I have a financial interest with the following companies:

Abbott Medical OpticsAlconCalhoun VisionNuLensOptimedicaOptivue

Financial Disclosure

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

3 categories of formulas

Double-K Holladay 1

and Haigis-L formulas

3 categories

Traditionally “Gold” standardKEY – accurate

historical dataData error 1:1

ratio

Use a fraction of ∆MR

Data error ↓ to 20 – 30%

Rely only on current data

Pop-up windows explain methods used

Prior hyperopic-LASIK/PRK

Prior RK

Monthly visits to the calculator in 2010

6,1736,570

7,8537,218

6,758 6,8256,369

6,7917,105

7,6668,249

7,257

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

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

-4.0

-2.0

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Variances of IOL prediction errors (SD2) - consistency of performance

Pre-LASIK Ks + ∆ MR

Clinical History

Feiz-Mannis

Corneal Bypass

2.06

2.53

1.99

∆ MR

Adjusted EffRP

Adjusted Atlas0-3

Masket

Modified-Masket

0.70

0.68

0.63

0.62

No prior data

Wang-Koch-Maloney

Shammas

Haigis-L

0.68

0.66

0.66* Significant differences (all P<0.05 with Bonferroni correction)

*

Methods ± 0.5 D ± 1.0 D

Pre-LASIK Ks + ∆MR*

Clinical History

Feiz-Mannis

Corneal Bypass

44

37

37

69

60

68

∆MR

Adjusted EffRP

Adjusted Atlas0-3

Masket

Modified-Masket

62

64

57

67

86

90

91

90

No prior data

Wang-Koch-Maloney

Shammas

Haigis-L

58

60

60

96

90

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

Refractive prediction errorProposed UK NHS

benchmark in normal eyes*:

85% ±1.0 D

55% ±0.5 D

Met benchmark in normal eyes but well below latest standards

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

Rp Ra

D

n0 = 1

n1 = 1.376

n2 = 1.336

aa R

nnK 01

pp R

nnK 12

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

*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

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 > 24.4mmpACD = personalized ACD (ACD-constant)

Refractive prediction error

Keratometry Method

Best IOL Formula

Prediction Error (D)

Range (D)

MAE (D)

Adjusted MAE (D)

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

OCT OCT-based

-0.01 ± 0.70 (-0.85, 1.79) 0.56 0.56*

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

Refractive prediction error

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

Within 0.5D: •Haigis-L: 11/20 •OCT: 10/20

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 Myopic LASIK correction: 4.28 ± 2.61 D

(range 0.88 to 8.50 D)

Refractive MAE with all methods (n=19)

Significant greater MAE with methods using pre-LASIK

Ks and ∆MR than those with (all P<0.05)

1.2

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0.93

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0.52

0.42 0.44

0.57 0.57

0.47

0.78 0.750.72 0.70

0.0

0.2

0.4

0.6

0.8

1.0

MA

E (

D)

Galilei

Refractive prediction error with all methods (n=19)C

linic

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Fei

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P-2

mm

TC

P-3

mm

TC

P-4

mm

TC

P-5

mm

85% ±1.0 D

55% ±0.5 D

UK NHS benchmark

32 32 32

42

58

68 68

5347

63

2621

32 32

5853

58

79 79

89 89

74 74

95

74 7479

84

0

10

20

30

40

50

60

70

80

90

100

% o

f ey

es

+/- 0.5 D+/- 1.0D

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

Galilei TCPannuli1-4 tended to produce smallest MAE (all P>0.05).

EyeSys EffRP IOLMasterK Atlaszone0-3 TCPannuli1-4

0.650.67 0.66

0.58

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

MA

E (

D)

Refractive prediction error

Proposed benchmark for normal eyes: Gale RP, et al. Benchmark standards for refractive outcomes after NHS cataract surgery. Eye. 2009;23:149-52.

UK NHS benchmark

85% ±1.0 D

55% ±0.5 D

EyeSys EffRP IOLMaster K Atlaszone0-3 TCPannuli1-4

52

3330

59

78

85 85 85

0

10

20

30

40

50

60

70

80

90

% o

f eye

s

+/- 0.50 D+/- 1.0 D

Galilei

Needs further work to improve IOL calculations after LASIK

Helpful in eyes that have undergone radial keratotomy

Thank you for your attention