Corneal Sagittal Depth When Fitting Scleral Contact Lenses: Medmont E300 Corneal Topographer vs. Visante Optical Coherence Tomography.

Background: Scleral contact lenses offer practitioners another option when fitting complicated contact lens patients. Vaulting the entire cornea, scleral contact lenses provide a new option for fitting patients with corneal dystrophies, ectasias and patients who have difficulty with traditional gas permeable lenses. Sagittal depth measurements are used in selecting an initial trial lens. Determining a more accurate sagittal depth will allow practitioners more accurate initial trial lens selection. Methods: Thirty patients, sixty eyes, were imaged using both the Medmont E300 corneal topographer, and the Visante OCT. Utilizing the analysis tool of the Medmont E300 and the built-in caliper tool of the Visante OCT, the sagittal depth at a 10.00 mm chord was measured for all
participants. The results from the 10.00 mm chord were analyzed to determine if there was a clinically significant correlation between the two instruments. Additionally, a 15.80 mm chord was drawn and the sagittal depth measured from the 10.00 mm chord to the 15.80 mm with the Visante OCT. Results: Statistical analysis showed no statistical significance when measuring the sagittal depth at a 10.00 mm chord with either the Medmont E300, or the Visante OCT. Analysis of the sagittal depth collected at the 15.80 mm chord showed a mean sagittal depth of 2391.83 ± 193.92 microns. A linear regression was used to determine the equation Visante OCT 15.80 mm chord= -258.192 + 1.482(1259.756 + .297 (Medmont E300 10.00 mm chord). Conclusion: A more accurate sagittal depth will allow practitioners better starting information when determining an initial scleral trial lens. This allows a better initial fit and fewer follow up
appointments for the patient. The determined equation allows practitioners who do not
have a Visante OCT to accurately determine the sagittal depth at 15.80 mm after obtaining the corneal height at a 10.00 mm chord with the Medmont E300 topographer.