**3.6 Outer retina-choroid complex (ORCC) splitting**

Patients at intermediate clinical stages in Best vitelliform macular dystrophy (BVMD) show split in the ORCC by OCT. The ORCC has multiple components, and it is split into subcomponents showing different patterns [56]. Such patterns of ORCC splitting represent the separation between the apical surface of the RPE and photoreceptors causing neurosensory macular retinal detachment (**Figure 8**) [57]. OCT shows a diffuse, irregular, and thickened ORCC by underlying hyporeflective area [3].

**73**

**Figure 9.**

*DRIL areas in SD-OCT.*

*New Landmarks, Signs, and Findings in Optical Coherence Tomography*

**3.7 Disorganization of retinal inner layers (DRIL)**

**Figure 8.**

*vitelliform macular dystrophy.*

a useful tool in the future therapeutic intervention [69].

DRIL is observed on OCT as the difficulty to identify limits between the ganglion cell-inner plexiform layer complex, inner nuclear layer, and OPL (**Figure 9**). It represents an interrupted transmission pathway between the photoreceptors and ganglion cells due to the disruptions of synaptic connections of amacrine, bipolar, and horizontal cells [58]. Several hypotheses explain the pathogenesis: **mechanical factor** (stretching of bipolar axons by edema) and **vascular factors** (ischemia, loss of the retinal capillary plexuses, or neuroglial degeneration as sequelae of inflammation) [58–62]. DRIL has been described as a strong predictive factor of worse visual acuity in patients with DME [58], uveitic macular edema [63], and central retinal vein occlusion [64]. Although the role of ischemia in DRIL is being studied, authors have found that areas of macular capillary nonperfusion were strongly correlated with DRIL on fluorescein angiography (FA) in severe nonproliferative and proliferative diabetic retinopathy (PDR) [59]. Moreover, more recently, OCT angiography has allowed researchers to study the positive correlation between DRIL and the size of the foveal avascular zone in diabetic retinopathy and retinal vein occlusion [60, 65]. Even, it has been associated with higher body mass index, longer diabetes duration, and increasing severity of PDR [66, 67]. Several studies have demonstrated that DRIL is a dynamic phenomenon. Its reversibility, with an anatomic improvement, decreases with increasing duration [58, 68]. Thus, DRIL seems to be a biomarker that may be incorporated into daily clinical practice and be

*SD-OCT shows a splitting of outer retina-choroid complex by hyporeflective area in a patient with Best* 

*DOI: http://dx.doi.org/10.5772/intechopen.84242*

**Figure 8.**

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

it was even spontaneously resolved in 47% of the cases [52].

**3.6 Outer retina-choroid complex (ORCC) splitting**

in patients without staphyloma, emmetropic, or hypermetropic eyes [44, 45]. A variety of hypotheses have been postulated to explain it: an adaptive mechanism to minimize defocus in highly myopic eyes [46], vitreomacular traction [47], ocular hypotony [47], resistance of the sclera to the staphylomatous deformation [48], or localized choroidal thickening [48]. However, it has been recently indicated that the

main problem is the different degrees of scleral thinning in the foveal region [46, 49, 50]. Subretinal fluid (SRF) in the fovea has been associated continuously with DSM in 28.5–66.6% of patients [51]. It may be due to RPE dysfunction [48] or as a consequence of not uniform scleral thickness that can affect choroidal fluid [46]. Although photodynamic therapy and anti-VEGF agents have been applied, they had no effects in terms of improvement in BCVA and resolution of SRF,

**3.5 Brush border pattern or elongation of photoreceptor outer segment**

because the fluid remained chronic and stable in most of the eyes over time [51], and

Brush border pattern is defined as an accumulation of waste products in the photoreceptor outer segment on the outer surface of the detached neurosensory retina over subretinal fluid (**Figure 7**). This provides an irregular, serrated, and thicker appearance of the detached neurosensory retina. Other authors denominate it as "elongation of the outer photoreceptor segment", and it can be found in almost 73–75% of OCT images from patients who suffer CSCR [53]. The loss of the contact between RPE and photoreceptor outer segments that occur in CSCR prevents the waste product of photoreceptors being phagocytosed by RPE [54]. These subretinal proteins or accumulated macrophages with outer photoreceptor segments can be observed as hyperfluorescent white-yellowish precipitates in the retinal examination if they contain precursors of lipofuscin [55]. If this process persists, despite subretinal fluid absorption, subretinal deposits may progress to be permanent with the subsequent poor visual outcome. Complete disappearance of outer segments as observed in very long-standing CSCR correlates with poor

Patients at intermediate clinical stages in Best vitelliform macular dystrophy (BVMD) show split in the ORCC by OCT. The ORCC has multiple components, and it is split into subcomponents showing different patterns [56]. Such patterns of ORCC splitting represent the separation between the apical surface of the RPE and photoreceptors causing neurosensory macular retinal detachment (**Figure 8**) [57]. OCT shows a diffuse, irregular, and thickened ORCC by underlying hyporeflective

*Brush border pattern in patient affected of chronic central serous chorioretinopathy (CSCR).*

**72**

**Figure 7.**

area [3].

visual prognosis [53].

*SD-OCT shows a splitting of outer retina-choroid complex by hyporeflective area in a patient with Best vitelliform macular dystrophy.*

### **3.7 Disorganization of retinal inner layers (DRIL)**

DRIL is observed on OCT as the difficulty to identify limits between the ganglion cell-inner plexiform layer complex, inner nuclear layer, and OPL (**Figure 9**). It represents an interrupted transmission pathway between the photoreceptors and ganglion cells due to the disruptions of synaptic connections of amacrine, bipolar, and horizontal cells [58]. Several hypotheses explain the pathogenesis: **mechanical factor** (stretching of bipolar axons by edema) and **vascular factors** (ischemia, loss of the retinal capillary plexuses, or neuroglial degeneration as sequelae of inflammation) [58–62]. DRIL has been described as a strong predictive factor of worse visual acuity in patients with DME [58], uveitic macular edema [63], and central retinal vein occlusion [64]. Although the role of ischemia in DRIL is being studied, authors have found that areas of macular capillary nonperfusion were strongly correlated with DRIL on fluorescein angiography (FA) in severe nonproliferative and proliferative diabetic retinopathy (PDR) [59]. Moreover, more recently, OCT angiography has allowed researchers to study the positive correlation between DRIL and the size of the foveal avascular zone in diabetic retinopathy and retinal vein occlusion [60, 65]. Even, it has been associated with higher body mass index, longer diabetes duration, and increasing severity of PDR [66, 67]. Several studies have demonstrated that DRIL is a dynamic phenomenon. Its reversibility, with an anatomic improvement, decreases with increasing duration [58, 68]. Thus, DRIL seems to be a biomarker that may be incorporated into daily clinical practice and be a useful tool in the future therapeutic intervention [69].

**Figure 9.** *DRIL areas in SD-OCT.*

#### **3.8 Pearl necklace sign**

The pearl necklace sign refers to HRD in a continuous ring around the cystoid spaces in the retina that has been seen in diseases with exudative maculopathy, vascular leakage, and chronic CME such as neovascular AMD, DME, retinal vein occlusion, retinal arterial macroaneurysm, or Coats disease (**Figure 10**) [70]. The authors speculated that HRD indicated the presence of lipid material from retinal vascular leakage similar to hard exudates. These pearls may represent lipid-filled macrophages along the inner wall of retinal edema [70]. Moreover, it is considered a frequent precursor sign on the location of the hard exudates which appear later. Therefore, this sign can change shape and may resolve under treatment or spontaneously. The presence of pearl necklace sign has not been associated with worse visual acuity in RD [71].

The pearl necklace sign should be differentiated from ORTs, which are located deeper in the ONL of the retina. In ORT, the ring is continuous and homogeneous, whereas the hyperreflective ring is as small foci in the pearl necklace sign [3].

#### **3.9 Focal choroidal excavation (FCE)**

FCE is a localized depression of the choroid detected only by using OCT, without any evidence of posterior staphyloma or scleral ectasia. It affects Bruch's membrane-RPE-choriocapillaris line complex line and photoreceptors (**Figure 11**). Patients are mostly asymptomatic and have good visual acuity. Nevertheless, some lesions may be associated with the development of choroidal neovascular membrane. It has been reported that FCE may appear in certain macular disorders such as CSCR, AMD, ERM, CNVM, polypoidal choroidal vasculopathy, BVMD, Vogt-Koyanagi-Harada disease, punctate inner choroidopathy, focal retinochoroiditis, foveoschisis, torpedo maculopathy, multiple evanescent white dot syndrome, multifocal choroiditis, and combined hamartoma of the retina and RPE [3]. OCT allows to identify retinal and choroidal structures that are affected in the excavation, which usually includes RPE, Bruch's membrane, EZ line, ELM, and ONL which followed the contour of the FCE. In some cases, it can be appreciated an attenuation or absence of IS/OS junction at the excavation, and ONL was thickened in most conforming eyes [72]. However, the layers from the OPL to the ILM were undisturbed, and also the sclerochoroidal junction appeared reasonably preserved without scleral excavation [72, 73]. FCE may be organized in two patterns, whether or not the photoreceptor layer is detached

**75**

*New Landmarks, Signs, and Findings in Optical Coherence Tomography*

from the RPE. Thus, conforming FCE describes those types of lesions without separation between the two layers and the photoreceptors adapt to the contour of the RPE layer. On the other hand, in nonconforming FCE, photoreceptors appeared to be detached from the RPE showing a hyporeflective space. Factors contributing to the formation of each pattern are unknown [74]. Other authors have classified the lesions into three morphological patterns based on SD-OCT findings: bowl shaped, cone shaped, and mixed shaped [75]. They observed that all bowl-shaped types showed atrophic changes and RPE irregularities, whereas in cone-shaped FCE, a less atrophic change is detected at the center of the lesion. The pathogenesis of FCE is still unknown. Some authors suggest it could be related to a congenital defect within the choroid, which is supported by the fact that shape and size remained stable during the follow-up in most of the reported cases [73]. Nevertheless, no family history and low prevalence in young people suggest that it may be an acquired condition [74]. Some authors proposed FCE is an entity related to inflammatory diseases like Vogt-Koyanagi-Harada disease, multiple evanescent white dot syndrome, and other

*Focal choroidal excavation (FCE) revealed by SD-OCT in a patient with chronic CSCR and systemic lupus* 

Foveal pseudocyst is an OCT pathologic sign that is caused by subretinal retention of perfluorocarbon liquid (PFCL) after vitreoretinal surgery. Subretinal PFCL is a serious complication if it affects fovea. The incidence ranges from 1 to 11% after retinal detachment surgery [77]. Main risk factors for this entity are the presence of a large size retinal tear, large retinotomy (especially in 360°), and retinal traction at retinal breaks [78]. It is rare to find it in conventional surgery, but in these cases, it is usually caused by small bubbles which can be produced by turbulence by the interface between PFCL and saline solution [77]. OCT is a useful tool to identify intraretinal bubbles of PFCL. In many cases, the bubbles remain stable without size changing. The most common signs in OCT are RPE pigment disorganization, disruption of ellipsoid layer, and hyperreflectivity at the base of the PFCL bubble (**Figure 12**) [77]. It has been reported several cases with retinal hole secondary to long-standing subretinal PFCL [79]. Subretinal PFCL is responsible for retinal damage resulting in loss of visual acuity, scotomas, and retinal thinning. Long-time exposure to PFCL can lead to RPE atrophy, photoreceptor damage because there is a direct toxic defect, or inflammatory response including macrophages phagocyted PFCL [77]. It is recommended to remove PFCL bubbles located beneath the macula

or if there is a tendency to move to the macular area [80].

*DOI: http://dx.doi.org/10.5772/intechopen.84242*

types of retinochoroiditis [76].

**3.10 Foveal pseudocyst**

**Figure 11.**

*erythematosus.*

**Figure 10.** *Pearl necklace sign in patients with severe diabetic macular edema.*

*New Landmarks, Signs, and Findings in Optical Coherence Tomography DOI: http://dx.doi.org/10.5772/intechopen.84242*

**Figure 11.**

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

The pearl necklace sign refers to HRD in a continuous ring around the cystoid spaces in the retina that has been seen in diseases with exudative maculopathy, vascular leakage, and chronic CME such as neovascular AMD, DME, retinal vein occlusion, retinal arterial macroaneurysm, or Coats disease (**Figure 10**) [70]. The authors speculated that HRD indicated the presence of lipid material from retinal vascular leakage similar to hard exudates. These pearls may represent lipid-filled macrophages along the inner wall of retinal edema [70]. Moreover, it is considered a frequent precursor sign on the location of the hard exudates which appear later. Therefore, this sign can change shape and may resolve under treatment or spontaneously. The presence of pearl necklace sign has not been associated with worse visual acuity in RD [71].

The pearl necklace sign should be differentiated from ORTs, which are located deeper in the ONL of the retina. In ORT, the ring is continuous and homogeneous, whereas the hyperreflective ring is as small foci in the pearl necklace sign [3].

FCE is a localized depression of the choroid detected only by using OCT, without any evidence of posterior staphyloma or scleral ectasia. It affects Bruch's membrane-RPE-choriocapillaris line complex line and photoreceptors (**Figure 11**). Patients are mostly asymptomatic and have good visual acuity. Nevertheless, some lesions may be associated with the development of choroidal neovascular membrane. It has been reported that FCE may appear in certain macular disorders such as CSCR, AMD, ERM, CNVM, polypoidal choroidal vasculopathy, BVMD, Vogt-Koyanagi-Harada disease, punctate inner choroidopathy, focal retinochoroiditis, foveoschisis, torpedo maculopathy, multiple evanescent white dot syndrome, multifocal choroiditis, and combined hamartoma of the retina and RPE [3]. OCT allows to identify retinal and choroidal structures that are affected in the excavation, which usually includes RPE, Bruch's membrane, EZ line, ELM, and ONL which followed the contour of the FCE. In some cases, it can be appreciated an attenuation or absence of IS/OS junction at the excavation, and ONL was thickened in most conforming eyes [72]. However, the layers from the OPL to the ILM were undisturbed, and also the sclerochoroidal junction appeared reasonably preserved without scleral excavation [72, 73]. FCE may be organized in two patterns, whether or not the photoreceptor layer is detached

**3.8 Pearl necklace sign**

**3.9 Focal choroidal excavation (FCE)**

**74**

**Figure 10.**

*Pearl necklace sign in patients with severe diabetic macular edema.*

*Focal choroidal excavation (FCE) revealed by SD-OCT in a patient with chronic CSCR and systemic lupus erythematosus.*

from the RPE. Thus, conforming FCE describes those types of lesions without separation between the two layers and the photoreceptors adapt to the contour of the RPE layer. On the other hand, in nonconforming FCE, photoreceptors appeared to be detached from the RPE showing a hyporeflective space. Factors contributing to the formation of each pattern are unknown [74]. Other authors have classified the lesions into three morphological patterns based on SD-OCT findings: bowl shaped, cone shaped, and mixed shaped [75]. They observed that all bowl-shaped types showed atrophic changes and RPE irregularities, whereas in cone-shaped FCE, a less atrophic change is detected at the center of the lesion. The pathogenesis of FCE is still unknown. Some authors suggest it could be related to a congenital defect within the choroid, which is supported by the fact that shape and size remained stable during the follow-up in most of the reported cases [73]. Nevertheless, no family history and low prevalence in young people suggest that it may be an acquired condition [74]. Some authors proposed FCE is an entity related to inflammatory diseases like Vogt-Koyanagi-Harada disease, multiple evanescent white dot syndrome, and other types of retinochoroiditis [76].

#### **3.10 Foveal pseudocyst**

Foveal pseudocyst is an OCT pathologic sign that is caused by subretinal retention of perfluorocarbon liquid (PFCL) after vitreoretinal surgery. Subretinal PFCL is a serious complication if it affects fovea. The incidence ranges from 1 to 11% after retinal detachment surgery [77]. Main risk factors for this entity are the presence of a large size retinal tear, large retinotomy (especially in 360°), and retinal traction at retinal breaks [78]. It is rare to find it in conventional surgery, but in these cases, it is usually caused by small bubbles which can be produced by turbulence by the interface between PFCL and saline solution [77]. OCT is a useful tool to identify intraretinal bubbles of PFCL. In many cases, the bubbles remain stable without size changing. The most common signs in OCT are RPE pigment disorganization, disruption of ellipsoid layer, and hyperreflectivity at the base of the PFCL bubble (**Figure 12**) [77]. It has been reported several cases with retinal hole secondary to long-standing subretinal PFCL [79]. Subretinal PFCL is responsible for retinal damage resulting in loss of visual acuity, scotomas, and retinal thinning. Long-time exposure to PFCL can lead to RPE atrophy, photoreceptor damage because there is a direct toxic defect, or inflammatory response including macrophages phagocyted PFCL [77]. It is recommended to remove PFCL bubbles located beneath the macula or if there is a tendency to move to the macular area [80].

**Figure 12.** *Subretinal retention of perfluorocarbon liquid (PFCL) after retinal detachment surgery.*
