OCT angiography features of paracentral acute middle maculopathy.

Paracentral acute middle maculopathy (PAMM) refers to retinal lesions with changes in the inner nuclear layer on spectral domain optical coherence tomography (OCT). PAMM is associated with retinal vascular pathology involving the deep capillary plexus. We report two cases of PAMM in Indian subjects using multimodal imaging highlighting the OCT angiography (OCTA) findings. The first case is of a middle-aged female with a paracentral scotoma with SS-OCT (swept-source optical coherence tomography) and OCTA findings suggestive of "chronic" PAMM. The second case presented with sudden decreased vision, and multiple creamy white lesions suggestive of "acute" PAMM, imaging features depicting a possible venular obstruction. These cases demonstrate the importance of considering PAMM as a differential diagnosis in patient presenting with nonspecific visual complains and apparently normal ophthalmic examination. The recognition of PAMM should prompt an appropriate evaluation and investigation.

Paracentral acute middle maculopathy (PAMM) is a recently recognized entity, as a variant of acute macular neuroretinopathy (AMN), manifesting as hyperreflective band-like lesion at inner nuclear layer (INL) and outer-plexiform layer (OPL) on spectral domain optical coherence tomography (SD-OCT).[1] With advent of OCT-A (optical coherence tomography-angiography), PAMM has emerged as vascular pathology resulting from ischemia of deep retinal layers.[23] Herein, we report a case each of “acute” and “chronic” PAMM and highlight the differences between the two.

Case Reports

Case 1

A 40-year-old lady presented with a complaint of dark spot obscuring her central vision of 7-month duration. Best-corrected visual acuity (BCVA) was 20/20 bilaterally. Fundus examination of right eye was normal; left eye revealed whitish-gray intraretinal lesion nasal to fovea [Fig. 1a and b]. Fundus autofluorescence [FAF; Fig. 1c] showed normal foveal hypo-reflectivity. Swept-source OCT (SS-OCT, Atlantis, Topcon Corporation, Tokyo, Japan) revealed an altered foveal contour along nasal foveal slope [Fig. 1d, arrowhead] with hyperreflectivity at OPL [Fig. 1d, arrow]. Fluorescein angiography (FA) did not reveal any abnormal pattern [Fig. 1e]. OCT-A (Cirrus HD-OCT 5000 Carl Zeiss Meditec, Dublin, USA) revealed an area of capillary dropout in deep retinal capillary plexus indicating an arteriolar pattern of ischemia [Fig. 2a-d]. Multifocal electroretinogram showed blunting of foveal and parafoveal responses with normal perifoveal ring responses [Fig. 2e]. Humphrey visual field testing (10-2) revealed a paracentral scotoma [Fig. 2f].

Figure 1

Case 1 at presentation. Color fundus photograph of the left eye appears grossly normal except for a speck-like whitish lesion superonasal to fovea (a). Red free imaging shows a small speck of hyperreflectivity superonasal to fovea (b). Fundus autofluorescence shows normal foveal hypoautofluorescence (c). SS-OCT shows hyperreflective, band-like lesion located at the junction of the outer-plexiform layer and inner nuclear layer with alteration of the nasal foveal slope (d). Fundus fluorescein angiography shows normal macular perfusion and foveal avascular zone (e)

Figure 2

En face structural OCT with segmentation at superficial capillary appears normal (a). En face structural OCT with segmentation at deep capillary plexus shows some ill-defined whitish areas corresponding to the lesion representing an area of resolving infarction (b). OCT angiography through superficial capillary plexus is normal (c). OCT angiography through deep capillary plexus shows capillary dropout superonasal to FAZ (d). MF-ERG shows blunting of the normal foveal and parafoveal responses with normal perifoveal ring responses (e). 10-2 Humphrey visual fields show a paracentral scotoma corresponding to the lesion (f)

Case 2

A 40-year-old healthy male came with complaint of diminution of vision in left eye of 2 years duration. BCVA was 20/20 bilaterally. Fundus examination of left eye revealed creamy-white, subretinal lesion superotemporal to fovea [Fig. 3a and b]. FAF showed normal foveal pattern with hypoautofluorescence at superotemporal lesion [Fig. 3c]. SS-OCT showed hyperreflectivity in the inner retinal layers [Fig. 3d and e]. FA showed blocked choroidal fluorescence at supero-temporal lesion area [Fig. 3f]. OCTA revealed area of capillary abnormalities in deep capillary plexus nasal to foveal avascular zone (FAZ) showing a fern-like pattern [Fig. 4a-f].

Figure 3

Case 2 at presentation. Color fundus photograph of the left eye showing an oval ring like area of retinal whitening of about 2DD in size along the distribution of the superotemporal vascular arcade and few ill-defined small similar areas in nasal parafoveal region (a). Red free imaging of the left eye shows more precise hyperreflective areas corresponding to the lesions (b). Fundus autofluorescence showing an area of hypoautofluoresence corresponding to the superotemporal lesion (c); Parafoveal lesions are not picked up. SS-OCT reveals hyperreflective lesion located at INL extending into IPL and ONL (d). SS-OCT through the superotemporal lesion showed hyperreflectivity of the inner retinal layers, including the nerve fibre and ganglion cell layers (possibly suggestive of concomitant ischemia of the superficial capillary plexus) (e). FFA shows blocked choroidal hyperfluoresence with thinned-out retinal capillaries and non-perfused areas indicating ischemia in the superotemporal lesion (f)

Figure 4

En face structural OCT with segmentation at superficial capillary plexus (a) and deep capillary plexus (b) show well defined whitish areas corresponding to the lesions representing the extent of the infarction. OCTA through superficial capillary plexus shows fern like pattern of capillary ischemia (c). OCTA through deep capillary plexus shows signal attenuation artefacts due to shadowing from the overlying hyperreflective bands (d). En-face structural OCT with segmentation at deep capillary plexus along with corresponding OCTA image through superotemporal lesion shows hyperreflective white areas of infarction with a fern like pattern of capillary ischemia (e and f)

Discussion

Recently, two forms of AMN have been defined by Sarraf et al. Type 1 AMN, or PAMM, is characterized by SD-OCT findings at the level of INL, whereas type 2 AMN is associated with abnormalities of outer-retinal layers at macula.[1] PAMM and AMN are distinct disorders with some overlapping features.First, the average age of patients with PAMM was 59 years and they were predominantly male, whereas the patients with traditional AMN lesions were on an average 33 years of age and tended to be of female gender. Second, PAMM is thus an OCT finding associated with various retinal vascular diseases, whereas AMN is an independent disease entity.

The primary etiology in PAMM may be ischemia of the intermediate and deep capillary systems, which are responsible for blood supply to middle retina.[45] Patients typically present with recent onset of one or multiple paracentral scotoma(s) in one or both eyes. Complaints can range from generalized blurring of central vision and difficulty focusing to more specific shapes of paracentral scotomas, such as a fixed “gray spot.” Visual acuity may be mildly reduced in affected eye, although patients can have 6/6 vision. Amsler grid testing may be useful in such cases to help document the scotoma.[1] Compared to cotton wool spots, the retinal whitening associated with PAMM lesions is noticeably distinct, appearing duller gray-white in color, less opaque, deeper in the retina, and not following the distribution of the nerve fiber layer.[167] Moreover, these lesions are evanescent and may already have resolved before clinical examination. PAMM lesions may resolve with thinning of INL, resulting in persistent paracentral scotomas for the patient (as seen in Case 1).[4] OCTA features of PAMM include abnormal vasculature at the level of deep capillary plexus at the site corresponding to the lesion on SD-OCT. Three patterns are described: arteriolar, globular, and fern-like. A combination of patterns is also possible.[6] 10-2 automated Humphrey visual field testing and Amsler chart recordings can help documentation and monitoring progression of scotoma.

Our first patient presented with small fleck-like lesion superotemporal to fovea [Fig. 1a-c]. On SS-OCT, the band-like lesion at OPL shows some undulations at its margins signifying reperfusion and subsequent resolution of the infarct of OPL and INL [Fig. 1d]. An arteriolar pattern of capillaries on the deep capillary plexus segment of OCT-A further denotes ischemia of inner retinal layers possibly following an arteriolar obstruction [Fig. 2a-d]. As the arterioles reperfuse, the band-shaped hyperreflectivity on OCT slowly resolves along with reduction in the area of capillary loss on OCT-A, nevertheless leaving behind a scotoma close to fixation. PAMM typically occurs in elderly males. However, our case is atypical for her gender and age at presentation. Our second case presented with multiple hyperreflective areas, the largest superotemporal to fovea [Fig. 3a-c]. The hyperreflective band-like lesions on SS-OCT are limited to inner plexiform layer (IPL) in smaller areas near fovea. However, the large superotemporal lesion shows involvement of all inner retinal layers from OPL to RNFL indicating the extent of ischemia [Fig. 3d and e]. These multiple lesions are all associated with fern-like capillary pattern on OCTA [Fig. 4a-f]. AMN typically occurs in younger females. However, our case is atypical for his gender and age at presentation.

PAMM generally presents as a focal area of hyperreflectivity; only a single case report has noted multiple PAMM lesions.[7] There is currently no treatment available for PAMM. Management is aimed at the identification and treatment of underlying vascular risk factors, if present.

Conclusion

In conclusion, our report adds to the growing knowledge on PAMM and its features on multimodal imaging.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

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