June 2016 Online Photo Diagnosis
By Luciano Bastos
Keratitis Due to Apical Touch Fitting in Keratoconus
The patient whose left eye is pictured in Figure 1 was first seen at the Instituto de Olhos Dr. Saul Bastos on April 17, 2007. He was 20 years old at that time and was diagnosed with bilateral keratoconus. In 2007, he was fit with aspheric, monocurve (base curve) UL GP lenses that provided great comfort, 20/15 vision OU, and good corneal physiological health. He wore these lenses until 2012, when we refit him with some mild adjustments. Figure 2 shows the OS fit in 2012 with an aspheric single-base-curve GP with the following parameters: 48.50D (6.96mm) base curve, 9.4mm diameter, –5.75D power, and 50 Dk material.
Figure 2. OS fit with a single aspheric monocurve GP lens in 2012.
The patient recently returned for a follow-up visit four years after this last fitting in 2012. He is now 29 years old, and it was clear that his condition has progressed significantly, especially OS. Slit lamp evaluation with fluorescein and a cobalt blue filter revealed a paracentral keratitis (Figure 1) OS that resulted from apical touch. We instructed the patient to suspend lens wear for three to four days and to instill Epitegel (Bausch & Lomb) t.i.d.
After four days, the patient returned with a crystal clear cornea. We refit him with a corneal specialty GP lens—a modified Soper keratoconus lens with a biaspheric design—in parameters of OS 54D (6.25mm)/46D (7.34mm) base curves, 9.4mm overall diameter, 6.5mm optical zone, –9.75D power, and 75 Dk material. The fit demonstrated no apical touch, with a light vaulting over the central apex and paracentral zones and a smooth landing at the midperipheral cornea (Figure 3). This lens once again resulted in a great fit.
Fitting Philosophy in Keratoconus
The contact lens fitting literature mention the so-called three-point-touch fitting technique; however, what really happens in most cases is that there is a great chance of inducing central apical abrasion. In this case, there was a significant amount of mechanical stress at the corneal apex due to the ectasia progression. The lens was clearly forcing against the apex and, with the movement after blinking, it caused the keratitis. We then opted to treat the cornea, take new keratometric and topographic measurements, and refit with a better design to achieve a better result.
Figure 4 shows a simulated keratometry corneal topography, obtained as a part of the follow-up exam in May 2016.
Figure 4. Corneal topography OS, May 2016.
Many patients can benefit from GP lenses without having to progress to scleral lens fitting. A successful keratoconus fit can help patients achieve great improvement in best-corrected vision, comfort, and corneal physiological health. The central cornea should always be fit with a small amount of vaulting to prevent any mechanical stress to the epithelium. Also, keratoconus patients must be educated so that they understand why follow-up examinations are required at least every 12 to 18 months. This is especially important during the ages of 17 up to 25 years, which is when the keratoconus presents its worst, most aggressive episodes of ectasia progression. The lens fit pattern is also a good way to monitor the condition. We also recommend that patients avoid eye rubbing and use preservative-free artificial tear eye drops during lens wear.
Luciano Bastos is the director and clinical instructor of specialty contact lenses at the Instituto de Olhos Dr. Saul Bastos (IOSB) and is the director and specialty lens consultant of Ultralentes, a small laboratory specializing in GP and scleral lens designs in Porto Alegre, RS, Brazil.