Abstract
Purpose :
Measurement of angle kappa (κ) is clinically important because a large κ can cause decentrations during intraocular lens (IOL) implantation, leading to decreased vision. However, it is difficult to directly measure κ in clinical practice. Hence, this angle is estimated from the magnitude of displacement of the light reflected from the cornea from the pupil center to the nasal aspect. However, there may be accurate methods to determine κ using optical coherence tomography (OCT). In this investigation, we report the κ measurements from a prototype swept-source (SS) OCT device that simultaneously captures images of the anterior segment and the fundus.
Methods :
We captured low-resolution and high-resolution images of healthy eyes with the wavelength sweep frequencies at low-speed and high-speed modes with a SS-OCT. This prototype uses vertical cavity surface emitting laser (VCSEL) technology that can change the wavelength sweep frequency. In low-speed mode, the anterior segment and the fundus were captured in one shot to image the cornea, iris, anterior chamber angle, and fovea. This image serves as a reference image for aligning each segment when constructing the whole eye OCT image. In high-speed mode, the OCT images of the anterior segment and the fundus are captured separately. During anterior segment image capture, we measured the corneal curvature and anterior chamber width as references for calculation of the magnitude of distortion in OCT images captured at low-speed mode. The whole eye OCT image was constructed by aligning the image captured in high-speed mode with the reference image captured in low-speed mode. The whole eye OCT image was used to geometrically establish the pupillary axis (PA). The visual axis (VA) was estimated from the whole eye OCT image considering that the central OCT beam and the ray from the internal fixation lamp to the fundus are coaxial. The angle formed by PA and VA was used to calculate κ.
Results :
The κ calculated from the whole eye OCT image was 4.78 deg.
Conclusions :
We have developed a SS-OCT that simultaneously acquires images of the anterior segment and fundus and κ measurements. This method for measuring κ is expected to contribute to improving the accuracy of intraocular lens surgery.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.