New Rose K Lens Designs
By Lee M. Buffalo
While Rose K specialty GP lenses have enjoyed a position as the #1 dispensed keratoconus GP lens in the world, Blanchard Contact Lens, Inc recognized that new designs were needed to meet the demands of patients across the entire range of indications associated with the irregular cornea.
Recent manufacturing advances have created new lens designs that expand the proven Rose K lens design and fitting process. These new designs allow patients to achieve better vision, better comfort, and a better lens/cornea relationship. Improving the interaction between the lens and cornea provides longer hours of comfortable wear with less insult to the cornea. The proven "Systematic Approach to Fitting" available with the original Rose K lens allows for a final lens choice in a shorter period of time (fewer office visits) with better vision performance while maintaining optimum corneal health.
New larger diameter Rose K lenses with aberration control aspheric optics provide numerous benefits while resolving problems associated with fitting specialty GP lenses for the keratoconus.
The Rose K2 lens was created to address two critical areas of performance for the keratoconic patient - spherical aberration and small optical zones. The base curve, or back of the lens, of the Rose K2 lens has an aspheric (non-spherical) optical zone unlike the spherical optical zone found on the original Rose K lens. This aspheric optical zone controls spherical aberration found on all contact lenses in higher minus powers, typically present with keratoconus lenses. The incorporation of aspheric optics into the lens design improves vision performance and enhances wearing comfort. The aspheric optical zone is larger than that of the original Rose K reducing glare, haloes and flare, common for many keratoconic patients in dim illumination (night time).
Clinical studies indicated a 96% patient preference in visual performance with the Rose K2 lenses when compared with their Rose K lenses and 91% of the patients reported improved comfort. (Data on file) Incorporating aberration control into the original Rose K lens was so successful it is now the standard in production for Rose K2 Post Graft and Rose K2 IC lenses.
Rose K2 IC (Irregular Cornea) and K2 Post Graft lenses are large diameter, reverse geometry, intralimbal lenses (diameters that extends to the outer edge of the cornea), with aberration control aspheric optics for applications in specialty GP lens fitting. Primary applications for Rose K2 IC lenses include: Pellucid Marginal Degeneration, Keratoglobus, Post Graft, LASIK- induced Ectasia, Post PRK, large oval, sagging cones and patients with irregular corneas due to trauma. Nipple and oval cones, found in some keratoconus patients, are secondary applications.
Eyecare providers fitting Rose K2 IC and Rose K2 Post Graft lenses report improvements in visual acuity, lens centration and comfort, an increase in overall fitting success, and, "reduced chair time to final fitting".
By nature, irregular and keratoconic corneas are asymmetric, where the inferior quadrant of the cornea is frequently significantly steeper than the superior portion of the cornea, causing the GP lens to lift off at the 6 o'clock position. Manufacturing technology now enables the incorporation of asymmetry into the lens design itself. Asymmetric Corneal Technology ("ACT") manufacturing is applied onto the base curve of the lens to accommodate this inferior asymmetry to enhance lens comfort and stability, resolve lens displacement from lower lid interaction, and deliver superior vision performance. The inferior quadrant of the lens is steeper than the superior and lateral quadrants providing better inferior (6 o'clock) alignment. "ACT" is available for all Rose K lens products. It simplifies fitting and improves lens performance for the irregular cornea patient. (see diagram) Utilizing "ACT" as part of the lens design resolves fitting/design complications created with more traditional approaches to overcome fitting the asymmetric cornea.
One approach is to decrease the overall lens diameter to fit above or inside the steeper inferior quadrant. This approach yields smaller optical zone diameters and associated haloes, glare, ghosting, and unstable lens positioning. Another option is to increase the overall lens diameter to vault over and below the inferior quadrant. Following the traditional path to fitting the highly asymmetric cornea typically results in excessive lens exchanges, an extended fitting process with compromised vision performance and a final fit with a less than optimal lens/cornea relationship. "ACT" optimizes final lens performance, improves the cornea/lens relationship promoting comfort, lens positioning and corneal health, while reducing the number of office visits (chair time) needed to arrive at the final lens fit.
Lee Buffalo is currently the Director of Sales and Marketing for Blanchard Contact Lens, Inc. During his 34 yr career in the contact lens industry, he has been involved in the manufacture and design of soft and specialty GP lens products, served the contact lens industry as a board member of the Contact Lens Society of America and provided educational assistance to numerous eyecare professional organizations.