Transcript STAAR Visian ICL

Sizing Nomogram for ICL Vault Determination Using
Sulcus-to-Sulcus Measurements Obtained with High
Frequency Ultrasound
Robert Rivera MD
ASCRS Symposium & Congress
Boston 2010
The author has received research support, travel support,
honoraria and consulting fees from the following:
Sonomed, STAAR Surgical, Alcon
Sizing of the Visian ICL
• ICL size chosen for implantation is based on white-towhite (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 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 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 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
Analysis 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
Prospective Study
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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
ICL Vault
Avg: 344
Min: 93
Max: 952
Results of STS vs. WTW Methods
• 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%)
Conclusions
• 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
Conclusions
• 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 You
[email protected]