Atrophy can occur in sharply defined areas of severe atrophy, known as geographic atrophy (GA), or in less well-defined, more granular regions of less severe atrophy, known as non-GA.

Both forms share the feature of RPE loss, more extensive and with associated atrophy of the overlying retina and underlying choriocapillaris in GA.

The angiographic appearance depends on the remaining pigment within the RPE and choriocapillaris vessels.

Non-GA shows mottled early hyperfluorescence, which fades late consistent with window defect (Figure 5).

Figure 5 - Non-geographic atrophy.

 

GA typically shows late well-defined hyperfluorescence from staining of the exposed deep choroid and sclera⁽⁹⁾.

In these cases, visual acuity depends on the foveal involvement (Figure 6).

Figure 6 - Geographic atrophy.

 

In advanced cases, larger choroidal vessels show a sclerotic appearance (Figure 7).

Figure 7 - Severe atrophic AMD with sclerotic appearance of larger choroidal vessels.

 

Classic CNV

Classic CNV is characterized by well-demarcated hyperfluorescence in early phases on FA and late leakage that obscures the boundaries of the lesion (Figure. 8).

Figure 8 - Classic CNV.

 

As defined by Donald Gass, classic CNV lies between the neurosensory retina and the RPE (type II CNV)⁽¹⁰⁾.

Angiographic classic CNV appears as a lacy or bicycle-wheel pattern.

Depending on its location, it can be classified as extrafoveal (>200 microns from the foveal center) (Figure 9), juxtafoveal (1-199 microns from the foveal center) (Figure 10) or subfoveal (involving the foveal center) (Figure 11).

Figure 9 - Extrafoveal classic CNV.

 

Figure 10 - Juxtafoveal classic CNV.

 

Figure 11 - Subfoveal classic CNV.

 

Sometimes, a feeder vessel can be localized (Figure 12).

Another typical feature is the presence of a hyperpigmented rim, hypofluorescent on FA, surrounding the CNV (Figure 12).

Figure 12 - Classic CNV with feeder vessel.

 

On occasion, classic CNV can be associated to loculated fluid (Figure 13).

Figure 13 - Classic CNV with loculated fluid.

 

In loculated fluid, dye pooling is well-demarcated in a confined space of a localized sensory retinal detachment or within intraretinal cystic spaces.

It was a common finding in patients with new subfoveal CNV in the Macular Photocoagulation Study (MPS) and may confuse the treating physician as to the boundary of the lesion⁽¹¹⁾.

Depending on their sizes, classic CNV can be classified as small (Figure 9-11) or medium (Figure 14) or large (Fig. 15).

Figure 14 - Medium size classic CNV.

 

Figure 15 - Large classic CNV.

 

Importantly, larger classic CNV are associated to a poorer visual prognosis since they represent long-term duration of the pathological disorder.

Classic CNV is an emergency and it requires early treatment to halt the progression of the disease.

Without treatment, CNV tend to enlarge and irreversible fibrosis appears (Figure 16).

Figure 16 - Old classic CNV with fibrosis.

 

In the last decade of the last century, the advent of photodynamic therapy (PDT) with verteporfin promoted a classification of the lesions depending on the percentage of classic CNV.

Thus, predominantly classic lesions were defined as having 50% or more of the total lesion size comprised of classic CNV (Figure 17).

Figure 17 - Predominantly classic CNV.

 

On the other hand, minimally classic lesions were characterized by classic CNV occupying less than 50% of the total lesion size (Figure 18)⁽¹²⁾.

Figure 18 - Minimally classic CNV.

 

The best results with PDT in wet AMD patients were obtained in the treatment of predominantly classic lesions.

Nowadays, in the antiangiogenic therapy era, this classification has lost popularity among ophthalmologists since lesion composition does not seem to be as relevant as it was with PDT.

Lesion components associated with neovascular AMD that can obscure the boundaries of CNV include changes that block fluorescence, such as blood, fibrous tissue, RPE hyperplasia, or RPE redundancy (from an RPE tear).

Likewise, CNV can be obscured by greater fluorescence from staining or pooling.

 

Occult CNV

Occult CNV has been categorized as fibrovascular PED or late leakage of undetermined source⁽¹³⁾.

Fibrovascular PED (type I occult CNV) is defined as an irregular elevation of the RPE associated with stippled hyperfluorescence apparent 1 to 2 minutes after fluorescein injection and ill-defined staining or leakage in the late frames (Figure 19-20).

Figure 19 - Fibrovascular PED (type I occult CNV).

 

Figure 20 - Fibrovascular plaque

 

It differs from classic CNV in that the early hyperfluorescence is not as bright and the boundaries usually are indeterminate.

Late leakage of undetermined source (type II occult CNV) lacks a discernible, well-demarcated area of leakage in the early angiographic frames.

Speckled hyperfluorescence with no visible source becomes apparent 2 to 5 minutes after dye injection (Figure 21).

Figure 21 - Late leakage of undetermined source (type II occult CNV).

 

Serous PED

Although serous PEDs can occur in the context of non-neovascular AMD, most of them are related to CNV.

On fundus biomicroscopy, a serous PED appears as a round or oval translucent elevation of the RPE.

On FA, it is characterized by progressive and uniform hyperfluorescence from early frames with intense pooling of fluorescein in late phases (Figure 22).

Figure 22 - Serous PED.

 

PEDs with a notch usually have occult CNV in the notch (Figure 23).

Figure 23 - Serous PED associated to occult CNV.

 

The association of occult CNV and a serous PED is frequently termed “vascularized PED”^{(14, 15)}.

On occasion, a serous PED is associated to classic CNV (Figure 24).

Figure 24 - Serous PED associated to classic CNV.

 

Retinal angiomatous proliferation

Retinal angiomatous proliferation (RAP) has been described and classified by Yannuzzi et al.⁽¹⁶⁾.

In RAP, the vasogenic process originates in the retina and begins as intraretinal neovascularization (stage I), which progresses to subretinal neovascularization (stage II) and finally to CNV (stage III).

In some cases it is possible to find a retinal-retinal anastomosis.

Angiographically, early lesions (stage I) show a focal area of intraretinal hyperfluorescence with indistinct borders corresponding to the intraretinal neovascularization and surrounding intraretinal edema (Figure 25).

Figure 25 - RAP (stage I).

 

Sometimes, these early lesions can mimic the appearance of a classic CNV. Later stages of RAP are often classified as minimally classic or occult CNV.

In stage II, it is very characteristic to find a serous PED with occult CNV associated to overlying cystoid macular edema (Figure 26).

Figure 26 - RAP (stage II).

 

Indocyanine green (ICG) angiography is often more useful than FA for the diagnosis and evaluation of RAP lesions.

 

Polypoidal Choroidal Vasculopathy

In polypoidal choroidal vasculopathy (PCV), the primary abnormality involves the choroidal circulation, and the characteristic lesion is an inner choroidal vascular network of vessels ending in an aneurismal bulge.

Clinically, PCV is associated with multiple, recurrent, serosanguineous detachments of the RPE and neurosensory retina secondary to leakage and bleeding from the choroidal vascular lesion⁽¹⁷⁾(Figure 27).

Figure 27 - Polypoidal choroidal vasculopathy.

 

Although FA can sometimes confirm the diagnosis of PCV, ICG angiography is the choice for imaging this entity.

 

RPE tears

Although RPE tears can occur spontaneously, it is not uncommon for them to occur after treatment with thermal laser, PDT or antiangiogenic therapy.

RPE tears are commonly related to PEDs, although they have been described in classic lesions too⁽¹⁸⁾.

The detached monolayer of RPE scrolls toward the CNV, leaving a denuded area of choroid exposed.

On FA, the denuded area becomes hyperfluorescent and the scrolled RPE is dark and blocks the underlying fluorescence (Figure 28).

Figure 28 - RPE tear.

 

Hemorrhagic AMD

FA is not very useful in hemorrhagic forms of macular degeneration since blood blocks the underlying fluorescence (Figure 29).

Figure 29 - Hemorrhagic AMD.

 

ICG angiography can detect the presence of occult CNV.

 

Disciform scar

A disciform scar is the end-stage manifestation of untreated CNV, namely formed by fibroblasts and inflammatory cells.

Angiographically, it typically shows late staining (Figure 30).

Figure 30 - Disciform scar.

 

FA for monitoring AMD treatment

In the era of PDT with verteporfin, FA was the gold standard for monitoring the response to treatment⁽¹⁹⁾.

Nowadays, with antiangiogenic therapy, OCT scanning has replaced FA for this purpose since it is highly effective to detect lesion activity and it is a non-invasive procedure⁽²⁰⁾.

However, in some cases FA is still very useful in the evaluation of treated patients.

 

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