Sizing Nomogram for ICL Vault Determination Using Sizing Nomogram for ICL Vault Determination Using Sulcus-to-Sulcus Measurements Obtained with High Sulcus-to-Sulcus Measurements Obtained with High

Frequency UltrasoundFrequency Ultrasound

Robert Rivera MDRobert Rivera MD

ASCRS Symposium & CongressASCRS Symposium & CongressBoston 2010Boston 2010

The author has received research support, travel support, The author has received research support, travel support, honoraria and consulting fees from the following:honoraria and consulting fees from the following:

Sonomed, STAAR Surgical, AlconSonomed, STAAR Surgical, Alcon

Sizing of the Visian ICLSizing of the Visian ICL

• ICL size chosen for implantation is based on white-to-white (WTW) measurement– US FDA Clinical Study was based on WTW– FDA approval based on WTW

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

• Subsequent results and studies have shown this is not a valid assumption

• Note that UBM technology was not available in earlier days of ICL implantation; WTW was the best approximation available

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)

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

had vaults less than 90 µ• 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

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

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

Subject had 0 vault

Prospective StudyProspective Study

• 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, potentially requiring explantation in a significant number 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

• Poor correlation (R2 value) between STS and ATA (58%); STS and WTW (46%)

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

ConclusionsConclusions

• Using our Sonomed study nomogram derived from STS Measurements, no cases fell within an unacceptable range of ICL vault compared to a reported 15%-20% of cases based upon WTW measurements

• Average Vault was 344 µ (range 93-952) • WTW methods would have resulted in different

sized ICLs in 34% to 65% of cases compared to the STS method

ConclusionsConclusions

• Further refinement of nomogram may allow improvement in higher and lower ranges of vault

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

• Despite the FDA label, surface WTW measurements may lead to incorrect ICL selection in a significant percentage of patients

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

Thank Yourpriveramd@aol.com