Measurement of the crystalline lens radius with artemis very high frequency ultrasound biomicroscopy for implantable collamer lens sizing.

To the Editor: In their recent article, Reinstein et al.1 described the use of the Artemis 2 very high frequency digital ultrasound (ArcScan, Inc., Morrison, CO) to calculate the fit of the Visian Implantable Collamer Lens (ICL). Another parameter previously proposed as influencing ICL vaulting is the crystalline lens anterior radius of curvature (ALR).2 The ALR has not yet been used in any previous studies that use ultrasonic measurement for predicting the ICL vault.3-5 Several assumptions are made in the formulas used to size the ICL and calculate the theoretical vault height of the ICL that would have been chosen by the white-to-white method: the sulcus-to-sulcus measurement is made at the iris base, which does not take into consideration sulcus peripheral widening at the ciliary processes. The “gap constant” assumes that the haptics rest on the zonules with “standard” compression (I have seen considerable variability in haptic compression when using the Artemis on postoperative cases). The crystalline lens height is a calculated value based on the previous two assumptions and is not an actual, measured value such as the aforementioned ALR measurement. Anatomical differences that result in the compression of the haptics against the ciliary processes, or the ALR (“lens rise”), could account for variability in the ICL vault. The measurement of the ALR can easily and accurately be performed preoperatively with the Artemis device. We have retrospectively looked at this parameter (ALR) in an earlier series of 82 consecutive ICLs, with a mean postoperative follow-up of 36.3 months. We used the Artemis base curve measuring device to calculate the ALR at a 7.0-mm optical zone in the preoperative undilated eye. In 29 eyes with an ICL vault of 150 mm or less, the mean ALR had an 8.70-mm base curve; for the 13 cases with ICL vault 300 mm or greater, the ALR was 12.08 mm. Thus, a steeper ALR may reduce the ICL vault. For the past 5 years, I have used the Artemis to measure the ALR as an aid in ICL sizing. The ALR may be a confounding variable for the relationship of either white-to-white or sulcus-to-sulcus to the ICL vault, and may indeed be an independent factor for predicting ICL vault. Furthermore, both the length and the base curve of the ICL could be customized to the sulcus width and the crystalline lens curvature (“L” reading, corresponding to the corneal “K” reading), respectively, to optimize the vault in each individual patient, similar to contact lens fit. I encourage the authors to evaluate the ALR in their current preoperative database, and the relationship to achieved ICL vault. I would like to point out an error in the article. In the Figure 6 text and graph, and “Results” paragraph 4, page 33 it is stated that the “achieved vault height was 0.9 mm.” This should be “0.09 mm.”