One OD's RGP Fits
BY GARY LINTON, OD
Some time ago I wished for a way to fit RGP contact lenses without the need for extensive trial lens sets or empirically fitting lenses from Ks and refraction, which was less than satisfactory. I heard about a new contact lens fitting software program, called Wave, which was linked to the Keratron corneal topography
system. I happened to be in the market for a more advanced topographer at the time, and it seemed a perfect time to take the plunge and kill two birds with one stone. Since then I have become more and more pleased by the impressive alignment fits and patient feedback of exceptional comfort with Wave-created lenses.
Fitting Wave Lenses
Wave receives thousands of data points from a Keratron corneal map to create an RGP multi-aspheric curve lens design. According to developer Jim Edwards, OD, the curvature changes on these lenses every 10 microns radially from the center toward the periphery. They contour closely to the cornea similar to a soft lens draping over the cornea. The lenses are fitted generally in larger diameters than traditional fits and sit in a more centered position. They have less decentration and dislodging problems with rapid gaze shifts, and patients report less foreign bodies under their lenses, perhaps because of the close alignment. Adaptation time for new wearers is shortened significantly over standard designs, and many of my patients say these lenses are as comfortable as soft contact lenses. Almost without exception, patients I've converted from standard designs find the Wave lenses more comfortable and experience extended wearing time later into the day.
Wave's design automatically creates a lens fit based on set norms. But as I have gained experience with the program, I frequently use manual override options of design parameters to customize the fit to my personal philosophy. This is very useful in working with more unusual corneal shapes. The lenses are always aspheric in the periphery but can be either spherical or aspheric within the optic zone. The junctions between each zone of the lens are blended so smoothly that they are practically invisible when viewing the fluorescein pattern on the eye. The tear layer profile display allows me to adjust the alignment of the lens across the entire surface with a degree of precision that fluorescein analysis cannot pick up.
Wave lenses are available in single vision, multifocal, reverse geometry and multifocal reverse geometry. You may add back surface toricity to any of these lens designs. Multifocals offer the benefits of front surface optics combined with back surface custom fitting. The Wave front surface multifocal uses a patent pending method of aberration control that, according to Dr. Edwards, offers distortion-free optics across the entire visual field. The back surface of the lens is designed with the same Wave multi-aspheric curves as a single vision lens, offering dramatically reduced corneal distortion and spectacle blur, which have plagued back surface aspheric multifocal designs.
I was concerned about support for this new technology, but my fears were groundless. Wave's installation CD contains several video tutorials divided into five to 10 minute segments. E-mail consultations are available, and I have always gotten a prompt reply with specific suggestions for difficult cases. As with any new technique, there is a learning curve when first working with it. That held true for me, but in a short time it has become my primary method of RGP selection and design. As a result, I am fitting a much higher number of RGP lenses, including multifocal lenses.
Dr. Linton has been in private practice emphasizing contact lenses in Puyallup, WA, since 1979. He is a past president of the Washington Optometric
Contact Lens Spectrum, Issue: November 2000