IOL Master

1. IOL Master
Moderator: Dr. A.Y.
Yakkundi
Presenter: Dr. Arushi
4th
March ‘15

2. History
• Theopticsof theeye
representsoneof theoldest
fieldsin ophthalmology
• Thehistory of IOL power
calculation began in 1949
when Sir Harold Ridley
implanted thefirst IOL.
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Department of Ophthalmology,
JNMC

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• Heused thehuman lensashismodel and
selected similar radii of curvatureto createa
biconvex disc whileusing approximately half
thethicknessand weight (∼5 mm thick and 230
mg for thehuman lens).
• Oneof hisoriginal lensesmadeby Rayner, a
23.00 diopter (D), wasmeasured at 8.5 mm in
diameter and 2.4 mm thick, with aweight of
108 g
History
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Department of Ophthalmology,
JNMC

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• TheRidley lenswasplaced in theposterior
chamber after ECCE.
• Theanterior capsulectomy of theday wasvery
large, and thuszonular support waspoor. Some
Ridley lensesdislocated into thevitreousbecause
of poor zonular support,
and partially becauseof
their weight, which was
approximately eight
timesthat of
current IOLs.
History
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Department of Ophthalmology,
JNMC

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• Becauseof thedifficulty with posterior chamber IOL
placement, pioneering surgeons spent thenext two
decadestrying to find abetter placeto fixatetheIOL.
• TheAC lens, pupil-fixated IOL, iris-fixated IOL, and
iridocapsular IOL were beplaced in largenumbers, only
to return to theposterior chamber in the1970s.
History
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JNMC

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• A major breakthrough camein thelateseventieswith
DoctorsBinkhorst and Worst in Europeand Dr. Shearing
in America
• They began putting their implants“in thebag”. Instead of
removing theentirecataract, they scooped out theinside
of thelens, leaving thecapsule, theouter envelopeof the
lensintact.
• They then implanted their lensesinto thiscavity which
gavethelensimplant anatural support system. Success
dramatically improved.
History
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Department of Ophthalmology,
JNMC

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• Whilethiswasgoing on, Dr. CharlesKelman, was
developing phacoemulsification, aradically new method
of removing cataracts.
• A small probeispassed into theeye, and ultrasonic
vibrationswereused to break up thecataract into tiny
particles, easily removed through thesmall probe.
• Thisallowed thecataract to beremoved through asmall
opening. Thisleft aproblem: theopening wastoo small to
allow theinsertion of theintraocular lens, so wound had to
beenlarged.
• Enter thefoldableimplant. First madeof silicone, these
lensescould befolded in half, inserted through asmall
opening, and then unfolded insidetheeyeto their original
shape, all thistaking place“within thebag”.
History
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March 2015
Department of Ophthalmology,
JNMC

8. • Implant materialsand designscontinued to improve
through thelate20th century and early 21st century.
Implantsweredeveloped that could berolled instead of
just folded, allowing insertion through smaller and smaller
incisions.
• Thenext major leap forward was
thedevelopment of specialty lenses
with opticsthat could allow the
patient to seeboth distanceand
near through thesamelens.
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History
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JNMC

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• Somepatientshavealargeamount of astigmatism.
• Thisdefect can beoptically corrected with proper glasses.
After cataract surgery, theshapeof thecorneadoesnot
changemuch.
• Therefore, patientswith astigmatism will still need
glassesfor distanceand near to seeclearly.
• Enter the toric implant. Thisimplant isconstructed with
astigmatism of variouspowersbuilt in, and allowsclear
vision, often without
glasses.
History
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Department of Ophthalmology,
JNMC

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JNMC 10
“Accurateand precisebiometry isoneof thekey
factorsin obtaining agood refractiveoutcome
after cataract surgery.”
An error of only 1.0 mm in
axial length will resultsin a
post-operativerefractive
error of threedioptres
Ocular Biometry

11. Ophthalmic
Ultrasonography
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March 2015
Department of Ophthalmology,
JNMC 11
Non- invasive, efficient and inexpensive
diagnostic tool to detect and differentiatevarious
ocular and orbital pathologies
Indispensibletool for calculation of IOL power,
evaluation of posterior segment behind dense
cataract / vitreoushaemorrhage, diagnosisof
complex vitreoretinal conditionsand the
differentiation of ocular masses

12. Physics of
Ultrasonography
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JNMC 12
• Based on propagation, reflection and
attenuation of sound waves
• Ultrasound arehigh frequency sound waves
(> 20,000 kilohertz)
• Thoseused for diagnostic ophthalmic
ultrasound haveafrequency of 7.5 to 12
megahertz

13. Physics of
Ultrasonography
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JNMC 13
• Speed of ultrasound dependson medium through
which it passes
• Astheultrasound passesthrough tissues, part of
thewavemay bereflected back towardsthe
probe, thisreflected waveisreferred to asan
echo.
• Echoesareproduced at thejunction of media
with different sound velocities
• Greater thedifferencein thesound velocitesof
themediaat theinterface, stronger istheecho

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 Examiner dependent
 Needs high level of skill and expertise
 Dynamic test
A scan ultrasound biometry isacontact method
and isoperator dependent. Experiencehas
shown that excessivecorneal indentation
compressestheeye, in theanterior-toposterior
direction. Thisproducesan artificially short eye,
producing themyopic refractiveresults
Limitation

15. Measurement of
Corneal Power
• Corneal power accountsfor about 2/3rd
sof
thetotal dioptric power of theeyeand isan
important component of theocular refractive
system.
• If thecorneal power isinaccurate, it will
induceerror propagation and haveprofound
consequenceson theremaining stepsin the
calculation of IOL power.
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JNMC

16. • Unfortunately calculation of corneal power is
not astraight forward process
• No keratometer measurescorneal power
directly.
• What ismeasured isthesizeof theimage
reflected from theconvex mirror constituted
by thetear film of thecorneal surface
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Measurement of
Corneal Power
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March 2015
Department of Ophthalmology,
JNMC

17. • A magnification iscalculated from theimage
sizewhich isdirectly related to theradiusof
curvatureof thereflecting corneal surface.
• To do this, thecorneaisnormally assumed to
beasperocylinder,
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Measurement of
Corneal Power
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Department of Ophthalmology,
JNMC

18. 18
Measurement of
Corneal Power
Department of Ophthalmology,
JNMC

19. Measurement of
Axial Length
• Measurement of axial length remainsoneof
themost crucial stepsin IOL power
calculation.
• Asa0.1 mm error isaxial length isequivalent
to an error of abut 0.27 D in thespectacle
plane(assuming normal eye dimensions),
accuracy of within 0.1mm isnecessary
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JNMC

20. Variable Error Refractive
Error
Corneal Radius 1.0 mm 5.7 D
Axial Length 1.0 mm 2.7 D
Postoperative
AC Depth
1.0 mm 1.5 D
IOL Power 1.0 D 0.67 D
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• Deviation from themean valuesof different
variablesand corresponding refraction errors
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Department of Ophthalmology,
JNMC

21. a = cornea spike
b = anterior lens spike
c = posterior lens spike
d = retinal spike
e = orbital spike
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Acoustic
Biometry• What isreally
measured by
ultrasound isthe
transit timetaken
by theultrasonic
beam to travel
through theocular
mediawhileit is
deflected from the
internal structures
of theeye.
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22. 22
Acoustic
Biometry• Thebest signal isobtained when the
ultrasonic beam strikesasurfaceat normal
incidencethat givesriseto asteep spikeon
theechogram
• With good alignment along theocular axis,
it ispossibleto detect acorneal signal
(sometimesadoublespike), the front and
back surfacesof thelensand theretinaat
thesametime
4th
March 2015
Department of Ophthalmology,
JNMC

23. • The‘retinal’ spikeisgenerally assumed to
ariseat theinternal limiting membraneof the
retina
• Thismay call for correction to account for
retinal thicknesswhen thereadingsareto be
used in an IOL power formula.
• It isimportant to know thevelocity of
ultrasound in order to calculatethedistances
in question
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Acoustic
Biometry
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March 2015
Department of Ophthalmology,
JNMC

24. • For thenormal phakic eye, velocity is
generally assumed to be1532/second for the
anterior chamber and vitreousand
1641m/second for thelens(Jansson & Knock)
• In an averageeye, thisisequivalent to 1550
m/second for thewholeeye.
• However, if weassumeaconstant lens
thickness, thisaveragevelocity islower in a
long eyeand higher in ashort eye, and should
becorrected to obtain an unbiased prediction
in theseunusual eyes
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25. Thepitfallsof ultrasound measurementsare
numerous
•Readingsshould becoaxial with theocular axis
•Thisrequiresasteep spikefrom theretinaas
well asgood spikesfrom theanterior and
posterior surfacesof thelens
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Acoustic
Biometry
limitations

26. • Someeyesdo not haveperfectly parallel
structures, however,
• readingscan bedifficult to obtain in eyeswith
densecataracts
• and eyeswith posterior staphyloma.
• Careshould betaken not to indent thecornea
if contact measurementsareused .
• For thisreason immersion readingsare
generally considered moreaccuratethan
contact measurements
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Acoustic
Biometry
limitations
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Optical
Biometry
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March 2015
Department of Ophthalmology,
JNMC

28. • Theintroduction of optical biometry using
partial coherenceinterferometry significantly
improved theaccuracy with which axial
length can bemeasured.
• Thefact that theretinal pigment epithelium is
theend– point of an optical measurement,
whereastheinterfacebetween thevitreous
and theneuro retinaistheendpoint of an
ultrasonic measurement, makesmeasurements
by PCLI longer than thosetaken with
ultrasound
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29. OPTICAL
BIOMETRY
29
• However, just asdistancemeasurementstaken
with ultrasound aredependent on theassumed
ultrasound velocity, optical biometry is
dependent on theassumed group refractive
indicesof thephakic eye.
• Theindicesused by theZeissIOL Master
wereestimated by Haigisand werepartly
based on extrapolated data.
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Optical Biometry –
Uses Optical Low-Coherence Reflectometry,
a similar technology that is used in OCT
devices. This technology results in highly
accurate measurements of the eye using
light in comparison to sound. The added
benefit is that this technology is also non
contact and can be performed with the
patient sitting comfortably in a chair without
the need for any topical anaesthesia, and
without the risk of damage to the cornea.
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March 2015
Department of Ophthalmology,
JNMC

31. Principle of Michelson
Interferometer
Xiaoyu Ding
Albert Michelson (1852~1931)
thefirst American scientist to
receiveaNobel prize, invented
theoptical interferometer.
TheMichelson interferometer has
been widely used for over a
century to makeprecise
measurementsof wavelengths
and distances.
Albert Michelson
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32. Principle of Michelson
Interferometer
A Michelson Interferometer for use on an optical table
Xiaoyu Ding
1)Separation
2)Recombination
3)Interference
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Department of Ophthalmology,
JNMC

33. 33
IOL master employstheprincipleof optical
coherencebiometry (OCB)
It usespartially coherent infrared light beamsof
780nm diodelaser light emitted issplit up into two
beamsin aMichelson interferometer onemirror of
theinterferometer isfixed and theother ismoved at
constant speed making onebeam out of phasewith
theother. Both beamsareprojected in theyeand get
reflected at corneaand retina.
Thelight reflected from thecorneainterfereswith
that reflected by theretinaastheoptical pathsof
both thebeamsareequal
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JNMC

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Thisinterferenceproducesalight and dark band
pattern which isdetected by aphoto detector
Thesignalsareamplified, filtered and recorded
asafunction of theposition of theinterferometer
mirror.
An optical encoder isused to convert the
measurementsinto axial length measurements
In interferometer, theeyeneedsto beabsolutely
stableso asnot to disturb interferencepatterns
4th
March 2015
Department of Ophthalmology,
JNMC

35. The Down Side
Sinceoptical Biometry useslight
thereisahigher probability of the
“scatter” effect. Meaning that if the
light beam isreflected prior to the
RPE then thesignal returning to the
devicesensor will bevery weak if
detected at all. Thiswill result in low
SNR. Patientswith DensePSC,
ExtremeCorneal Abnormalities, or
WhiteCataractsarevery tough to
measure.
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JNMC

36. IOL Master (Carl Zeiss)
Lenstar LS 900 (Haag-Streit)
Manufacturers
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JNMC

37. IOL Master
A combined biometry instrument. It measures
parametersof thehuman eyeneeded for
intraocular lenscalculation.
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JNMC

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JNMC 38
1.Joystick with
release button
2.Display
3.Red eye
level marks
4.Lock knob
5.Connector
panel
6.Mouse
connector
7.Keyboard
connector
8.keyboard
PAR
TS
Department of Ophthalmology,

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JNMC 39
1.DVD Drive
2.Adjustment
of headrest
3.Chin rest
4.Holding
pins for paper
pads
5.Forehead
rest
6. aperture
for diode
laser
PAR
TS
Department of Ophthalmology,

40. IOL Master
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JNMC 40
It measuresquickly and precisely :
1. Axial length
2. Corneal curvature
3. Anterior chamber depth (ACD)
4. White-To-White(optional)
5. IOL power

41. It measures quickly and precisely
Axial length : Based on partial coherence interferometry
( Michelson interferometer)
Corneal curvature is determined by measuring the distance
between reflected light images.
ACD : as the distance between the optical sections of the
crystalline lens and the cornea produced by lateral slit
illumination.
White to white is determined from the image of the iris.
IOL power calculation : by software incorporating
internationally accepted calculation formulae.
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42. How do we operate
IOLmaster ?
After switching on the device, patient manager screen will
appear
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43. Screen layout
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44. Axial length
measurement(alm)Activate the axial length measurement mode by clicking on
ALM icon.
Switching to ALM mode will automatically change the
magnification ratio: a smaller section of the eye becomes
visible with the reflection of the alignment light and a
vertical line.
The patient should look at the red fixation point in the
center . A crosshair with a circle in the middle will appear
on the display.
Fine align the device so that the reflection of the alignment
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Department of Ophthalmology,
JNMC

45. Note : The patient should be asked if he or she sees the
fixation point. If the patient fails to fixate properly, the visual
axis will not be correctly recognized, which may result in
measuring errors.
In the case of poor visual acuity/high ametropia (> 4 D) it is
advisable to measure through the spectacles. If the
procedure is followed correctly, no measuring errors will be
produced. Measurements should not be taken while a
patient is wearing contact lenses, as this will result in
measuring errors.
The corresponding display field next to the video image will
show the measured axial length.
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Axial length
measurement
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March 2015
Department of Ophthalmology,
JNMC

46. The IOL Master requires five measurements to be taken.
The message Measure again will thus appear. Only then
will the composite signal be calculated and displayed as a
blue measurement curve following the red individual
measuring signal.
With stronger lens opacities, it may be advisable to defocus
the device. Defocusing and shifting the reflection within the
circle will have no effect on the result, because
interferometric axial length measurement is completely
independent of distance.
46
Axial length
measurement
4th
March 2015
Department of Ophthalmology,
JNMC

47. Axial Length Modes
1.Phakic
2.Pseudophakic
3.Aphakic
4.Silicone filled eyes
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Axial length
measurement
4th
March 2015
Department of Ophthalmology,
JNMC

48. IOLMaster produces a primary maxima (narrow, well-defined,
centered peak identified by a circle above it), secondary
maxima (discrete lower peaks, sometimes disappearing into
the baseline), and a baseline (which is low and even, but may
become high and uneven with decreasing signal-to-noise ratio
(SNR)).
Triple peak
curve

49. SNR categories :SNR is a measure of accuracy and
decreases with increasing cataract density.
The SNR is automatically analyzed while the system is
internally calculating the axial length from the interference
signal.
SNR display at GREEN  reading is valid.
SNR display at YELLOW  reading is uncertain
SNR display at RED reading should not be used
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Axial length
measurement
4th
March 2015
Department of Ophthalmology,
JNMC

50. Keratometric
measurementAsk the patient to relax and look at the fixation
light. If the patient cannot see the fixation light,
he or she should look straight ahead into the
device.
When adjusting the device, make sure that all 6
peripheral points are visible and located in the
field between the two auxiliary circles, as
closely as possible to the center of the display.
The images of the measuring marks on the
display must be optimally focused by varying
the distance between patient and device.
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JNMC

51. Focus points
51
TheIOLMaster
reflectssix pointsof
light, arranged in a2.3
mm diameter
hexagonal pattern
(measured by digital
callipers), from the
air/tear film interface.
Theseparation of
oppositepairsof lights
ismeasured
objectively by the
instrument’sinternal
softwareand the
toroidal surface
curvaturescalculated
from threefixed
meridians
Keratometric
measurement
Department of Ophthalmology,
JNMC

52. Acd measurement
Ask the patient to relax and look at the fixation
light. If the patient cannot see the fixation light, he
or she should look straight ahead into the device.
When the anterior chamber depth mode is turned
on, the system automatically activates the lateral
slit illumination. The illumination always originates
from a temporal direction.
An image similar to that of a slit lamp (optical
section through the anterior segment of the eye) is
visible on the display. Align the device to the
patient’s eye by lateral adjustment using the
joystick until:
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53. The image of the anterior crystalline lens is visible in the
pupil.
The image of the fixation point may not lie in the image of
the lens or cornea.
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Acd measurement
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Department of Ophthalmology,
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55. Measuring errors
The"Error" messagemay havetwo basic
causes:
• Theresultsof thefiveinternal individual
measurementsvary by morethan 0.15 mm (very
rare), or
• Theimagesproduced (optical sections) do not
contain relevant structures(normally without the
edgeof thecrystallinelens) or disturbancesare
preventing their detection.
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Acd measurement
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Department of Ophthalmology,
JNMC

56. Ask the patient to relax and look at the fixation light.
Focus on the iris, not on the light spots.
After the image has been taken, the operator should check
if the software has correctly detected the edge of the iris. If
the circle segments drawn in the image do not define the
iris correctly, the result must be discarded.
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WTW
measurement
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JNMC

58. Once all measurements have been taken (depending on
the IOL calculation formula), options can be generated for
intraocular lenses to be implanted.
Start the calculation by: clicking on IOL
Click on the appropriate tab to select the desired formula.
The IOL Haigis, HofferQ, Holladay, SRK II, and SRK®/T
formulae are implemented as standards.
After refractive corneal surgery the Haigis-L formulae may
be selected.
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IOL
CALCULATION
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59. 59
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60. result
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61. Measuring ranges Axial length : 14 – 40 mm
Corneal radii : 5 – 10 mm
Depth of anterior chamber : 1.5 – 6.5 mm
White-to-white : 8 – 16 mm
formulas SRK® II, SRK®/T, Holladay, Hoffer Q, Haigis
Haigis-L for IOL calculation for eyes after
myopic/hyperopic LASIK/PRK/LASEK
Optimization of IOL constants
Line voltage 100 – 240 V +/– 10% (self sensing)
Line frequency 50 – 60 Hz
Power consumption max. 90 VA
Technical data
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62. 62
Biometry Formulas
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JNMC

63. IOL Formulas
1st
Generation – The first theoretical formula
(based on Geometric Optics as applied to
schematic eye models) was developed in 1967.
These formulas were very primitive and usually
resulted in large amounts of post-cataract surgery
refractive errors. (Regression)
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JNMC

64. IOL formulas
1st
generation
•Most are based on regression formula developed
by Sander ,Retzlaff & Kraff
•Known as SRK formula.
•P = A - 2.5(L) - 0.9(K)
•P=lens implant power for emetropia
•L= Axial length (mm)
•K=average keratometric reading (diopters)
•A= lens constant
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65. IOL formulas
2nd
Generation – With an extreme need for
increased IOL Calculation, the second generation
formulas (Hoffer, SRK II) listed manual
correction factors for long or short eyes. (These
formulas are now considered obsolete.)
(Regression)
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Department of Ophthalmology,
JNMC

66. IOL formulas
• IOL FORMULA 2nd
generation
• SRK II formula
• modification of SRK
• works on ELP
• P = A1 – 2.5L – 0.9K
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Department of Ophthalmology,
JNMC

67. IOL formulas
3rd
Generation – In 1988 Dr. Holladay published
a formula (Holladay I)that predicted the AC
Depth on the basis of K Height and the distance
from the iris plane to the IOL optical plane called
the “Surgeon Factor”. This change in the physics
greatly increased the visual outcomes for Cataract
Surgery. This generation also includes the
SRK/T and Hoffer Q.
4th
Generation – Consist of Holladay II as well as
the modern post-refractive formulas
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68. IOL formulas
• IOL FORMULA 3rd
generation
• Third generation formulas-
• SRK/T -very long eyes >26mm
• Holladay I -long eyes 24-26 mm
• HofferQ -Short eyes<22mm
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JNMC

69. IOL formulas
• IOL FORMULA 4th
generation
• Holladay II
• Haigis formula-
• d = a0 + (a1 * ACD) + (a2 * AL)
• ACD is the measured anterior chamber depth
• AL is the axial length of the eye
• The a0, a1 and a2 constants are set by optimizing
• a set of surgeon- and IOL-specific outcomes for a wide
• range of ALs and ACDs.
• SRK/T formula — uses "A-constant“
• Holladay 1 formula — uses "Surgeon Factor“
• Holladay 2 formula — uses "Anterior Chamber Depth“
• Hoffer Q formula — uses "Anterior Chamber Depth"
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JNMC

70. IOL formulas
• When capsular tear does not allow bag
placement of the lens → change IOL
power for sulcus placement
• >=28.5 D Decrease by 1.5 D
• +17 To 28 D Decrease by 1.0 D
• +9 To 17 D Decrease by 0.5 D
• <+ 9 D
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JNMC

71. LensConstants
A-Constants are used with all IOL formulas, and
are determined by the anticipated position within
the eye.
Surgeon Factor – is used with the first Holladay
formula, and is determined by the distance from
the Iris plane to the Optical plane of the implant.
Effective Lens Position (ELP) is used for the
Holladay II formula, and is based on the depth of
the AC following Cataract surgery with the new
IOL in place. 71
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72. Typesof Formulas
Regression formulas are based upon mathematical
analysis of a large sampling of post-operative results.
The most familiar regression formula is the SRK
formula. The basic SRK formula works well for eyes in
the "average" measurement range; 22.5 to 25.0 mm in
axial length, with certain combinations of K readings.
The formula does not work well for "long" (>25 mm) or
"short" (<22.5 mm) eyes.
Advantage - relatively simple to calculate. A factor
can be added to a simple regression formula to
compensate for a long or a short eye
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73. Typesof Formulas
Theoretical formulas are optical formulas based on the
optical properties of the eye. They do a better job of
predicting post-op outcomes for long and short eyes.
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Department of Ophthalmology,
JNMC

74. Formula Requirements
Haigis Hoffer Q SRK/2 SRK/T HOLLADAY 1 HOLLADAY 2 Olsen
Axial Length YES YES YES YES YES YES YES
ACD YES NO NO NO NO YES* YES
Keratometry YES YES YES YES YES YES YES
Lens Thickness NO NO NO NO NO YES YES
Corneal Thickness NO NO NO NO NO NO NO
White to White NO NO NO NO NO YES YES
Pupil Size NO NO NO NO NO NO NO
Visual Axis NO NO NO NO NO NO NO
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JNMC

75. Formula Preferences
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Short Eyes (<22.0mm) Hoffer Q / Holladay 2
Average Eyes (22.1-
24.4mm)
Hoffer Q /
Holladay I / SRK/T
Medium-Long Eyes
(24.5-25.9mm
Holladay I / Hoffer Q
Long Eyes (25.0mm +) SRK/T / Holladay I
(Holladay II All eye
lengths.)
(Haigis All eye lengths
w/o optimization)

76. Post-Refractive Surgery Patient
One of the most challenging problems facing modern
Cataract Surgery is the Post-Refractive patient. Following
refractive surgery (RK, PRK, LASIK, ect) accurate K
readings cannot be obtained from topography, automated
or manual keratometry because the central cornea has
been flattened causing the mires of the measuring device
to measure roughly 4.5mm versus 3.0mm for which they
were designed. This causes erroneous K readings
compromising the effectiveness of all modern IOL
formulas.
76
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Department of Ophthalmology,
JNMC

77. Post Refractive Formulas
Haigis L - The Haigis-L formula offers predictable outcomes
after laser refractive surgery for myopia based only on current
measurements without refractive history.)
Masket Method - The Masket Method of post-LASIK corneal
power estimation is a postoperative regression method developed
by Samuel Masket and Clinical History Method – Is usable when
both the pre-op and post-op Keratometry values are known.
Contact Lens Method - The Contact Lens Method, originally
outlined by Dr. Holladay is considered a helpful way to estimate
the average central corneal power following radial keratotomy.
This technique required a special PMMA contact lens, of a known
base curve and power.
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78. Shammas – Used when no pre-op data is available such as
refraction and keratometry.
Double K SRK/T – Utilizes pre-op refraction and keratometry
Post Refractive Formulas
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Department of Ophthalmology,
JNMC

79. Advantages
# Learned very quickly (User Friendly)
# Extensiveintegrated safety features
# Non-contact measurements.
# It givesthetruerefractivelength than anatomical
axial length
79
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Department of Ophthalmology,
JNMC

80. Advantages
# Accuracy of IOL Master is0.02 µm which is
operator independent
# It isupright, non contact, ultrahigh resiltuion
biometry
# Highly ametropic patient can wear glasseswhile
sitting on theIOL master which aidsin fixation
# It hastheadvantageof measuring foveain cases
of posterior staphyloma
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Department of Ophthalmology,
JNMC

81. Limitations
# Cannot measureaxial length in media
opacitieslikecorneal opacities, dense
cataract, nuclear sclerosisgradeIV, posterior
Polar Cataract
# Cannot measureaxial length in casesof
vitreoushaemmorrhage
# Difficulty in measuring axial lengthsin
infants, small children and mentally
handicapped patients
# Patientswith poor fixation
81
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Department of Ophthalmology,
JNMC

82. Do not throw away old ultrasound
machine
Immersion
ultrasound
IOL
master
Posterior staphyloma
Silicone oil
Pseudophakia
4++brunescent lens
Central PSC plaque
Vitreous hemorrhage
Central corneal scar
Difficult
Difficult
Variable
•Yes
•Yes
•Yes
•Yes
•Yes
•Yes
•Yes
No
No
No
No

83. Lenstar 900
4th March 2015 Department of Ophthalmology,
JNMC
83
4th
March 2015

84. Lenstar 900
Lenstar featuresauniquedual zonekeratometer with a
total of 32 marker pointson two concentric ringsof 1.65
and 2.3 mm in diameter for improved refractive
outcomeswith toric lense.
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85. Lenstar 900
It hasbeen complemented with
an optional T-Conetopography
add-on and an optional toric
surgery planning platform.
TheT-ConeenablestheLenstar
to providetruePlacido
topograph of thecentral 6 mm
optical zone.
Thetoric surgery planning
platform allowsplanning and
optimization of thesurgical
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86. Lenstar 900
• Thetoric planner showstheimplantation axis, the
incision location and user-defined guiding meridiansin
thereal patient image.
• Incision optimization toolsallow for preciseplacement
of theincision to minimizetheresidual astigmatism
based on thesurgically induced astigmatism.
• Planning of theoperation on real eyeimagesallowsthe
user to definerecognizable, additional guiding linesto
anatomical landmarksin theintraoperativeview.
• They either serveasabaselinepoint for the
intraoperativeorientation or asafallback strategy if
external marking isnot successful.
• Theplanning sketch can easily beprinted and hung near
themicroscope
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87. • The LENSTAR LS 900 ® measures:
·· Axial eye length
·· Corneal thickness
·· Anterior chamber depth
·· Aqueous depth
·· Lens thickness
·· Radii of curvature of flat and
steep meridian
·· Axis of the flat meridian
··White-to-white distance
·· Pupil diameter4th March 2015 Department of Ophthalmology,
JNMC
87
Lenstar 900
4th
March 2015

88. 88
Olsen formula
calculatesthepostoperativelens
position asafraction of the
crystallinelensthicknessand the
ACD.
Thisapproach allowsaccurate
calculation of thelensposition
independent of thecorneal status
of theeye.
Thelensposition isthen used to
calculatetheIOL power based
on ray tracing, thesame
technology that physicistsuseto
design telescopesand camera
4th
March 2015

89. Post -refractive IOL
calculation
4th March 2015 Department of Ophthalmology,
JNMC
89
• ShammasNo-History and Masket – for
premium results
• TheLenstar EyeSuitesoftwareprovides
theuser with acomprehensiveset of
cutting-edgeIOL calculation formulae
for normal eyes. IOL Power calculation
in patientswith prior LASIK or PRK,
presenting with no history, iseasily
achieved with theon-board Shammas
No-History method.
• If thechangein refraction isknown, then
theMasket and modified Masket
formulaemay also beused.
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90. Optical Biometer Properties
90
Feature Device
IOL Master Lenstar
Axial Length X X
White to White X X
Keratometry X X
ACD X X
Pachymetry X
Lens Thickness X
Retinal
Thickness
X
Pupillometry X
Visual Axis X
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91. Summary
With state of the art technology
and modern IOL calculation
formulas, excellent refractive
outcomes can be achieved after
IOL implantation in challenging
eyes, that approach the
benchmarks postulated for
91
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Department of Ophthalmology,
JNMC

92. 08/22/15 01:46 PM Dept. of Ophthalmology, JNMC 92