Abstract
Purpose: :
To study the effect of Inlay implantation on corneal thickness and curvature over one month post-operative period by comparing results obtained from OCT images using customised image analysis software and Medmont Topography instrument.
Methods: :
Positive powered corneal Inlays were implanted in one eye of three rabbits. Three vertical and horizontal cross-sectional OCT scans using the Optovue were taken and averaged prior to implantation and at 1 hour, 1 week and 1 month post-op. Medmont topographies were taken prior to implantation. Thickness profiles of the central corneas and radii of curvature for anterior and posterior surfaces of the cornea were calculated for the central 6 mm diameter range using customised image analysis software. Pre and post-operative results of thickness and curvature parameters from the OCT scans were compared. Anterior curvature values were also compared to the values obtained from Medmont Topography.
Results: :
Compared to pre-op values, central corneal thickness mean ± STDEV changed by +0.16 ± 0.04 mm, +0.05 ± 0.05 mm and +0.02 ± 0.01 mm for the 1 hour, 1 week and 1 month time points respectively. The change in thickness at 1 month corresponds to the thickness of the implanted Inlays. For the same time frame, the anterior/posterior curvature changed by +0.27 ± 0.43 mm/ +0.27 ± 0.13 mm, -0.25 ± 0.47 mm/ +0.05 ± 0.03 mm, -0.44 ± 0.50 mm/ -0.32 ±0.44 mm. Anterior curvature values obtained from the Medmont topography instrument measured 0.01 - 0.18 mm flatter than OCT obtained curvatures from horizontal and vertical scans but within the general measurement error for both instruments.
Conclusions: :
Central corneal thickness immediately after Inlay implantation and at 1 week increased by more than the expected Inlay thickness, presumably due to surgery induced corneal swelling. This may also cause the inconsistent change in anterior curvature as well as the measured change in posterior curvature. Measurements at Month1 appear to give more accurate data for comparison as surgical effects such as corneal swelling will have resolved. Both methods are suitable and comparable in obtaining corneal curvatures.
Keywords: refractive surgery: other technologies • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • imaging/image analysis: non-clinical