1. Sonomed, STAAR Surgical, Alcon
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

2. Sizing 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

3. Sizing of the Visian ICL
17% of patients in the US clinical trial did not have optimal vault ( 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

4. 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 µ

5. 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

6. 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

7. Prospective Study 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

8. ICL Vault Avg: 344 Min: 93 Max: 952

9. 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%)

10. 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 )
WTW methods would have resulted in different sized ICLs in 34% to 65% of cases compared to the STS method

11. 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

12. Thank You