Ординатура / Офтальмология / Английские материалы / Atlas of Fundus Autofluorescence Imaging_Holz, Schmitz-Valckenberg, Spaide, Bird_2007

306 Richard F. Spaide

Fig. 17.29  The father of the patient shown in Figs. 17.27 and 17.28. a The right eye had an almost complete absence of the yellowish subretinal material except at the outer edges of the lesion. In the central portion of the lesion, there was what appeared to be fibrous metaplasia of the retinal pigment epithelium (RPE). The visual acuity was 20/50. b The fluorescein angiogram shows staining centrally with slight leakage of fluorescein into the inferior portions of the lesion. c The autofluorescence photograph shows a relative lack of autofluorescence centrally, with hyperautofluorescence in the periphery of the lesion corresponding to the material seen in image a. d Optical coherence tomography shows elevation of the macula by subretinal fluid. There is an accumulation of material on the outer retina (arrows). The material has almost no thickness in the central macula and becomes thicker at the edges of the retinal elevation. There is an elevation at the level of the RPE (arrowhead), which may represent RPE metaplasia (From Spaide RF, Noble K, Morgan A, Freund KB. Vitelliform macular dystrophy. Ophthalmology 2006;113:1392–1400)

308 Richard F. Spaide

Fig. 17.30  a Color photography of a 42-year-old with vitelliform macular dystrophy type 2 shows the asymmetrical distribution of the lesion around the macula with the dependent extension of the lesion inferiorly. The visual acuity was 20/80. b The yellowish material at the outer border is hyperautofluorescent, and there is a lack of autofluorescence centrally. c,d The earlyand late-phase fluorescein angiographic pictures show the transmission defects within the lesion and the suggestion of late staining and subtle leakage present. e Optical coherence tomography done horizontally through the superior macula (as shown in image a) illustrates the macular elevation by subretinal fluid. Note that the material on the outer retina is thin centrally and thicker at the edges of the lesion (arrows) (From Spaide RF, Noble K, Morgan A, Freund KB. Vitelliform macular dystrophy. Ophthalmology. 2006;113:1392–1400)

310 Richard F. Spaide

Fig. 17.31  Proposed pathophysiologic changes in vitelliform macular dystrophy type 2 (VMD2). Eyes with VMD2 uniformly have subretinal fluid as seen by optical coherence tomography. The physical separation of the retina from the retinal pigment epithelium (RPE) would prevent proper apposition of the outer segments with the RPE. Shed but nonphagocytosed outer segments could build up in the subretinal space. Infiltrating this material could be macrophages. There is no intrinsic mechanism to prevent the formation of A2-PE-H2 , A2-PE, all-trans-dimers, and other precursors to A2E in the degenerating outer segments. The shed outer segments could eventually make their way to the RPE, but the phagocytosed material would theoretically load the RPE cells with the precursors to A2E and also oxidized lipids and proteins. The toxic effect of this material may cause RPE atrophy, metaplasia, and choroidal neovascularization

Monika Fleckenstein, Richard F. Spaide

18.1

Macular Holes

Full-thickness macular holes are associated with corresponding markedly increased intensity in autofluorescence (Fig. 18.1) [5, 7, 15, 23]. In the absence of neurosensory retina, there is also no luteal pigment. Hence, the excitation and emission light can directly pass to and from the uncovered retinal pigment epithelium (RPE). The affected area also corresponds well to hyperfluorescence seen with fluorescein angiography. By optical coherence tomography, the edges of the macular hole are often upturned, presenting an increased thickness for the excitation light to pass through, which may explain the decreased autofluorescence intensity sometimes seen surrounding the hole. The attached operculum in stage 2 macular holes and the preretinal operculum in stage 3 macular holes show a focally decreased autofluorescence from blocking.

Following successful surgical treatment, the area with increased autofluorescence disappears, and almost normal or normal distribution of autofluorescence is seen. Partial-thickness macular holes are usually associated with an increased fundus autofluorescence (FAF) signal, whereby the degree increment depends on the amount of luteal pigment left in the remaining neurosensory retinal tissue.

18.2

Foveal Hypoplasia

Isolated foveal hypoplasia is considered a rare congenital condition [6, 18]. Fundus changes such as an absent or abnormal maculofoveal reflex and distinct capillary alterations in the central macula may be only very subtle, and it may be difficult to diagnose this cause of poor central visual function. Optical coherence tomography is helpful in establishing the diagnosis [13, 14]. Because of the absence of macular luteal pigment, FAF imaging in patients with foveal hypoplasia shows no decreased intensity, but rather normal background signal in the central area (Fig. 18.2).

314 Frank G. Holz et al.

18.3

Chloroquine Maculopathy

Kellner and colleagues demonstrated that FAF imaging may show distinct alterations in patients taking chloroquine/hydroxychloroquine medication [9]. A pericentral ring of increased intensity was present in patients with mild changes. More advanced stages showed a more mottled appearance with levels of increased and decreased intensity in the pericentral macula (Fig. 18.3). Electrophysiology is thought to remain the most sensitive tool to diagnose early chloroquine maculopathy. However, FAF imaging appears to be more sensitive than fundus photograph or fluorescein angio­ graphy in detecting toxic alterations at the level of the RPE.

18.4

Optic Disc Drusen

Optic disc drusen have autofluorescent properties and can be readily visualized by a bright nodular autofluorescence (Fig. 18.4) [10, 16, 17]. Drusen buried within the nerve may be more visible by autofluorescence photography than by ophthalmoscopy, although deeply buried disc drusen may require B-mode ultrasonography for detection. Optic nerve drusen are highly associated with nerve fiber layer loss and visual field defects [8, 21]. It is unknown whether the drusen or the nerve fiber layer defect is the primary defect.

18.5

Pseudoxanthoma Elasticum

Pseudoxanthoma elasticum (PXE) has a prevalence of 1 in 25,000 and causes abnormal­ ities chiefly involving the eye, skin, and cardiovascular system [4]. The gene defect in PXE has been characterized as a loss of function mutation in the ATP-binding cassette subtype C number 6 gene (ABCC6) [2, 11, 20]. The function of the protein encoded by this gene is not known, but it is probably a transport protein. ABCC6 is in the same superfamily as the ABCA4 mutation which causes Stargardt disease [1, 22].

PXE can cause angioid streaks, which appear as hypoautofluorescent fissures; optic nerve drusen, which are intensely autofluorescent; and peau d’ orange, which causes a subtle granular stippling (Fig. 18.5). More serious complications include RPE atrophy, the extent of which was not appreciated prior to autofluorescence imaging, as well as choroidal neovascularization (CNV). Patients with PXE can have RPE atrophy that generally falls into three categories: large cracks that look like rips, multilobular areas of discrete atrophy, and diffuse poorly defined regions of atrophy (Fig. 18.5). In

some patients the atrophy is preceded by hyperautofluorescent flecks or spots. CNV can be recognized by its typical features during autofluorescence photography. The potential ingrowth of CNV may be potentiated in PXE by the angioid streaks and the RPE atrophy [22].

18.6

Bilateral Diffuse Uveal Melanocytic Proliferation

Patients with bilateral diffuse uveal melanocytic proliferation have proliferation of benign melanocytes in the outer choroid; this proliferation is histopathologically unrelated to the primary non-ocular carcinoma [24]. These patients also develop numerous round or oval areas of loss of RPE cells. Fluorescein angiography shows these nummular areas to be transmission defects, autofluorescence photography shows them to be devoid of autofluorescence, and optical coherence tomography reveals them to have no visible cellular elements at the level of the RPE (Fig. 18.6). This loss of RPE cells has been attributed to a paraneoplastic process.

18.7

Congenital Hypertrophy of the Retinal Pigment Epithelium

Congenital hypertrophy of the RPE (CHRPE) is a hyperpigmented, generally flat lesion with well-demarcated borders that may mimic other pigmented lesions in the eye such as ocular nevi and melanomas. The cells show hypertrophy, but they do not appear to be involved in outer segment turnover. The overlying photoreceptor cells are degenerated [3] and melanosomes are distributed uniformly in the RPE cell, but there is no lipofuscin [12, 19], and there is an absolute scotoma within the lesion. Unlike choroidal nevi, which generally have minimal autofluorescence changes unless there is subretinal fluid or orange pigment, CHRPE lesions are markedly hypoautofluorescent (Fig. 18.7). By comparison, choroidal melanomas frequently have hyperautofluorescent collections from orange pigment or from chronic detachment. Although the differentiation of these lesions is usually straightforward, autofluorescence photography can supply supplemental information.

References

1.Allikmets, R, Singh, N, Sun, H, et al. (1997) A photoreceptor cell-specific ATP-binding transporter gene (ABCR) is mutated in recessive Stargardt macular dystrophy. Nat Genet 15:236–246