Comparative study of cornea and anterior segment Comparative study of cornea and anterior segment biometric features between scanning slit beam biometric features between scanning slit beam

technology, Placido disk topography, and a technology, Placido disk topography, and a Scheimpflug imaging systemScheimpflug imaging system

Juan Carlos Serna-Ojeda MD, Arturo Ramirez-Miranda MD, Alejandro Juan Carlos Serna-Ojeda MD, Arturo Ramirez-Miranda MD, Alejandro Navas MD, MSc, Aida Jimenez-Corona MD, PhD and Enrique O. Navas MD, MSc, Aida Jimenez-Corona MD, PhD and Enrique O.

Graue-Hernandez MD, MScGraue-Hernandez MD, MSc

Department of Cornea and Refractive Surgery Department of Cornea and Refractive Surgery Instituto de Oftalmologia “Conde de Valenciana”, Mexico City, Mexico Instituto de Oftalmologia “Conde de Valenciana”, Mexico City, Mexico

JCS-O, AJ-C and EOG-H have no financial interests to disclose. AR-M is a JCS-O, AJ-C and EOG-H have no financial interests to disclose. AR-M is a consultant for Carl Zeiss Meditec. AN is a consultant for Carl Zeiss Meditec consultant for Carl Zeiss Meditec. AN is a consultant for Carl Zeiss Meditec

and speaker for Alcon Laboratories and and speaker for Alcon Laboratories and STAAR SurgicalSTAAR Surgical..

PurposePurpose• We studied the interdevice We studied the interdevice

agreement of three systems in the agreement of three systems in the different measurements of the different measurements of the corneal and anterior segment corneal and anterior segment biometric parameters.biometric parameters. The Pentacam HR ® (Oculus, The Pentacam HR ® (Oculus,

Wetzlar, Germany). Wetzlar, Germany). The Orbscan ® (Bausch & Lomb, The Orbscan ® (Bausch & Lomb,

New York, USA).New York, USA). The Aladdin ® (Topcon, Tokyo, The Aladdin ® (Topcon, Tokyo,

Japan).Japan).

MethodsMethods• Randomly selected individuals aged 18 years or older Randomly selected individuals aged 18 years or older

were prospectively recruited from the were prospectively recruited from the general consultation general consultation from a Department of Cornea and Refractive Surgery.from a Department of Cornea and Refractive Surgery.

• Patients with previous ocular surgery, dry eye and use of Patients with previous ocular surgery, dry eye and use of contact lens in the previous month were excluded.contact lens in the previous month were excluded.

• All eyes were examined undilated with the three devices.All eyes were examined undilated with the three devices.

• Only high-quality measurements were included.Only high-quality measurements were included.

MethodsMethods

• Cornea and anterior segment biometric Cornea and anterior segment biometric features:features:

• Anterior corneal radius of curvature at Anterior corneal radius of curvature at 3 and 7 mm (Sim-Kmin and Sim-Kmax)3 and 7 mm (Sim-Kmin and Sim-Kmax)

• Anterior chamber depth (ACD)Anterior chamber depth (ACD)• White-to-whiteWhite-to-white

Statistical analysisStatistical analysis

• Interdevice intraclass correlation coefficient.Interdevice intraclass correlation coefficient.

• Interdevice agreement was assessed by the Interdevice agreement was assessed by the Bland–Altman comparison analysis.Bland–Altman comparison analysis. 95% limits of agreement (LoA) as mean difference 95% limits of agreement (LoA) as mean difference

± 2 standard deviations of the differences.± 2 standard deviations of the differences.

• Data were processed and analyzed using Data were processed and analyzed using Microsoft Excel 2011© and SPSS version 17 (IBM Microsoft Excel 2011© and SPSS version 17 (IBM Corp., NY)Corp., NY)

ResultsResults• Thirty-four eyes of 17

patients. Nine subjects (52.9%)

were female and eight (47.1%) were male.

Median age of 26 years (range 21 – 50 years).

15 candidates for refractive surgery, 1 suspect for keratoconus and 1 with keratoconus diagnosis.

Median and Interquartile Range for the Measurements of Each Examined Variable

PARAMETER Aladdin Orbscan Pentacam

HR

Sim-Kmin (D) 42.80 (41.40 to 43.60)

42.3 (41.32 to 43.37)

42.40 (41.15 to 43.37)

Sim-Kmax (D) 45.11 (43.75 to 45.96)

44.8 (43.75 to 46.37)

44.95 (43.55 to 45.87)

ACD (mm) 3.76 (3.47 to 3.83)

3.01 (2.79 to 3.20)

3.14 (2.98 to 3.32)

White-to-white (mm)

11.74 (11.46 to 12.05)

11.65 (11.42 to 11.90)

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Sim-K = simulated keratometry values; D = diopters; ACD = anterior chamber depth

Interdevice intraclass correlation coefficient and interdevice agreement analysis of the three systems.

Parameter Aladdin - Orbscan Aladdin - Pentacam HR

SimK-min (D) 

ICC

(95%CI)

0.937

(0.885 to 0.968)

0.968

(0.940 to 0.984)

95% LoA (mean difference,

P value)

-0.767 to 1.408

(0.321, p=0.898)

-0.595 to 1.008

(0.206, p=0.851)

SimK-max (D)

ICC

(95%CI)

0.983

(0.969 to 0.991)

0.976

(0.955 to 0.988)

95% LoA (mean difference,

P value)

1.119 to 1.287

(0.084, p= 0.566)

1.193 to 1.503

(0.155, p>0.01)SimK = simulated keratometry; D = diopters; ICC = intraclass correlation coefficient; CI = confidence interval; LoA = limits of agreement.

ICC>0.9

P≤0.05

Interdevice intraclass correlation coefficient and interdevice agreement analysis of the three systems.

Parameter Aladdin - Orbscan Aladdin - Pentacam HR

ACD (mm)

ICC

(95%CI)

0.930

(0.872 to 0.965)

0.888

(0.801 to 0.944)

95% LoA (mean difference,

P value)

0.458 to 0.908

(0.683, p=0.237)

0.285 to 0.834

(0.560, p=0.05)

White-to-white (mm)

ICC

(95%CI)

0.727

(0.550 to 0.860)

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95% LoA (mean difference,

P value)

-0.645 to 0.517

(-0.064, p=0.921)

----------

ACD = anterior chamber depth; ICC = intraclass correlation coefficient; CI = confidence interval; LoA = limits of agreement

ICC>0.9

P≥0.05

K-minK-min

Aladdin vs Orbscan95% LoA -0.767 to 1.408

p=0.898

Aladdin vs Pentacam95% LoA -0.595 to 1.008

p=0.851

K-maxK-max

Aladdin vs Orbscan95% LoA -1.119 to 1.287

p=0.566

Aladdin vs Pentacam95% LoA 1.193 to 1.503

p>0.01

ACDACD

Aladdin vs Orbscan95% LoA 0.458 to 0.908

p=0.237

Aladdin vs Pentacam95% LoA 0.285 to 0.834

p=0.05

W-to-WW-to-W

Aladdin vs Orbscan95% LoA -0.645 to 0.517

p=0.921

ConclusionsConclusions• All the analyzed parameters show a good to excellent

Interdevice intraclass correlation coefficient.Interdevice intraclass correlation coefficient.

• Interdevice agreement is higher between Orbscan and Aladdin.

• Orbscan and Pentacam may be used interchangeably with the Aladdin when analyzing Sim-Kmin and white-to-white.

• ACD and Sim-Kmax should be carefully analyzed.