Advanced Imaging Using Advanced Imaging Using High Frequency Ultrasound: High Frequency Ultrasound:

Techniques for Phakic IOL SizingTechniques for Phakic IOL Sizing

Robert P. Rivera MDRobert P. Rivera MDBarnet Dulaney Perkins Eye CenterBarnet Dulaney Perkins Eye Center

Phoenix, AZ USAPhoenix, AZ USA

ASCRS SymposiumASCRS SymposiumCourse 10-304 Course 10-304

Boston, MABoston, MAApril 10, 2010April 10, 2010

Financial DisclosuresFinancial Disclosures

• Sonomed• STAAR Surgical• Alcon• Bausch & Lomb• Ellex

Sizing of the Visian ICLSizing of the Visian ICL

• The Visian ICL is a posterior chamber phakic IOL implanted in the ciliary sulcus

• ICL length selected for each patient is based on horizontal white-to-white (WTW) measurement– US FDA Clinical Study based on WTW– FDA approval based on WTW

• Assumption was that external surface WTW measurement would closely follow sulcus-to-sulcus (STS) length

Sizing of the Visian ICLSizing of the Visian ICL

• Subsequent results and studies showed this was an inaccurate assumption– The WTW measurement could in fact be either

longer or shorter than the STS– Since the ICL haptics reside in the sulcus, the

sulcus dimensions are more important than any external measurement

• To be fair, UBM technology was not available in earlier days of ICL implantation

Sizing of the Visian ICLSizing of the Visian ICL

• 17% of patients in the US clinical trial did not have optimal vault (90-1000 µ)

• Exchange of an ICL for sizing related issues places patient at higher risk for additional complications

• Primary concerns of incorrect ICL size:– Angle closure, pupillary block

ICL too long, excessive vault– Cataracts

ICL too short, shallow vault

ICL & Ocular Anatomical RelationshipsICL & Ocular Anatomical Relationships

• Gonvers, et al, 2003 75 ICL cases, 27% cataract rate, all cataracts

had vaults less than 90 µ• Shin, et al, 2007

WTW technique is inaccurate at predicting the horizontal diameter of the ciliary sulcus

• Other pioneering work by Matamoros, Lovisolo, Zaldivar showed poor relationship between WTW and STS

ICL Sizing & OCTICL Sizing & OCT

• Rheinstein, et al– OCT imaging devices cannot image the sulcus– ATA has weak correlation to STS – ATA cannot be relied upon for ICL sizing

• Ciliary sulcus resides in an optical shadow not visible to OCT

Why UBM for Phakic IOL Sizing?Why UBM for Phakic IOL Sizing?

• Choi and Chung, 2007 – ICL length determined by UBM achieved ideal

vault compared to conventional WTW– 100% of UBM group had ideal vault after 6

months, compared to 52.9% in the WTW group

Ideal VaultIdeal Vault

• Truly “ideal” vault would be 500 µ• Inadequate vault defined as <90 µ (Gonvers 27%

cataract rate = vaults less than 90 µ)• Excessive vault defined as >1000 µ (Choi, Chung, Chung

& Chung)• Good vault range 90-1000 µ

Ideal Vault – 300-600 micronsIdeal Vault – 300-600 microns

Case Study—ICL MismatchCase Study—ICL Mismatch

• WTW called for 13.2 mm ICL• Surgeon implanted 13.2 in 1st eye (OS)

– 1 week postop OS vault looked excessive

• 2nd eye surgery (OD) in 1 week• Downsized and implanted 12.6 in OD

– 1 week postop OD vault looked better, but still excessive

OS (1OS (1stst eye) eye)

Ideal Vault – 300-600 micronsIdeal Vault – 300-600 microns

OD (2OD (2ndnd eye) eye)

STS Clearly Called for 12.1 mm ICLSTS Clearly Called for 12.1 mm ICL

STS Method Redefines ICL SizingSTS Method Redefines ICL Sizing

• Goal is to avoid sizing mismatches like these• Obtain consistent measurements that are accurate,

reproducible • Obtain valuable information that is pertinent to ICL

selection• If this could be accomplished, sizing mismatches

would become nonexistent

Development of a Sizing NomogramDevelopment of a Sizing Nomogram

• Retrospective Study– 73 eyes of 48 subjects with STS and vault

measurements taken on Sonomed VuMax II• Matamoros regression equation

– Modified with input from experienced ICL and Sonomed users

– Outcome analysis used to generate a spreadsheet of ideal ICL length, based upon STS measurements

Multi-Center Prospective Multi-Center Prospective Analysis of UBM for ICL SizingAnalysis of UBM for ICL Sizing

• Prospective multi-center trial• Sonomed VuMax II used to image sulcus images• Investigators:

– David Brown, MD– Paul Dougherty, MD – Stephen Lane, MD – Robert Rivera, MD– David Schneider, MD– John Vukich, MD

• 61 eyes of 61 subjects• Age 21-45• Average myopia treated –7.6D• No history of previous refractive surgery• IRB approval and informed consent obtained• 1 eye excluded after enrollment

– Wrong length ICL placed – Nomogram suggested 13.2mm– 12.6mm ICL implanted

Subject had 0 vault

Prospective StudyProspective Study

• Poor correlation (R2 value) between STS and ATA58%

• Poor correlation (R2 value) between STS and WTW46%

Relationship Between STS, ATA & WTWRelationship Between STS, ATA & WTW

• If the FDA label WTW method of sizing ICLs was used, 65% of cases would have received a different

size ICL than the STS Method requiring explantation in a significant percentage of patients

• If the improved PreVize Optimized WTW method of sizing ICLs was used,

34% of cases would have received a different size ICL than the STS Method

Results of STS vs. WTW MethodsResults of STS vs. WTW Methods

ConclusionsConclusions

• Using the new nomogram derived from STS measurements, we eliminated all instances of unacceptable ICL vault

• WTW methods would have resulted in different sized ICLs in 34% (PreVize Optimized) to 65% (FDA Label) of cases

ConclusionsConclusions

• Continued refinement of nomogram may improve cases of higher and lower ranges of vault

• UBM STS measurements are far superior to WTW for ICL selection with a far greater margin of safety

• Despite the FDA label, surface WTW measurements may lead to incorrect ICL selection

• In our opinion, careful systematic UBM STS should become the standard of care in ICL size selection

Is the Procedure Difficult?Is the Procedure Difficult?

Identifying LandmarksIdentifying Landmarks

• Quality scan is important• Certain landmarks must be seen• Not all images will show the landmarks• Start by identifying the appropriate landmarks to

confirm good positioning• Freeze the frame for caliper positioning• Take your measurements

Landmarks for Proper PositioningLandmarks for Proper Positioning

• Corneal echo– Anterior– Posterior to lens capsule

• Anterior lens capsule• Posterior iris pigment—hyperdense stripe• Ciliary sulcus

LandmarksLandmarks

Anterior corneal echo

Anterior lens capsuleICL

Posterior corneal echos

Posterior iris pigment

Ciliary sulcus

Applying the NomogramApplying the Nomogram

• Submitted for publication in JCRS• STS is what it is; no fudge factor is added to the

length• Nomogram identifies what length ICL to use• Technically this is “off label” for ICL surgery until FDA

decides otherwise• Personally I do STS on 100% of my ICL patients • Particularly important if you are doing Short Interval

Bilateral Surgery—avoid sizing mismatch in both eyes

Thank Yourpriveramd@aol.com