ASCRS ♦ ASOA Symposium & Congress

Technicians & Nurses Program

April 17-21, 2015 – San Diego, California

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Intraocular Lens Decision Making

Christopher Gelston, MD Assistant Professor University of Colorado School of Medicine Rocky Mountain Lions Eye Institute

Disclosure

S  No financial interests in this presentation.

Background

S  Cataract surgery is the most common procedure performed with more than 3 million procedures each year.1

S  Patient expectations with cataract surgery have changed: S  From simply restoring vision S  Increased emphasis on refractive outcomes and patient’s desires to be spectacle

independent.

S  Cataract surgery is also a leading source of malpractice complaints. In 2007 5% of Ophthalmologists insured by OMIC reported a claim. S  Typically the wrong intraocular lens (IOL) is the culprit for more than half the

“wrong” cases.2

Background

S  Patient safety bulletin issued by AAO identified potential errors identifying why the “wrong” IOL is used.3

S  Use of an outdate IOL formula or incorrect formula for axial length (AL) S  Incorrect biometry S  Incorrect data entry for IOL calculation program S  Incorrect labeling or packaging of IOL S  Mistakes in providing the IOL at time of surgery (switching IOL meant for another

patient) S  Minimize error with a “Time Out” to confirm IOL before each case

Key Points

S  Review optical biometry and IOL calculation formulas to improve post-operative refractive accuracy.

S  Determine which IOL may be best for certain patients to improve their post-operative satisfaction.

S  The most flawless surgery could be performed but if measurements are inaccurate or failure to understand patients’ post-operative refractive goals – they may consider it a complication.

Biometry

S  IOL power calculations depend on precise biometry for accurate outcomes.

S  In order to determine the power of the IOL several values need to be measured: S  Axial length (AL) of the eye S  Corneal power or keratometry (K) S  Effective lens position (ELP)

S  The AL and K readings are measured pre-operatively and the ELP is then calculated using these measurements.

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Biometry

S  Ultrasound axial length measurements had been the gold standard for many years.

S  Uses a 10 MHz sound wave to measure axial length.

S  Look for steep retinal spike S  Slopping or steps in the retinal spike

may indicate a misalignment error.

Cornea Anterior and Posterior Lens Retina Sclera

Biometry

S  Applanation vs. Immersion

S  Operator error may occur with direct applanation of the cornea. S  Indentation of cornea may induce error in axial

length measurements.

S  Immersion uses a fluid chamber where the ultrasound probe doesn’t come in contact with the cornea and can reduce error in axial lengths.

S  Need keratometry readings (from topography) to calculate IOL power using the different formulas.

Biometry

S  Partial coherence interferometry base biometry (Zeiss IOL Master or Haag Streit LENSTAR) uses a 780 um infrared light wave that has 8x the resolution of a 10 MHz sound wave making measurement of axial length precise.

S  Measures to center of macula giving the refractive axial length versus the anatomical axial length achieved with ultrasound biometry.

S  Able to measure, corneal diameter, corneal curvature, and anterior chamber depth.

Biometry

S  Partial coherence interferometry base biometry such as IOL Master can not be used for everyone.

S  May not be able to capture measurements in patients with hypermature cataracts or patients who can not position appropriately. S  Require ultrasound axial length

measurement.

Biometry

S  Prior to taking measurements certain steps can be taken to improve accuracy. S  Recommend using artificial

tears prior to taking the measurements to obtain a reliable topography and keratometry readings

Biometry

S  No contact lens use prior to taking measurements.

S  1 week for soft contact lens

S  3 weeks for hard contacts

S  Contact lenses may induce corneal warpage with an appearance similar to keratoconus and keratometry results may change after not wearing them.

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Biometry

IOL formula and Target Refraction

Axial Length Keratometry Readings

IOL Power

Biometry

S  Need to analyze results to ensure accuracy.

S  Axial lengths should be < 0.3 mm between the two eyes.

S  If > 0.3 mm confirm the difference unless evidence suggests differently S  Prior scleral buckle S  Anisometropia S  Keratoconus S  Prior refractive surgery.

Biometry > 0.3 mm

A-scan ultrasound confirms axial length difference.

Biometry

Axial length difference of nearly 7 mm.

Prior scleral buckle left eye.

IOL Formulas

S  The 3rd generation IOL calculation formulas require axial length (AL and corneal power (K) obtained by optical biometry: S  Hoffer Q S  Holladay 1 S  SRK/T

S  They use theoretical formulas rather than earlier regression formulas such as the SRK (P = A - 0.9K - 2.5L).

Effective Lens Position

S  Differ in how they calculate the post-operative effective lens position (ELP).4

S  Holladay 1 and SRK/T formulas use a corneal height equation to predict post-operative ELP.

S  Hoffer Q formula uses a different formula in which the tangent of corneal power is used.

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IOL Formulas

S  The third generation formulas (Hoffer Q, Holladay 1 and SRK/T) use a two-variable formula to predict the ELP based on axial length and keratometry.

S  The two-variable formula assumes several factors that may result in inaccurate calculation: S  Short eyes will produce a shallower ELP and a longer eye will have a deeper ELP S  Flat K’s will result in a more shallow ELP and steeper K’s will result in a deeper

ELP.

IOL Formulas

S  The Holladay 2 formula was developed to more accurately determine the ELP and uses several additional variables to adjust the recommended IOL power: S  Axial length S  Keratometry S  Horizontal corneal diameter S  Lens thickness S  Anterior chamber depth S  Age S  Preoperative refraction

Which Formula?

S  Mean absolute error or deviation from predicted post-operative refractive error. S  Hoffer Q most accurate with short

axial lengths (<22mm)4

S  Holladay 1 most accurate with average axial length (>22mm - <26mm)5

S  SRK/T most accurate with longer axial lens (>26mm)5

S  Holladay 2 equal to Hoffer Q in shorter axial lengths, similar to Holladay 1 in average axial lengths6

S  Using the appropriate IOL formula can improve the accuracy of the refractive outcome.

AL Formula

<22mm

22mm - 26mm

>26mm

Hoffer Q

Holladay 1

SRK/T

Which Formula?

> 26 mm use SRK/T Post-Op Refraction: -0.25+0.50x67 à 20/20

Post-Refractive Surgery

S  3rd generation IOL formulas in post-refractive surgery are less accurate as the true corneal power following refractive surgery is difficult to measure.

S  Keratometry assumes a normal relationship between the anterior and posterior corneal curvatures.

S  Post-myopic refractive surgery (Lasik and PRK) flattens the anterior cornea radius and leaves the posterior cornea mostly unchanged. S  Keratometry overestimates the corneal power

and underestimates the IOL power.

Post-Refractive Keratometry

S  Standard keratometry measures an intermediate area and extrapolates the central power.

S  Corneal topography typically over estimates the central corneal power and underestimation of the ELP leading to hyperopic surprises.

S  Important to counsel patient pre-operatively about these inaccuracies and the potential need for refractive correction after surgery.

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Post-Refractive Calcs

S  Several different formulas have been developed for post-refractive surgery patients. S  The Aramberri Double-K method S  Haigis-L formula S  Shammas formula

S  To facilitate the process of determining which IOL power should be used the ASCRS website has a post-refractive IOL calculator that uses several different methods. S  www.iolcalc.org

Post-Refractive Calcs 9/6/14 8:44 AM

Page 1 of 2http://iolcalc.org/wbfrmCalculator.aspx

IOL Calculator for Eyes with Prior Myopic LASIK/PRK(Your data will not be saved. Please print a copy for your record.)

Please enter all data available and press "Calculate"

DoctorName XXX Patient

Name XXX Eye OD IOLModel ZCBOO

Pre-LASIK/PRK Data:Refraction* Sph(D) Cyl(D)* Vertex (If empty, 12.5 mm will be used)

Keratometry K1(D) K2(D)

Post-LASIK/PRK Data: Refraction*§ Sph(D) -1.25 Cyl(D)* +1.00 Vertex(mm)

Topography EyeSysEffRP

Atlas 9000 4mm zone

Tomey ACCPNidek#ACP/APP

Galilei TCP**

V5.2.1 or later

V5.2 or earlier

Atlas Ring Values 0mm 1mm 2mm 3mm

Optical (IOLMaster/Lenstar)/Ultrasound Biometric Data:

Ks K1(D) 41.41 K2(D) 42.03 Keratometric Index (n)*** 1.3375 1.332 Other

AL(mm) 23.92 ACD(mm) 3.33 Target Ref (D) 0

Lens Constants**** A-const(SRK/T) 119.1 SF(Holladay1)

Haigis a0 Haigis a1 Haigis a2

*If entering "Sph(D)", you must enter a value for "Cyl(D)", even if it is zero. §Most recent stable refraction prior to development of a cataract.# Magellan ACP or OPD-Scan III APP 3-mm manual value (personal communication Stephen D. Klyce, PhD).**Select the version of your Galilei device: "V5.2 or earlier" or "V5.2.1 or later". ***Select the keratometric index (n) of your device. Instruments in North America typically default to 1.3375.****Enter any constants available; others will be calculated from those entered. If ultrasonic AL is entered, be sure to use your ultrasoundlens constants.

Calculate Reset Form

IOL calculation formulas used: Double-K Holladay 11, Shammas-PL2, & Haigis-L3

Using Pre-LASIK/PRK Ks + ∆MR Using ∆MR Using no prior data

History --Feiz-Mannis --

Corneal Bypass --

1Adjusted EffRP --2Adjusted Atlas 9000 (4mm zone) --

1Adjusted Atlas Ring Values --Masket Formula --Modified-Masket --

1Adjusted ACCP/ACP/APP --

2Wang-Koch-Maloney --2Shammas 23.86 D

3Haigis-L 23.58 D1Galilei --

Average IOL Power (∆MR only & No Prior Data): 23.72 D

Average IOL Power (All Available Formulas): 23.72 D

Min: 23.58 D

Post-Op hyperopic refraction would have occurred if no adjustments made. Post-Op Refraction: -0.25 sphere à 20/20

ORA – Future?

S  Optiwave Refractive Analysis (ORA) system is an intraoperative refractive biometry system. Attaches to the operative microscope and can be used during surgery to determine aphakic refractive measurements.

S  Utilizes intraoperative wavefront aberrometer based on Talbot-Moire interferometry to determine sphere, cylinder and axis.

S  Developed to minimize or eliminate dependence of pre-operative anatomical measurements such as AL or keratometry.

S  Calculate the IOL power based on the aphakic spherical equivalent to estimate the ELP.

ORA – Future?

S  Potential benefit in patients with prior refractive surgery including RK, PRK or Lasik.

S  Ianchulev T. et al used the ORA in a series of 246 eyes with a history of Lasik or PRK to determine the IOL power choice.7

S  67% within +0.5D S  94% within 1.0D of predicted target S  More accurate than Haigis-L or Shammas method.

Which IOL?

S  A successful cataract surgery not only depends on optical biometry and IOL calculation but also the IOL type used to meet the patient’s post-operative desire and target distance. S  Monofocal IOL S  Toric IOL S  Multifocal IOL

Monofocal IOL

S  Monofocal IOL targets one distance leaving individuals dependent on some post-operative correction.

S  Pre-operative refractive error is important in deciding the target distance. S  Aim for distance vision in both eyes with anticipation for reading glasses after

surgery. S  Beware of the -2.00 patients!

S  Aim for near vison in both eyes with anticipation for distance glasses after surgery.

S  Monovision outcome that respects ocular dominance, targeting the dominant eye for distance and the non-dominant eye for near vision.

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Toric IOL

S  Toric IOL used for patient’s with astigmatism. Targets one distance leaving individuals dependent on some correction. Use for patients who are interested in spectacle independence even if for only one distance.

S  Corneal astigmatism measured by corneal topography. Only corneal astigmatism needs to be addressed. IOLs may correct up from 1D – 4D.

S  acrysoftoriccalculator.com or amoeasy.com

Toric IOL

S  Caution in patients with irregular astigmatism. S  Keratoconus S  Corneal ectasia S  Corneal scar

S  May not be able to fully neutralize the corneal astigmatism.

Toric IOL

S  Difference between keratometry readings and manifest refraction

S  Refraction: +0.75 +1.50 x 66

S  K-readings: 45.06 x 45.79 (0.73 D of astigmatism)

S  Not a candidate for toric

Toric IOL Calculator 9/10/14 8:45 PMAcrySof® IQ Toric IOL Calculator Online

Page 1 of 2http://www.acrysoftoriccalculator.com/aspheric/Calculator.aspx

Alcon does not receive or retain any patient data. Please print a copy of the final output for yourrecords. Contact your Alcon representative for available AcrySof® IQ Toric IOL models and diopter

ranges. Print

Lens RecommendationSurgeon & Patient Information

OD (Right)

Temporal

Nasal

Surgeon Name XXXPatient Name XXX Additional Patient Information (I.D., Case, etc.)

Lens Details

AcrySof® IQ Toric IOL SN6AT3 IOL Spherical Equivalent (SE) 14.5 D Axis of Placement 128° Cylinder Power(IOL Plane) 1.50 D Cylinder Power (Corneal Plane) 1.03 D

Calculation Details

Pre-Op Corneal Astigmatism: 1.26 D X 125°

Surgically InducedAstigmatism: 0.50 D X 30°

Crossed-Cylinder Result(corneal plane): 0.77 D X 128°

Anticipated ResidualAstigmatism: 0.26 D X 38°

Pre-Op InformationPatient Data

Temporal

Steep AxisFlat AxisIncision

Nasal

Flat K 41.46 D@ Flat Axis 35°Steep K 42.72 D@ Steep Axis 125°IOL SphericalPower (P-IOL) 14.5 D

Surgically Induced Astigmatism(SIA) 0.50 D

Incision Location (IL) 120°

Notes:

b97077017437e6969163efbdcd278f56 9/10/14 22:44:57

V: 3.2.1

9/10/14 8:53 PMAMOeasy IOL Calculators

Page 1 of 1https://www.amoeasy.com/toric2(bD1lbiZjPTA1MA==)/ToricPrintResul…m?sap-params=cF9jYWxjdWxhdG9yPVRPUklDJnBfaW9sdG9vcmRlcj0wMDE%3d

V: 3.8

Return To Calculator V: 3.8

Surgeon Name Patient Information Date Patient AgeXXX XXX 09/10/2014

IOL Details

Residual RefractionIOL Model Orientation Cylinder Axis

ZCB00 128 ° +0.71 D 128°

Calculation DetailsSE IOL power K Index Refractive Cylinder Convention

+14.50 1.3375 Plus

Keratometry and BiometryFlat K1 @ Axis Steep K2 @ Axis SIA @ Axis AxL Length Biometry Method A-constant41.46@35° 42.72@125° 0.50@120° 24.74 Optical or Immersion 119.30

IOL Details Residual AstigmatismIOL Model Orientation Cylinder AxisZCB00 128 ° +0.71 D 128 °

Notes

OD (Right)

Temporal

Nasal

(Incision Location) 120° Calculated Orientation

128 °

Multifocal IOL

S  Multifocal IOLs provide another option for patient’s who desire to be spectacle independence post-operatively. S  ReSTOR (apodized diffractive IOL with +3.0D add power) S  Technis Multifocal (full diffractive IOL with +4.0 add power)

Multifocal IOL

S  Inform patients that with a multifocal IOL they may not have absolutely crisp vision at multiple distances at all times and they must be prepared for the possibility of at least some visual distortions. S  Glare and halos around light sources at night S  Decreased contrast sensitivity S  Possibility of post-operative enhancements

S  Astigmatism correction at time of surgery (> 0.75D).

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Multifocal Candidates

S  Positive characteristics S  Easy-going personality with

realistic expectations S  Willing to accept a few

tradeoffs in exchange for reduced dependency on eyeglasses

S  Younger patients with an active lifestyle

S  High myopes

S  Negative characteristics S  Patients with unrealistic

expectations S  Corneal dystrophies – Fuchs S  Macular pathology – epiretinal

membrane or macular degeneration

S  Specific occupations with heavy dependence on night vision

S  Low myopes

Case 1

S  A 72 y/o female presents for blurry vision left eye.

S  Visually significant cataract with BCVA 20/50. S  MRx -7.00 + 0.50 x 85 S  IOL Master with an AL of 27.25mm

S  Which IOL Formula? S  SRK/T

Case 2

S  76 y/o male with visually significant cataracts is planned for surgery.

S  MRx: -4.00 + 1.75 x 85 à 20/40

S  Pre-operative corneal topography shows irregular astigmatism suggestive of keratoconus.

S  Which IOL should you use? S  Monofocal IOL with appropriate

refractive target rather than using as toric or multifocal IOL.

Case 3

S  61 y/o male is scheduled for cataract surgery and the technician performs biometry.

S  What’s wrong? S  Change the IOL formula for

the correct AL S  Confirm the AL with

immersion ultrasound (> 0.3mm).

Case 4

S  64 y/o female with history of myopic Lasik has recently developed a visually significant cataract in her right eye. She doesn’t have any pre-operative records. She elects to have a monofocal IOL.

S  MRx: -2.25 + 0.50 x 112 à 20/50

S  How do you want to counsel the patient? S  Refractive target S  Possibility of needing post-operative refractive correction

S  What steps could you use to improve the post-operative refractive target? S  Post-refractive IOL calculator on ASCRS website S  Intra-operative ORA measurement

Summary

S  Understand which IOL formulas to use in patients with various axial lengths.

S  Understand modifications to the calculations needed in post-refractive state.

S  Understand that with new technology we may be able to increase the accuracy by which IOL power is determined and the ELP.

S  Determine the IOL type to meet patient’s post-op refractive goal.

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References

1.  Center for Disease Control and Medicare

2.  Weber P. Wrong eye, wrong IOL, wrong patient. Ophthalmic Mutual Insurance Company Ophthalmic Risk Management Digest 2008;18:1-5.

3.  Minimizing Wrong IOL Placement. Patient Safety Bulletin Number 2: A joint statement of the American Academy of Ophthalmology, the American Society of Ophthalmic Registered Nurses and the American Association of Eye and Ear Hospitals. Available at: http://webeye.ophth.uiowa.edu/asorn/Safety/SafetyBulletin2.htm. Accessed December 3, 2008.

4.  Hoffer KJ. The Hoffer Q formula: a comparison of theoretical and regression formulas. J Cataract Refract Surg 1993;19:700-12..

5.  Aristodemou P, Knox Cartwright NE, Sparrow JM, Johnston RL. Formula choice: Hoffer Q, Holladay 1, or SRK/T and refractive outcomes in 8108 eyes after cataract surgery with biometry by partial coherence interferometry. J Cataract Refract Surg 2011;37:63-71.

6.  Hoffer KJ. Clinical results using the Holladay 2 intraocular lens power formula. J Cataract Refract Surg 2000;26:1233-37.

7.  Ianchulev T et al. Intraoperative refractive biometry for predicting intraocular lens power calculation after prior myopic refractive surgery. Ophthalmology 2014;121:56-60.