Evaluation of enhanced corneal compensation in scanning laser polarimetry -: Comparison with variable corneal compensation on human eyes undergoing LASIK

Purpose: To investigate the potential advantages of an enhanced corneal compensation algorithm (ECC) compared with variable corneal compensation (VCC), in scanning laser polarimetry. Methods: One eye of 15 healthy ametropic subjects was imaged immediately before and 7 days after uncomplicated LASIK surgery. Anterior segment bireffingence was assessed at each measurement session. For post-LASIK calculations, either actual post-LASIK corneal retardation (VCC and ECC groups), or the pre-LASIK corneal retardation (VCC* and ECC* groups) was used. Results: The typical scan score-value was higher for ECC both before and after LASIK (P < 0.01), and it was not influenced by LASIK in either compensation method. Botfi the axis and the magnitude of comeal birefringence altered after LASIK (P < 0.01). After LASIK, with VCC* all eyes showed uncompensated bireftingence, but with ECC* none did. LASIK had no effect on retinal nerve fiber layer measurements in VCC and ECC methods. In VCC* the LASIK-induced retinal nerve fiber layer thickness change was significant (P < 0.01) in the temporal, superior, and nasal quadrants. After LASIK, the number of significantly altered sectors along the TSNIT plot showed no difference when comparing VCC and ECC, VCC and ECC*, or ECC and ECC*. In contrast, significantly more sectors were altered in VCC* than in either VCC or FCC* (P < 0.001). Conclusions: The new ECC software is more effective than VCC in neutralization of atypical polarization pattern and the uncompensated corneal retardation.