9.3  Optical Coherence Tomography - Macula

Optical Coherence Tomography (OCT) is a crucial tool for diagnosing and monitoring retinal and glaucomatous disease. It produces cross-sectional images by studying interference patterns formed between infrared light reflected off the retina and a reference beam. Candidates should have an understanding of normal and pathological OCT scans. It is important to appreciate that OCT layers represent reflective interfaces, not true anatomy. High definition spectral domain OCT allows for greater precision in identifying these interfaces than time domain OCT. The addition of colour is artificially introduced and does not add further information than grey-scale scans.

Figure 9.2.1 Normal Cornea

Figure 9.3.1
Normal OCT – Spectral Domain/EDI (Heidelberg Spectralis®)

Pathology

Figure 9.3.2 Adult Vitelliform Macular Degeneration

Figure 9.3.2
Adult Vitelliform Macular Degeneration
The subretinal vitelliform material consists of degenerate photoreceptor outer segments, retinal pigment epithelium and lipofuscin.

Figure 9.3.3 Best Disease

Figure 9.3.3
Best Disease
Intra-RPE accumulation of lipofuscin is demonstrated.

Figure 9.3.4 Central Serous Chorioretinopathy

Figure 9.3.4
Central Serous Chorioretinopathy

Figure 9.3.5 Choroidal Folds

Figure 9.3.5
Choroidal Folds
Vertical raster slice showing sawtooth configuration of choroid, RPE and overlying retina. Note the horizontal striations present on the fundus image.

Figure 9.3.6 Choroidal Haemangioma

Figure 9.3.6
Choroidal Haemangioma
A large dome-shaped intrachoroidal lesion is demonstrated with low internal optical reflectivity.

Figure 9.3.7 Choroidal Naevus (Amelanotic)

Figure 9.3.7
Choroidal Naevus (Amelanotic)
An intrachoroidal lesion is demonstrated with moderate internal optical reflectivity.

Figure 9.3.8 Choroidal Naevus (Pigmented)

Figure 9.3.8
Choroidal Naevus (Pigmented)
An intrachoroidal lesion is demonstrated with very high reflectivity at the anterior surface and optical shadowing present posteriorly.

Figure 9.3.9 Choroidal New Vessel with Fibrovascular Pigment Epithelial Detachment, Outer Retinal Tubulation and Retinal Cysts

Figure 9.3.9
Choroidal New Vessel with Fibrovascular Pigment Epithelial Detachment, Outer Retinal Tubulation and Retinal Cysts

Figure 9.3.10 Choroidal New Vessel with Pigment Epithelial Detachment and Subretinal Fluid

Figure 9.3.10
Choroidal New Vessel with Pigment Epithelial Detachment and Subretinal Fluid

Figure 9.3.11 Cystoid Macular Oedema (Gross)

Figure 9.3.11
Cystoid Macular Oedema (Gross)

Figure 9.3.12 Drusenoid Pigment Epithelial Detachment (PED)

Figure 9.3.12
Drusenoid Pigment Epithelial Detachment (PED)
Confluent areas of soft drusen, clustering in the central macula, leaving to pigment epithelial detachment.

Figure 9.3.13 Enhanced Depth Imaging OCT (EDI-OCT)

Figure 9.3.13
Enhanced Depth Imaging OCT (EDI-OCT)
This EDI image demonstrates greater detail of the choroid and sclera at the cost of decreased inner retinal resolution.

Figure 9.3.14 Epiretinal Membrane with Diffuse Retinal Oedema

Figure 9.3.14
Epiretinal Membrane with Diffuse Retinal Oedema

Figure 9.3.15 Full Thickness Macular Hole with Cystoid Macular Oedema and Operculum

Figure 9.3.15
Full Thickness Macular Hole with Cystoid Macular Oedema and Operculum

Figure 9.3.16 Geographic Atrophy

Figure 9.3.16
Geographic Atrophy

Figure 9.3.17 Hard Exudate and Retinal Oedema

Figure 9.3.17
Hard Exudate and Retinal Oedema
The hyperreflective dots in the outer retina are hard exudate, whereas the hyporeflective expansion of the outer retinal layers represents more diffuse oedema. Hard exudates usually develop in the setting of chronic retinal oedema. These findings are non-specific.

Figure 9.3.18 Macular Telangiectasia (Type 2) – “MacTel 2”

Figure 9.3.18
Macular Telangiectasia (Type 2) – “MacTel 2”
Inner retinal cavitations and pigment aggregation without significant disruption of the retinal contour are observed.

Figure 9.3.19 OCT Cube

Figure 9.3.19
OCT Cube
Multiple raster images are automatically acquired together and stacked to give information about a volume of retina (the “cube”). This is then displayed as a heat map showing retinal thickness (top left panel). Software-generated segmentation lines for the individual raster slices are shown in the bottom left panel. Software registration of the acquisition allows for the same volume of retina to be imaged at different points in time and compared (as shown in the right panel of three scans of time point A, time point B, and change map A – B).

Figure 9.3.20 Onion Sign

Figure 9.3.20
Onion Sign
Linear cholesterol crystals in the subRPE space.[i]

See Pang et al, The Onion Sign in neovascular age-related macular degeneration represents cholesterol crystals. Ophthalmology. 2015 Nov; 122(11): 2316–2326.

Figure 9.3.21 Optic Disc Pit Maculopathy

Figure 9.3.21
Optic Disc Pit Maculopathy
Intra- and sub-retinal fluid accumulation up to the optic disc, arising from an optic disc pit.

          

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