What is frequency doubling technique?
Frequency doubling technology (FDT) perimetry is based on a flicker illusion created by counterphase flickering of a low spatial frequency sinusoidal grating at a high temporal frequency. This phenomenon essentially creates an image that appears double its actual spatial frequency.
What is frequency doubling technology FDT perimetry?
PURPOSE: Frequency Doubling Technology (FDT) perimetry is a novel perimetric test that provides rapid screening (45 to 60 seconds) and full-threshold (4 to 5 minutes) testing for detection of vision loss.
What does the FDT visual field instrument measure electronically?
Humphrey FDT is an AC-powered device intended to determine the extent of the peripheral visual field of a patient. The device is intended to determine the amount of visual field loss in a patient, which can then be used to diagnose/track the progression of glaucoma and other eye diseases.
What is a 24 2 visual field?
The visual field (VF) pattern most widely used to detect glaucomatous damage, the 24-2 test pattern, does not adequately test the macular region, as the 6° grid of the 24-2 pattern has only four points within ± 8°.
What is MD in visual field test?
The mean deviation or mean defect (MD) gives an overall value of the total amount of visual field loss, with normal values typically within 0dB to -2dB. The MD value becomes more negative as the overall field worsens—a common example is when a cataract progresses.
What is Sita faster?
SITA™ Faster is the newest addition to the SITA family of testing strategies for the Humphrey® Field Analyzer 3 (HFA3) perimeter. b. SITA Faster testing takes about two-thirds of the time required by SITA Fast and about half the time required by SITA Standard.
How does the Humphrey field Analyzer work?
The analyser projects a series of white light stimuli of varying intensities (brightness), throughout a uniformly illuminated bowl. The patient uses a handheld button that they press to indicate when they see a light. This assesses the retina’s ability to detect a stimulus at specific points within the visual field.
Does cataract affect visual field test?
Thus, cataracts depress an automated visual field fairly uniformly. Clinical grading of cataracts by a single experienced clinician was generally a poor predictor of visual field loss.
How does a frequency doubling crystal work?
Due to nonlinear atomic polarization, crystals can emit a different frequency of light than absorbed. In order to see the second order effects of atomic po- larization, which cause a doubling in the frequency of the incident light, the incident light must be an intense and coherent source, like a laser.
What is frequency doubling technology (FDT)?
Frequency doubling technology (FDT) perimetry is based on a flicker illusion created by counterphase flickering of a low spatial frequency sinusoidal grating at a high temporal frequency. This phenomenon essentially creates an image that appears double its actual spatial frequency.
What is the role of frequency doubling technology in visual fields?
This page will focus specifically on the role of frequency doubling technology in assessing visual fields. Frequency doubling technology (FDT) perimetry is based on a flicker illusion created by counterphase flickering of a low spatial frequency sinusoidal grating at a high temporal frequency.
What is the frequency doubling illusion?
This phenomenon essentially creates an image that appears double its actual spatial frequency. The frequency doubling illusion (see example here) has previously been attributed specifically to the nonlinear response of the My cells in the magnocellular layer.
Does frequency doubling perimetry correlate with glaucoma visual field defects?
A study was done to correlate frequency doubling perimetry (FDP) results with glaucomatous visual field defects, as assessed by standard automated perimetry (SAP), in a glaucoma suspect population.