Evaluation of the performance of a non-contact and non-invasive Hyperparallel optical coherence tomography device in measuring retinal layers of normal eyes and eyes with diseases.

A total of 90 eyes (30 healthy (normal) eyes, 30 glaucomatous eyes and 30 diseased retina eyes) will be analysed within this study. A wide refractive range of normal participants will be sought with particular focus on recruiting a number of high myopes (>5 D). In order to achieve this, it is anticipated that a total of 100 participants aged 18 years and over will be screened for this study. Only one eye of an individual will be measured if they meet the inclusion criteria. Following the study screening, if both eyes of an individual meet the inclusion criteria, the eye to be tested will be determined from a randomisation list using a Latin Square design. The instrument testing order for each participant will also be randomised. After informed consent process and screening examination, each eligible subject will undergo the following scans. On Cylite's HP-OCT, • One valid biometry scan will be taken. • Three valid retinal images will then be taken for two separate posterior eye modes. - The first employs a central fixation target and focusses on the macula - The second utilises a nasal fixation target focusing on the optic nerve head. • An additional scan will be captured using the macula scanning protocol with a varied working distance. For example, the additional image may be taken in positive delay when the three original images may have been captured in negative delay. On Spectralis, • Three valid horizontal macula scans will be collected. The macula scans will be volumetric and will match the parameters of the HP-OCT as closely as possible. • Two optic nerve head scanning protocols will be implemented on the Spectralis SD-OCT instrument. - Firstly, 3 valid radial circle maps will be captured which consist of 24 radial scans and three circle scans of varying diameter. - Secondly, 3 optic nerve head volume scans will be captured. All scans are non-contact and non-invasive. The HP-OCT and Spectralis are both imaging OCT devices. They are not applied to a subject, rather a subject is imaged on these devices by placing their chin on a chin rest and the forehead on a forehead rest and a non-invasive image is taken. Both devices utilize spectral domain (SD-OCT) OCT technology, the key different between the two devices is the HP-OCT includes micro-optics to create a parallel grid of 1008 beamlets to capture an image whereas the Spectralis uses just one scanning beam. All eligible subjects will receive the same required scans on all the devices as described above. All scans are completed in a single imaging session. Imaging time will be no more than 20min at each device, this time allows for the subject to sit back and take the time they need in between the imaging. The repeatability of HP-OCT measurements will be characterised and the agreement of the measurements between HP-OCT and Spectralis will be studied for the following segmentation parameters. • Macular - ETDRS thickness maps (centred at the fovea and oriented horizontally) each ETDRS quadrant for the mean (+/-SD) retinal nerve fibre layer (RNFL), combined ganglion cell and inner plexiform layer (GCL+IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), retinal pigment epithelium (RPE) as well as total retinal thickness. • Optic Disc - Optic nerve head retinal nerve fibre layer thicknesses within a peripapillary zone of 3.45 mm diameter; Average RNFL thickness as well as quadrant-specific (superior, inferior, temporal and nasal) RNFL thicknesses; Macula and GC-IPL thicknesses within an elliptical annulus area around the fovea; Optic nerve head parameters including cup-disc ratios (vertical, horizontal and mean) as well as minimum rim-width (superior, inferior, nasal, temporal and overall). The user interface of each device provides the user with quality indicators to guide the user on the scan quality. These indicators are outlined within the user manual of each device and will make up part of the training for the user prior to the study commencing, The different scan locations (e.g. macular) needed for this study are also outlined in the user interface and will again be addressed during the training to ensure the scan protocols are met.