likely due to
 increased posterior curvature (increased minus
lens effect)
 Decreased anterior curvature (decreased plus
lens effect)??
► Spherical
surgery.
aberration is variable after DSAEK