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OCT aids scleral lens evaluation
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ATLANTA – Line, cross line and pachymetry scans with optical coherence tomography can help you do a better job of evaluating your contact lens patients, Jeffrey Sonsino, OD, told attendees here at SECO.
“Scleral lenses are built to not touch the cornea,” and OCT imaging can help ensure this, Sonsino said during this course that was cosponsored by Primary Care Optometry News.
Using line scans, the beam can be rotated to image something in particular, he said.
“You can manipulate the line scans to go where you’re most worried about,” Sonsino said.
A cross line scan provides simultaneous vertical and horizontal scans.
“I love to use cross line scans because it gives you double the information – on two meridians rather than just one,” he said. “We follow that up with multiple line scans.”
Pachymetry scans can be used when patients are not wearing their contacts lenses as well as when they are wearing a vaulting lens, Sonsino said.
“It gives you slices all the way throughout the cornea,” he said. “If you have a nipple cone, you can use it to look everywhere around the cone to make sure you’re not touching it.”
Sonsino credited Langis Michaud, OD, MSc, FAAO (Dipl), FSLS, FBCLA, with developing criteria for success with scleral lenses:
Use the highest Dk lens material available;
You have to have a post lens tear reservoir vault of no more than 200 microns; and
You have to have a lens thickness of no greater than 250 microns (however, most manufactured lenses are 400 microns thick, Sonsino noted).
Sonsino said that Giasson and colleagues stated in an article yet to be published that going from 200 microns to 400 microns of vault results in a 30% drop in oxygen tension available to the cornea.
“We want to fit these with enough vault to account for settling during the day (they settle an average of 113 microns throughout the course of the day), but not too much vault to act as a resister to oxygen,” Sonsino said. “So now we have criteria that says we have to be a lot more accurate with our scleral lenses and fittings.”
He noted that OCTs were not intended to image outside the visual axis and may produce warped images if pushed too far out to the edge.
“We use the fixation light to move the patient’s gaze over,” Sonsino noted. “The OCT is taking an image straight back, and this de-warps the image. On any OCT, instead of taking a straight-on view of the periphery, take the patient’s point of gaze and move it over.”
He said he generates six OCT scans for “each and every patient. One in the center, one on the right periphery and one on the left, for both eyes. The edge of the lens is almost as critical as what’s happening in the center to make sure you have enough vault.”
Sonsino advised billing 92132, anterior segment OCT.
“It can’t be billed the same day as optic nerve or retina,” he said. “And it’s bilateral. It’s considered an experimental procedure with many insurers except when used for ‘evaluation and planning treatment for patients with disease of the cornea, iris, lens or other anterior segment structures.’”
He advised using this type of language in the medical record to avoid attracting audits from insurers.
If the procedure is not reimbursed by the patient’s insurance, he said he reviews the images with the patient, and “when they see the technology you’re using, you will get no resistance if you have to pass that cost along to them. They will see the value in it.” – by Nancy Hemphill, ELS, FAAO
Reference:
Sonsino J. A different view: Using OCT to evaluate contact lenses. Presented at: SECO; March 1-5, 2017; Atlanta.
Disclosures: Sonsino is a consultant for Alcon, Art Optical, Contamac, Johnson & Johnson Vision Care, LVR Technology, Optovue, Shire and SynergEyes.