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FloM-ONH

The FloM-ONH is 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.
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 used. 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. An add-on can be used to excite the fovea with flicker light.


Spécifications :

Instrument :

  • Size: 30 cm x 26 cm x 6 cm
  • The instrument has to be mounted on a table.

Optical systems

  • 1. Observation and illumination are restricted to the optic nerve head.
  • 2. Observation at the cornea of the probing beam.
  • 3. Fixation points placed at 15° of the ONH observation.
  • 4. Add-on for flicker light in the fovea region.

Subject

  • The instrument required a cooperative subject who is asked to look at a faint point.
  • No pupil dilatation is required for choroidal blood flow measurement
  • Pupil dilatation is required for ONH blood flow measurement

Probing light

  • Wavelength: 795 nm
  • Intensity: 100 µW

Probing intensity

  • Less than 100 µW (micro-watt)

Optical principle

  • Schlieren: the illumination spot is excluded from the detected scattered light.

Ametropia correction

  • +/- 2.5 Dioptres

Data Analysis

  • The instrument delivers an electrical signal, which is analysed by FloM-acquisition.

Reference

  • This instrument is derived from the one described in the following publication. It has the same optical arrangement but another mechanical support: Compact instrument for Laser Doppler velocimetry. Geiser MH, Diermann U, Riva CE. Biomedical Optics, Journal of Biomedical Optics, October 1999, Volume 4, Issue 4, pp. 459-464