**4. Secondary choriocapillaritis: acute zonal occult outer retinopathy (AZOOR)**

AZOOR is a primary disease of the outer retina (photoreceptoritis) with a secondary choriocapillaris involvement. It was first described by JD Gass in 1992 [52] and affects young- to middle-aged patients (13–63 years), predominantly myopic women which present an acute onset of scotomas and photopsias in one or both eyes, sometimes associated with mild vitritis. Furthermore, there may be recurrences in one-third of cases [53].

Fundus photography is normal at presentation, but later can present zonal or multizonal retinochoroidal atrophy, often seen as peripapillary depigmentation, occasionally with a demarcation line if there is active disease expansion or pigment clumping, retinal arteriolar attenuation, and focal perivenous sheathing in later stages (**Figure 9**).

FAF shows a trizonal distribution (**Figure 9**) of normal autofluorescence outside the lesion (zone 1), speckled hyperautofluorescence in the rim of the expanding lesion (zone 2) which correspond to loss of photoreceptor outer segments and increased exposure of RPE lipofuscin and/or the result of accumulated lipofuscin in RPE cells due to metabolic overactivity as a response of photoreceptor outer segment turnover [54, 55], and a central area of hypoautofluorescence within the lesion (zone 3) that indicates RPE and choriocapillaris atrophy [56].

OCT also demonstrates a trizonal pattern corresponding to FAF characterized by normal retina outside the lesion (zone 1), subretinal hyperreflective deposits and loss or irregularity of EZ (zone 2) in the rim of the lesion, and EZ, RPE and choriocapillaris atrophy (zone 3) inside the lesion (**Figure 9**), although thinning can also extend to the inner retina [56].

OCT-A detects markedly reduced flow in choriocapillaris in areas of retinochoroidal atrophy [57]. Active lesions may present an increase in the deep flow density which may be the source of mediators of inflammation, in contrast to inactive phase where it is decreased, but further studies are needed [55]. En-face OCTA demonstrates hyperreflective dot structures at the level of ellipsoid zone that might represent degenerating photoreceptor segments (**Figure 9**) [58].

*Multimodal Imaging of White Dot Syndromes DOI: http://dx.doi.org/10.5772/intechopen.106467*

## **Figure 9.**

*This patient present a retinochoroidal atrophic lesion inferotemporal to the disk in right eye and two lesions in the left eye located in peripapillary area and another nasal to the optic disk. (a) Fundus autofluorescence (FAF) shows hypoautofluorescence inside the lesions and a rim with faint hyperautofluorescence. (b) Optical coherence tomography (OCT) shows outer retina/EZ atrophy and choroidal thinning, (c) and en-face optical coherence tomography angiography (OCT-A) at the level of EZ shows hyperreflective dots (more evident in the left eye) in a hyporreflective background. (d) EZ: Ellipsoid zone.*

ICGA also shows a trizonal pattern of preserved fluorescence (zone 1) indicating choriocapillaris integrity, a late hyperfluorescence with minimal leakage in subacute areas demarcating the lesion (zone 2), and an inner area of hypofluorescence due to retinochoroidal atrophy [56].

FFA depicts faint late hyperfluorescence indicating loss of photopigment of outer segments, except in those areas with retinochoroidal atrophy that are early and late hyperfluorescent due to window effect. Retinal arteriolar narrowing in the areas of involvement may be seen. Retinal vessel staining and leakage may be present [24].
