contact lens case reports
A New CRT Delivery System
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
Lens manufacturers strive to develop innovative, more cost-effective techniques for practitioners to deliver products to patients. Unlike soft lenses in which one base curve and diameter can fit about 80 percent of the population, GPs require significantly more radii to fit the wide range of corneal shapes in our practices. Therefore, inventory fitting of GP lenses, while effective, can often be a costly endeavor.
Shortly after corneal reshaping with Paragon CRT (Paragon Vision Sciences) received FDA approval in 2002, the modality was introduced to practitioners with a 100-lens diagnostic/dispensing set. While this remains our preferred technique for fitting CRT lenses, some have expressed interest in an alternative technique.
To address this need, Paragon recently introduced the SureFit CRT delivery system. With Sure-Fit, a practitioner provides a laboratory consultant with a patient's K readings and prescription. The lab then provides three new, sterile lenses for each eye with parameters selected from a database of thousands of successful fits.
Utilizing the Delivery System
A 26-year-old male with an eightyear history of daily wear soft lenses heard about corneal reshaping and presented to our clinic interested in the modality. His Ks were OD 42.50 @ 170/43.12 @ 080 and OS 42.87 @ 009/43.37 @ 099 with a spectacle prescription of −2.50D sphere OD and OS. We ordered CRT lenses because his parameters fell within those currently available in the SureFit system: flat K readings between 41.00D and 45.00D and a spectacle prescription of up to −4.00D with less than 1.25D of with-the-rule astigmatism.
At the dispensing visit, we applied the lenses marked #1 to the patient's right and left eyes and examined with fluorescein. A properly fitted lens will exhibit centration, 3.00mm to 4.00mm of central fluorescein thinning, a midperipheral doughnut ring pattern, acceptable edge clearance, and an over-refraction of plano to +0.50D. Lens #1 on the right eye showed these qualities. However, the lens #1 on the left eye decentered slightly, indicating an inadequate (too flat) sagittal depth (Figure 1). We applied the steeper lens #2 with a greater sagittal depth to the left eye. This lens provided optimum centration and movement.
Figure 1. Lens #1 on the right eye shows an optimum fit while lens #1 on the left eye shows decentration, requiring a lens with a greater sagittal depth.
We dispensed the lenses and scheduled a follow-up visit for the next morning. On follow up, both lenses moved and centered well with the blink. The patient's uncorrected visual acuities were 20/30 OD and OS, and within seven days the treatment was completed with 20/15 uncorrected vision throughout the day (Figure 2).
Figure 2. The patient's left eye at two weeks. Note the excellent centration of the treatment zone.
Fitting for Many Patients
SureFit CRT is a fitting and delivery system that provides a simple, cost-effective technique for managing a wide range of patients interested in the many benefits of corneal reshaping. CLS
Patrick Caroline is an associate professor of optometry at Pacific University. He is also a consultant to Paragon Vision Sciences. Mark André is an associate professor of optometry at Pacific University. He is also a consultant for CooperVision.