We have designed an instrument to measure blood flow in the subfoveal region of the human eye (choroid) or in the optic nerve head. The instrument can be mounted on a slit lamp. It requires a cooperative subject, which is asked to look at a faint coherent light source.
In order to ensure a good reproducibily of the measurements, we have implemented a vision system of the cornea track the position of the probing beam, a fundus illumination and a short viewing angle to see the position of the probing beam in the optical nerve head.
For choroidal measurement: By doing this, the probing light is focused on the fovea of the subject, an avascular zone where the LDF measurements are done. No pupil dilatation is required for that measurement.
For ONH measurement: In that case a movable fixation point is uesd. The instrument has two observation systems, one for the ONH with its own illumination and a second to observe the position of the probing beam at the cornea. A add-on can be used to excite the fovea with flicker light.