**7. Stratus OCT in clinical practice**

atrophic, it preserves the barrier function, keeping the macular region dry [20]. The current OCT systems allow the identification of drusen. The small and intermediary size ones ap‐ pear as discrete elevations of the RPE with variable reflectivity, according to the underlying material. In the large drusen (or so-called drusenoid PEDs) the RPE displays greater, often dome-shaped elevations separated from the Bruch membrane by a hypo or medium reflec‐ tive material. On OCT images drusen are often accompanied by modifications in the neuro‐ sensory retina, translated by the thinning of the outer nuclear layer and disruption at the level of the external limiting membrane and of the inner segment (IS)-outer segment (OS) junctions. These observations are in agreement with the histopathological ones that demon‐ strated the loss of photoreceptor cells in patients with drusen [28]. Geographic atrophy (GA) appears on OCT as sharply demarcated areas of choroidal hyperreflectivity due to the loss of RPE. If retinal atrophy is associated, thinning or loss of the outer nuclear layer, absence of the external limitting membrane and of the IS-OS junctions are seen. In the areas of GA, is‐ lands of preserved retina may be identified, as well as regressing drusenoid materials ap‐ pearing as hyperreflective plaques at the RPE band. In the GA in the inner nuclear layer may be identified small cystic-like spaces in the absence of any macular edema [28]. The evaluation of GA in terms of size, location and rate of progression is crucial in assessing the visual prognosis of the patients. An important finding that identifies the rapidly progressive cases is the autofluorescence surrounding the GA areas. OCT also revealed in the junctional zones of GA that the outer plexiform layer approaches the Bruch membrane suggesting that photoreceptor loss extends beyond the limits of the lesion. OCT reveals dynamic changes in the junctional zones of GA: pigment migration, variation in drusen height. In conclusion, OCT examination in dry AMD is important in two main directions: it provides insights in

144 Age-Related Macular Degeneration - Etiology, Diagnosis and Management - A Glance at the Future

the disease pathogenesis and it allows the prediction of visual outcome [28].

The advantages of OCT over fluorescein angiography (FA) are represented by: better struc‐ tural identification of CNV, identification of a CNV masked by the pooling of dye or by thin haemorrhages. On FA, in order to suspect the retinal edema the source of leakage has to be active, whereas on OCT even the minimal edema can be objectivized, no matter if the source of leakage is active or not. Cystoid macular edema in exudative AMD is difficult to be vi‐ zualized on FA because of the leakage that obscures the accummulation of fluid in the inner retina. Based on the OCT findings, the prevalence of cystoid macular edema in the cases of subfoveal CNV due to AMD in a retrospective study was estimated to be arround 46%. It has been demonstrated that during all the phases the ICGA substantially underestimated the size of the neovascular complex in comparison to SD-OCT. This could be explained by the high molecular weight and affinity of indocyanine green for the albumin molecules that prevented its even distribution through the entire lesion. Well defined hyperfluorescence during the early phase of FA defining the neovascular complex also underestimated the size of the lesion measured with SD-OCT. On the other hand, despite the SD-OCT capabilities of delivering high resolution images, the components of a fibrovascular complex may repre‐ sent other subretinal material, particularly of inflammatory origin. Another important obser‐ vation refers to the extent of leakage during the late phase of FA that did not reach the

**6.10. OCT versus angiography in AMD**

We used the Stratus OCT device (Carl Zeiss Meditech) with the fast macular map scan pro‐ tocol that consists in 6 radial scans oriented 30 degrees from one another, each having a 2 mm axial depth and 6-mm transverse length. Each image had 10 μm axial and 20 μm transverse resolutions in tissue with a maximum scan velocity of 400 axial scans per second.

Figures 1a and b depict the case of a patient with wet AMD with significantly increased macular thickness (central foveal thickness of 427 μm). Macular edema is provoqued not on‐ ly by the CNV visible on the cross-sectional images of the retina, but also by an increased vitreo-macular adhesion. The relatively long evolution of the disease is suggested by the modifications in the internal retinal layers, with hyporeflective cysts within their structure. The OCT aspect confirms the theory that the maximal vitreo-macular adhesion is located in front of the subretinal neovascular membrane.

**Figure 1.** a and b Retinal thickness: increased macular thickness due to CNV but also to vitreo-macular adhesion (cour‐ tesy of dr. H. Demea, Review Centre, Cluj-Napoca, Romania)

**Figure 2.** a and b: Patient with bilateral wet AMD before Bevacizumab injections (courtesy of dr. H. Demea, Review

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**Figure 3.** a and b: The case depicted in figure 2, after two intravitreal injections with Bevacizumab (courtesy of dr. H.

Centre, Cluj-Napoca, Romania)

Demea, Review Centre, Cluj-Napoca, Romania)

In figures 2a and b a bilateral AMD case is illustrated. In both eyes the RPE is elevated by a hyperreflective structure (CNV) and the macular thickness is increased. After 2 intravitreal injections with Bevacizumab (Avastin) the RPE elevation and the macular thickness de‐ creased, as shown in figures 3a and b.

Figure 4a shows a macular edema in the left eye of a patient with AMD and figure 4b dis‐ plays its aspect 20 months after periodic intravitreal injections with Bevacizumab (Avastin). Improvement is obvious, both regarding the central macular thickness and the cross-section‐ al aspect of the macula. Decision whether to treat or not was based on the OCT aspects, tak‐ en on a monthly basis.

The Stratus OCT images in figure 5a and 5b prove an elevation of the RPE in the right eye with moderately increase of central macular thickness (279 μm). One month after intravi‐ treal injection with Bevacizumab (Avastin) the central macular thickness decreased to 246 μm, as shown is figure 6a and 6b.

Figures 7a and 7bare illustrating the Stratus OCT aspects of the left eye of a patient with AMD: there is a marked increase in the central macular thickness (684 μm) and the retinal structure appears disorganized. One year after periodic intravitreal injections with Bevaci‐ zumab (Avastin) the central macula appears considerably thinner (380 μm) and the retinal layers much better arranged, as proved in figures 8a and 8b.However, in the internal retinal layers cystic structures appear, suggesting cystoid macular edema. As in case illustrated in figure 4, the decision of treatment was taken exclusively according to the OCT aspects.

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**Figure 2.** a and b: Patient with bilateral wet AMD before Bevacizumab injections (courtesy of dr. H. Demea, Review Centre, Cluj-Napoca, Romania)

**Figure 1.** a and b Retinal thickness: increased macular thickness due to CNV but also to vitreo-macular adhesion (cour‐

146 Age-Related Macular Degeneration - Etiology, Diagnosis and Management - A Glance at the Future

In figures 2a and b a bilateral AMD case is illustrated. In both eyes the RPE is elevated by a hyperreflective structure (CNV) and the macular thickness is increased. After 2 intravitreal injections with Bevacizumab (Avastin) the RPE elevation and the macular thickness de‐

Figure 4a shows a macular edema in the left eye of a patient with AMD and figure 4b dis‐ plays its aspect 20 months after periodic intravitreal injections with Bevacizumab (Avastin). Improvement is obvious, both regarding the central macular thickness and the cross-section‐ al aspect of the macula. Decision whether to treat or not was based on the OCT aspects, tak‐

The Stratus OCT images in figure 5a and 5b prove an elevation of the RPE in the right eye with moderately increase of central macular thickness (279 μm). One month after intravi‐ treal injection with Bevacizumab (Avastin) the central macular thickness decreased to 246

Figures 7a and 7bare illustrating the Stratus OCT aspects of the left eye of a patient with AMD: there is a marked increase in the central macular thickness (684 μm) and the retinal structure appears disorganized. One year after periodic intravitreal injections with Bevaci‐ zumab (Avastin) the central macula appears considerably thinner (380 μm) and the retinal layers much better arranged, as proved in figures 8a and 8b.However, in the internal retinal layers cystic structures appear, suggesting cystoid macular edema. As in case illustrated in figure 4, the decision of treatment was taken exclusively according to the OCT aspects.

tesy of dr. H. Demea, Review Centre, Cluj-Napoca, Romania)

creased, as shown in figures 3a and b.

en on a monthly basis.

μm, as shown is figure 6a and 6b.

**Figure 3.** a and b: The case depicted in figure 2, after two intravitreal injections with Bevacizumab (courtesy of dr. H. Demea, Review Centre, Cluj-Napoca, Romania)

**Figure 6.** a and b: The case depicted in figure 5, one month after Avastin injection (courtesy of dr. H. Demea, Review

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Centre, Cluj-Napoca, Romania)

**Figure 7.** a and b: Advanced case of AMD before Bevacizumab injection

**Figure 4.** a: Macular edema in AMD (left eye) b: The same patient 20 months after Avastin

**Figure 5.** a and b: RPE elevation in AMD patient before Avastin injection (courtesy of dr. H. Demea, Review Centre, Cluj-Napoca, Romania)

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**Figure 6.** a and b: The case depicted in figure 5, one month after Avastin injection (courtesy of dr. H. Demea, Review Centre, Cluj-Napoca, Romania)

**Figure 7.** a and b: Advanced case of AMD before Bevacizumab injection

**Figure 4.** a: Macular edema in AMD (left eye) b: The same patient 20 months after Avastin

148 Age-Related Macular Degeneration - Etiology, Diagnosis and Management - A Glance at the Future

**Figure 5.** a and b: RPE elevation in AMD patient before Avastin injection (courtesy of dr. H. Demea, Review Centre,

Cluj-Napoca, Romania)

fiber layer and the inner boundary of the RPE complex, though it has been reported that Stratus OCT has two outer reference lines: one at the junction between the inner/outer seg‐ ment of the photoreceptor cells and the other at the inner boundary of the RPE. In conse‐ quence, the Cirrus outer reference band is deeper than the first mentioned Stratus external band and is closer to the second mentioned one. The correlation of thickness measurements between the two devices is modest, the Cirrus OCT provides greater measurement depth.

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Figure 12: irregularities and thinning of the RPE band especially in the right eye, fluid in the

Figure 13: RPE band appears thinned and elevated by a moderately reflective tissue: fluid,

Figure 14: comparative aspects of the two eyes of the same patient: in the Right Eye the RPE

Figure 15: macular cube 200x200 shows increased central macular thickness, elevations of the RPE band, associated with increased vitreo-macular adhesion revealed by the 3D pre‐

retina, increased macular thickness.

sentation of the macular cube.

CNV, increased central macular thickness. 3D macular cube

band appears irregular and there is some fluid in the retina.

**Figure 9.** a: 5 line raster of a normal retina b: Normal macular thickness map

**Figure 8.** a and b: The same case depicted in figure 7, one year after Avastin injections
