Abstract
Purpose :
To evalutate the performance of auto-centration for corneal lenticule extraction treatment on a femtosecond laser.
Methods :
Eye images from 9 human eyes were collected on a new femtosecond laser. Before imaging on the femtosecond laser, 3 peripheral marks were created on the nasal, temporal, and inferior cornea of which the nasal and temporal marks were aligned to the horizontal axis when the subject was at upright position. When the subject was under the femetosecond laser at supine postion, one infrared (IR) image and one visible image were captured nearly simultaneously when the eye was about 40mm away from the patient interface viewing a coaxial fixation target. Pupil center was detected from the IR image and the 3 peripheral marks were detected from the visible image before applanation. Another visible image was captured right after the eye was applanated which detected the peripheral marks. Then a transformation matrix was created with the detected mark positions in the visible images before and after applanation. The pupil center detected in the pre-applanated IR image was transformed by the transformation matrix to the visible image under applanation and used as the lenticule treatment center. The rotation angle calculated from the detected nasal and temporal marks in the visible image under applanation was used to correct cyclotorsion axis for lenticule treatment.
Results :
Pupil centers were detected correctly in the IR images captured on the femetosecond laser before applanation. Peripheral marks were detected in the visible images before applanation and after applanation from the 9 eyes. On average, the lenticule treatment was automatically adjusted 421.756±173.337µm (range from 136.641 to 692.903µm) from the applanated image center. The cyclotorsion axis was corrected -3.94±5.28° (range from -11.85 to 4.66°). The corrected lenticule treatment center was offset 230.014±179.147µm (range from 57.673 to 648.079µm) from the pupil center in the visible images under applanation.
Conclusions :
Auto-centration improves the accuracy of treatment centration by placing the treatment center on the corneal position corresponding to the pupil center of the eye before applanation.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.