AOSLO datasets from five CHM subjects ages 14 to 38 years were included for validation of our method for assessing photoreceptor visibility in AOSLO images. All subjects gave informed consent prior to being enrolled, the institutional review board at the University of Pennsylvania approved the study, and the study followed the tenets of the Declaration of Helsinki. Subjects were imaged using a custom-built multimodal AOSLO equipped with both confocal and split-detection imaging modalities. This system has been described previously.
21 Briefly, wavefront sensing was done using an 848 Δ26 nm superluminescent diode (Superlum, Cork, Ireland), and aberration compensation was completed using a 97-actuator deformable mirror. Confocal and non-confocal split-detection reflectance imaging was obtained using a 795 Δ15.3 nm superluminescent diode imaging source. Three photomultiplier tubes were arranged with one detector centered to collect the confocal reflectance, and two detectors were arranged to collect the non-confocal reflectance split between right and left halves, as first reported by Scoles et al.
3 Subjects were cyclopledged using one drop each of tropicimide and phenylephrine, and their viewing position in the apparatus was stabilized using a bite bar. Subjects were instructed to fixate on a target while AOSLO video sequences of the fovea, parafovea, and meridians in the macula were acquired at a rate of 18 Hz. A reference frame was automatically selected from the image sequence using a custom algorithm.
22 Image sequences were desinuoided, aligned to the reference frame, and averaged using a strip-based registration algorithm to account for both intra- and inter-frame eye motion as previously described.
23 Images then were de-distorted to compensate for the estimated eye motion that occurred within the reference frame.
12,24 Finally, registered images from adjacent retinal locations were automatically montaged using a feature-matching algorithm.
10
To compile a test dataset for validation of our algorithm, we identified five to seven locations that contained a minimum of four overlapping images from the montages for each of the five CHM subjects. These locations were selected such that, for each montage, at minimum two locations were from the foveal region, two locations were from the arms away from the fovea, and the remaining locations were from anywhere in the montage that met the minimum image overlap condition. Each location served as a different test, resulting in 29 test locations across the five montages. The test locations each had between four and 10 overlapping images, with a mean of 5.76 images for the 29 locations.