OCTs ushering new era in complex contact lens fittings
Atlanta—Innovative uses of optical coherence tomographer (OCT) scans are ushering a new era in contact lens fitting, according to one expert in the field.
Complex contact lenses, including scleral lenses, have unique fitting considerations that may be augmented with additional optic scans, says Jeffrey Sonsino, OD, FAAO, of Nashville, TN, at SECO 2017.
Dr. Sonsino cited the physical dimensions of complex lenses that make them challenging to fit, arguing that OCTs have proven to be effective in augmenting eye topography analyses when fitting complex contact lenses because such lenses are designed to avoid contact with the central cornea.
“The reason OCT is powerful in scleral and hybrid lenses is that these are vaulted lenses,” he says.
Related: 6 OCT pitfalls to avoid
The number one application of OCT in lens fitting is in measuring the corneal bulge, which allows for superior accuracy to the traditionally used slip beam estimation method. While standard measures of success with patients allow for some wiggle room in measurements—in some cases, even up to 800 µm, according to his research—that wisdom is coming into question following recent studies that looked deeper into the cornea-oxygen relationship.
One study found that the difference between a 200 µm vault and a 400 µm vault resulted in a 30 percent reduction in oxygen levels after just five minutes. This is especially important in patients who have oxygen problems with very low endothelial cell count. It’s especially important to fit these patients with thin lenses no thicker than 300 µm to allow for better oxygen permeation.
“Now all of a sudden, we have criteria that tells us we have to be a lot more accurate with our scleral lens evaluations and fittings,” Dr. Sonsino says.
Related: Affording OCT in your practice
Rise of OCT in eye care
Although ophthalmologic use of OCTs had been established in the 1990s, imaging technology had not advanced far enough to show image resolution in great detail. However, Dr. Sonsino says this trend has changed.
“When you compare modern-day OCTs to that,” he says, “the brand doesn’t matter—the resolution is so much better, and you can see so much more detail.
Originally developed to help visualize posterior eye tissue, OCTs are now used in the diagnosis of a myriad of retinal, anterior segment, and optic nerve diseases such as macular degeneration and glaucoma.
But in recent years, usage of OCTs has expanded. Today, OCTs are being adopted by more and more eyecare professionals looking to properly fit patients with complex contact lenses.