Optical coherence tomography (OCT) has been useful for diagnosing and monitoring age-related macular degeneration (AMD). There are two types of AMD - dry (atrophic) and wet (neovascular). Dry AMD involves geographic atrophy of the retinal pigment epithelium. Wet AMD involves the growth of abnormal blood vessels under the retina or retinal pigment epithelium. OCT can detect fluid, hemorrhage, and exudation associated with wet AMD, as well as delineate drusen, pigment abnormalities, and changes in the retinal layers that indicate disease progression. While OCT provides detailed images, it cannot replace angiography in fully characterizing choroidal neovascularization.

2. Use of OCT Imaging in the
Diagnosis and Monitoring of
Age Related Macular Degeneration
By
Dr. doaa ali mahmoud
(md)

3. 1. Introduction
• Optical Coherence Tomography (OCT) is a
non-invasive, high-resolution imaging
technique that has been introduced in the
clinical practice at the beginning of the last
decade. The first application of this method has
been recorded in the field of ophthalmology.

4. • Retinal diseases such as Age-related Macular
Degeneration (AMD), central serous
chorioretinopathy, macular hole, vitreo-macular
interface syndrome and diabetic maculopathy
have taken advantage of this relatively new
imaging method. Among these, AMD is by far the
ocular condition that has benefited the most from
the enormous advantages offered by OCT, in
terms of diagnosis, response to treatment and
monitoring.

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6. Pathology of AMD
Despite recent progress, age-related macular
degeneration (AMD) remains the leading cause of
vision loss in high-income countries, and its incidence
appears to be increase probably due to longer life
span and improved methods of detection. Loss of
visual acuity typically results from progressive
degeneration of the choriocapillaris, retinal pigment
epithelium (RPE), and photoreceptors although the
earliest manifestation of the disease appears to be
abnormalities within Bruch’s membrane.

7. There are two variants: atrophic (dry) and
neovascular (wet/exudative), with the latter
being less common and accountable for
more severe visual loss. Involvement is
usually bilateral although there may be
asymmetry in progression.

9. Exudative ARMD precursors:
(a) Soft drusen can be recognised by
irregular tapering edges and a fluffy eosinophilic content.
(b) Basement membrane deposits (other names: basal
linear, basal laminar are different to soft drusen in their location,
staining characteristics, and ultrastructural appearance. The
deposits form broad strips beneath the RPE and have a striated
pattern

10. Retina - Central degeneration
ARMD
Deposits - Basement membrane deposit

11. 1-Dry type:
AMD there is also concomitant thickening of the collagenous layers
within Bruch’s membrane, degeneration of elastin and collagen within
Bruch’s membrane with calcification of Bruch’s membrane, increased
levels of advanced glycation end products, and accumulation of lipids as
well as exogenous proteins. [These changes may serve as a hydrophobic
barrier to impede the passage of fluid and nutrients between the
choroid and outer retina resulting in relative ischemia.

12. Apearance of the macula:
1 Atrophic ARMD: geographic atrophy characterised by
pale areas of patchy loss of the RPE. These areas may grow in size
and coalesce.
a well demarcated area of depigmentation is seen at the macula.
The depigmented oval areas have a petaloid pattern and are
surrounded by a rim of hyperpigmentation . At the histological
level, there is total atrophy of the outer retina in the region.

16. Wet type:
Neovascular AMD Neovascular AMD represent 50%
to 65% of advanced AMD, while the other cases
correspond to atrophic forms without
neovascularization.
Risk factors influencing the course of wet AMD are:
similar to those of age-related maculopathy
(ARM) and essentially comprise risk factors for
arteriosclerosis (hypertension And hyperlipidemia),
environmental, and lifestyle factors. However,
recently identified genetic factors also probably
play a very important role in the pathogenesis of
AMD

17. Most CNV can be classified into three main
categories:
- occult,
- classic,
-and/or mixed;
They May also be recognized as:
-Type 1: Pre-epithelial,
▬ Type 2: Sub-epithelial (sub-RPE), and/or
▬Mixed.

19. Exudative ARMD: at the early stage, small capillaries are
present between the RPE and Bruch’s membrane
This abnormality is referred to as a type 1 SRNVM and progression
takes the form of an established Fibrovascular membrane in which
arterioles And venules can be identified. A vicious circle arises
when the small capillaries leak or burst with further inflammation
and fibrovascular repair. Subsequently, interference with
photoreceptor metabolism is followed by atrophy and degeneration
of the outer retina.

20. 2-WET ARMD:
characterised by the presence of :
subretinal neovascular membrane. There may be associated
subretinal exudation, haemorrhage, or a fibrovascular
(disciform) scar. The haemorrhage may
track through the retina into the vitreous. Pigmented pithelial
detachment (PED) may develop in subretinal
neovascularisation with serous exudate or haemorrhage.

21. A type 2: subretinal neovascular membrane in exudative
ARMD refers to an extension of fibrovascular proliferation
between the RPE and the neural retina (subretinal space).
This potential space provides an easy extension of haemorrhage
from the fragile capillaries.
Continuing leakage and haemorrhage from the capillaries
lead to large submacular fibrous scars. This is termed a
disciform scar. Continuous subretinal traction may lead to
retinal distortion and rupture of the retina and its blood vessels
may be followed by bleeding into the vitreous. Haemorrhage
may be complicated by a massive retinal Detachment.

22. Retina - Central degeneration
ARMD - Wet/Neovascular
Sub-RPE (Type I),(2)

23. 1- ocult CNV:
OCT showed a minimal, regular, thin PED. However,
separation of the RPE from Bruch’s membrane
(BM) that became clearly visible, confirmed the
presence of a PED with a homogeneous,
moderately reflective cavity And minimal
shadowing.
• The exudative reaction was very minor,causing
only a slight increase in retinal thickness, but no
SRF or cysts . The outer nuclear layer was also
thinned over the juxtafoveal PED, which extended
as far as the center of the fovea.

30. OCCULT CNV Initial, dormant lesion, discovered on clinical
examination of the fellow eye .
• Lesion at the initial clinical stage, after onset
of the first symptoms .

32. LARGE, ADVANCED, OCCULT CNV
Longstanding vascularized PED, present for more than one
year

37. Classic CNV:

41. Clinical applications of OCT in AMD
The antero-posterior sections on OCT reveal the succession of the
retinal layers and of the
Retinal Pigmented Epithelium (RPE), as well as the presence of
any spaces between these
layers. The information offered by OCT is detailed, simple and
easily interpretable.
Basis of OCT interpretation:
The OCT signs in AMD are extremely valuable for the
ophthalmologist.
- Retinal thickening (the thickness of the retina is
measured between the internal limiting membrane and
the RPE) is determined by the exudation from the
choroidal new vessels. -The occult Choroidal
Neovascularization (CNV) is revealed by the constant
presence of the elevation or detachment of the RPE band.
Frequently, the occult CNV is suggested by
various alteration of the RPE: irregularities,
fragmentation, thickening, thinning.

42. The subretinal fluid appears as diffuse infiltration or as the
constitution of cystic spaces in the macular area.
The classic CNV is translated on OCT as hyper-reflective
zones adjacent to or away from the RPE. They must be
differentiated from other hyper-reflective structures:
fibrous tissue, exudate, pigment, pseudo-vitelliform
material.
Other signs of prognostic value can be visualized at the level
of the outer retinal layers
(outer nuclear layer and external limiting membrane):
hyper-reflective spots and areas of densification. They
prove the progression of the disease.

43. Limits of OCT
OCT cannot precisely describe a CNV network, nor can it
define its nature: active or pre-fibrotic. Therefore, the
OCT scan must be interpreted in correlation with the
fundus photography, direction of scan and ideally, the
angiography .
Another limitation of OCT is revealed in evaluating the
extension of the geographic atrophy (GA). In a recent
study, the GA areas identified in SLO scans were
significantly larger than the ones detected on the OCT
maps. Spectralis OCT showed significantly more mild and
severe segmentation errors than 3D and Cirrus OCT. Taking
into account the fact that GA is a frequent form of AMD,
this limitation should be resolved in order to identify and
document RPE loss in a realistic manner.

44. • Associated findings
1- Drusen
subretinal pale areas are either small and dis-crete
(hard) or are larger with indistinct edges (soft).
2 -Irregular pigment hyperpigmentation (clumping).
3- Much interest has also centred on changes in Bruch’s
membrane
(for example calcification and lipid accumulation)
Which could interfere with metabolism of the RPE cells.

45. • The following deposits between Bruch’s membrane and
• the retinal pigment epithelium are commonly found in
• A1 Hard drusen are easily identified clinically as tiny,
• discrete, non-pigmented elevations beneath the retina
• between the basement membrane and Bruch’membrane,
• but are not considered to be precursors of
neovascularisation.
• 2 Soft drusen possess indistinct borders and may be more
• easily identified with fluorescein angiography. These
structures are located between the cell basement membrane
and Bruch’s membrane and are implicated in the attraction
of blood vessels beneath the RPE (choroidal/subretinal
neovascularisation).

46. Retina - Central degeneration
ARMD Deposits - Soft drusen

48. 3 A third deposit has been variously termed basal linear/basal
laminar/basement membrane deposit :
This material is located between the cell membrane and
the basement membrane and is so thin that it can be
difficult to identify clinically. This deposit is often found
in relation to neovascular tissue proliferating beneath
the macula. Some authors use the term “basal linear
deposit” as synonymous with confluent soft drusen .

51. Shadowing by a large vessel (arrow)
in the peri-papillary region is clearly
visible.