PS-OCT: a novel technique to study birefringence properties of LASIK flap and SMILE cap
First Author: P.Paritekar INDIA
Co Author(s): P. Khamar R. Patil R. Shetty A. Sinha Roy
To analyse changes in Birefringence properties in the human cornea undergoing laser in situ keratomileusis (LASIK) flap cut and small incision lenticule extraction (SMILE) cap cut.
Longitudinal case study conducted on 50 eyes in an eye institute after appropriate institutional ethics committee approval
In this longitudinal case study, 50 eyes of 25 patients were randomised to undergo LASIK and SMILE contralaterally. Measurements were performed preoperatively, intraoperatively, postoperative after 1 week and 1 month of surgery using custom-built Ultrahigh resolution Polarization Sensitive (PS) – OCT. For intraoperative measurements, the flap was cut but not lifted for the LASIK eyes and the cap and side cut incision was made for the SMILE eyes. Phase retardation and axis orientation enface maps were generated through the depth of stroma and at the posterior corneal surface, to see changes in collagen fibril arrangement
Similar phase retardation and axis orientation were observed in the enface maps generated through the depth of stroma just below the flap and cap cuts. However, these were observed to be very different as compared to a preoperative emmetropic cornea. LASIK eyes and SMILE eyes showed similar arrangement of fibril structures in retardation enface at the posterior corneal surface. Whereas, axis orientation enface at intra-op showed abrupt changes in case of SMILE as compared to LASIK while post-operative wound healing showed similar arrangement in both the cases.
Birefringence properties in LASIK and SMILE eyes were comparable showing similar wound healing outcomes at later time points. Data derived from PS-OCT can be used as a reliable technique to study and observe wound healing process post operatively based on the posterior enface maps exhibiting preferential alignment of collagen fibrils.