**5. Optovue-RTVue 100 glaucoma scanning protocol**

In glaucoma research, four scanning models for the Optovue-RTVue spectral domain OCT (RTVue Optovue Inc. Fremont, CA) device are used.

circular RNFL area whose center is the optic disc head and the RNFL area located at the rim

OCT in Glaucoma Diagnosis, Detection and Screening http://dx.doi.org/10.5772/intechopen.78683 163

This scan is used to analyze the RNFL and it has shown that RNFL parameters of the RTVue-100°CT has good specificity for the detection of glaucoma [45]. The RNFL scanning pattern completes four circular scans with diameters of 3.45 mm in 0.16 s by aiming for the optic disc head. The average of these four scans is calculated and the result is presented with normative parameters. The RNFL thickness profile at the optic disc head is the circular RNFL thickness with a diameter of 3.45 mm, which is the central optic disc and not the center of the scan itself. Ultimately, cases where the optic disc is decentralized do not affect the measurements. The RNFL thickness map is exhibited at the lower right area and the areas that are measured to be thin have a

darker color while areas that are measured to be thick have a lighter color (**Figure 5**).

RNFL and the optic disc head parameters are located at the left section.

In the lower right section, there is the thickness profile. Here, the RNFL thickness profile is charted temporally, superiorly, nasally, inferiorly and temporally again, in that order, beginning from around the optic disc. This thickness profile is charted as a black line by being superimposed on normative data (so that values within the normal range remain in the greenshaded area, while values outside of the normal range remain in the red-shaded area). The

of the optic disc, 2 mm away.

**Figure 5.** RNFL scan in RTVue.

**5.3. RNFL scan**

#### **5.1. Optic disc scanning**

The optic disc is calculated through a 6 × 6 mm cube consisting of 101 lines. 3D optic disc scanning is used especially for the formation of reference lines and the determination of optic disc veins. The 3D reference line represents the optic disc limits created automatically by a software that uses the 3D optic disc scan.

#### **5.2. Map of the optic disc head**

In this protocol, 13 circular and 9 radial scans with 1.3–4.9 mm diameters around the optic disc head are performed. These scans limit the area between the retinal pigment epithelium and the optic disc head. Here, the device automatically calculates the center of the optic disc and not the center of the scan itself. The same calculation is also automatically used in progression maps (**Figure 4**).

The map of the optic disc head provides significant information about the morphology of the optic disc. It provides insight, especially on the cup-to-disc ratio of the optic disc, the 3.45 mm

**Figure 4.** Optic disc head map in RTVue.

circular RNFL area whose center is the optic disc head and the RNFL area located at the rim of the optic disc, 2 mm away.

#### **5.3. RNFL scan**

This scan is used to analyze the RNFL and it has shown that RNFL parameters of the RTVue-100°CT has good specificity for the detection of glaucoma [45]. The RNFL scanning pattern completes four circular scans with diameters of 3.45 mm in 0.16 s by aiming for the optic disc head. The average of these four scans is calculated and the result is presented with normative parameters.

The RNFL thickness profile at the optic disc head is the circular RNFL thickness with a diameter of 3.45 mm, which is the central optic disc and not the center of the scan itself. Ultimately, cases where the optic disc is decentralized do not affect the measurements. The RNFL thickness map is exhibited at the lower right area and the areas that are measured to be thin have a darker color while areas that are measured to be thick have a lighter color (**Figure 5**).

In the lower right section, there is the thickness profile. Here, the RNFL thickness profile is charted temporally, superiorly, nasally, inferiorly and temporally again, in that order, beginning from around the optic disc. This thickness profile is charted as a black line by being superimposed on normative data (so that values within the normal range remain in the greenshaded area, while values outside of the normal range remain in the red-shaded area). The RNFL and the optic disc head parameters are located at the left section.

**Figure 5.** RNFL scan in RTVue.

**Figure 4.** Optic disc head map in RTVue.

**5. Optovue-RTVue 100 glaucoma scanning protocol**

(RTVue Optovue Inc. Fremont, CA) device are used.

software that uses the 3D optic disc scan.

**5.2. Map of the optic disc head**

gression maps (**Figure 4**).

**5.1. Optic disc scanning**

162 OCT - Applications in Ophthalmology

In glaucoma research, four scanning models for the Optovue-RTVue spectral domain OCT

The optic disc is calculated through a 6 × 6 mm cube consisting of 101 lines. 3D optic disc scanning is used especially for the formation of reference lines and the determination of optic disc veins. The 3D reference line represents the optic disc limits created automatically by a

In this protocol, 13 circular and 9 radial scans with 1.3–4.9 mm diameters around the optic disc head are performed. These scans limit the area between the retinal pigment epithelium and the optic disc head. Here, the device automatically calculates the center of the optic disc and not the center of the scan itself. The same calculation is also automatically used in pro-

The map of the optic disc head provides significant information about the morphology of the optic disc. It provides insight, especially on the cup-to-disc ratio of the optic disc, the 3.45 mm

#### **5.4. RNFL glaucoma progression report**

The RNFL 3.45 protocol identifies the RNFL thickness of the peripapillary area by performing circular scans with a diameter of 3.45 mm around the optic disc. What is important here is the sum of four 1024-A scans performed in 0.15 s, that is, the data of 4096 scans in total.

of the same cell are located at the inner plexiform layer and as this layer is affected, the inner plexiform layer gets thinner. So, the GCC scan measures the thickness of each of these three

OCT in Glaucoma Diagnosis, Detection and Screening http://dx.doi.org/10.5772/intechopen.78683 165

Another advantage of the GCC thickness analysis is the macula's inclusion of the 50% of the ganglion cells in the retina. However, NFL is very thin in the macula and since NFLs change places to form a foveal cup there are none of them in the foveola. In the perifoveal region, the

The scan includes 12 vertical lines and 1 horizontal line with a length of 7 mm. These lines are placed 0.5 mm away from each other and are focused on the temporal of the 1 mm fovea so that they include as many ganglion cells as possible. With this scan, the thickness map and the

The deviation map illustrates the deviations of normal values for different ages and races that are available in the normative database. The significance map reports the findings for the patient by comparing them with the normal values in the normative database on the basis of race. Red, yellow and green colors are used to note the differences in the follow-ups. It demonstrates the significance level or the statistical significance of the deviation when compared with a normal value. In short, the significance map demonstrates how significant the differ-

Another parameter here is the focal loss volume (FLV), which gives us the significant loss of GCC numerically. FLV is the sum of the significant loss of GCC topography, in terms of volume and is expressed as a percentage. At the same time, FLV is the most sensitive parameter which provides the difference between normal eyes and glaucomatous eyes (it is more

As it can be seen, while RTVue provides an excellent assessment of the ganglion cell layer it also allows a comparison to be made with the normal values, based on age and race. In follow-ups, progression analysis by RTVue compares the RNFL thickness measurements and the GCC map over time and thus, determines whether statistically significant changes have

The GCC progression report displays a total of four scans at the same time for both eyes, one of which is basal and the remaining three are for follow-ups. The output is divided into four sections. The first three sections are the GCC thickness map, the deviation map and the significance map. The GCC thickness map is the one coded with colors indicating the GCC thickness of the macular region. The deviation map is the one coded with colors indicating the loss percentages that the device determined according to the normal values based on the normative database. The significance map is the one demonstrating the statistically significant changes in comparison to the normal values by coding them in green, yellow and red colors. Finally, the fourth section includes the average, superior and inferior GCC chart. In this scan, the GCC thickness of the lower and upper hemisphere of the entire retina is scanned by excluding the foveal ring. Scan data are presented as changes between the basal scan and the

NFL is very thin but the ganglion cell layer and the IPL are much thicker [47, 48].

layers which are affected by the glaucoma [46].

ence is compared to the normal value.

occurred or not [1, 26, 49].

**5.6. GCC glaucoma progression report**

last scan, calculated in microns.

sensitive than the GCC thickness parameters).

abnormal changes in the inner retina can be demonstrated.

The RNFL output is divided into three sections. In the first section, regional RNFL thickness results are demonstrated with basal RNFL values and RNFL values of each subsequent check. The second section demonstrates the comparative TSNIT chart of RNFL, which is defined by a double hump pattern. The third section includes the value chart for average, superior and inferior RNFL. In addition, it illustrates the scans for each follow-up as a table including the changes between the basal scan and the last scan calculated in microns.

### **5.5. The map of the ganglion cell complex (GCC)**

The GCC scan has provided new parameters for the diagnosis of glaucoma. The nerve fiber layer (NFL), the ganglion cell layer and the inner plexiform layer (IPL) make up the GCC in the macular area. Today, more emphasis is placed on GCC rather than the thickness of the whole retina in the diagnosis of glaucoma [44]. In studies regarding this issue, it has been shown that glaucoma mostly thins the nerve fibers, the ganglion cells and the IPL; and the inner nuclear layer at an intermediate level and that it does not affect the outer layers [44]. The GCC study is quite useful for the early diagnosis of glaucoma and the determination of the disease's progression, since the loss of ganglion cells occur before the visual pathway lesions and thinning of the nerve fibers [13]. RTVue, by having a mapping protocol of macular ganglion cell complex, exhibits a positive value in detecting glaucoma.

The GCC thickness is defined as the distance consisting of three inner retinal layers (nerve fiber layer, ganglion cell layer and the inner plexiform layer) beginning from the inner limiting membrane and ending at the inner plexiform layer. (**Figure 6**) All three layers are affected in glaucoma [44].

When the ganglion cells die, the ganglion cell layer gets thinner and when the axon nerve fiber layer which is a part of this cell is damaged, the nerve fiber layer gets thinner. The dendrites

**Figure 6.** Anatomy of ganglion cell complex (GCC).

of the same cell are located at the inner plexiform layer and as this layer is affected, the inner plexiform layer gets thinner. So, the GCC scan measures the thickness of each of these three layers which are affected by the glaucoma [46].

Another advantage of the GCC thickness analysis is the macula's inclusion of the 50% of the ganglion cells in the retina. However, NFL is very thin in the macula and since NFLs change places to form a foveal cup there are none of them in the foveola. In the perifoveal region, the NFL is very thin but the ganglion cell layer and the IPL are much thicker [47, 48].

The scan includes 12 vertical lines and 1 horizontal line with a length of 7 mm. These lines are placed 0.5 mm away from each other and are focused on the temporal of the 1 mm fovea so that they include as many ganglion cells as possible. With this scan, the thickness map and the abnormal changes in the inner retina can be demonstrated.

The deviation map illustrates the deviations of normal values for different ages and races that are available in the normative database. The significance map reports the findings for the patient by comparing them with the normal values in the normative database on the basis of race. Red, yellow and green colors are used to note the differences in the follow-ups. It demonstrates the significance level or the statistical significance of the deviation when compared with a normal value. In short, the significance map demonstrates how significant the difference is compared to the normal value.

Another parameter here is the focal loss volume (FLV), which gives us the significant loss of GCC numerically. FLV is the sum of the significant loss of GCC topography, in terms of volume and is expressed as a percentage. At the same time, FLV is the most sensitive parameter which provides the difference between normal eyes and glaucomatous eyes (it is more sensitive than the GCC thickness parameters).

As it can be seen, while RTVue provides an excellent assessment of the ganglion cell layer it also allows a comparison to be made with the normal values, based on age and race. In follow-ups, progression analysis by RTVue compares the RNFL thickness measurements and the GCC map over time and thus, determines whether statistically significant changes have occurred or not [1, 26, 49].

#### **5.6. GCC glaucoma progression report**

**Figure 6.** Anatomy of ganglion cell complex (GCC).

in glaucoma [44].

**5.4. RNFL glaucoma progression report**

164 OCT - Applications in Ophthalmology

The RNFL 3.45 protocol identifies the RNFL thickness of the peripapillary area by performing circular scans with a diameter of 3.45 mm around the optic disc. What is important here is the

The RNFL output is divided into three sections. In the first section, regional RNFL thickness results are demonstrated with basal RNFL values and RNFL values of each subsequent check. The second section demonstrates the comparative TSNIT chart of RNFL, which is defined by a double hump pattern. The third section includes the value chart for average, superior and inferior RNFL. In addition, it illustrates the scans for each follow-up as a table including the

The GCC scan has provided new parameters for the diagnosis of glaucoma. The nerve fiber layer (NFL), the ganglion cell layer and the inner plexiform layer (IPL) make up the GCC in the macular area. Today, more emphasis is placed on GCC rather than the thickness of the whole retina in the diagnosis of glaucoma [44]. In studies regarding this issue, it has been shown that glaucoma mostly thins the nerve fibers, the ganglion cells and the IPL; and the inner nuclear layer at an intermediate level and that it does not affect the outer layers [44]. The GCC study is quite useful for the early diagnosis of glaucoma and the determination of the disease's progression, since the loss of ganglion cells occur before the visual pathway lesions and thinning of the nerve fibers [13]. RTVue, by having a mapping protocol of macular

The GCC thickness is defined as the distance consisting of three inner retinal layers (nerve fiber layer, ganglion cell layer and the inner plexiform layer) beginning from the inner limiting membrane and ending at the inner plexiform layer. (**Figure 6**) All three layers are affected

When the ganglion cells die, the ganglion cell layer gets thinner and when the axon nerve fiber layer which is a part of this cell is damaged, the nerve fiber layer gets thinner. The dendrites

sum of four 1024-A scans performed in 0.15 s, that is, the data of 4096 scans in total.

changes between the basal scan and the last scan calculated in microns.

ganglion cell complex, exhibits a positive value in detecting glaucoma.

**5.5. The map of the ganglion cell complex (GCC)**

The GCC progression report displays a total of four scans at the same time for both eyes, one of which is basal and the remaining three are for follow-ups. The output is divided into four sections. The first three sections are the GCC thickness map, the deviation map and the significance map. The GCC thickness map is the one coded with colors indicating the GCC thickness of the macular region. The deviation map is the one coded with colors indicating the loss percentages that the device determined according to the normal values based on the normative database. The significance map is the one demonstrating the statistically significant changes in comparison to the normal values by coding them in green, yellow and red colors. Finally, the fourth section includes the average, superior and inferior GCC chart. In this scan, the GCC thickness of the lower and upper hemisphere of the entire retina is scanned by excluding the foveal ring. Scan data are presented as changes between the basal scan and the last scan, calculated in microns.

#### **5.7. RTVue OCT normative database**

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

It must be noted that comparisons with normative databases are only for statistical purposes and there may be normal people with values that are outside the normal range.
