Specially designed algorithms
The DeyeRECTOR ® is designed as software packet in combination with the CHRONOS VISION’s OneK+ tracking camera. It is primarily intended as a set of OEM components or modules for eye tracking applications throughout ophthalmic surgery.
The modules are perfectly matched and always aligned with the latest in technical and medical research.
All DeyeRECTOR® software components are also available as optional hardware-independent modules.
The DeyeRECTOR.pupil module determines the x-and y-coordinates
of the puil centre. Considerable attention has been given to enhancing
the performance of the algorithm with regard to occlusions, instrument
artefacts and spurious reflections. This component provides spatial
tracking resolution of 0.01°, respectively ≈ 3 µm, is achieved.
Integrated into the OneK+ camera, the DeyeRECTOR.pupil module offers high speed pupil tracking with latency of less than 1 ms (processing delay). The entire image processing architecture is integrated into the extremely compact housing of the camera. This represents a standalone pupil tracker without need of an external computer. The On-chip image processing provides pupil tracking at rates beyond 1 kHz.
Pupil size is known to be influenced by a number of physiological factors –
typically patient vigilance, anxiety and visual accommodation, as well as
lighting conditions and refractive optical effects. With changing size the
pupil centre can shift relative to the cornea, or limbus; the resultant
error in corneal coordinates leads to a sub-optimal surgical outcome.
During surgery the DeyeRECTOR.shift module compensates for this effect by correcting the current pupil position with respect to the limbus. If desired it can also be integrated into a pre-op diagnostic system.
Based on state-of-the-art algorithms the DeyeRECTOR.ident module
provides reliable patient recognition and/or eye identification.
As with a fingerprint, individual patterns of the iris are extracted
from images acquired immediately prior to surgery and compared with
those determined during pre-op diagnosis.
In this manner the DeyeRECTOR.ident module ensures the correct patient and/or eye identification and the likelihood of ensuing errors are eliminated.
During refractive surgery the eye may also rotate about the horizontal and vertical
axes relative to the tracking camera. Unfortunately the resultant displacement of the
pupil or limbus on the video image does not reflect the true motion of the treatment
zone which is located at the corneal surface approximately 4 mm above the pupil.
As a consequence - if the procedure is based solely on the lateral position of the pupil - the applied laser pulses will ablate corneal tissue at incorrect positions. A refractive operation that does not take account of such rotational movements is likely to be detrimental to the patient‘s vision since the resultant refraction can differ significantly from the intended correction.
The DeyeRECTOR.tilt module measures horizontal and vertical tilt of the eye relative to the camera axis with a resolution of 0.25°. In addition the DeyeRECTOR.tilt module provides a measure of the eye distance (z coordinate).
Cyclorotation of the eyeball can significantly impair the surgical outcome of refractive
surgery or IOL-operations. Cyclorotation, or ocular torsion, can occur for a number of reasons.
First, differences in head position relative to camera between the diagnosis and operation
scenarios can lead to static changes in cyclorotation. Switching from head upright to supine can
also induce small changes in torsional eye position, particularly in patients with latent vestibular
disorders. The anaesthetics employed during surgery may also affect the tonus of the extra ocular muscles.
In addition, dynamic cyclorotation can occur during surgery. Accurate measurement of cyclorotation is
therefore important for optimising surgical outcome.
The DeyeRECTOR.torsion module provides robust and accurate measurement of static cyclorotation occurring between the diagnosis and operating units, as well as providing continuous online measurement of dynamic torsional movements during surgery.