**10.1 Qualitative assessment using AS-OCT**

An important landmark to identify when interpreting AS-OCT images is the scleral spur. This is visible as an inward projection of the sclera at the junction between the inner scleral and corneal curvatures. Studies have shown that scleral spur may not be visible in 25% cases [45]. The apposition between the iris and the inner corneo-scleral wall has been used in several studies as a qualitative method

*A Practical Guide to Clinical Application of OCT in Ophthalmology*

Ganglion cell complex diagnostic accuracy for detecting glaucoma has been shown to be similar to that of peripapillary RNFL thickness making it potentially

Progression analysis is currently available with Cirrus HD-OCT (Carl Zeiss

The RTVue offers progression analysis that includes side-by-side RNFL thickness measurements and overlay of the RNFL profiles for the consecutive scans. The RT Vue also provides similar analysis for ganglion cell complex thickness along with thickness change plots (**Figure 10**). However, a formal statistical analysis of change over time is not currently included in the latest version of the software for this

Meditec, Dublin, CA) and RTVue (Optovue, Fremont, CA). Of these two devices, statistical analyses in form of event- and trend-based mechanism for progression detection is available only in the Cirrus HD-OCT. Data sampling of the RNFL is obtained from the 3.4-mm diameter peripapillary circle and the software also displays RNFL thickness changes from baseline for each pixel in the scanned area. Possible or likely RNFL thickness loss is reported if change exceeds the expected test-retest variability in a single or two consecutive followup examinations, respectively. In addition, linear regression is performed to determine the rate of change, confidence limits, and statistical significance of

valuable for monitoring glaucoma progression [38–42].

*RNFL change analysis (adapted: Optovue, Fremont, CA).*

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the trend (**Figure 9**).

**Figure 10.**

device (version 6.1) (**Figure 11**).

of detecting closure of the anterior chamber angle [46, 47]. The degree of apposition however may not correlate exactly with appositional closure as defined by gonioscopy.
