The EYESTAR 900 with software version i9.5.1.0 includes new analysis functionality. Since its clinical performance cannot be assessed based solely on clinical literature as found in the Clinical Evaluation Report, further data from a clinical trial is required. The objective of this trial is to assess the clinical performance of the new features of the EYESTAR 900 with software version i9.5.1.0.

This study is a necessary part of the clinical evaluation process of the investigational device. The results of this study are used for the clinical evaluation, and for reporting of in-vivo repeatabilities in the instructions for use of the investigational device, as required by topography standards.

Ocular biometry is the act of measuring the geometric properties of the eye, in particular distances between and thicknesses of the visual axis of the cornea, lens and retina, as well as curvature of the anterior cornea. These measurements are used mainly to determine implant type and dimensions for cataract surgery.

Corneal topography is the act of measuring the shape of the cornea, in particular of the anterior cornea, but, depending on the device and the application, also of the posterior cornea, as well as the distance between the anterior to the posterior of the cornea. These measurements can be used in the context of ocular biometry, but are also useful for many other applications where knowledge of the optical and structural properties of the cornea are of interest.

Optical coherence tomography (OCT) is a well-established imaging modality in ophthalmology. It uses interferometry to obtain a scattering profile of the eye along the direction of propagation of a laser beam which is directed onto the eye. In analogy to ultrasound imaging, this scattering profile is called A-Scan. By laterally translating the measurement beam, several A-scans can be combined to form a 2-dimensional image or 3-dimensional (3D) tomogram of the eye. The main use of OCT is the cross-sectional imaging of the retina or the cornea, primarily for diagnostic purposes[4]. Recently, anterior segment OCT has also been used for corneal topography[5], as well as for biometry and cross-sectional imaging along the entire length of the eye[6].

EYESTAR 900 is a device developed by Haag-Streit which utilises 3D OCT for quantitative measurements of the geometry of the entire eye, including ocular biometry and corneal topography. CE approval for EYESTAR 900 with software version i9.4.0.0 is pending and expected before the start of this clinical trial.

The development of this device has been continued, and the following additions have been made in software version i9.5.1.0 used for this clinical study with respect to the software version i9.4.0.0:

• Extended corneal topography: corneal topography can be evaluated over an extended area (diameter of trajectory d=13mm with respect to d=8.6mm in "standard corneal topography").
• Irregularity segmentation: segmentation methods (identification of corneal surfaces) used in corneal topography now incorporate an improved algorithm for segmentation of irregular corneal surfaces.
• Irregularity visualization: visualization of topography maps has been supplemented by an overlay of regions with irregular corneal surfaces.
• Zone-based keratometry: visualization of topography maps has been further supplemented by an overlay of local keratometry values (power and axes of flat and steep meridians in the centre, middle and outer corneal surface).
• Crystalline lens tilt: the tilt of the crystalline lens normal vector with respect to the visual axis can be visualized and quantified.

Both irregularity visualization and zone-based keratometry are applicable to corneal topography data acquired with the standard corneal topography protocol, as well as corneal topography acquired over the extended area (diameter 13mm, extended corneal topography).

The primary objective of this clinical trial is to assess the clinical performance of extended corneal topography using irregularity segmentation, standard corneal topography using irregularity segmentation and crystalline lens tilt. To that end, for each measurand, the in-vivo repeatability will be quantified. For "standard corneal topography" and "extended corneal topography", the limits of agreement and the mean measurement deviation, with respect to three comparators are analyzed.

As a secondary objective of the study, raw measurement data will be collected to allow for the improvement of existing algorithms, development of additional measurands and for retrospective analysis.

Examinations with EYESTAR 900 and the other study devices are non-contact examinations. No diseases are studied as part of this study.

Inclusion Criteria:

voluntary participation of subjects of legal age, irrespective of age, gender, ethnicity, of which:

• participants with healthy eyes,
• participants with corneal scarring,
• participants with irregular astigmatism.

Exclusion Criteria:

• Involuntary participation or inability to provide consent,
• persons of vulnerable populations,
• persons unable or unwilling to follow instructions,
• persons unable to maintain fixation for the duration of the examinations,
• persons with active inflammation or infections of the eye,
• persons with a tear film break up time of less than 5 sec.