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IOL Master
Moderator: Dr. A.Y.
Yakkundi
Presenter: Dr. Arushi
4th
March ‘15
History
• Theopticsof theeye
representsoneof theoldest
fieldsin ophthalmology
• Thehistory of IOL power
calculation began ...
4th March 2015 3
• Heused thehuman lensashismodel and
selected similar radii of curvatureto createa
biconvex disc whileusi...
4th March 2015 4
• TheRidley lenswasplaced in theposterior
chamber after ECCE.
• Theanterior capsulectomy of theday wasver...
4th March 2015 5
• Becauseof thedifficulty with posterior chamber IOL
placement, pioneering surgeons spent thenext two
dec...
4th March 2015 6
• A major breakthrough camein thelateseventieswith
DoctorsBinkhorst and Worst in Europeand Dr. Shearing
i...
4th March 2015 7
• Whilethiswasgoing on, Dr. CharlesKelman, was
developing phacoemulsification, aradically new method
of r...
• Implant materialsand designscontinued to improve
through thelate20th century and early 21st century.
Implantsweredevelop...
4th March 2015 9
• Somepatientshavealargeamount of astigmatism.
• Thisdefect can beoptically corrected with proper glasses...
4th
March 2015
Department of Ophthalmology,
JNMC 10
“Accurateand precisebiometry isoneof thekey
factorsin obtaining agood ...
Ophthalmic
Ultrasonography
4th
March 2015
Department of Ophthalmology,
JNMC 11
Non- invasive, efficient and inexpensive
di...
Physics of
Ultrasonography
4th
March 2015
Department of Ophthalmology,
JNMC 12
• Based on propagation, reflection and
atte...
Physics of
Ultrasonography
4th
March 2015
Department of Ophthalmology,
JNMC 13
• Speed of ultrasound dependson medium thro...
4th
March 2015
Department of Ophthalmology,
JNMC 14
 Examiner dependent
 Needs high level of skill and expertise
 Dynam...
Measurement of
Corneal Power
• Corneal power accountsfor about 2/3rd
sof
thetotal dioptric power of theeyeand isan
importa...
• Unfortunately calculation of corneal power is
not astraight forward process
• No keratometer measurescorneal power
direc...
• A magnification iscalculated from theimage
sizewhich isdirectly related to theradiusof
curvatureof thereflecting corneal...
18
Measurement of
Corneal Power
Department of Ophthalmology,
JNMC
Measurement of
Axial Length
• Measurement of axial length remainsoneof
themost crucial stepsin IOL power
calculation.
• As...
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
...
a = cornea spike
b = anterior lens spike
c = posterior lens spike
d = retinal spike
e = orbital spike
21
Acoustic
Biometry...
22
Acoustic
Biometry• Thebest signal isobtained when the
ultrasonic beam strikesasurfaceat normal
incidencethat givesriset...
• The‘retinal’ spikeisgenerally assumed to
ariseat theinternal limiting membraneof the
retina
• Thismay call for correctio...
• For thenormal phakic eye, velocity is
generally assumed to be1532/second for the
anterior chamber and vitreousand
1641m/...
Thepitfallsof ultrasound measurementsare
numerous
•Readingsshould becoaxial with theocular axis
•Thisrequiresasteep spikef...
• Someeyesdo not haveperfectly parallel
structures, however,
• readingscan bedifficult to obtain in eyeswith
densecataract...
27
Optical
Biometry
4th
March 2015
Department of Ophthalmology,
JNMC
• Theintroduction of optical biometry using
partial coherenceinterferometry significantly
improved theaccuracy with which ...
OPTICAL
BIOMETRY
29
• However, just asdistancemeasurementstaken
with ultrasound aredependent on theassumed
ultrasound velo...
30
Optical Biometry –
Uses Optical Low-Coherence Reflectometry,
a similar technology that is used in OCT
devices. This tec...
Principle of Michelson
Interferometer
Xiaoyu Ding
Albert Michelson (1852~1931)
thefirst American scientist to
receiveaNobe...
Principle of Michelson
Interferometer
A Michelson Interferometer for use on an optical table
Xiaoyu Ding
1)Separation
2)Re...
33
IOL master employstheprincipleof optical
coherencebiometry (OCB)
It usespartially coherent infrared light beamsof
780nm...
34
Thisinterferenceproducesalight and dark band
pattern which isdetected by aphoto detector
Thesignalsareamplified, filter...
The Down Side
Sinceoptical Biometry useslight
thereisahigher probability of the
“scatter” effect. Meaning that if the
lig...
IOL Master (Carl Zeiss)
Lenstar LS 900 (Haag-Streit)
Manufacturers
36
4th
March 2015
Department of Ophthalmology,
JNMC
IOL Master
A combined biometry instrument. It measures
parametersof thehuman eyeneeded for
intraocular lenscalculation.
37...
4th
March 2015
Department of Ophthalmology,
JNMC 38
1.Joystick with
release button
2.Display
3.Red eye
level marks
4.Lock ...
4th
March 2015
Department of Ophthalmology,
JNMC 39
1.DVD Drive
2.Adjustment
of headrest
3.Chin rest
4.Holding
pins for pa...
IOL Master
4th
March 2015
Department of Ophthalmology,
JNMC 40
It measuresquickly and precisely :
1. Axial length
2. Corne...
It measures quickly and precisely
Axial length : Based on partial coherence interferometry
( Michelson interferometer)
Cor...
How do we operate
IOLmaster ?
After switching on the device, patient manager screen will
appear
42
4th
March 2015
Screen layout
43
4th
March 2015
Axial length
measurement(alm)Activate the axial length measurement mode by clicking on
ALM icon.
Switching to ALM mode wil...
Note : The patient should be asked if he or she sees the
fixation point. If the patient fails to fixate properly, the visu...
The IOL Master requires five measurements to be taken.
The message Measure again will thus appear. Only then
will the comp...
Axial Length Modes
1.Phakic
2.Pseudophakic
3.Aphakic
4.Silicone filled eyes
47
Axial length
measurement
4th
March 2015
Dep...
 IOLMaster produces a primary maxima (narrow, well-defined,
centered peak identified by a circle above it), secondary
maxi...
SNR categories :SNR is a measure of accuracy and
decreases with increasing cataract density.
The SNR is automatically anal...
Keratometric
measurementAsk the patient to relax and look at the fixation
light. If the patient cannot see the fixation li...
Focus points
51
TheIOLMaster
reflectssix pointsof
light, arranged in a2.3
mm diameter
hexagonal pattern
(measured by digit...
Acd measurement
Ask the patient to relax and look at the fixation
light. If the patient cannot see the fixation light, he
...
The image of the anterior crystalline lens is visible in the
pupil.
The image of the fixation point may not lie in the ima...
54
4th
March 2015
Measuring errors
The"Error" messagemay havetwo basic
causes:
• Theresultsof thefiveinternal individual
measurementsvary by...
Ask the patient to relax and look at the fixation light.
Focus on the iris, not on the light spots.
After the image has be...
57
4th
March 2015
Department of Ophthalmology,
JNMC
Once all measurements have been taken (depending on
the IOL calculation formula), options can be generated for
intraocular...
59
4th
March 2015
result
60
4th
March 2015
Measuring ranges Axial length : 14 – 40 mm
Corneal radii : 5 – 10 mm
Depth of anterior chamber : 1.5 – 6.5 mm
White-to-whi...
62
Biometry Formulas
4th
March 2015
Department of Ophthalmology,
JNMC
IOL Formulas
1st
Generation – The first theoretical formula
(based on Geometric Optics as applied to
schematic eye models)...
IOL formulas
1st
generation
•Most are based on regression formula developed
by Sander ,Retzlaff & Kraff
•Known as SRK form...
IOL formulas
2nd
Generation – With an extreme need for
increased IOL Calculation, the second generation
formulas (Hoffer, ...
IOL formulas
• IOL FORMULA 2nd
generation
• SRK II formula
• modification of SRK
• works on ELP
• P = A1 – 2.5L – 0.9K
66
...
IOL formulas
3rd
Generation – In 1988 Dr. Holladay published
a formula (Holladay I)that predicted the AC
Depth on the basi...
IOL formulas
• IOL FORMULA 3rd
generation
• Third generation formulas-
• SRK/T -very long eyes >26mm
• Holladay I -long ey...
IOL formulas
• IOL FORMULA 4th
generation
• Holladay II
• Haigis formula-
• d = a0 + (a1 * ACD) + (a2 * AL)
• ACD is the m...
IOL formulas
• When capsular tear does not allow bag
placement of the lens → change IOL
power for sulcus placement
• >=28....
LensConstants
A-Constants are used with all IOL formulas, and
are determined by the anticipated position within
the eye.
S...
Typesof Formulas
Regression formulas are based upon mathematical
analysis of a large sampling of post-operative results. ...
Typesof Formulas
Theoretical formulas are optical formulas based on the
optical properties of the eye.  They do a better ...
Formula Requirements
Haigis Hoffer Q SRK/2 SRK/T HOLLADAY 1 HOLLADAY 2 Olsen
Axial Length YES YES YES YES YES YES YES
ACD ...
Formula Preferences
75
4th
March 2015
Short Eyes (<22.0mm) Hoffer Q / Holladay 2
Average Eyes (22.1-
24.4mm)
Hoffer Q /
Ho...
Post-Refractive Surgery Patient
One of the most challenging problems facing modern
Cataract Surgery is the Post-Refractiv...
Post Refractive Formulas
Haigis L - The Haigis-L formula offers predictable outcomes
after laser refractive surgery for m...
Shammas – Used when no pre-op data is available such as
refraction and keratometry.
Double K SRK/T – Utilizes pre-op ref...
Advantages
#  Learned very quickly (User Friendly)
#  Extensiveintegrated safety features
#  Non-contact measurements.
# I...
Advantages
# Accuracy of IOL Master is0.02 µm which is
operator independent
# It isupright, non contact, ultrahigh resiltu...
Limitations
# Cannot measureaxial length in media
opacitieslikecorneal opacities, dense
cataract, nuclear sclerosisgradeIV...
Do not throw away old ultrasound
machine
Immersion
ultrasound
IOL
master
Posterior staphyloma
Silicone oil
Pseudophakia
4+...
Lenstar 900
4th March 2015 Department of Ophthalmology,
JNMC
83
4th
March 2015
Lenstar 900
Lenstar featuresauniquedual zonekeratometer with a
total of 32 marker pointson two concentric ringsof 1.65
and...
Lenstar 900
It hasbeen complemented with
an optional T-Conetopography
add-on and an optional toric
surgery planning platfo...
Lenstar 900
• Thetoric planner showstheimplantation axis, the
incision location and user-defined guiding meridiansin
there...
• The LENSTAR LS 900 ® measures:
·· Axial eye length
·· Corneal thickness
·· Anterior chamber depth
·· Aqueous depth
·· Le...
88
Olsen formula
calculatesthepostoperativelens
position asafraction of the
crystallinelensthicknessand the
ACD.
Thisappro...
Post -refractive IOL
calculation
4th March 2015 Department of Ophthalmology,
JNMC
89
• ShammasNo-History and Masket – for
...
Optical Biometer Properties
90
Feature Device
IOL Master Lenstar
Axial Length X X
White to White X X
Keratometry X X
ACD X...
Summary
With state of the art technology
and modern IOL calculation
formulas, excellent refractive
outcomes can be achieve...
08/22/15 01:46 PM Dept. of Ophthalmology, JNMC 92
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Iol master

IOL Master

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Iol master

  1. 1. IOL Master Moderator: Dr. A.Y. Yakkundi Presenter: Dr. Arushi 4th March ‘15
  2. 2. History • Theopticsof theeye representsoneof theoldest fieldsin ophthalmology • Thehistory of IOL power calculation began in 1949 when Sir Harold Ridley implanted thefirst IOL. 2 Department of Ophthalmology, JNMC
  3. 3. 4th March 2015 3 • 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 3 4th March 2015 Department of Ophthalmology, JNMC
  4. 4. 4th March 2015 4 • 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 4 4th March 2015 Department of Ophthalmology, JNMC
  5. 5. 4th March 2015 5 • 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 5 4th March 2015 Department of Ophthalmology, JNMC
  6. 6. 4th March 2015 6 • 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 6 4th March 2015 Department of Ophthalmology, JNMC
  7. 7. 4th March 2015 7 • 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 7 4th March 2015 Department of Ophthalmology, JNMC
  8. 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. 4th March 2015 8 History 8 4th March 2015 Department of Ophthalmology, JNMC
  9. 9. 4th March 2015 9 • 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 9 4th March 2015 Department of Ophthalmology, JNMC
  10. 10. 4th March 2015 Department of Ophthalmology, 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. 11. Ophthalmic Ultrasonography 4th 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. 12. Physics of Ultrasonography 4th March 2015 Department of Ophthalmology, 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. 13. Physics of Ultrasonography 4th March 2015 Department of Ophthalmology, 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
  14. 14. 4th March 2015 Department of Ophthalmology, JNMC 14  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. 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. 15 4th March 2015 Department of Ophthalmology, JNMC
  16. 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 16 Measurement of Corneal Power 4th March 2015 Department of Ophthalmology, JNMC
  17. 17. • A magnification iscalculated from theimage sizewhich isdirectly related to theradiusof curvatureof thereflecting corneal surface. • To do this, thecorneaisnormally assumed to beasperocylinder, 17 Measurement of Corneal Power 4th March 2015 Department of Ophthalmology, JNMC
  18. 18. 18 Measurement of Corneal Power Department of Ophthalmology, JNMC
  19. 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 19 4th March 2015 Department of Ophthalmology, JNMC
  20. 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 20 • Deviation from themean valuesof different variablesand corresponding refraction errors 4th March 2015 Department of Ophthalmology, JNMC
  21. 21. a = cornea spike b = anterior lens spike c = posterior lens spike d = retinal spike e = orbital spike 21 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. 4th March 2015
  22. 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. 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 23 Acoustic Biometry 4th March 2015 Department of Ophthalmology, JNMC
  24. 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 24 4th March 2015
  25. 25. Thepitfallsof ultrasound measurementsare numerous •Readingsshould becoaxial with theocular axis •Thisrequiresasteep spikefrom theretinaas well asgood spikesfrom theanterior and posterior surfacesof thelens 25 Acoustic Biometry limitations
  26. 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 26 Acoustic Biometry limitations 4th March 2015
  27. 27. 27 Optical Biometry 4th March 2015 Department of Ophthalmology, JNMC
  28. 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 28 4th March 2015
  29. 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. 4th March 2015
  30. 30. 30 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. 4th March 2015 Department of Ophthalmology, JNMC
  31. 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 31 4th March 2015
  32. 32. Principle of Michelson Interferometer A Michelson Interferometer for use on an optical table Xiaoyu Ding 1)Separation 2)Recombination 3)Interference 32 4th March 2015 Department of Ophthalmology, JNMC
  33. 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 4th March 2015 Department of Ophthalmology, JNMC
  34. 34. 34 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. 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. 35 4th March 2015 Department of Ophthalmology, JNMC
  36. 36. IOL Master (Carl Zeiss) Lenstar LS 900 (Haag-Streit) Manufacturers 36 4th March 2015 Department of Ophthalmology, JNMC
  37. 37. IOL Master A combined biometry instrument. It measures parametersof thehuman eyeneeded for intraocular lenscalculation. 37 4th March 2015 Department of Ophthalmology, JNMC
  38. 38. 4th March 2015 Department of Ophthalmology, 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,
  39. 39. 4th March 2015 Department of Ophthalmology, 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. 40. IOL Master 4th March 2015 Department of Ophthalmology, 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. 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. 41 4th March 2015
  42. 42. How do we operate IOLmaster ? After switching on the device, patient manager screen will appear 42 4th March 2015
  43. 43. Screen layout 43 4th March 2015
  44. 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 44 4th March 2015 Department of Ophthalmology, JNMC
  45. 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. 45 Axial length measurement 4th March 2015 Department of Ophthalmology, JNMC
  46. 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. 47. Axial Length Modes 1.Phakic 2.Pseudophakic 3.Aphakic 4.Silicone filled eyes 47 Axial length measurement 4th March 2015 Department of Ophthalmology, JNMC
  48. 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. 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 49 Axial length measurement 4th March 2015 Department of Ophthalmology, JNMC
  50. 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. 50 4th March 2015 Department of Ophthalmology, JNMC
  51. 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. 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: 52 4th March 2015
  53. 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. 53 Acd measurement 4th March 2015 Department of Ophthalmology, JNMC
  54. 54. 54 4th March 2015
  55. 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. 55 Acd measurement 4th March 2015 Department of Ophthalmology, JNMC
  56. 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. 56 WTW measurement 4th March 2015 Department of Ophthalmology, JNMC
  57. 57. 57 4th March 2015 Department of Ophthalmology, JNMC
  58. 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. 58 IOL CALCULATION 4th March 2015
  59. 59. 59 4th March 2015
  60. 60. result 60 4th March 2015
  61. 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 61 4th March 2015 Department of Ophthalmology, JNMC
  62. 62. 62 Biometry Formulas 4th March 2015 Department of Ophthalmology, JNMC
  63. 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) 63 4th March 2015 Department of Ophthalmology, JNMC
  64. 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 64 4th March 2015 Department of Ophthalmology, JNMC
  65. 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) 65 4th March 2015 Department of Ophthalmology, JNMC
  66. 66. IOL formulas • IOL FORMULA 2nd generation • SRK II formula • modification of SRK • works on ELP • P = A1 – 2.5L – 0.9K 66 4th March 2015 Department of Ophthalmology, JNMC
  67. 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 67 4th March 2015
  68. 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 68 4th March 2015 Department of Ophthalmology, JNMC
  69. 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" 69 4th March 2015 Department of Ophthalmology, JNMC
  70. 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 70 4th March 2015 Department of Ophthalmology, JNMC
  71. 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 4th March 2015
  72. 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 72 4th March 2015
  73. 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. 73 4th March 2015 Department of Ophthalmology, JNMC
  74. 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 74 4th March 2015 Department of Ophthalmology, JNMC
  75. 75. Formula Preferences 75 4th March 2015 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. 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 4th March 2015 Department of Ophthalmology, JNMC
  77. 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. 77 4th March 2015 4th March 2015
  78. 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 78 4th March 2015 Department of Ophthalmology, JNMC
  79. 79. Advantages #  Learned very quickly (User Friendly) #  Extensiveintegrated safety features #  Non-contact measurements. # It givesthetruerefractivelength than anatomical axial length 79 4th March 2015 Department of Ophthalmology, JNMC
  80. 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 80 4th March 2015 Department of Ophthalmology, JNMC
  81. 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 4th March 2015 Department of Ophthalmology, JNMC
  82. 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. 83. Lenstar 900 4th March 2015 Department of Ophthalmology, JNMC 83 4th March 2015
  84. 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. 84 4th March 2015
  85. 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 85 4th March 2015
  86. 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 86 4th March 2015
  87. 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. 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. 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. 4th March 2015
  90. 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 4th March 2015
  91. 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 4th March 2015 Department of Ophthalmology, JNMC
  92. 92. 08/22/15 01:46 PM Dept. of Ophthalmology, JNMC 92

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