# IC-08_Koch_Handout

Document Sample

```					Financial Disclosure
I have a financial interest with the following
companies:

Abbott Medical Optics
Alcon
Calhoun Vision
NuLens
Optimedica
Optivue
IOL power calculations in
post-LASIK/PRK eyes

Douglas D. Koch, M.D.
Cullen Eye Institute,
Baylor College of Medicine,
Houston, TX
Challenges
   Difficulties in determining true corneal
refractive power
   Keratometric inaccuracy
   Invalid use of effective refractive index of
cornea (1.3375)
   Problems in 3rd and 4th generation IOL
formulas
   Inaccurate estimation of ELP
   Exception: Haigis formula
So many formulas. . So we developed:
http://www.ascrs.org/
IOL power calculation
Prior myopic-LASIK/PRK
Double-K
and Haigis-L
formulas

3 categories of
formulas
3 categories

“Gold” standard     Use a fraction
KEY – accurate        of ∆MR
historical data    Data error ↓    Rely only on
Data error 1:1     to 20 – 30%      current data
ratio
Pop-up
windows
explain
methods
used
Prior
hyperopic-
LASIK/PRK
Prior RK
Monthly visits to the calculator in 2010

9,000                                                                                 8,249
7,853                                                 7,666
8,000                                                                                         7,257
7,218                                 7,105
6,570                   6,758 6,825           6,791
7,000                                                 6,369
6,173
6,000
5,000
4,000
3,000
2,000
1,000
0
Jan    Feb     Mar     Apr     May   Jun      Jul    Aug     Sep     Oct     Nov     Dec
Patients

   2 study centers
   Consecutive cases of IOL implantation in
eyes with prior myopic-LASIK
   SN60WF
   72 eyes of 57 patients included
   Mean age: 58 ± 8 years (range 42 to 77
years)
   Myopic LASIK correction: 5.10 ± 2.55 D
(range 0.98 to 11.21 D)
Methods

   IOL prediction error
   = IOL implanted – IOL calculated
   Negative value  myopic results
   Consistency of prediction performance
   F-test for variances
0.0
2.0
4.0

-4.0
-2.0

A
A
A
A
S

Clinical History

A
A
A

Feiz-Mannis
A
A

Corneal Bypass

A

A

A

Wang-Koch-Maloney

Shammas
A

Haigis-L
A
A
A
A

Average IOL power
Variances of IOL prediction errors (SD2)
- consistency of performance
Pre-LASIK Ks + ∆ MR
Clinical History             2.06
Feiz-Mannis                  2.53
Corneal Bypass               1.99
∆ MR
No prior data
Wang-Koch-Maloney            0.68
Shammas                      0.66
Haigis-L                     0.66
* Significant differences (all P<0.05 with
Bonferroni correction)
Refractive prediction error
± 0.5                      Proposed UK NHS
Methods                            D         ± 1.0 D        benchmark in normal
Pre-LASIK Ks + ∆MR*                                               eyes*:
Clinical History                 44          69               85% ±1.0 D
Feiz-Mannis                      37          60
55% ±0.5 D
Corneal Bypass                   37          68
∆MR
in normal
eyes but
No prior data                                                       latest
Wang-Koch-Maloney                 58          96                  standards
Shammas                           60          90
Haigis-L                          60          94
*Significant lower % with historical methods (P<0.05). Gale RP, et al.
Benchmark standards for refractive outcomes after NHS cataract
surgery. Eye. 2009;23:149-52
Summary

   Using double-K Holladay 1 formula
   Greater prediction errors and variances with
methods requiring Pre-LASIK Ks and ∆MR
   Use 100% of historical data
   Superior and essentially equivalent results
with:
   Methods using a fraction of ∆MR and
   Methods using no prior data
Optical coherence tomography (OCT)

   RTVue-CAM: an Fourier domain OCT
system for both retinal and corneal
imaging
RTVue with CAM
module
Net Corneal Power (NCP):

Combines anterior & posterior
curvature measurements from OCT
meridional scans

1.5mm                  1.5mm

n0 = 1
D

n1 = 1.376

Rp                     Ra

n2 = 1.336

Kp 
n2  n1          n1  n0
Ka 
Rp               Ra
Evaluation of OCT-based formula
   IOL power calculation in post-LASIK
eyes
 12 eyes at Cullen Eye Institute
 8 eyes at Doheny Eye Institute
 Refractive correction: -4.04 ± 3.60 D
(range -0.88 to -9.81 D)
OCT-based IOL power formula
ELP = 0.711 * (AL – ACD) – 0.25 * Pp + 0.623 * ALadj + pACD – 8.11
Where
AL = axial eye length (mm)
ACD = Anterior chamber depth (mm)
Pp = posterior corneal power (D)
ALadj = sqrt(AL)                 if AL < 24.4mm
sqrt(AL+0.8*(AL-24.4)),  if AL > 24.4mm
pACD = personalized ACD (ACD-constant)

*Tang M, Li Y, Huang D. An Intraocular Lens Power Calculation Formula Based on Optical Coherence
Tomography: a Pilot Study. J Refract Surg. 2010;26(6):430-437
Refractive prediction error

Keratometry   Best IOL   Prediction     Range         MAE    Adjusted
Method      Formula    Error (D)       (D)          (D)    MAE (D)

IOL-Master    Haigis-L    -0.23 ±     (-1.93, 1.30)   0.66    0.65*
0.83

OCT         OCT-       -0.01 ±     (-0.85, 1.79)   0.56    0.56*
based        0.70

*P=0.65, n = 20 eyes of 15 subjects.
Refractive prediction error

Haigis-L     OCT formula
8

6                                                     Within 0.5D:
# of eyes

•Haigis-L: 11/20
4                                                     •OCT: 10/20

2                                                     Within 1D:
•Haigis-L: 15/20
0                                                     •OCT: 19/20

Predicted – Actual Postoperative Refraction (D)
Summary

   Limitation:
   Small numbers
   Performance of OCT-based IOL formula was
not compared to many methods on the
ASCRS calculator

   Further studies desirable
Recent study

   Accuracy of Galilei in IOL power
calculation in eyes with prior myopic
LASIK/PRK
   Consecutive cases of IOL implantation
between April 08 to Feb. 11
Patients

   19 eyes of 16 patients had all
historical data
 MyopicLASIK correction: 4.28 ± 2.61
D (range 0.88 to 8.50 D)
Refractive MAE with all methods (n=19)
1.2

0.99
1.0   0.94                             0.93

0.78
0.8                                                                                                                                                                           0.75
0.72 0.70
0.65

MAE (D)

0.6                                                                        
0.52                                          0.57 0.57
0.47
0.42 0.44
0.4

0.2

0.0

Haigis-L
Shammas

TCP-5mm
TCP-4mm
TCP-2mm

TCP-3mm
Feiz-Mannis

Wang-Koch-Maloney
Clinical History

Corneal Bypass

Galilei

Significant greater MAE with methods using pre-LASIK
Ks and ∆MR than those with  (all P<0.05)
Refractive prediction error with all methods
(n=19)                                     UK NHS
100                                                                                                                                                          95                                                     benchmark
89          89
90                                                                                                                                                                                                       84
79                79                                                                                                            79
85%
80                      +/- 0.5 D                                                                                              74                74                     74         74                                ±1.0 D
+/- 1.0D                                                               68       68
70
63
60          58                               58                            58
% of eyes

53                                                                                          53                                                                                         55%
47
50
42                                                                                                                                                         ±0.5 D
40
32                   32             32                                                                                                                                                  32         32
30                                                                                                                                                                     26
21
20

10

Haigis-L

TCP-5mm
TCP-4mm
TCP-2mm

TCP-3mm
0
Shammas
Feiz-Mannis

Wang-Koch-Maloney
Clinical History

Corneal Bypass

Galilei
Accuracy of IOL power
calculation in eyes with prior
RK
Purpose

   Because RK eyes have variable front and
back curvatures, IOL calcs are especially
challenging
   To evaluate the accuracy of 4 devices for
calculating corneal power for IOL
calculations in RK eyes undergoing
cataract surgery
   IOLMaster, EyeSys, Atlas, Galilei
Patients

   Consecutive cases of IOL implantation
between April 08 to February 11

   27 eyes of 18 patients, age 47 to 79 years
Refractive mean absolute error (MAE)
with different devices
0.8

0.7                     0.67           0.66
0.65

0.6                                                     0.58

0.5
MAE (D)

0.4

0.3

0.2

0.1

0.0
EyeSys EffRP   IOLMasterK     Atlaszone0-3   TCPannuli1-4

Galilei TCPannuli1-4 tended to produce smallest
MAE (all P>0.05).
Refractive prediction error                                                      UK NHS
benchmark
+/- 0.50 D
90                         85                85                85
+/- 1.0 D                                                  85%
80         78                                                             ±1.0 D

70
59
60
52                                                                   55%
% of eyes

50                                                                        ±0.5 D

40
33
30
30

20

10

0
EyeSys EffRP    IOLMaster K       Atlaszone0-3     TCPannuli1-4
Proposed benchmark for normal eyes: Gale RP, et al. Benchmark
standards for refractive outcomes after NHS cataract surgery. Eye.
2009;23:149-52.
Galilei

 Needs further work to improve IOL
calculations after LASIK
 Helpful in eyes that have undergone