The EYESTAR 900 is a non-contact device for measuring the human eye, consisting of a swept source OCT sub-unit (OCT: optical coherence tomography, a measurement method to acquire tomographic images by optical interferometry) and an imaging system sub-unit.
The OCT sub-unit performs a three-dimensional measurement of all refractive ocular structures in the anterior eye segment (curvatures and locations of the anterior corneal surface, posterior corneal surface, the anterior crystalline lens surface, posterior crystalline lens surface), as well as a one-dimensional measurement of axial eye length. It also generates cross-sectional images of the anterior eye section and the central retina. The measurement is implemented by scanning the eye with a low-power near-infrared laser beam and measuring the light which is back-reflected to the device.
The imaging system sub-unit is used to obtain photographic images of the eye. Based on these images, the keratometry (anterior corneal curvature of the steepest and flattest meridian), the white-to-white distance and the pupil diameter are measured. Additionally, these images can serve to document the locations of special landmarks on the eye, such as blood vessels. The imaging system sub-unit is based on conventional digital photography technology. Illumination for imaging is provided by infrared and white-light LEDs (light emitting diodes). Measurement of keratometry additionally requires measuring the distance to the eye using the OCT sub-unit.
The EYESTAR 900 is designed as standalone-device with integrated PC (personal computer) and display for device operation, measurement acquisition and processing, and presentation of the measurement results. After a patient is placed in front of the device and the chin rest is adjusted, the device can perform the remaining positioning procedures and acquire the measurements in a fully automated manner. Position information is derived from the OCT and digital camera system sub-units.
Both implemented measuring methods, optical coherence tomography (OCT), as well as digital photography are non-invasive, contactless methods. OCT uses a laser beam of λ=1060nm central wavelength and less than 2 mW optical power, which is focussed to a beam diameter of approximately 80µm at the anterior lens plane, and is continuously scanned in the lateral direction. Digital photography uses diffuse illumination of the eye by white-light LEDs (425nm ≤ λ ≤ 725nm) and infrared LEDs with central wavelength λ=850nm. All light sources emit levels that comply with ISO 15004-2 ("Ophthalmic Instruments - Fundamental requirements and test methods - Part 2: Light hazard protection"), under normal operating conditions as well as in case of a single fault condition.
The main application of this device is to acquire biometric measurements of cataractous eyes which are used to calculate suitable intraocular lens power and dimension.
The patient population must be capable of sitting up straight and keeping their head still and their eyes opened. They must be physically and mentally able to cooperate and mentally capable of following the examination. Patients must be at least 18 years old.
The target device user is an ophthalmologist or a trained specialist.
The investigational device EYESTAR 900 is developed and manufactured by HAAG-STREIT AG, Koeniz (Switzerland).
For the duration of the examination (approximately 1-2 minutes), the patient is in contact with the device at following applied parts:
1. the chin rest shell (Edistir RK451 G naturally coated with HAERATEX Aqua 2K-structural coater BW89 10K RAL 9005);
2. the forehead rest band (Saxamid 126-N001 uncoated PA6 white FK 6659 PA);
3. (depending on the subject's requirements) the patient handles (aluminium EN AW-6060 (AlMgSi 0.5) colourless anodized class 20 with sealing chemically polished and sandblasted).
No other contact with body tissues or fluids takes place. No critical biocompatibility issues were identified.
