What information does OCT provide?
OCT combines a large number of individual scans to produce a digital tomographic image.
The three principal OCT scan patterns available for assessment are:
- RNFL thickness
- This is the RNFL thickness measured on a 3.4-mm diameter scan centered on the optic disc. There are 2 principal acquisition protocols: RNFL Thickness (3.4), which is a single scan with 512 A-scans, and Fast RNFL (3.4), which is 3 scans of 256 A-scans acquired in rapid succession.
- Optic nerve head map
- This is a topographic map of the optic disc constructed from line scans through the optic disc center. The principal acquisition protocol is the Fast Optic Disc, which is composed of six 4-mm line scans of 128 A-scans each.
- Macular thickness map
- This is a topographic map of the macula constructed from line scans through the fovea. The principal acquisition protocol is the Fast Macular Thickness Map, which is composed of six 6-mm line scans acquired in rapid succession.
Quantitative information provided by OCT includes RNFL thickness measurements:
- The RNFL thickness report displays the RNFL thickness profiles for the right and left eyes in relation to the statistically normal range, derived from a normative database. The heavy black line gives the RNFL thickness profile for the subject; the colored bands display various regions of the statistically normal range: green 5% to 95%; yellow 1% - 5%; and red 0% - 1%. The same data are displayed in the center panel pie charts (top: 30 degree sectors; bottom: quadrants). The panels on the right display the video image of the scan location and the color-coded reflectivity image of the retinal tomograph.
- The table displays various parameters for the 2 eyes and the difference in the parameters between the 2 eyes. The parameter values are color-coded according to significance values in relation to the normative database.
- The RNFL thickness values discriminate well between normal and glaucomatous nerves.
Stratus OCT RNFL Thickness Report
A standard Stratus OCT RNFL thickness report is shown below.
Figure: Standard Stratus OCT RNFL thickness report View Large
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