## 2 OCT-A Applications in Pediatric Population
### Applications of OCT-A in Other Pediatric Retinopathies  
OCT-A has been used in the study of other pediatric retinal pathologies including X-linked retinoschisis (XLRS) [78; 98; 99], an X-linked recessive disorder that occurs almost exclusively in young males and that entails an early-onset bilateral visual loss due to foveal schisis. In these studies, a reduced macular deep vessel density was seen. This finding was attributed to a displacement and disruption of the vessels due to schitic cysts [98; 99]. OCT-A has also been used to study epiretinal membranes in children, which are a rare condition and usually secondary to other pathologies or personal past ophthalmic histories [78]. However, an erroneous segmentation due to an important anatomic disruption made it difficult to interpret the images provided by OCT-A [78]. OCT-A use has also been reported in the study of Best vitelliform macular dystrophy (BVMD) [78], the most frequent macular dystrophy characterized by yellowish vitelliform or egg yolk-like lesions  
Figure 1: (**A**,**B**) Optical coherence tomography angiography (OCT-A) of 4.5 \(\times\) 4.5 mm (DRI OCT Triton (plus), TOPCON Co., Japan) corresponding to the right eye of a patient with ROP that required laser treatment. In the superficial capillary plexus (SCP) segmentation (**A**), a decreased foveal avascular zone (FAZ) (43.97 μm2) and disorganization of the capillaries in the deep capillary plexus (DCP) (**B**) were observed. (**C**,**D**) OCT-A of 4.5 \(\times\) 4.5 mm (DRI OCT Triton system, Topcon) corresponding to a patient born at term of the same age as the first patient. We can appreciate a bigger FAZ (265,694 μm2) in this case and a normal capillary architecture in the DCP (**D**). that are usually localized in the macular area [100; 101]. In these patients, OCT-A was found to be useful to detect choroidal neovascularization (CNV) associated with BVMD. Furthermore, OCT-A has been used to investigate retinal vascular networks in patients with Coats' disease [78; 102], of which etiology and pathophysiology remain to be studied in greater depth. In this ocular disease, OCT-A demonstrated saccular aneurysmal dilatations [78] and suggested that a distortion of the inner blood-retinal barrier takes place in this entity, probably due to a bilateral defect in midcapillary angiogenesis [102]. Furthermore, OCT-A has been used to study children with idiopathic and secondary-to-laser-pointer-exposure CNV. Thus, children with idiopathic CNV showed type 1 CNV on OCT-A, while patients with secondary-to-laser-pointer-exposure CNV had type 2 CNV on OCT-A [79]. Regarding CNV in the pediatric population, it is interesting to remember that, unlike what happens in the adult population, CNV in children is more often a classic type 2 membrane affliction and they do not have thickening or calcification of Bruch's membrane, nor diffuse disruption of the retinal pigment epithelium [103]. Moreover, CNV in the pediatric population usually has a solitary vascular in-growth site, as opposed to what happens in age-related macular degeneration-associated CNV [103]. Some patients with foveal hypoplasia, a condition that can be present in airidia, albinism, nanoftalmos, incontnentia pigmenti, retinopathy of prematurity, and achromatopsia, have been studied with OCT-A [12]. The findings in these cases commonly include the presence of SCP and the absence of DCP [12]. OCT-A may be particularly useful in the study of patients with paracentral acute middle maculopathy (PAMM) as it has been proposed that an ischemia of the capillaries in the DCP is the possible cause and FFA is limited in visualizing vascular lesions located in this vascular plexus [103]. Thus, OCT-A of patients with PAMM show images corresponding to perfusion of the acute focal lesions followed by a reduction of blood flow in the deep vascular plexuses in long term cases. On the other hand, this entity may also be idiopathic or secondary to vascular diseases of the retina or systemic vascular diseases.