The current study aimed to assess the choroidal profile in treatment–requiring ROP neonates and compare it with ROP neonates not requiring treatment. Our study showed that foveal choroidal thickness was significantly lower in ROP patients with the plus disease compared to non-plus ROP (P value = 0.03. ANOVA, Bonferroni posthoc test). However, CT was not significantly different between plus and pre-plus patients (P-value = 0.9, ANOVA, Bonferroni posthoc test). We found no significant relationship between the different staging of ROP and choroidal thickness. It might be explained partly by that choroidal vasculature especially choriocapillaris might be involved other than choroidal thickness. The assessment of choriocapillaris is very difficult in premature infant.
Retinopathy of prematurity (ROP) is considered a disease of retinal vascularization; however, recent evidence demonstrates that choroidal vasculature abnormality is also important and is responsible for outer retinal dysfunction and visual loss(13). Several clinical studies have demonstrated choroidal thinning associated with ROP in older children and adults using OCT imaging (8–11). Anderson and colleagues reported lower subfoveal choroidal thickness in children and young adults with a history of ROP treatment with laser ablation and/or cryotherapy compared with healthy controls(14). Similar results have been shown by Bowl et al. in a study that compared choroidal thickness in 17 young children with a history of treated ROP or spontaneously regressed ROP. They also showed that reduced choroidal thickness was linked to ROP severity(11). However, few studies in the literature evaluated choroidal thickness in infants with ROP (7, 8, 15). Erol and his colleagues studied subfoveal choroidal thickness in 80 premature infants. They found that the thickness of the choroid decreased with the severity of ROP(8). In another study by Mangalesh et al., it is shown that the presence of pre-plus/plus disease versus without accompanied by thinner choroid(16). In consensus with previous studies(16), we also demonstrated the choroid was thinner in ROP neonates with the plus disease compared to not-plus disease. It has been suggested that thinning of the choroid in ROP neonates may be due to oxidative stress and choroidal vascular loss (4, 7, 17, 18). This choroidal vascular loss has been proven angiographically. In a study by Islam et al., the presence of choroidal hypo fluorescence in the central and or peripheral retina of ROP patients was demonstrated(19).
Interestingly, our results indicated that the choroidal thickness didn’t significantly differ in ROP neonates requiring treatment (tROP) in comparison with no need treatment group (nROP). A previous study by Erol and colleagues showed that choroidal thickness in ROP patients with a grade 2 or 3 was lower than grade 0. However, they showed no significant difference between the choroidal thickness of grade 1 and grade 2 /3 ROP patients(8). These findings agree with our results, as 60% of the untreated group was stage 1 ROP, and 92.7% of the treated group was grade 2/3 ROP. Also, Mangalesh et al. reported thinner choroid was associated with pre-plus or plus disease and lower gestational age and birth weight but not the ROP stage(16).
Consistent with previous studies, we found that choroidal involution is associated with the presence of pre-plus/plus, not with the ROP stage.
According to our data, the choroidal vascularity index (CVI) and choroidal stromal index (CSI) weren’t significantly different in the treatment and untreated groups. CVI is a novel means of choroidal evaluation introduced by Agrawal et al. in 2016(12). It has been shown that this parameter is less variable than the choroidal thickness and less influenced by systemic and ocular circumstances(12). This marker is rarely studied in ROP patients. Consistent with our results, Lavric et al. reported CVI preterm children aged 5–15 years had the same CVI compared to preterm children with a history of ROP(20).
For the first time, we used the decision tree method to analyze the use of choroidal parameters to treat ROP patients. In contrast to more traditional statistics, such as linear regression, the decision tree method analyzed the nonlinear and interactive patterns between factors. This study successfully used decision tree analysis to detect the most important choroidal factor for identifying the treatment group and determining cut points for each parameter. The results presented in Fig. 2 showed that in ROP patients, the most important choroidal factor for predicting the need for treatment was CSI. All subjects, associated with CSI higher than 29.1, required treatment. This novel index represents the avascularity of the choroid. Therefore patients with the higher value might benefit from treatment to stop the vicious circle of oxidative stress in ROP patients. Further studies are required to evaluate the addition of choroidal parameters to the current practice of ROP screening regarding effectiveness and outcomes.
The current study focused on the choroidal parameters; this does not exclude the importance of retinal parameters in ROP. This study has other limitations. The handheld OCT imaging was time-consuming and prone to imaging artifacts; future handheld OCT with faster imaging acquisition would improve their imaging quality and feasibility. We measured choroidal measurements manually, and therefore, although reliability analysis showed acceptable observer agreement, the measurements might be susceptible to imprecision. We have a small number of ROPs did not require treatment. Also, the role of gestational age and preexisting systemic and neurological disorders in choroidal parameters were not evaluated, and future studies should be planned to evaluate these factors.