**6. Heidelberg spectral glaucoma scanning protocol**

Heidelberg Spectral Domain OCT (Spectralis, Heidelberg Engineering, Dossenheim, Germany) is an OCT device with a high scanning speed and axial resolution, allowing better reproducibility for image acquisition compared to time-domain OCT (TD-OCT) [31]. It is possible to obtain a very high-quality optic disc head image and perform peripapillary RNFL thickness analysis with this device.

In scans performed circularly, the scanned areas are automatically divided into sections while the RNFL thickness is measured and compared with the values in the normative database.

#### **6.1. RNFL thickness profile**

The OCT output in this device displays the peripapillary RNFL thickness classification by six standard pie charts:


In the ring which is in the middle of the pie chart, the average of the circular scan (G) is provided.

On top of the output, the optic disc head scan and the real scan image of the optic disc head surroundings are provided, while the scanned image corresponding to the RNFL thickness

OCT in Glaucoma Diagnosis, Detection and Screening http://dx.doi.org/10.5772/intechopen.78683 167

Heidelberg spectral OCT obtains the changes in RNFL through time by using a special software formula and uses them for monitoring the patient. This software displays the rate of difference

chart is provided on the right side.

**Figure 7.** RNFL thickness map in Heidelberg.

**6.2. RNFL monitoring**

The chart in the lower right corner of the window demonstrates the RNFL thickness profile that has been measured through the circular scan and its comparison with the normal ranges. The black curve represents the RNFL thickness of the patient. In both charts, three colors are available where green represents the normal RNFL thickness, yellow represents the limit value and red represents the abnormal RNFL thickness (**Figure 7**).

**Figure 7.** RNFL thickness map in Heidelberg.

On top of the output, the optic disc head scan and the real scan image of the optic disc head surroundings are provided, while the scanned image corresponding to the RNFL thickness chart is provided on the right side.

#### **6.2. RNFL monitoring**

**5.7. RTVue OCT normative database**

166 OCT - Applications in Ophthalmology

thickness analysis with this device.

**6.1. RNFL thickness profile**

**2.** Temporal Superior (TS) **3.** Temporal Inferior (TI)

**5.** Nasal Superior (NS) **6.** Nasal Inferior (NI)

standard pie charts:

**1.** Temporal (T)

**4.** Nasal (N)

provided.

green (normal), yellow (doubtful) and red (abnormal) are used.

**6. Heidelberg spectral glaucoma scanning protocol**

The normative database of RTVue OCT is the largest OCT normative database. As mentioned earlier, these databases allow to distinguish between normal cases and pathological ones. In this database, there are a total of 1600 eyes, 600 of which are from the USA and 1000 of which are from around the world. The data allow us to compare the measurements of the patients with measurements of other patients in the same age group. In the display coded with colors,

It must be noted that comparisons with normative databases are only for statistical purposes

Heidelberg Spectral Domain OCT (Spectralis, Heidelberg Engineering, Dossenheim, Germany) is an OCT device with a high scanning speed and axial resolution, allowing better reproducibility for image acquisition compared to time-domain OCT (TD-OCT) [31]. It is possible to obtain a very high-quality optic disc head image and perform peripapillary RNFL

In scans performed circularly, the scanned areas are automatically divided into sections while the RNFL thickness is measured and compared with the values in the normative database.

The OCT output in this device displays the peripapillary RNFL thickness classification by six

In the ring which is in the middle of the pie chart, the average of the circular scan (G) is

The chart in the lower right corner of the window demonstrates the RNFL thickness profile that has been measured through the circular scan and its comparison with the normal ranges. The black curve represents the RNFL thickness of the patient. In both charts, three colors are available where green represents the normal RNFL thickness, yellow represents the limit

value and red represents the abnormal RNFL thickness (**Figure 7**).

and there may be normal people with values that are outside the normal range.

Heidelberg spectral OCT obtains the changes in RNFL through time by using a special software formula and uses them for monitoring the patient. This software displays the rate of difference between the average measured thickness values for each section and the normal thickness values as a chart of change. Thanks to these software, changes that occur in the RNFL profile or the deterioration that occurs in the thickness over time can be detected at an early stage [50, 51].

profile in the early glaucoma where inferior and superior quadrants damaged earlier than in

OCT in Glaucoma Diagnosis, Detection and Screening http://dx.doi.org/10.5772/intechopen.78683 169

Although all these three devices represent difference in axial resolution and in time of acquisition, the final diagnostic performance for detection of glaucomatous defect generally reported

Different results may of course be obtained due to different clinical settings, race differences,

In conclusion, since glaucoma is a condition that shows variations over time, it is crucial that it should be closely monitored. Especially, the change of the RNFL thickness values and the values of variation for the first and last exam of the patient must be analyzed carefully.

Department of Ophthalmology, Canakkale Onsekiz Mart University, School of Medicine,

[1] Akashi A, Kanamori A, Nakamura M, Fujihara M, Yamada Y, Negi A. Comparative assessment for the ability of Cirrus, RTVue, and 3D-OCT to diagnose glaucoma.

[2] Basic and Clinical Science Course (BCSC). Section 10: Glaucoma. San Francisco, CA:

[3] Weinreb RN, Aung T, Medeiros FA. The pathophysiology and treatment of glaucoma: A

Investigative Ophthalmology & Visual Science. 2013;**54**:4478-4484

American Academy of Ophthalmology; 2016. pp. 20-38

review. JAMA. 2014;**311**:1901-1911

the nasal and temporal quadrants.

age and the severity of the disease.

**Acknowledgements**

**Conflict of interest**

No conflict of interest.

Address all correspondence to: aydinyildiz@comu.edu.tr

**Author details**

Canakkale, Turkey

**References**

Aydin Yildiz

to be similar.

None.

#### **6.3. The normative database of Heidelberg spectra OCT**

There are 201 individuals registered in the normative database of this device, all of whom are Caucasian. Ages of these individuals range from 18 to 78, and 111 of them are male while 90 are female. The criteria for these people to be included in the database are naturally, their lack of a glaucoma history and the fact that they have normal intraocular pressure, visual field and optic disc appearance. The results have been organized as a normative database.

#### **6.4. Posterior pole analysis**

A new software called Posterior Pole Analysis is offered by the Heidelberg spectral OCT [33, 52]. Thickness of the entire posterior pole retina can be measured through this software. The posterior pole is scanned point by point, and the thickness asymmetry between the two eyes and the intraocular hemispheres are analyzed. Furthermore, the GCC loss is also assessed and findings for glaucoma at an early stage are analyzed through this software [53, 54].

OCT output for the analysis provides two basic maps. The first one is the map of hemisphere asymmetry while the second one is the map of RNFL thickness. The map of hemisphere asymmetry is in the form a grid where the average thicknesses of the upper and lower hemisphere are compared. Here, the squares that vertically have the same distance from the axe between the fovea and the optic disc are compared. While the squares in the upper half of the grid represent the differences between the RNFL thickness values in the superior and inferior regions, squares in the lower half represent the differences between the RNFL thickness values in the inferior and superior regions. If the difference between these values is zero or a positive value, the colored area looks white. If the area is dark gray or black, this refers to a local asymmetry in terms of RNFL thickness values.

In the literature, there are several studies evaluating the diagnostic ability of abovementioned devices with some minor differences in the results [1, 2, 6, 10, 16–21, 23–41].

Leung et al. reported that, in Spectralis, the global thickness parameter had the largest area under curve (AUC) in eyes with severe glaucoma [34]. Leite et al. reported that in Spectralis, superior quadrant RNFL followed by global RNFL, had the largest AUC and in Cirrus, global thickness was the parameter that has the largest AUC, with superior and inferior RNFL quadrants being the second and the third [54]. Park et al. and Leung et al. reported similar results with inferior, average and superior quadrant RNFL's having the best diagnostic performance for device Cirrus as Sehi et al. [29, 30, 34].

In their study, Leite et al. also showed that the diagnostic ability of all three devices for the nasal and temporal quadrants for glaucoma diagnosis was lower than the results received from the other quadrants [54]. This finding may be associated with the optic nerve damage profile in the early glaucoma where inferior and superior quadrants damaged earlier than in the nasal and temporal quadrants.

Although all these three devices represent difference in axial resolution and in time of acquisition, the final diagnostic performance for detection of glaucomatous defect generally reported to be similar.

Different results may of course be obtained due to different clinical settings, race differences, age and the severity of the disease.

In conclusion, since glaucoma is a condition that shows variations over time, it is crucial that it should be closely monitored. Especially, the change of the RNFL thickness values and the values of variation for the first and last exam of the patient must be analyzed carefully.
