**4. A-Cirrus Zeiss glaucoma scanning protocol**

Cirrus TM High Definition (HD)-OCT Spectral Domain (Carl Zeiss Meditec, Dublin; CA) used for the analysis of glaucoma.

At present, Cirrus high-definition (HD)-OCT is a widely used device to evaluate circumpapillary RNFL (cp-RNFL) thickness in clinical practice similarly as RTVue-100.

The device automatically identifies the center of the optic disc through data in this cube and forms a 3.46 mm circle around the disc, which enables the RNFL thickness around the peripapillary ring to be analyzed and compared with normative data. The most important point here is the ability to perform RNFL analysis with a reliable level of precision repetitively, even

OCT in Glaucoma Diagnosis, Detection and Screening http://dx.doi.org/10.5772/intechopen.78683 159

The value of the signal power is a value between 0 and 10 for the entire scan, with 10 being the maximum value. The threshold value is 5 and signal power values lower than that represent the values that are below the acceptable threshold value. In some patients, it may not be possible to obtain high signal power. In such cases, the clinician should assess whether the signal

While the fundus image is being created, the fundus image obtained through scanning laser ophthalmoscopy and the OCT fundus image are superimposed. This image appears on the upper section of the RNFL analysis screen. (**Figure 2**) The location of the calculation ring for the temporal, superior, nasal, inferior and temporal (TSNIT) section analyses is displayed in red. The operator can adjust the location of this ring following the shot if she/he likes to; however, that is often not necessary since this task is usually performed accurately through the automatic centering functionality. The B-mode scan image is the calculation ring gener-

though the optic disc is not placed in the center during the scan.

ated from the cube of data and is flattened for the TSNIT orientation.

obtained for scan analyses are acceptable or not.

**Figure 2.** RNFL analysis screen in Cirrus Zeiss.

Signal Power.

**4.2. Fundus image**

It is possible for us to find the necessary quantitative and qualitative data for a good management of glaucoma in this OCT device. It allows us to study the morphology and manometry of the optic disc and the peripapillary nerve fibers [37].

Even the first generation of these devices was able to display the retinal layers for us in vivo during the RNFL thickness measurement. In fact, many studies have shown the similarity between the OCT measurements and the histological sections. For this reason, the thickness of the RNFL is crucial for the early diagnosis of glaucoma and for being able to have an opinion on its progression [27, 29].

Cirrus Zeiss TM HD-OCT is an advanced technology in glaucoma research which is easy to use. It is possible for us to obtain precise and thorough information about the peripapillary area and the RNFL with this system [38, 39]. Main scanning models are provided below.

#### **4.1. Optic disc scanning**

Optic disc is recorded by Cirrus Zeiss TM HD-OCT within a 6x6 mm cube consisting of 200-B mode scans, each of which consists of 200-A mode scans. This area is divided into sections for analysis. (**Figure 1**).

**Figure 1.** Optic disc scanning in Cirrus Zeiss.

The device automatically identifies the center of the optic disc through data in this cube and forms a 3.46 mm circle around the disc, which enables the RNFL thickness around the peripapillary ring to be analyzed and compared with normative data. The most important point here is the ability to perform RNFL analysis with a reliable level of precision repetitively, even though the optic disc is not placed in the center during the scan.

#### Signal Power.

The value of the signal power is a value between 0 and 10 for the entire scan, with 10 being the maximum value. The threshold value is 5 and signal power values lower than that represent the values that are below the acceptable threshold value. In some patients, it may not be possible to obtain high signal power. In such cases, the clinician should assess whether the signal obtained for scan analyses are acceptable or not.

#### **4.2. Fundus image**

While the fundus image is being created, the fundus image obtained through scanning laser ophthalmoscopy and the OCT fundus image are superimposed. This image appears on the upper section of the RNFL analysis screen. (**Figure 2**) The location of the calculation ring for the temporal, superior, nasal, inferior and temporal (TSNIT) section analyses is displayed in red. The operator can adjust the location of this ring following the shot if she/he likes to; however, that is often not necessary since this task is usually performed accurately through the automatic centering functionality. The B-mode scan image is the calculation ring generated from the cube of data and is flattened for the TSNIT orientation.

**Figure 2.** RNFL analysis screen in Cirrus Zeiss.

**Figure 1.** Optic disc scanning in Cirrus Zeiss.

At present, Cirrus high-definition (HD)-OCT is a widely used device to evaluate circumpapil-

It is possible for us to find the necessary quantitative and qualitative data for a good management of glaucoma in this OCT device. It allows us to study the morphology and manometry

Even the first generation of these devices was able to display the retinal layers for us in vivo during the RNFL thickness measurement. In fact, many studies have shown the similarity between the OCT measurements and the histological sections. For this reason, the thickness of the RNFL is crucial for the early diagnosis of glaucoma and for being able to have an opinion

Cirrus Zeiss TM HD-OCT is an advanced technology in glaucoma research which is easy to use. It is possible for us to obtain precise and thorough information about the peripapillary area and the RNFL with this system [38, 39]. Main scanning models are provided below.

Optic disc is recorded by Cirrus Zeiss TM HD-OCT within a 6x6 mm cube consisting of 200-B mode scans, each of which consists of 200-A mode scans. This area is divided into sections for

lary RNFL (cp-RNFL) thickness in clinical practice similarly as RTVue-100.

of the optic disc and the peripapillary nerve fibers [37].

on its progression [27, 29].

158 OCT - Applications in Ophthalmology

**4.1. Optic disc scanning**

analysis. (**Figure 1**).

#### **4.3. RNFL thickness map**

The RNFL thickness map is calculated based on all the data of the scanned cube. The color scale used here is similar to that of a topographic map, where cold colors represent thinned areas while hot colors represent thick areas. In this way, the RNFL thickness at all points of the 6 × 6 mm area can be seen. The map excludes the optic disc displayed in dark blue. (**Figure 3**).

**4.5. TSNIT thickness profile**

**4.6. The normative database for RNFL**

indicators must be considered as abnormal.

yellow and should be interpreted as doubtful.

**4.7. The deviation map**

**4.8. Analysis of the results**

described earlier.

ing a diagnosis.

in, with the data of other individuals in the same age group.

age group, the RNFL normative database uses the colors as below:

(**Figure 3**).

The TSNIT thickness profile demonstrates the RNFL thickness for each point across the peripapillary ring and compares these values to the normative database. In these comparisons of patients in the same age group, color codes (white, green, yellow and red) are used.

OCT in Glaucoma Diagnosis, Detection and Screening http://dx.doi.org/10.5772/intechopen.78683 161

The RNFL normative database is used for glaucoma patients who are older than 18. This database allows us to compare the patient's data in the area that we are clinically interested

In order to demonstrate the normal distribution percentages of the individuals in the same

Red: The lowest portion of 1% with regard to all measurements is in the red zone and these

Yellow: In case the measurements are within the lowest portion of 5%, they are displayed in

The patient's RNFL thickness is compared with the normative data through the deviation map. Data that are out of the range of normal values are displayed in red and yellow as

The analysis of the results for glaucoma can be easily performed at a single glance with this device. On the first row, the fundus images are provided at the top, followed by the B-mode images of the peripapillary area neighborhood. On the second row, the map of the thickness of the nerve fibers is provided, accompanied by the deviation map indicating the difference between the normal thickness and the measured thickness. On the third row, rings indicating the thickness of the nerve fibers in the quadrants are provided. On the fourth row, a colored table where the thickness of nerve fibers is indicated in microns and that allows us to understand if the values are within the normal (green), doubtful (yellow) or pathological (red) range, thanks to different colors, is provided. In the resulting analysis, data for the right eye

In conclusion, Cirrus Zeiss TM HD-OCT device offers us good qualitative and quantitative information about the glaucomatous damage in patients [42–44]. However, the diagnosis and follow-up of glaucoma can be quite complicated at times. Therefore, since making a diagnosis with one device can mislead the physicians especially in difficult cases, comprehensive clinical exam data including the patient's visual field must be gathered while mak-

are provided on the left, while data for the left eye are provided on the right.

Green: 90% of all measurements are in this section and should be considered as normal.

In the color scale used to demonstrate the normal and defective areas in the RNFL, thickness of the nerve fiber layers ranging from zero (blue) to 350 μm (white) are indicated using color codes.

#### **4.4. Average thickness values**

The RNFL thickness across the TSNIT calculation ring is also displayed in a numerical chart format. In this chart, the average thickness of each point across the calculation is demonstrated for both eyes. (**Figure 3**) In addition, average thickness for each quadrant is also demonstrated separately and in time zones. Ultimately, in all these charts, the values of the patient are compared to normative data.

**Figure 3.** RNFL thickness map in Cirrus Zeiss.

#### **4.5. TSNIT thickness profile**

The TSNIT thickness profile demonstrates the RNFL thickness for each point across the peripapillary ring and compares these values to the normative database. In these comparisons of patients in the same age group, color codes (white, green, yellow and red) are used. (**Figure 3**).

#### **4.6. The normative database for RNFL**

The RNFL normative database is used for glaucoma patients who are older than 18. This database allows us to compare the patient's data in the area that we are clinically interested in, with the data of other individuals in the same age group.

In order to demonstrate the normal distribution percentages of the individuals in the same age group, the RNFL normative database uses the colors as below:

Red: The lowest portion of 1% with regard to all measurements is in the red zone and these indicators must be considered as abnormal.

Yellow: In case the measurements are within the lowest portion of 5%, they are displayed in yellow and should be interpreted as doubtful.

Green: 90% of all measurements are in this section and should be considered as normal.

#### **4.7. The deviation map**

The patient's RNFL thickness is compared with the normative data through the deviation map. Data that are out of the range of normal values are displayed in red and yellow as described earlier.

#### **4.8. Analysis of the results**

**Figure 3.** RNFL thickness map in Cirrus Zeiss.

**4.3. RNFL thickness map**

160 OCT - Applications in Ophthalmology

**4.4. Average thickness values**

compared to normative data.

codes.

The RNFL thickness map is calculated based on all the data of the scanned cube. The color scale used here is similar to that of a topographic map, where cold colors represent thinned areas while hot colors represent thick areas. In this way, the RNFL thickness at all points of the 6 × 6 mm area can be seen. The map excludes the optic disc displayed in dark blue. (**Figure 3**). In the color scale used to demonstrate the normal and defective areas in the RNFL, thickness of the nerve fiber layers ranging from zero (blue) to 350 μm (white) are indicated using color

The RNFL thickness across the TSNIT calculation ring is also displayed in a numerical chart format. In this chart, the average thickness of each point across the calculation is demonstrated for both eyes. (**Figure 3**) In addition, average thickness for each quadrant is also demonstrated separately and in time zones. Ultimately, in all these charts, the values of the patient are

> The analysis of the results for glaucoma can be easily performed at a single glance with this device. On the first row, the fundus images are provided at the top, followed by the B-mode images of the peripapillary area neighborhood. On the second row, the map of the thickness of the nerve fibers is provided, accompanied by the deviation map indicating the difference between the normal thickness and the measured thickness. On the third row, rings indicating the thickness of the nerve fibers in the quadrants are provided. On the fourth row, a colored table where the thickness of nerve fibers is indicated in microns and that allows us to understand if the values are within the normal (green), doubtful (yellow) or pathological (red) range, thanks to different colors, is provided. In the resulting analysis, data for the right eye are provided on the left, while data for the left eye are provided on the right.

> In conclusion, Cirrus Zeiss TM HD-OCT device offers us good qualitative and quantitative information about the glaucomatous damage in patients [42–44]. However, the diagnosis and follow-up of glaucoma can be quite complicated at times. Therefore, since making a diagnosis with one device can mislead the physicians especially in difficult cases, comprehensive clinical exam data including the patient's visual field must be gathered while making a diagnosis.
