Is This the New Norm?
Is Anterior Segment OCT the New Norm for Fitting Sclerals?
BY MILE BRUJIC, OD, FAAO, & DAVID L. KADING, OD, FAAO
Scleral lenses continue to appear in the contact lens literature. They have become a valuable tool in helping to restore visual functionality in patients who have irregular corneas. Others are even introducing them as a viable option for patients who have high levels of ametropia, in particular those who have high levels of astigmatism.
With that said, there is a new level of responsibility when fitting these lenses. They require an adequate knowledge of ideal fitting characteristics and an understanding of how to manipulate lens parameters to achieve an ideal fit. With scleral lenses, the ideal scenario is corneal clearance, with the lens bearing all of its weight on the conjunctiva and underlying sclera.
At the slit lamp, after filling the bowl of the lens with non-preserved saline and fluorescein, the clearance of the lens can be estimated using an optical cross section and comparing the width of the fluorescein band with that of the thickness of the contact lens. This can be performed at any portion of the lens and cornea. (For a good resource on grading scleral lens fitting characteristics, view the Scleral Lens Fit Scales developed by the Michigan College of Optometry’s Vision Research Institute, available at www.ferris.edu/ScleralLensFitScales).
Anterior Segment OCT
With the advent of newer technologies such as anterior segment optical coherence tomography (OCT), imaging of the anterior segment has become much more readily available and is a highly valuable tool in assessing scleral lens clearance.
Current OCT technologies allow us to view corneal clearance with a high level of accuracy during both fitting and follow-up visits. A strong advantage to anterior segment OCT is that fluorescein is not required to optimize visualization of the scleral lens clearance. This is significant when following up with scleral lens patients. Oftentimes, these patients return for evaluation after several hours of wear with no fluorescein behind the lens.
Anterior segment OCT accurately measures clearance both centrally and at the limbus. This allows for a highly accurate comparison between measurements taken shortly after the lenses are applied to the eye and at the end of the day after the lenses settle and the lens clearance has typically decreased (Figure 1).
Figure 1. Anterior segment OCT of a scleral lens fit at the beginning of the day and at the end of the day, showing the decreased clearance that occurs throughout the day.
With accurate measurements that can be acquired in seconds, anterior segment OCT is quickly becoming an increasingly important tool for managing scleral lens wearers. Although slit lamp evaluations also allow us to assess scleral lens clearance, the level of accuracy obtained with anterior segment OCT is truly a fortunate advancement in scleral lens fitting and management. CLS
Dr. Brujic is a partner of Premier Vision Group, a three-location optometric practice in northwest Ohio. He has received honoraria in the past two years for speaking, writing, participating in an advisory capacity, or research from Alcon Laboratories, Allergan, B+L, Optovue, Nicox, Paragon, SpecialEyes, TelScreen, Transitions, Valeant Pharmaceuticals, Valley Contax, VMax Vision, VSP, and ZeaVision. Dr. Kading owns the Specialty Dry Eye and Contact Lens Center in Seattle, Wash. He is the co-owner of Optometric Insights with Dr. Brujic. He has received honoraria for consulting, performing research, speaking, and/or writing from Alcon Laboratories, Allergan, Bausch + Lomb, Biotissue, Contamac, Essilor, Nicox, Oculus, RPS Detectors, TearScience, Valley Contax, and ZeaVision. Follow him on Twitter @davekading.