Contact Lens Case Reports
Lessons in Soft Orthokeratology
BY PATRICK J. CAROLINE, FAAO, & MARK P. ANDRÉ, FAAO
In previous columns we have described an orthokeratology-like corneal flattening effect that occurs with wear of everted (inside out) silicone hydrogel lenses. Over the past seven years, clinical experience has taught us: 1. overnight wear of everted minus lenses can flatten the central cornea approximately 0.50D to 1.75D; 2. the everted lenses center extremely well in the closed eye environment and are surprisingly well tolerated; 3. the greatest effects occur with silicone hydrogel lenses that have a higher modulus; 4. maximum flattening occurs with lens powers between −9.00D and −10.00D; 5. the result (the amount of corneal flattening) is extremely unpredictable and varies from patient to patient; 6. using minus lenses greater than −10.00D frequently has a reverse effect, resulting in central corneal steepening; and 7. the number-one complication of the technique is formation of a central island, which is a zone of central steepening. To eliminate this, use lower-powered minus lenses, i.e., if an island occurs with overnight wear of a −10.00D lens, decrease the power to −9.50D or −9.00D.
A Soft Lens Case
Our patient is a 25-year-old optometry student who has low myopia, right eye −1.25 −0.25 × 030, 20/15, left eye −1.00 −0.25 × 140, 20/15. After hearing about the soft ortho-k technique in class, she requested to try it herself. We diagnostically fitted her with everted 8.4mm base curve, −10.00D, 13.8mm diameter Ciba Vision Night & Day lenses. The lenses centered well, moved well, and were exceptionally comfortable. The fluorescein patterns showed a midperipheral zone of touch across a cord of approximately 7mm to 8mm with an area of pooling at a cord of 6mm to 7mm (Figure 1). The everted lens fluorescein pattern very much mimics that seen with a reverse geometry GP lens for orthokeratology.
Figure 1. Fluorescein pattern of patient's everted high minus lenses.
The lenses were dispensed for overnight wear, and maximum corneal flattening was achieved within three days. Follow-up topography revealed well-centered treatment zones with −1.75D of corneal flattening OD and −1.25D OS (Figures 2 and 3).
Figure 2. Corneal topography of the right eye after one week of soft ortho-k.
Figure 3. Corneal topography of the left eye after one week of soft ortho-k.
This case illustrates that while still unpredictable, everted minus powered lenses can provide an option for patients who have low myopia. It also demonstrates the future potential for a much more refined version of soft ortho-k lens designs. 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.