Frequency Doubling Perimetry

Frequency doubling perimetry (FDP) (synonyms: frequency doubling technology, FDT) is a modern diagnostic procedure in ophthalmology, which is mainly used in glaucoma diagnosis (early detection of glaucoma/increased intraocular pressure).

Indications (areas of application)

  • Early detection or follow-up of glaucoma.

The procedure

The FDP is used to systematically measure the visual field and thus detect scotomas (failures in the visual field). The visual field corresponds to the space of the external world that is imaged and perceived on the retina (retina) when the eye is not moving.

In a classic perimetry (visual field measurement), the ophthalmologist uses an optical stimulus (e.g., a light spot) that he slowly moves into the patient’s visual field (dynamic perimetry) or whose intensity he changes (static perimetry). The patient indicates when he can perceive the light spot.Frequency doubling perimetry differs in the way the optical stimulus is presented. It is a fringe pattern in low spatial resolution that alternates between black and white at high frequency. The high speed of the change leads to the illusion that the pattern has doubled its frequency. This particular stimulus is particularly sensitive in exciting the ganglion cells (sensory cells whose processes form the optic nerve), which are very susceptible to glaucomatous damage (damage caused by increased intraocular pressure).The eye not being examined is covered while the procedure takes place under constant conditions (constant brightness, compensation for refractive errors, and constant pupil width when the examination is repeated). FDP provides overview results in as little as 45 seconds and complete examination results in less than 4 minutes per eye.

Frequency doubling perimetry is an effective diagnostic procedure that detects minute optic nerve damage before it is consciously perceived.