Combining Intacs® and C3-R® in the Treatment of Keratoconus
By Dr. Brian S. Boxer Wachler
Published on August 24, 2007
Halting the Progression of Keratoconus with C3-R®
Patients with keratoconus, a condition in which the cornea becomes conical in shape, are divided into two categories: those with progressive keratoconus and those with a non-progressive, or stable, version of the disorder. Progressive keratoconus is characterized by continuing herniation of the cone, which in turn leads to higher astigmatism and an impaired ability to see clearly, even with spectacles. As the disease progresses, glasses and soft contact lenses are no longer viable vision correction options, leaving gas permeable contact lenses as the only means of achieving functional vision. Fortunately for those suffering from progressive keratoconus, there is now a treatment to halt the progression of the disorder and prevent future deterioration of the cornea: C3-R®.
The corneal collagen crosslinking with riboflavin (C3-R®) procedure increases the amount of collagen in the cornea through the one-time application of riboflavin drops followed by the exposure of the cornea to a low amount of ultraviolet A light. This activates the riboflavin, which then enhances corneal strength and integrity by increasing collagen crosslinking. The effectiveness of the procedure in halting the progression of keratoconus has been demonstrated in clinical tests, and the results have been published in peer-reviewed literature. The in-office procedure requires only 30 minutes, and patients are able to return to work and resume contact lens wear the very next day.
C3-R® therapy is safe, as the riboflavin absorbs the ultraviolet light in the cornea, thereby preventing transmission of light past Descemet’s membrane (the membrane that covers the inner surface of the cornea). The crystalline lens and retina are not exposed to ultraviolet A light, so there are no complications from this treatment. In a three-year study of patients with actively progressing keratoconus, the pattern of increasing topography values was not only halted, but also reversed and flattened by a mean of two diopters. That result persisted over the three follow-up period, during which time there was not a single complication to report.
Using C3-R® to Increase the Effects of Intacs®
As Intacs® are effective in reducing the conical protrusion associated with keratoconus and improving vision, we have found that placement of single-segment Intacs® has advantages over implanting two segments. A single segment placed outside the cone creates a unique effect, flattening the cone below as well as elevating the “overly flattened” cornea in the upper topography area. Because of this effect, we use single segments for peripheral cones (90 percent of keratoconus cases) and two segments for central cones (10 percent of keratoconus cases) due to its global flattening effect.
In order to better evaluate the progress of keratoconus, we devised a new system to describe the degree of corneal irregularity associated with the disorder and named it the “L-U ratio.” L-U characterizes the asymmetry of lower topography and upper topography based on the meridian of the cone. L-U improves upon the original I-S ratio, which is based on the assumption that all cones are located directly inferior but does not account for oblique cones that actually comprise most keratoconus cases. As with the I-S ratio, the higher the L-U ratio, the more advanced the topographic cone.
In a study we performed evaluating the effect of single-segment Intacs® with and without C3-R®, we found that C3-R® added to the improvement in L-U ratio compared to Intacs® alone. This finding showed that even in patients with stable keratoconus, C3-R® increases the effects of Intacs® and enhances the improved corneal shape postoperatively (postoperative L-U with Intacs® alone was 26.1, while it was 16.1 with the combination of C3-R® and Intacs®).
The ability to permanently strengthen an inherently weakened cornea is a major advance in the treatment of keratoconus. C3-R® treatments provide real results for patients with this challenging and life-altering disease. More information about C3-R® treatments and Intacs® for keratoconus can be found at www.keratoconusinserts.com or www.boxerwachler.com. If you have any further questions, please call the Boxer Wachler Vision Institute at 310-860-1900. We would be happy to discuss options for treating keratoconus with you.