Improvement Strategies: Biometry, The Promise of...
Transcript of Improvement Strategies: Biometry, The Promise of...
Biometry for Premium IOLs 2016
Jack T. Holladay MD MSEE FACS Page 1 of 6
4/10/2016 JTH 1
Improvement Strategies: Biometry,
Topography, Power Calcs to
Ref Surprises
Jack T. Holladay, MD, MSEE, FACSClinical Professor of Ophthalmology
Baylor College of MedicineHouston, Tx 4/10/2016 JTH 2
The Promise of No Glasses
or Contact Lenses !
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Requirements
Accurate Biometry – Optical
(IOL Master or LenStar)
Accurate K’s- Repeatable
4th Generation Formula (WTW)
Personalized Lens Constant
Eliminate Corneal Astigmatism4/10/2016 JTH 8
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Subtractfrom Ascanmeasured
Axial Length~ 0.8 mm
Zeiss - IOL Master - 2000Zaldivar-Holladay JCRS May 2000
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J Cataract Refract Surg 2011; 37:2018–2027
Biometry for Premium IOLs 2016
Jack T. Holladay MD MSEE FACS Page 2 of 6
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Linear Regression to compensate for AVERAGE Index of Refraction in Long Eyes
Measured 36 34 mm
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Requirements
Accurate Biometry – IOL Master
Accurate K’s- Repeatable
4th Generation Formula (WTW)
Personalized Lens Constant
Eliminate Corneal Astigmatism
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IOL Power Calculations Pentacam can measure FRONT &
BACK SURFACE POWER
Can Calculate: Equivalent K-Reading (EKR)
65% Mean, Peak & Average
NET POWER4/10/2016 JTH 14
EKR Reports Keratometry value but adjusts
for Back Surface Power from Normal (Current IOL Formulas)
If corneal front surface is 7.5 mm (45 D), but if back surface -0.3 D > normal:
EKR = 45.0 – 0.3 = 44.7 D
Note: Net Power = 43.3 D
4/10/2016 JTH 15Holladay Report Equivalent K-Reading
EKR
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Biometry for Premium IOLs 2016
Jack T. Holladay MD MSEE FACS Page 3 of 6
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IOL Calcs – Abnormal Cornea(Use 65% MEAN EKR) Post Refractive Surgery
Post PKP
Keratoconus
Corneal Scar
Any Irregular Astigmatism4/10/2016 JTH 24
Use 65% Mean EKR( @ 4.5, 4 & 3 mm zones)
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Normal LASIK RK41 to 44 D3 D Range
36 to 41 D5 D Range
32 to 45 D13 D Range
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POST LASIK
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Post LASIK CALC Kmean = 39.8 D
Used 39.8 D => SEQ = +1.12 D
(+1.00 + 0.25 X 155 = 20/20)
65% mean = 38.8 D => +0.12 D
Use 65% mean K4/10/2016 JTH 30
Conclusions EKR – Use 65% Mean for all
IOL Calcs
Look @ smaller zones than 4.5 mm if pupil very small
(< 3.0 mm in dim light)
Biometry for Premium IOLs 2016
Jack T. Holladay MD MSEE FACS Page 4 of 6
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Requirements
Accurate Biometry – IOL Master
Accurate K’s- Repeatable
4th Generation Formula (WTW)
Personalized Lens Constant
Eliminate Corneal Astigmatism4/10/2016 JTH 32
Vergence Formula
IOLAL ELP
DPostRxV
K(Post R)ELP
1336 13361336
10001000
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CONCLUSION: 9 EYESA
nter
ior
Seg
men
t Siz
e
Axial LengthShort Normal Long
Large
Normal
Small
Megalocornea Large Eye
+ axial Megalocornea Buphthalmos
hyperopia Megalocornea
+ axial myopia
axial hyperopia normal axial myopia
Small eye Microcornea
Nanophthalmia Microcornea + axial mopia
(20%)
(10%)(2%)
(2%)
(80%) (96%) (90%)
(0%)
(0%)
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Measurements taken forPredictors of ELP
Axial Length
Average K (Pre Ref)
Horizontal WTW
ACD
LT
Pre-opRefraction
Age4/10/2016 JTH 36
FORMULA PERFORMANCE
15 20 25 300
12
34
56
Axial Length (mm)Mea
n A
bsol
ute
Err
or (
D)
Holladay 1Hoffer QSRK/THolladay 2
N = 997
Biometry for Premium IOLs 2016
Jack T. Holladay MD MSEE FACS Page 5 of 6
4/10/2016 JTH 37
Requirements
Accurate Biometry – IOL Master
Accurate K’s- Repeatable
4th Generation Formula (WTW)
Personalized Lens Constant
Eliminate Corneal Astigmatism4/10/2016 JTH 38
Personalized Lens Constant Never use Manufacturer’s Constant
except to start 20 to 40 cases and continue Factors IOL Style Lens placement Post op medications Biometer, keratometer, …
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Requirements
Accurate Biometry – IOL Master
Accurate K’s- Repeatable
4th Generation Formula (WTW)
Personalized Lens Constant
Eliminate Corneal Astigmatism
TORIC IOL Calculations Commercial Calculators use a constant ratio (1.46) for
the corneal cylinder to the IOL cylinder Exact Calculation depends on IOL SEQ Power and ELP
… to correct 2D of corneal astigmatism 10 D IOL => 3.5 D Cylinder 22 D IOL => 2.9 D Cylinder 34 D IOL => 2.4 D Cylinder
A 1.1 D difference from 10 D to 34 D!
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Toric Optimization
Biometry for Premium IOLs 2016
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PREOP 6 D Toric IOLLEF
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PREOP 6 D Toric IOL -- ODLEF
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PREOP 6 D Toric IOL -- OSLEF
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!Thank You!