**4. OCT findings in neonatal ROP**

The standard for ROP screening has been the eye examination using an indirect ophthalmoscope. OCT allowed to visualize structures and characteristics that have been previously clinically unnoticed. Among those are preretinal tissue, epiretinal membrane, shallower foveal depression, presence of distinct inner retinal layers at the foveal center, macular edema, retinoschisis, retinal detachment, changes associated with plus disease, and optic nerve changes. Occult findings that can be visualized by OCT imaging might play a considerable role in the vision abnormalities in children with history of ROP. OCT findings have the potential to be used as an adjunct for ROP screening and monitoring. Widefield imaging using swept source OCT combined with scleral depression has the capability to visualize peripheral retinal pathology. This may have the ability to allow objective quantitative evaluation of the ROP classification. The components of ROP classification can be measured more discreetly with the use of OCT compared to indirect ophthalmoscopy [25]. In the future, it might be achievable to segment the peripheral vascular-avascular junction, create objective cutoffs for ROP stages and quantify plus disease with more objectivity using artificial intelligence derived metrics [26].

### **4.1 Preretinal tissue**

The exact histopathologic makeup of preretinal tissue is not precisely known, but it is thought to represent remnants of hyaloidal vasculature or small isolated lumps of neovascular tissue overlying the retina [27]. These lesions also have been referred to as popcorn retinopathy [28]. It has been previously reported that the presence of popcorn retinopathy increases the risk of disease progression as well as the development of plus disease and requirement for laser photocoagulation [28]. The ability to monitor the preretinal tissue may be of importance in disease surveillance.
