**5. OCT in children with history of ROP**

OCT has been studied for assessment of premature children beyond the neonatal period and infancy as well. The impact of prematurity itself, ROP and ROP treatment have been studied. Features that were observed during infancy also persist in childhood and throughout adolescence, these include shallow foveal pit (**Figures 3**–**5**),

#### **Figure 3.**

*Abnormal foveal contour in a premature-born child. Foveal OCT B-scan in an eye of a 12 years old prematureborn child with shallow foveal pit and retain inner retinal layers at foveal center (yellow vertical line).*

#### **Figure 4.**

*Epiretinal membrane (ERM). Foveal OCT cross-sectional B-scan in an eye of a 10 years old premature-born child. ERM is presented as hyperreflective layer (yellow arrowhead) overlaying on the retina.*

#### **Figure 5.**

*OCT images demonstrating examples of retinoschisis. OCT B-scan image of temporal retinoschisis in a 17-year-old with history of ROP without treatment. Note the macular anomalies including blunting or shallow of the foveal depression and the presence of the inner retina at the foveal center.*

remain inner retinal layers at foveal center (**Figures 3**–**5**), ERM (**Figure 4**), retinoschisis (**Figure 5**), and Optic nerve changes (**Figure 6**).

OCT findings demonstrated that total thickness of the retina is increased in premature children with and without ROP compared with their term counterparts [57, 58]. Tariq et al. reported increased thickness of the central macula and thinning of the outer macula in prematurely born teenagers when compared to those born at term [59].

**Figure 6.** *Optic nerve atrophy.*

Foveal avascular zone (FAZ) is a landmark that has been studied broadly in the recent years. It was found to be remarkably reduced or absent in children children with a history of prematurity with or without ROP [57, 60]. Smaller avascular zone presumably denotes arrest of normal development of retinal neurovasculature induced by premature birth [21, 61]. Positive correlation has been described between FAZ and gestational age and birth weight [62]. At the same time, FAZ was found to be smaller in children with history of treated ROP compared with those with history of spontaneously regressed ROP [21, 57]. However, the former group of patients had lower gestational age and birth weight. As such, the described differences in FAZ might be induced by more significantly immature vasculature at the time of birth [57]. Regarding vessel density, studies have reported that children with a history of prematurity have higher vessel density at the fovea when compared to healthy children [63–65], while other studies did not reveal a difference in vessel density [21, 66, 67].

Children that were born prematurely have been shown to have significantly smaller choroidal thickness 3.0 mm temporal to the fovea than children born at term. Though, choroidal thickness in other locations did not significantly differ. ROP stage had marginally significant inverse correlation with choroidal thickness 3.0 mm temporal to the fovea [68].

Children who were subject to laser treatment of ROP have been shown to have significantly narrower anterior chamber angle (ACA) compared to prematurely born children not treated with laser. In its turn, the ACA was correlated with the degree of myopia. Given the lack of statistically significant difference between ACA in preterm controls versus term controls, it can be assumed that laser treatment and not gestational age contributes to the narrow ACA [60].

Another finding reported in children with history of ROP is increased disc-tofovea ratio, which can be detected by OCT. This finding may be caused by foveal

dragging which in turn is a consequence of cicatricial ROP. However, this association needs to be evaluated further in studies with larger cohorts [69].
