Non-adaptive Optics Cone Imaging: A comparative study with the Imagine Eyes RTX1

Abstract

Purpose: To compare a novel, non-adaptive optics based cone imaging modality using the modified spectral domain optical tomography (Heidelberg® Retinal Angiogram) system, with the current commercialized Imagine Eyes RTX1™ adaptive optics system.

Methods: Sixteen undilated eyes of 8 emmetropic (less than 1 diopter of refractive error) normal subjects were imaged on both the modified HRA and the RTX1 systems by a single operator. Subjects with any media opacity, retinal pathology or previous ocular surgery were excluded. Images from five fixation points (foveal center, and at 2.4 degrees superior, inferior, nasal and temporal) were obtained for each eye. Image quality from both systems were compared by 2 independent graders for the clarity of cone identification. The comfort during imaging (determined by the subjects) for the 2 systems were also compared.

Results: Cone photoreceptors were clearly visible in 7 out of the 8 subjects with RTX1 and in all 8 subjects with HRA. The subject that was unable to image with the RTX1 had a pupil size of 2mm. When comparing the quality of the two devices the proportion of "better image quality" for RTX1 versus HRA versus no difference is 53.9%, 18.4% and 27.6% respectively for Grader 1, and 63.2%, 11.8% and 25.0% respectively for Grader 2 (Kappa 0.492, 95% CI 0.299 to 0.684). Six (out of 8) subjects found imaging with RTX1 easier due to larger fixation target and lesser scanning laser intensity.

Conclusions: Imaging of cone photoreceptors was possible using both RTX1 and modified HRA. The latter is capable of capturing cone images reliably in normal subjects using non-adaptive optics mechanism. Under optimal condition with clear media and pupil size of greater than 3mm, the RTX1 currently produces better image quality. The qualities of the HRA images are less affected by the pupil size.

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)