Stromal surface topography-guided custom ablation as a repair tool for corneal irregular astigmatism.

PURPOSE

To illustrate the concept of using a stromal surface topography-guided procedure for therapeutic repair after a complication following primary laser refractive surgery.

METHODS

One case example of therapeutic retreatment for short nasal flap after primary LASIK performed in September 2000 is presented. The Artemis very high-frequency digital ultrasound arc-scanner (Arc-Scan, Inc., Morrison, CO) was used to obtain layered corneal thickness including epithelial thickness profile. Corneal front surface elevation was measured with the Orbscan II (Bausch & Lomb, Salt Lake City, UT). Stromal surface height was then calculated by subtracting epithelial thickness data from corneal front surface elevation data and used to calculate the ablation profile applied to the eye. The treatment was performed using the Ultralink system (ArcScan, Inc.), linking the ultrasound corneal thickness data with the Technolas 217c laser (Bausch & Lomb). Postoperative data were available at 30 days and 13 years.

RESULTS

One month after treatment, the epithelial thickness map demonstrated that the difference in thickness between the thinnest and thickest points located 2.5-mm nasally was reduced by 26 µm (from 56 to 30 µm). The axial difference map demonstrated an increase in corneal curvature of approximately 4 diopters where the cornea was the flattest nasally, thereby reducing the corneal asymmetry. The anterior elevation map also showed a reduced depression nasally. The patient reported significant improvement of her night vision.

CONCLUSIONS

This case example of stromal surface topography-guided treatment demonstrated a significant reduction in the irregularity of the stromal surface and an improvement in the topography, and the visual quality. Stromal surface topography-guided ablation might become the tool of the future for therapeutic repairs because it offers advantages over the current alternative of transepithelial phototherapeutic keratectomy.