Improving Scleral Lens Fitting Efficiency
BY GREGORY W. DENAEYER, OD, FAAO
The fit and power of scleral contact lenses used in managing corneal irregularity are determined by diagnostic lens fitting. Practitioner experience directly determines the proficiency of this process.
Following the steps below will help you become a more efficient scleral lens fitter as you gain experience with prescribing this specialty lens modality.
Diameter Selection The potential vault of a scleral lens increases with increasing diameter, which allows relatively larger lenses to be more forgiving for difficult fits. Fitting mild-to-moderate amounts of corneal irregularity is often equally successful with mini- or full scleral lenses. However, it is much easier and more efficient to fit severe irregularity with full scleral lenses that have diameters of 18mm or larger.
Familiarize Yourself With Design Specifics Knowing the fitting characteristics and available options is critical to successfully fitting a specific scleral lens design. This is especially important if you have to deviate from the design’s standard parameters to optimize fit and performance. Examples include the manufacturer’s allowance for peripheral curve adjustment (“steps” or millimeter increments), the availability of front- or back-surface toricity, and adjustable center thickness.
Initial Lens Selection Practitioners who are new to scleral lens fitting commonly ask which diagnostic lens from their fitting set should they should start with. The simplest and often quickest method is to determine whether the anterior surface looks relatively flat or steep by observing the profile of the eye with or without the use of the slit lamp, and then choose your first diagnostic lens accordingly. For example, if the eye looks relatively steep, then choose your first lens from the steep side of your fitting set. If in doubt, start with the median diagnostic lens.
Evaluating the Fit
After the diagnostic lens application, you want to evaluate the fit from the inside out. First check the amount of corneal clearance. Bracket the amount of lens vault using large steps. For example, if the first diagnostic lens has insufficient clearance, then go at least two or three lenses steeper in your fitting set and then bracket your way back as needed.
Once you achieve the desired amount of lens vault and corneal clearance, then evaluate the haptic section and adjust the peripheral curves if needed.
Estimate the Amount of Lens Settling The haptic section of a scleral lens settles into the bulbar conjunctiva after initial application. Additional amounts of settling may take place over weeks of lens wear. To compensate, fit the lens with approximately 200 microns more vault than what you want to ideally achieve for the final fit. Reassess the vault and adjust if necessary after patients have worn their scleral lenses for several weeks.
When in doubt, contact the manufacturer’s consultant for a specific design to help optimize the fit or troubleshoot complications. Working with consultants will not only help you to be more successful, it will also decrease the inevitable learning curve if you’re new to scleral lenses or working with an unfamiliar design. E-mailing a photograph of the best-fitting diagnostic lens taken with a digital camera or smartphone will help them more accurately assess and adjust the lens as necessary.
Better Success in Less Time
Fitting scleral lenses efficiently will help you minimize chair time with these lenses while maximizing your success. CLS
Dr. DeNaeyer is the clinical director for Arena Eye Surgeons in Columbus, Ohio, and a consultant to Visionary Optics, B+L, and Aciont. You can contact him at firstname.lastname@example.org.
Contact Lens Spectrum, Volume: 28 , Issue: October 2013, page(s): 15