Abstract
Purpose :
To improve a gonioscopy lens (Goniolens) design coupled to a pupil-steerable Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) for high-resolution imaging of the iridocorneal angle (ICA). While glaucoma is a multifactorial disease, intraocular pressure (IOP) is the only modifiable risk factor and many treatments are aimed at the trabecular meshwork (TM). We recently reported using AO gonioscopy to image the TM at high resolution (King et al. 2019). However, the source of optical aberrations in normal gonioscopic imaging is unclear, and most Goniolenses are not optimized for this purpose. We propose a new Goniolens design to improve optical image quality and light coupling from an enhanced AOSLO to allow imaging of different regions of the TM.
Methods :
The design of the Indiana University AOSLO was altered to 1) increase distance to the patient and 2) allow beam steering to image different regions of the ICA while maintaining optical quality. A Goniolens was designed using ray tracing software (Zemax®) to improve performance given manufacturing and operating constraints. Light coupling from the AOSLO was improved by steering the imaging beam as it enters the Goniolens, while maintaining optical performance. Optical aberrations induced at the surfaces of the lens and model eye, as well as image quality at different positions of the ICA were analyzed.
Results :
The AOSLO design allows beam steering via a tiltable field mirror over an area of 45x70mm at the pupil plane within the diffraction limit, allowing rotation of the Goniolens on the eye to image different sectors of the ICA. An air-spaced doublet button lens design reduced spherical aberration and improved RMS from 0.4λ, with the original singlet, to 0.04λ. Beam steering in the button lens enables access to the anterior segment with precise localization from the iris surface to the corneal endothelium with spot sizes of ~5µm with only defocus and astigmatism AO correction.
Conclusions :
A novel Goniolens was designed to improve optical quality and coupling between a new AOSLO and the TM. Beam steering facilitates imaging as the lens is rotated to different sectors of the ICA, and the beam can be steered from the pupil plane to target different tissues within the angle. This technique may allow further structural characterization of the TM in patients, and to monitor changes in glaucoma and following treatment.
This is a 2021 ARVO Annual Meeting abstract.