This document summarizes key details about optical coherence biometry, a new optical method for measuring eye dimensions as an alternative to ultrasound biometry. It discusses the measurement principles, comparisons to ultrasound measurements, and evaluation of the Zeiss IOLMaster device which combines optical coherence biometry with keratometry and anterior chamber depth measurements. Studies found excellent correlation between optical and ultrasound axial length measurements, with optical lengths on average 0.3mm longer than ultrasound lengths. Reproducibility of measurements was high for both optical coherence biometry and ultrasound.

1. Kohnen, T (ed): Modern Cataract Surgery.
Dev Ophthalmol. Basel, Karger, 2002, vol 34, pp 119–130
Optical Coherence Biometry
Wolfgang Haigis
University Eye Hospital, Würzburg, Germany
With optical coherence biometry (OCB), also termed partial coherence
interferometry (PCI), laser interference biometry (LIB) or laser Doppler inter-
ferometry (LDI), an innovative optical method for measuring axial lengths has
recently become available as a possible alternative to commonly applied ultra-
sound biometry. In the IOLMaster [7, 14, 18], introduced in autumn 1999 by
Carl Zeiss Jena, this new distance-measuring technique is combined with a
classical measurement setup to determine central corneal curvatures together
with a slit image-based method to measure anterior chamber depths. All three
measurements are noncontact procedures – easy to apply for the examiner and
well acceptable for the patient. With these measurement facilities, all data nec-
essary for the calculation of intraocular lenses is thus acquired by one stand-alone
device. The system software allows IOL calculation with all popular formulas
and includes databases for IOL and surgeon data.
The application of PCI to measuring human ocular dimensions dates
back to the mid-1980s, when Vienna physicist Fercher [2] performed the first
optical axial length measurement in vivo. Since autumn 1997, our laboratory
(Biometry Department of the University Eye Hospital, Würzburg) has been
involved in the development and transformation of this fascinating new technique
into clinical applications [5, 7, 9, 13, 14].
Measurement Principle
In the IOLMaster, a laser diode is mounted in one arm of a Michelson
interferometer setup (fig. 1). An infrared laser beam (␭ ϭ 780nm) of short
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

2. coherence length is emitted onto a beam splitter which produces two coaxial
beams by means of a fixed reference mirror and a moving measurement mirror.
These beams are directed into the eye, where they are reflected at the cornea and
the retina. Interference between the reflected beam components occurs if the
delay between each other is equal to the optical path length of the eye. The
resultant intensity distribution is sensed by a photodetector and recorded as a
function of the displacement of the measurement mirror. The accuracy of this
technique stems from the fact that the mirror position can be determined very
precisely. Due to using coaxial beams, the optical measurement is insensitive
against longitudinal eye movements.
Optical and Acoustical Biometry
Axial lengths measured by ultrasound and laser interference are not
directly comparable (fig. 2). To obtain a ‘good’echogram, the sound beam must
impinge vertically onto all segmental interfaces within the eye. This can be
achieved along the geometrical (optical) axis of the eye. With PCI biometry
relying on fixation, the direction of measurement is along the visual axis.
Haigis 120
M"
E"
E"R
E"C
E'R
E'C
E'
M'
d
LS
2L
L
LS Light source with
short coherence length
Interferometer mirrors
Photodetector
Distance to be measuredL
PD
M', M"
C R
PD
2d
Fig. 1. Principle setup of a dual-beam partial coherence interferometer [after 3, 9].
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

3. Furthermore, whereas an ultrasound axial length extends from the anterior
corneal vertex to the inner limiting membrane (ILM), an optical axial length is
confined by the retinal pigment epithelium, because this is where the dominant
reflection usually originates [11]. Thus, optical (ALop) and acoustical (ALac)
axial lengths are different distances from different directions. With RT denoting
the retinal thickness we may write to a first approximation:
ALop Ϸ ALac ϩ RT
Another difference stems from the fact that ultrasound allows simultaneous seg-
mental measurements of the eye, not so – at least with the present IOLMaster
hardware – optical coherence biometry. Although ACD and lens thickness mea-
surements have been reported in the literature [1], these measurements were car-
ried out separately and not simultaneously during axial length determination.
This is due to the small amount of light returning from the obliquely intersected
lens surfaces along the line of sight [1]. It may, however, well be that future PCI
equipment will also offer this modality. Until then – equivalent to applying a mean
velocity in ultrasound – a mean (group [17]) refractive index nPCI (ϭ1.3549
[11]) has to be used in order to translate the measured optical path length (OPL)
into a geometrical eye length (ALop), i.e.:
ALop ϭ OPL/nPCI
Up to now, all clinical experience in IOL implantation and refractive out-
come is built on ultrasound data. To make this vast experience available for
Optical Coherence Biometry 121
ALop
ALac
RPEILM
Fig. 2. Optical (ALop) and acoustical (ALac) axial lengths: different distances in different
directions: ALac ϭ anterior corneal vertex to internal limiting membrane (ILM); ALop ϭ inter-
section of visual axis with anterior cornea to retinal pigment epithelium (RPE).
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

4. optical biometry (and vice versa), it was necessary to determine the relationship
between optical path lengths measured by PCI and the respective ultrasound axial
lengths. In a pilot study with one of the IOLMaster’s prototypes (‘ALM’) com-
paring axial lengths of more than 600 eyes, the following relation was found
[5, 7, 13, 14]:
ALop ϭ OPL/1.3549 ϭ 0.9571 ؒALac ϩ 1.3033
As an ultrasound reference instrument, a high precision Grieshaber Biometric
System (GBS) was used at 10MHz in immersion technique which is known to
be superior in accuracy to the commonly applied contact coupling method. This
instrument allows simultaneous segmental measurements with a spatial resolu-
tion of 22␮m and a reproducibility of 22Ϯ24␮m. The correlation between
optical and acoustical eye lengths is excellent (99%) as can be seen from figure 3.
Optical axial lengths, as expected, were longer than acoustical ones (by 0.30 Ϯ
0.17mm on an average [7]). The difference was found to be more pronounced in
short eyes which can be explained by an underestimation of the lens thickness in
these eyes as a consequence of using an average refractive index. Today, the
regression line shown above is wired into the market version of the Zeiss
IOLMaster which thus emulates an immersion ultrasound instrument – as far as
the displayed axial length values are concerned – with the high precision of PCI
technology.
Haigis 122
20
20
22
22
24
24
26
26
28
28
ALac (mm)
ALop(mm)
Fig. 3. Optical and acoustical biometry: PCI axial length ALop (Zeiss) vs. immersion
US axial length ALac (GBS).
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

5. In a follow-up study [unpubl. data] an IOLMaster individual out of
the regular production line was rechecked with 101 patients against our high
precision immersion ultrasound system. With a correlation coefficient of
98.8%, the following dependance between indicated axial lengths ALIOLMaster on
the IOLMaster and immersion ultrasound reference values ALimmUS from the
GBS was found:
ALIOLMaster ϭ 1.0006 ؒ ALimmUS ϩ 0.0337
If the average standard deviation for five consecutive axial length measurements
is taken to be a measure for reproducibility, we obtained values of 22 Ϯ 24␮m for
the GBS ultrasound immersion measurements and 23 Ϯ 15␮m for the IOLMaster
[6, 8, 9]. In another study [8], based on 146 comparative axial length measure-
ments between IOLMaster and GBS, a mean difference ALIOLMaster – ALimmUS of
Ϫ10 Ϯ 19␮m (median 10␮m, range Ϫ770 to ϩ420␮m) was found.
Keratometry and ACD Measurement with the IOLMaster
As an all-in-one-instrument, the Zeiss IOLMaster also features a kerato-
metry module as well as the facility to measure anterior chamber (ACD) depth.
For these two measurements, however, classical optical techniques are applied.
Corneal curvatures are conventionally deduced from the positions of
the images of 6 infrared light-emitting diodes (LEDs) illuminating the cornea
in a hexagonal pattern. ACD is determined from a slit image of the anterior
ocular segment with the help of sophisticated image analysis software. It is
measured from the anterior corneal vertex to the anterior vertex of the lens, just
like an ultrasound ACD would be measured. In fact, IOLMaster ACDs are
calibrated against immersion ultrasound ACDs on the basis of more than
800 comparative measurements which have been carried out in our laboratory.
Thus, with respect to an ACD measured ultrasonically in contact coupling
mode, the IOLMaster ACD is likely to be a bit longer (0.1–0.2mm), since it
is not affected by a possible globe impression as might be the case in contact
ultrasound.
In an already mentioned study [8], IOLMaster keratometry results were
compared to those obtained with an Alcon (Renaissance Series) handheld ker-
atometer. A mean difference (IOLMaster – handheld keratometer) of the average
corneal radius of Ϫ10 Ϯ 50 ␮m was found for 154 patients (median Ϫ10 ␮m,
range Ϫ200 to ϩ130 ␮m). Additionally, a comparison between IOLMaster
ACDs (n ϭ151) and the respective immersion ultrasound data obtained with the
GBS was carried out yielding a mean difference (IOLMaster – GBS) in ACD
values of 30 Ϯ 180␮m (median 0␮m, range Ϫ400 to ϩ680 ␮m).
Optical Coherence Biometry 123
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

6. Observer Dependance and Learning Curve
In contact echography, which is widely used for axial length determination,
the measured value depends, inter alia, on the experience of the examiner.
An experienced examiner will e.g. exert less pressure on the eyeball than a begin-
ner; hence, he or she will produce slightly longer axial lengths with less data
scatter when repeating the measurement. To check the inter- and intra-examiner
variability for the IOLMaster measurement modes, 4 examiners (2 experienced
ones, 2 beginners) measured axial length, anterior chamber depth and mean
corneal radius of 29 volunteers at three different times. Results for repeated meas-
urements by one and the same examiner (intra-examiner variability) were 10.9␮m
for axial length, 31.9␮m for ACD and 11.3␮m for corneal radius. For different
examiners measuring one and the same patient/volunteer (inter-examiner variabil-
ity), the respective values were 11.8␮m for axial length, 37.7␮m for ACD and
13.4␮m for corneal radius. Similar results have been published by Vogel et al.
[19]. In terms of reliability, the following results were deduced: 100.0% for axial
length, 97.8% for ACD and 99.6% for corneal radius measurements.
A criterion for measurement quality in optical coherence biometry is the
ratio of the usable interference signal relative to background noise (signal-
to-noise ratio – SNR). The higher the SNR, the better the measurement.
Learning to apply this new biometry technology thus implies trying to achieve
high SNR values. An example for a ‘learning curve’ in terms of mean SNR of
five consecutive measurements on a test sphere, repeated on subsequent days by
an absolute novice, is shown in figure 4.
Haigis 124
10
9
8
SNR
Date
10/1/00 11/1/00 12/1/00 13/1/00 14/1/00 15/1/00 16/1/00 17/1/00 18/1/00
Fig. 4. ‘Learning curve’ for axial length measurement with the Zeiss IOLMaster:
improvement of signal-to-noise ratio (SNR) as time progresses.
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

7. Optical Biometry and IOL Calculation
Optical biometry with the Zeiss IOLMaster – as has already been
mentioned – produces axial lengths as if stemming from an immersion ultra-
sound measurement. However, although known to be less precise, the contact
ultrasound method is the procedure which is mostly used for axial length deter-
mination. Accordingly, manufacturers’constants for the calculation of intraocu-
lar implant lenses are meant for and adapted to contact ultrasound data.
Therefore, it is of utmost importance to adjust the published IOL constants (like
e.g. the A constant or the ACD constant) to optical biometry – individually for
any given intraocular lens type. This can be done on the basis of pre- and post-
operative clinical data. We have shown [9] that after proper individualization of
lens constants there is virtually no difference between refractive results based on
optical coherence biometry and high precision immersion ultrasound.
Optimization of IOL constants for optical biometry is one of the main
concerns of EULIB – the European User Group for Laser Interference
Biometry. EULIB is an independent interest group of scientists and users, work-
ing in the field of optical biometry or applying this technique clinically.
Founded in autumn 1999, EULIB can be contacted through its website at
www.augenklinik.uni-wuerzburg.de/eulib.
From the EULIB site, general information regarding PCI biometry as well
as the clinical application of the Zeiss IOLMaster can be obtained. Also, a
spreadsheet form designed to accept pre- and postoperative clinical data for the
purpose of constants’ optimization can be downloaded [20]. Patient data sent
back via this form are processed in our laboratory to produce optimized IOL
constants for all popular IOL formulas. The results are then published on the
EULIB site [21] (see fig. 5).
The necessary adjustments e.g. in A constants for the SRK/T formula
are typically of the order of 0.6 D, ranging from 0.2 to 1.3D. This can be seen
from figure 5, if only lens type results for n Ͼ50 are considered. Generally,
immersion-based IOL constants are higher than constants for contact ultra-
sound. This is due to the fact that a ‘contact’ axial length which would lead to a
correct IOL power will be measured longer in immersion which then would call
for a weaker IOL if the IOL constants were not set to higher values.
Advantages and Disadvantages of Optical Biometry
Optical biometry is definitely advantageous over ultrasound biometry in
cases of staphylomatous ocular backwalls [12, 16]. With ultrasound it is
often difficult to decide among different axial length results from e.g. a highly
Optical Coherence Biometry 125
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

8. Haigis 126
IOLNominalHaigisHofferQ/Holl.2Holl.1SRK/TSRKIInRef.
Acritec12CAϭ118.9a0ϭ1.42;a1ϭ0.40;a2ϭ0.10pACDϭ5.64sfϭ1.91Aϭ119.2Aϭ119.516[2]
AlconAcrySofMA60BMAϭ118.9a0ϭ1.582;a1ϭ0.084;a2ϭ0.157pACDϭ6.11sfϭ2.36Aϭ119.9Aϭ120.5227[2]
AlconAcrySofMA30BAAϭ118.9a0ϭ1.50;a1ϭ0.40;a2ϭ0.10pACDϭ5.68sfϭ1.89Aϭ119.1Aϭ119.3134[7]
AlconAcrySofMA30BAAϭ118.9a0ϭ1.81;a1ϭ0.40;a2ϭ0.10pACDϭ5.91sfϭ2.10Aϭ119.4Aϭ119.749[8]
AlconSA30ALAϭ118.4a0ϭ1.26;a1ϭ0.40;a2ϭ0.10pACDϭ5.45sfϭ1.66Aϭ118.8Aϭ118.9102[5]
AlconSA30ALAϭ118.4a0ϭ1.29;a1ϭ0.40;a2ϭ0.10pACDϭ5.43sfϭ1.63Aϭ118.7Aϭ118.9240[7]
AlconSA30AL(*)Aϭ118.4a0ϭ1.38;a1ϭ0.40;a2ϭ0.10sfϭ1.6225[3]
AlconSA60AT(*)pACDϭ5.18sfϭ1.43Aϭ118.4[3]
AllerganSI40NBAϭ118.0a0ϭ-0.954;a1ϭ0.244;a2ϭ0.206pACDϭ5.24sfϭ1.46Aϭ118.4Aϭ118.6267[2]
AllerganSI40NBAϭ118.0a0ϭ1.16;a1ϭ0.40;a2ϭ0.10pACDϭ5.32sfϭ1.52Aϭ118.5Aϭ118.7215[7]
AllerganSI30NBAϭ117.4a0ϭ1.03;a1ϭ0.40;a2ϭ0.10pACDϭ5.51sfϭ1.60Aϭ118.6Aϭ118.533[9]
ThefollowingtablemaybedownloadedandfeddirectlyintotheIOLMaster.Fordetailsclickhere.
OptimizedIOLConstantsfortheZEISSIOLMaster(asofNovember15,2001):
(Pleasenote:constantsarepreliminary,especiallyifnϽ50!Fordetailshowtocreateyourowntentativeconstants,pleaseseebelow).
ULIB
UserGroupforLaserInterferenceBiometry
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

9. Optical Coherence Biometry 127
AllerganClariFlexAϭ118.0a0ϭ0.83;a1ϭ0.40;a2ϭ0.10pACDϭ5.05sfϭ1.28Aϭ118.2Aϭ118.423[2]
AllerganAR40Aϭ118.4a0ϭ1.12;a1ϭ0.40;a2ϭ0.10pACDϭ5.35sfϭ1.57Aϭ118.6Aϭ118.8164[2]
AllerganSA40ArrayAϭ118.0a0ϭ0.63;a1ϭ0.40;a2ϭ0.10pACDϭ4.85sfϭ1.10Aϭ117.9Aϭ118.1117[2]
AllerganSI55Aϭ118.0a0ϭ0.78;a1ϭ0.40;a2ϭ0.10pACDϭ5.00sfϭ1.26Aϭ118.2Aϭ118.420[2]
AllerganPS60ANBAϭ116.7a0ϭ1.15;a1ϭ0.40;a2ϭ0.10pACDϭ5.46sfϭ1.65Aϭ118.7Aϭ118.918[2]
CornealBR110Aϭ118.5a0ϭ1.25;a1ϭ0.40;a2ϭ0.10pACDϭ5.48sfϭ1.65Aϭ118.7Aϭ119.040[4]
CornealBR110Aϭ118.5a0ϭ1.51;a1ϭ0.40;a2ϭ0.10pACDϭ5.65sfϭ1.86Aϭ119.0Aϭ119.319[2]
DomilensSiflex4Aϭ118.4a0ϭ1.12;a1ϭ0.40;a2ϭ0.10pACDϭ5.38sfϭ1.65Aϭ118.8Aϭ119.439[2]
DomilensFlex65LAϭ118.4a0ϭ1.36;a1ϭ0.40;a2ϭ0.10pACDϭ5.59sfϭ1.76Aϭ118.8Aϭ118.821[2]
Gen.Innov.XP-55Aϭ118.0a0ϭ1.00;a1ϭ0.40;a2ϭ0.10pACDϭ5.24sfϭ1.46Aϭ118.4Aϭ118.7111[2]
LenstecLS-106Aϭ118.4a0ϭ1.61;a1ϭ0.40;a2ϭ0.10pACDϭ5.84sfϭ2.07Aϭ119.4Aϭ119.833[2]
Pharm.-Upj.CeeOn911AAϭ118.3a0ϭ0.283;a1ϭ0.311;a2ϭ0.155pACDϭ5.47sfϭ1.70Aϭ118.8Aϭ119.2279[2]
Pharm.-Upj.808CAϭ118.0a0ϭ1.64;a1ϭ0.40;a2ϭ0.10pACDϭ5.79sfϭ2.03Aϭ119.3Aϭ119.986[2]
Rayner755UAϭ118.0a0ϭ1.60;a1ϭ0.21;a2ϭ0.11pACDϭ5.42sfϭ1.67Aϭ118.8Aϭ119.098[1]
StaarAQ2010Aϭ118.5a0ϭ1.42;a1ϭ0.40;a2ϭ0.10pACDϭ5.60sfϭ1.78Aϭ118.8Aϭ119.0111[7]
StaarAQ2010Aϭ118.5a0ϭ1.56;a1ϭ0.40;a2ϭ0.10pACDϭ5.77sfϭ2.02Aϭ119.3Aϭ119.749[6]
Constantsaregivenwithoutanylegalresponsibility!
Fig.5.OptimizedIOLconstantsforopticalbiometrywiththeZeissIOLMasteraspublishedbyEULIB–theEuropeanuserGroup
forLaserInterferenceBiometry–ontheirwebsitewww.augenklinik.uni-wuerzburg.de/eulib.const.htm(EULIBhasrecentlychangeditsname
intoULIBpayingtributetothefactthatithasevolvedintoaglobalcommunitywithcolleaguesfromallovertheworld).
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

10. myopic eye. Since optical biometry measures along the visual axis, the PCI
results are more reliable as long as the patient is able to fixate. An example is
shown in figure 6. A patient presented a myopic refractive surprise of 4D in
the right eye. His axial length was 27.06mm by ultrasound, 29.19mm by
PCI. IOL calculation had been based on the ultrasound length. The refractive
surprise is fully explained by the difference between acoustical and optical axial
lengths.
Another application where optical biometry is superior to classical ultra-
sound is the measurement of pseudophakic and silicone oil filled eyes. Every
medium along the propagation path of light affects the optical path length by its
individual propagation velocity (expressed in its group refractive index).
Compared to a normal phakic eye, a pseudophakic eye will thus have a different
optical path length. In ultrasound, opposite to PCI, propagation velocities of
IOL materials are considerably different from those of ocular tissues. Therefore,
considerable correction factors are needed for measuring e.g. a pseudophakic
axial length by ultrasound, ranging typically from Ϫ0.6mm for silicone to
0.4mm for PMMA lenses [4]. For optical biometry, on the other hand, typical
pseudophakic correction factors [10] are of the order of 0.1mm and nearly inde-
pendent of IOL material.
The same applies to silicone oil filled eyes: a normal eye with its vitreous
cavity completely filled with silicone oil, measured as phakic eye will seem-
ingly be some 0.7 mm too long when using PCI. The same eye measured with
ultrasound in phakic mode will also appear to be too long – this time however
by some 8.9 mm [unpubl. data].
Haigis 128
Result of axial length measurement:
Ultrasound
Laser interference
AL ϭ 27.06 mm
AL ϭ 29.19 mmnasal
SNR ϭ 7.5
AL ϭ 29.19
n ϭ 1.3549
14 40 mm
Fig. 6. Ultrasound B scan and optical A scan of a staphylomatous eye: an intraocular
lens calculated from ultrasound biometry produced a Ϫ4 D refractive surprise.
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

11. The evident advantage of optical biometry is of course its ease of use both
for patient and examiner due to its noncontact mode of operation. No topical
anesthesia is needed, no possible infection hazard involved. (Infrared) light,
however, must be able to pass through the eye and return back to the PCI instru-
ment. Therefore, a certain amount of transparency along the propagation path is
mandatory with no obstructions blocking out the light. Furthermore, a mini-
mum in fixation is needed. This requires cooperation on the side of the patient.
Sometimes a measurement may not be possible due to very dense cataracts as
well as general inabilities to cooperate.
From our experience with more than 2,500 eyes (mostly unpublished data
yet) some 5–15% of patients in a university hospital surrounding cannot be
measured optically. In one study [14], no PCI measurements were possible in
58 eyes out of 678 (9%). Similar results between 7 and 12% are reported in
the literature [18]. Among the reasons for optical biometry to fail were inability
to cooperate (fixate), tremor, respiratory distress, severe tear film problems,
keratopathy, corneal scarring, mature cataract, nystagmus, lid abnormalities,
vitreous hemorrhage, membrane formation, maculopathy and retinal detachment.
Finally, some possible pitfalls in optical biometry should also be men-
tioned. An A-scan from an ultrasound biometry device – although the instru-
ment was not designed for ultrasound diagnosis – still carries some diagnostic
information, since echoes of neighboring structures and tissues along the path
of the sound beam are also displayed. The IOLMaster interferogram, however,
shows no such information but rather a small window into retinal reflectivity.
Thus, without careful interpretation, optical signals may hide possible patho-
logies. It may e.g. happen, as we have recently demonstrated, that good quality
signals of high SNR acceptable as good axial length measurements turn out to
actually stem from a detached retina [15]. It takes a trained person and clinical
background information to avoid traps like this.
In summary: Optical coherence biometry as available today in the Zeiss
IOLMaster is easy to use for the operator and well acceptable for the patient
since it is a noncontact procedure without the need for local anesthetics and
without possible hazards which are characteristic for contact methods. By
means of its wired-in calibration curves, the instrument simulates precise seg-
mental immersion ultrasound measurements. Its accuracy is equivalent to high
precision immersion ultrasound and superior to the commonly used applanation
method. The innovative technique may well become a routine method for IOL
calculation in cataract surgery in cases of ‘normal’ cataract eyes without addi-
tional pathologies with visual acuities у0.1. For some 5–15% of cataract
patients, PCI fails out of different reasons. In these cases ultrasound will
continue to be the method of choice. The same is true for all other biometrical
applications apart from axial length determination.
Optical Coherence Biometry 129
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM

12. References
1 Drexler W, Baumgartner A, Findl O, Hitzenberger CK, Sattmann H, Fercher AF: Submicrometer
precision biometry of the anterior segment of the human eye. Invest Ophthalmol Vis Sci 1997;38:
1304–1313.
2 Fercher AF, Roth E: Ophthalmic laser interferometer. Proc SPIE 1986;658:48–51.
3 Fercher AF, Mengedoht K, Werner W: Eye length measurement by interferometry with partially
coherent light. Optics Lett 1988;13:186.
4 Haigis W: Biometrie; in Straub W, Kroll P, Küchle HJ (eds):Augenärztliche Untersuchungsmethoden.
Stuttgart, Enke, 1995, pp 255–304.
5 Haigis W, Lege B: Optical and acoustical biometry. ASCRS/ASOA Meeting, Seattle, April 1999.
6 Haigis W, Lege B: First experiences with a new optical biometry device. XVIIth Congress of the
European Society of Cataract and Refractive Surgeons, Vienna, September 1999.
7 Haigis W, Lege B: Ultraschallbiometrie und optische Biometrie; in Kohnen T, Ohrloff C, Wenzel
M (eds): 13. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und
refraktive Chirurgie, Frankfurt 1999. Köln, Biermann, 2000, pp 180–186.
8 Haigis W, Lege B: Akustische und optische Biometrie im klinischen Einsatz; in Wenzel M,
Kohnen T, Blumer B (eds): 14. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-
Implantation und refraktive Chirurgie, Luzern, February 2000. Köln, Biermann, 2000, pp 73–78.
9 Haigis W, Lege B, Miller N, Schneider B: Comparison of immersion ultrasound biometry and
partial coherence interferometry for IOL calculation according to Haigis. Graefes Arch Clin Exp
Ophthalmol 2000;238:765–773.
10 Haigis W, Lege B: Konstanten für die optische Biometrie. 98. Tagung der Deutschen Ophthal-
mologischen Gesellschaft DOG, Berlin, September 2000.
11 Hitzenberger CK: Optical measurement of the axial eye length by laser Doppler interferometry.
Invest Ophthalmol Vis Sci 1991;2:616–624.
12 Hoffmann PC, Schulze KC: IOL-Berechnung mittels Laserinterferenz- und Ultraschallbiometrie
bei hochmyopen Augen. Klin Monatsbl Augenheilkd 2001;218(suppl 1):8.
13 Lege B, Haigis W: Optical biometry – First clinical experiences. ASCRS/ASOA Meeting, Seattle,
April 1999.
14 Lege B, Haigis W: Erste klinische Erfahrungen mit der optischen Biometrie; in Kohnen T, Ohrloff
C, Wenzel M (eds): 13. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-
Implantation und refraktive Chirurgie, Frankfurt 1999. Köln, Biermann, 2000, pp 175–179.
15 Lege B, Haigis W: Probleme der optischen Biometrie in Fällen gravierender Pathologie
entlang der visuellen Achse. Klin Monatsbl Augenheilkd 2001;218(Suppl 1):9.
16 Lege B, Haigis W: Laserinterferenzbiometrie und konventionelle Ultraschallbiometrie in staphylo-
matösen Augen; in Wenzel M, Kohnen T, Blumer B (eds): 14. Kongress der Deutschsprachigen
Gesellschaft für Intraokularlinsen-Implantation und refraktive Chirurgie, Luzern, February 2000.
Köln, Biermann, 2000, pp 92–94.
17 Pancharatnam S: Partial polarisation, partial coherence and their spectral description for poly-
chromatic light. II. Proc Indian Acad Sci 1963;57:231.
18 Schrecker J, Strobel J: OptischeAchsenlängenmessung mittels Zweistrahl-Interferometrie; in Kohnen
T, Ohrloff C,Wenzel M (eds): 13. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-
Implantation und refraktive Chirurgie, Frankfurt 1999. Köln, Biermann, 2000, pp 169–174.
19 Vogel A, Dick HB, Krummenauer F, Pfeiffer N: Reproduzierbarkeit der Messergebnisse bei der
optischen Biometrie: Intra- und Interuntersucher-Variabilität; in Wenzel M, Kohnen T, Blumer B
(eds): 14. Kongress der Deutschsprachigen Gesellschaft für Intraokularlinsen-Implantation und
refraktive Chirurgie, Luzern, February 2000. Köln, Biermann, 2000, pp 85–91.
20 www.augenklinik.uni-wuerzburg.de/eulib/dload.htm
21 www.augenklinik.uni-wuerzburg.de/eulib/const.htm
Dr. rer. nat. Wolfgang Haigis, Universitäts-Augenklinik, Josef-Schneider-Strasse 11,
D–97080 Würzburg (Germany)
Tel. ϩ49 931 201 5640, Fax ϩ49 931 201 2454, E-Mail w.haigis@augenklinik.uni-wuerzburg.de
Haigis 130
Downloadedby:
UCONNStorrs
198.143.38.1-6/20/20157:46:08AM