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Evaluating Central Corneal Thickness
Measurements With Noncontact
Optical Low-Coherence
Reflectometry and Contact
Ultrasound Pachymetry
Suzanna Airiani, MD, Stephen L. Trokel, MD,
Shing M. Lee, MSc, and
Richard E. Braunstein, MD
PURPOSE:
To compare the central corneal thickness
(CCT) measurements obtained with noncontact optical
low-coherence reflectometry (OLCR) and ultrasound
(US) pachymetry.
DESIGN:
Prospective, comparative observational study.
METHODS:
Three sequential ultrasonic measurements and a
set of five OLCR scans of 52 eyes of 26 healthy subjects
were recorded. Noncontact measurement was repeated
five minutes after anesthetic drop instillation.
RESULTS:
Mean CCT values for noncontact OLCR and
US pachymetry were 544.03 m and 548.66 m,
respectively, with mean SDs of 0.97 m and 4.63 m,
respectively. Noncontact OLCR measured on average
4.64 m less than US pachymetry (95% confidence
interval ؊7.56 to ؊1.72; P ؍ .003). The OLCR
measured 1.68 m less than US pachymetry in the
thinner cornea group (<548.7 m, n ؍ 24) and 7.48
m less in the thicker group (n ؍ 25). This difference
was statistically significant (P ؍ .04).
CONCLUSIONS:
There was agreement between the two
pachymetric measurements. Noncontact OLCR appeared
to measure slightly smaller than US pachymetry. (Am
J Ophthalmol 2006;142:164 –165. © 2006 by Elsevier
Inc. All rights reserved.)
C
ENTRAL CORNEAL THICKNESS (CCT) DETERMINATION
has become essential in corneal refractive surgery and
glaucoma patient management.
1
Ultrasound (US) pachym-
etry has been the current standard for CCT measurement.
The purpose of this study is to compare the CCT of normal
human corneas measured with noncontact optical low-
coherence reflectometry (OLCR) vs contact US pachym-
etry. We also evaluated the CCT five minutes after
anesthetic drop instillation to assess its effect on the OLCR
pachymetric analysis.
CCT of 52 eyes of 26 patients was measured at our
center. This study was approved by the institutional review
board, and each patient provided informed consent. The
mean age of patients was 38 years Ϯ 9.9 (mean Ϯ SD) with
a male/female ratio of 14:12. Mean manifest refraction
spherical equivalent was Ϫ4.07 diopters Ϯ 2.56 (range
Ϫ10.50 to ϩ0.25 diopters). All patients had unremarkable
ocular history and had not worn contact lenses for at least
24 hours. In the following sequence, OLCR (Pachmeter,
Haag-Streit AG, Koeniz, Switzerland) (Figure 1) immedi-
ately followed by US pachymetry (DGH500 Pachette;
DGH Technology Inc, Exton, Pennsylvania, USA) and a
second set of OLCR measurements five minutes after US
pachymetry was performed on each study eye. Final CCT
measurements comparing the two pachymetry methods
were available in 49 eyes of 26 patients. Thirty-nine eyes of
20 patients were studied to compare the thickness before
and five minutes after anesthetic drop instillation by
OLCR pachymetry. All of the measurements were taken
between 10:00 am and 4:00 pm.
The principal operations of the OLCR and US pachymetry
used in this study have been described elsewhere.
2,3
Briefly,
Accepted for publication Jan 13, 2006.
From the Department of Ophthalmology, College of Physicians and
Surgeons of Columbia University (S.A., S.L.T., R.E.B.), and Department
of Biostatistics, Mailman School of Public Health (S.M.L.), Columbia
University, New York, New York.
Haag-Streit AG, Koeniz, Switzerland, provided noncontact optical
low-coherence reflectometry to the Department of Ophthalmology,
Columbia University, New York, New York.
Presented in part as a poster session at the 2004 ARVO Annual
Meeting, April 25, 2004, Ft Lauderdale, Florida.
Inquiries to Richard E. Braunstein, MD, Edward S. Harkness Eye
Institute, 635 W 165th Street, Box 39, New York, NY 10032; e-mail:
reb10@columbia.edu
A
MERICAN
J
OURNAL OF
O
PHTHALMOLOGY
164 J
ULY 2006