Sulcus-to-sulcus more accurate in measuring lens vault in keratoconic eyes

ATLANTA — Sulcus-to-sulcus measurement was more accurate and predictable than the white-to-white method in measuring vault of implantable Collamer lenses in keratoconus eyes, according to a study presented here.

"The goal is that you want to have clearance of the ICL (STAAR) itself ... and the crystalline lens," Brian S. Boxer Wachler, MD, said at the American Academy of Ophthalmology meeting. "We always ideally want to have a vault. You don't want to have crystalline lens touching the ICL because of the risk of anterior opacity in the lens."

The study included two groups, with eight eyes in each group. One group underwent the white-to-white measurement, in which vault was measured as a percentage of corneal thickness. The other group underwent ultrasound biomicroscopy to measure sulcus-to-sulcus distance.

The variability of vault distance in the white-to-white group was double that of the sulcus-to-sulcus group. One patient in the sulcus-to-sulcus group and three patients in the white-to-white group had vault less than one corneal thickness, Dr. Boxer Wachler said.

"Potentially over time, this may or not be a factor, but you always want to be as accurate as possible," he said. "They were both very valid measurements in keratoconus patients. But the smaller standard deviation in the sulcus-to-sulcus group really reflects that using this technology may certainly have a benefit."

This study compared eight eyes with white-to-white with sulcus-to sulcus-measurements using ultrasound in a group of keratoconic eyes. Vault size was then independently evaluated by a masked examiner postoperatively. No difference was noted in the mean amount of vault between groups, but the standard deviation was roughly two times greater in the white-to-white group compared with the sulcus-to-sulcus group measured by ultrasound. The sample size was small so it is hard to know the importance of this, and the authors noted they need a larger sample to detect a significant difference. A more precise way to predict the postop vault would be very helpful since the Visian ICL is gaining popularity and proper vaulting minimizes the risk of secondary cataract development.

– Scott MacRae, MD
University of Rochester