Ординатура / Офтальмология / Английские материалы / Scanning Laser Imaging of the Retina Basic Concepts and Clinical Applications_Theelen_2011

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CENTRAL AREOLAR CHOROIDAL DYSTROPHY

During the course of the disease, lipofuscin accumulates in the macular RPE and gradually leads to RPE loss and outer retinal degeneration. RPE atrophy can be nicely documented by FAF488. However, there may be more residual retina than FAF488 examination may suggest. Therefore, additional NIR or OCT examinations are necessary.

This case of CACD demonstrates the disparate information of different imaging modalities on tissue changes in CACD. The FAF488 image (A) shows a large, darkened lesion corresponding to RPE atrophy on funduscopy. A thin peninsula of positive autofluorescence signal is visible in the upper part. The lesion is surrounded by a thin area of stippled FAF488 increase, similar to end-stage geographic atrophy in age-related macular degeneration. On NIR (B) the retained tissue peninsula appears much broader then on FAF488 and correlates with a preserved part of outer retina on Fourier domain OCT (C, arrows). It appears that FAF488 is superior for RPE imaging and NIR is better for obtaining an overview of the outer retinal situation.

A longitudinal FAF488 image series documents the disease progression in a female patient aged 52 years at baseline. Typically, the CACD lesion consists of speckled FAF488 increase of the whole macula. When atrophy starts, one or more dark lesions occur within this area of changed autofluorescence. From left to right enlargement of the atrophy from baseline to 2 and 4 years follow-up can be observed.

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DISCRETE ARCS IN FUNDUS AUTOFLUORESCENCE

Hereditary diseases with primary photoreceptor involvement and centrifugal or centripetal spread of the disease show a peculiar phenomenon on FAF488 imaging, namely ring-like increase of autofluorescence around the macula. Those rings are at the border of clinically healthy tissue and affected parts of the fundus and may be of varying intensity and thickness. Typical diseases that show discrete arcs on FAF488 are retinitis pigmentosa, cone dystrophy and cone-rod dystrophy. Various other disorders may, however, display the phenomenon as well.

RETINITIS PIGMENTOSA

On color fundus photography (A) the macula appears unaffected, surrounded by the atrophic peripheral retina, which shows the so-called tapeto-retinal reflex. A sample OCT (B) demonstrates preserved central photoreceptors with gradual loss of outer segments to the periphery (arrows). In that area, a zone of circular FAF488 enhancement (C) is visible. The periphery shows generally low FAF488 with some spots of darkening. On FAF787 (D) the central signal of normal intensity diminishes at the location of the discrete arc of increased FAF488. In the periphery, only choroidal and no RPE autofluorescence is visible.

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CONE-ROD DYSTROPHY

The typical bulls-eye appearance of eyes with CRD is visible on fluorescein angiography. The outer border of the diseased area is darker and centrally, a bright ring is visible around the fovea due to window effects.

NIR imaging shows only very discrete changes with spotted increase of reflectivity at the two rings on fluorescein angiography.

On FAF488 a double ring structure is also visible. Here, the outer ring shows considerable signal increase and the inner ring is dark. This suggests RPE atrophy at the central arc and increased visibility of fundus fluorophores at the outer ring.

Fundus autofluorescence at longer wavelengths (green-yellow) with a fundus camera demonstrates a less attenuated signal from the outer ring. This implies that lipofuscin is not an important fluorophore for the appearance of the ring, because if it was, the signal would increase at the yellow-orange spectrum. Therefore, it is probable that precursors of lipofuscin, located in the photoreceptors, are responsible for the discrete arc of increased autofluorescence. Those precursors fluoresce at shorter wavelengths. Note the pseudo-fluorescence of the optic nerve and the peripheral retina by the lens autofluorescence.

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CONE DYSTROPHY

The color fundus photo shows increased reflectivity of the macula with some yellowish subretinal spots around this. The peripheral retina appears normal.

At the lesion site, NIR is markedly reduced with some dots of increased NIR in that area. The periphery is of normal reflectivity on NIR.

FAF488 appears mottled at the lesion with spots of increased and decreased signal. In general, the affected area appears somewhat smaller on FAF488 than on infrared imaging, suggesting subretinal changes not visible at short wavelengths. The ring of increased FAF488 is weakly indicated.

On FAF787 the lesion contains many spots of decreased and only few of increased autofluorescence. The spots of decreased signal a largely co-located on FAF787 and FAF488, which suggests multifocal RPE loss with little (melano-)lipofuscin formation but with increase of retinal fluorophores and photoreceptor loss.

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DISEASES WITH MACULAR PIGMENT LOSS

If macular pigment is not built up or fades away retinal damage can occur, which leads to typical changes in scanning laser ophthalmoscopy. To date, two disorders with macular pigment loss are known, Sjögren-Larsson syndrome (autosomal recessive inheritance, congenital loss) and idiopathic macular teleangiectasia type 2 (unknown inheritance, acquired loss).

SJÖGREN-LARSSON SYNDROME (1)

Color fundus photography reveals intraretinal crystals around the fovea (A). At the location of the crystals, the attenuation of confocal blue light reflectance is missing due to absence of macular pigment (B). The crystals are split into two fractions, one reflecting blue and one near-infrared light. In addition, a slight attenuation of NIR is visible at the fovea (C), corresponding to a minuscule loss of photoreceptors on Fourier domain OCT (D). Fluorescein angiography reveals no leakage but mottled staining at the macula in the late phase (E). On FAF488 a signal increase instead of attenuation is visible at the fovea (F), suggesting accumulation of lipofuscin.

IDIOPATHIC MACULAR TELEANGIECTASIA (2)

The color fundus photo shows the typical grayish appearance of the macula in this disease

(A). In that area macular pigment is missing and confocal blue reflectance is increased (B). NIR shows macular signal decrease (C), which is co-located with slight thickening and pseu- do-cyst formation on Fourier-domain OCT (D). The area of increased blue reflectance shows strong leakage from teleangiectatic vessels on late phase fluorescein angiograohy (E). FAF488 is less affected than in SLS and shows increase at cyst locations and in areas of photoreceptor loss (F).