**5. Pigmented paravenous retinochoroidal atrophy**

PPCRA is a rare chorioretinal atrophy characterized by perivenous aggregations of pigment clumps associated with peripapillary and radial zones of RPE atrophy following the course of retinal veins, usually bilateral and symmetric [75]. The etiopathogenesis of PPCRA is still unknown, and it is considered sporadic in most cases [76]. Patients are frequently asymptomatic, and the diagnosis is based on the typical fundus appearance. The natural history of the disease may be either nonprogressive or slowly progressive [75, 76]. In this chapter, we included PPCRA since many previous reports showed a familiar transmission of the disease, thus justifying the hypothesis of a genetic origin [77–82]. Interestingly, PPCRA has been also associated with pathogenic variants of *CRB1*

#### **Figure 4.**

*Multimodal retinal imaging in PPCRA. Fundus image (A) shows evident hypopigmentation following the course of the vascular arcades, together with sparse alterations of the macular pigment. FAF image (B) confirms both the perivascular and the central alterations, detected as mainly hypoautofluorescent signals. Structural OCT (C) shows the disappearance of the peripheral outer retinal bands and some focal alterations localized at the level of the inner retina. OCTA shows almost preserved SCP (D), strongly altered DCP with many projection artifacts (E), and markedly altered CC (F).*

gene [83]. The typical onset occurs between 10 and 67 years of age [84]. However, this time might be underestimated by the fact that PPCRA is usually asymptomatic, thus representing an incidental finding during routine ophthalmologic examinations. When present, the most common symptoms are mild visual loss, although visual acuity is usually preserved, reduction of the peripheral visual field and nyctalopia [84]. PPCRA has been classified into three categories based on the distribution of pigmentary changes: (I) "paravenous" type, distinguished by characteristic chorioretinal atrophy with pigment clumping that is geographically connected; (II) "focal" type, characterized by isolated chorioretinal atrophy with pigment clumping; (III) "confluent" type showing chorioretinal atrophy with diffuse bone spicules [76]. A complete noninvasive multimodal retinal imaging PPCRA case is shown in **Figure 4**.

FAF imaging is characterized by continuous hypoautofluorescent signal along the large retinal veins, surrounded by linear hyperautofluorescent signal extending to the periphery [76]. As expected, FAF alterations are different when considering the "paravenous", "focal", or "confluent" types.

OCT shows severe disruption of the RPE and outer retinal layers, usually associated with choroidal thinning, which may sometimes be the only pathological modification detected in PPCRA [76]. Moreover, OCTA may be normal in the early stages of the disease [85]. However, significant changes in deep capillary plexus and choriocapillaris have been recently described in a cohort of 12 patients affected by PPCRA [86]. The scientific interest in PPCRA is growing and noninvasive retinal imaging will undoubtedly provide clinically relevant data in the next future.
