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Evaluation of enhanced corneal compensation in scanning laser polarimetry: comparison with variable corneal
1Department of Ophthalmology Semmelweis University, Budapest.
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 birefringence 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. Both the axis and the magnitude of corneal birefringence altered after LASIK (P < 0.01). After LASIK, with VCC* all eyes showed uncompensated birefringence, 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 ECC* (P < 0.001).
Conclusions:
The new ECC software is more effective than VCC in neutralization of atypical polarization pattern and the uncompensated corneal retardation.
