**3.5 Brush border pattern or elongation of photoreceptor outer segment**

Brush border pattern is defined as an accumulation of waste products in the photoreceptor outer segment on the outer surface of the detached neurosensory retina over subretinal fluid (**Figure 7**). This provides an irregular, serrated, and thicker appearance of the detached neurosensory retina. Other authors denominate it as "elongation of the outer photoreceptor segment", and it can be found in almost 73–75% of OCT images from patients who suffer CSCR [53]. The loss of the contact between RPE and photoreceptor outer segments that occur in CSCR prevents the waste product of photoreceptors being phagocytosed by RPE [54]. These subretinal proteins or accumulated macrophages with outer photoreceptor segments can be observed as hyperfluorescent white-yellowish precipitates in the retinal examination if they contain precursors of lipofuscin [55]. If this process persists, despite subretinal fluid absorption, subretinal deposits may progress to be permanent with the subsequent poor visual outcome. Complete disappearance of outer segments as observed in very long-standing CSCR correlates with poor visual prognosis [53].
