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

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HERIDITARY RETINAL DISEASE

In most cases of genetically driven retinal disease the primary pathology is located in the retinal photoreceptors or the RPE. This leads to significant changes in confocal scanning laser imaging of FAF and fundus reflectance. The reasons for change may be manifold, from lipofuscin accumulation and serous retinal detachment to photoreceptor loss and scarring.

AUTOSOMAL RECESSIVE STARGARDT DISEASE (STGD1)

STGD1 is characterized by excessive accumulation of lipofuscin within the RPE with retinal degeneration and consecutive RPE atrophy, leading to yellowish, pisciform flecks (A). In this case a central retinal atrophy is already present. Typically, STGD1 shows a dark choroid on FFA (B), possibly caused by diffuse lipofuscin accumulation in the RPE. On NIR (C) the central photoreceptor atrophy shows decreased reflectivity, the flecks have centrally increased NIR with a dark halo, and pigment clumping is associated with a markedly increased signal. The dim NIR signal in STGD1 may be caused by a loss of photoreceptors. FAF488 imaging

(D) of STGD1 is characterized by hyper-autofluorescent flecks by lipofuscin in the RPE and loss of FAF488 at RPE atrophies. Areas with photoreceptor loss but with undamaged RPE show a slightly increased signal, possibly by absent bleaching effects compared to the surrounding clinically healthy retina. FAF787 signals (E) are largely decreased at the fundus lesions, which is probably due to changes in the melanin content. Only on odd occasions do flecks show increased FAF787, which may point to melanolipofuscin accumulation at such flecks.

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MULTIFOCAL PATTERN DYSTROPHY SIMULATING STGD1

The imaging appearance of Pseudo-Stargardt is similar to that of STGD1. However, in most cases, no dark choroid is seen on FFA. The color image (A) shows irregular, yellow-white flecks and clear-cut, paracentral atrophic areas as well as a slightly glowing macula. On NIR (B), the atrophic parts show high reflectivity from the sclera and some decrease if NIR can be seen at the macula, possibly due to some photoreceptor damage. The flecks in PseudoStargardt show greater variation in hyperand hyporeflectivity for infrared light than those in STGD1. On FAF488 (C) the atrophic areas appear dark with some minor signal increases inside, pointing to only partial atrophy with preserved parts of retina and RPE. The flecks have largely increased FAF488 with a thin hypfluorescent ring around. The FAF787 (D) shows flecks of increased and decreased fluorescence. A paramacular ring of hypoautofluorescence indicates decrease of RPE melanin content exceeding the clinically visible lesions.

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BEST VITELLIFORM MACULAR DYSTROPHY

Except for the carrier stage, patients with Best disease will show abnormalities in all imaging modalities. The abnormalities vary dependent on the clinical stage.

VITELLIFORM STAGE (1)

The color fundus photograph (a) shows an egg-yolk like lesion at the macula with relatively homonymous increased FAF488 (c). However, infrared imaging reveals irregular NIR (b) and FAF787 (d). Obviously, near-infrared imaging can detect some RPE change that is masked by the yellow, lipofuscin containing subretinal material.

PSEUDOHYPOPYON STAGE (2)

All imaging techniques show inferior-located, subretinal material with increased NIR (a), FAF488 (b) and FAF787 (c). A central change visible in the near-infrared also becomes apparent on FAF488 due to demasking by displacement of the subretinal material.

VITELLIRUPTIVE STAGE (3)

Autofluorescence imaging at both 488 (b) and 787 (c) nm shows dispersed signals, pointing to partially resorbed subretinal material. Some darkening in FAF488 indicated focal RPE atrophy. In NIR (a), a membrane-like structure in visible. However, this is not demarked on autofluorescence.

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BEST VITELLIFORM MACULAR DYSTROPHY

In the late stages of the disease, atrophy and scarring may occur and change the typical appearance visible in earlier stages.

ATROPHIC STAGE

A well-demarcated area of central atrophy is visible on color fundus photography. NIR at the lesion is relatively normal, with a thin ring of decreased NIR around this. FAF488 is centrally attenuated with spots of increased autofluorescence around this as well as within the atrophic area. On FAF787 the lesion appears dark. The results suggest partial damage of the RPE and the outer retina.

CICATRICIAL STAGE

This case shows central scarring with residual pseudohypopyon and subretinal fluid on color fundus photography. The scar is highly reflective on NIR and shows a ring-like increase of FAF488 and FAF787. The imaging results imply atrophic changes on top of the scar with surrounding lipofuscin increase within residual RPE.

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ADULT ONSET FOVEOMACULAR VITELLIFORM DYSTROPHY

The lesions in AFVD patients have a similar appearance to those in Best patients. The subretinal, yellow material has an increased FAF488 and is partially invisible in the nearinfrared.