terminology and guidelines for glaucoma ii - Kwaliteitskoepel

central 24 or 30 central degrees respectively. Testing points are aligned 3° off the vertical and horizontal meridians in
order to facilitate detection of “nasal steps” field defects.
Octopus Program G1 measures the retinal sensitivity at 73 points. 59 points are in the central 26 degrees (phase 1 and
2) at full threshold; 14 points are in the periphery, between 30 and 60 degrees (phase 3), and are tested at suprathreshold
levels.
SITA Standard and Fast for Humphrey and TOP for Octopus
Offers the advantage of a short test time.
Available data are promising but need to be confirmed before this technique is generally applied 1 .
Exams performed with the same instrument but with different strategies should not be used to assess progression.
1.4.2.1.2 - Non conventional techniques
SWAP (Short Wavelength Automated Perimetry) is based on the theory that the yellow light of the background can
reduce the sensitivity of some photoreceptors and leave active the blue cones that carry the stimulus using “Parvo” ganglion
cells. It is greatly affected by lens density.
FDT (Frequency doubling technology) is based on the theory that “My “ganglion cells are the first to be involved in
glaucoma and that using low spatial and high temporal frequency stimuli it is possible to detect the loss of these cells.
Motion and Flicker perimetry have been applied in clinical research; further developments are pending.
HRP (High Pass Resolution Perimetry) is based on the theory that “Parvo” ganglion cells can be detected particularly
well by high spatial and low temporal stimuli. This technology not been widely disseminated.
Available data are promising especially for early detection of functional damage. The role of these techniques in the
routine management is yet to be defined 2-10.
1.4.3 - THE EVALUATION OF PERIMETRY EXAMINATION
Possible sources of errors:
• Name: if mistyped the patient can be easily misdiagnosed, and the automated analysis of progression during
the follow-up is impossible.
• Date of the exam
• Birthdate: if mistyped patient identification is not possible, and the analysis may be incorrect, since
threshold testing takes into account age in the normative database. After the age of 20 there is a loss of differential
light sensitivity of 0.6 dB per decade, which is more pronounced in the peripheral visual field. If a false
lower age is entered, the normal field is evaluated as a field with pathologically low sensitivity; if false higher
age is entered, even pathological visual fields can be evaluated as normal.
• Refraction: the test should be done using near vision correction after the age of 40 or in aphakes and pseudophakes.
Astigmatism of more than 1 diopter can produce a refractive temporal peripheral scotoma. If the correcting
lens is not centered, a peripheral scotoma can be observed. Aphakic spectacle correction causes up to
50% of constriction of the visual field (called annular scotoma). An anterior chamber intraocular lens can cause
a slight constriction of the visual field.
• Pupil size: ideally 3.5 to 4 mm. Very small and very dilated pupils cause low or high sensitivity, respectively,
which may be misleading both as regards diagnosis and the evaluation of progression. If the size of the pupil is
outside the normal range (2 to 4 mm diameter) when the visual field is tested, the influence of the pupil-size
must be considered.
• Strategy / method / program: Differences between the algorithms used for sensitivity testing and processing
cause differences in the indices shown in the report. This must be considered when the visual field is evaluated.
In general, shorter programs (Humphrey, SITA, Octopus TOP Dynamic test) show better sensitivity (i.e. smaller
MD) than conventional, longer programs (e.g. Humphrey full threshold test or OCTOPUS normal strategy).
• Duration of the test: approximately 15 minutes per eye. Poor reliability should be suspected if the test time is
too long. In these cases a shorter test should be considered. Fatigue can be responsible for false visual field defects
Ch. 1 - 25 EGS