# OCT-Derived Quantitative Measurement of Extent of Vascularization (“Zone”) in Retinopathy of Prematurity

## TL;DR

This paper introduces a new method using ultra-widefield OCT to objectively measure the extent of retinal vascularization in retinopathy of prematurity.

## Contribution

The study introduces a quantitative framework using UWF-OCT and automated segmentation to measure retinal zones in ROP.

## Key findings

- Retinal arclength and vascularized area significantly differ between clinical zones I and II.
- Automated measurements achieved high diagnostic accuracy (AUROC > 0.97) for identifying zone I ROP.
- Posterior zone II showed intermediate values between zone I and zone II for all metrics.

## Abstract

To provide a quantitative approach to the measurement of zone in retinopathy of prematurity (ROP) using ultra-widefield OCT (UWF-OCT).

Diagnostic accuracy study.

Infants undergoing ROP screening at Oregon Health Science University between June 2023 and October 2024, whose parents consented for research imaging.

An investigational UWF-OCT captured scans from the first week of examination in which stage 1 or worse disease was noted on en face imaging in zone I, posterior zone II, or zone II, and image quality was adequate for quantitative analysis. A U-Net automatedly segmented B-scans to isolate the retina and choroid. En face images and retinal depth maps were used to manually identify the position of the optic nerve, fovea, and visualized temporal vascular border. Mean and minimum retinal arclength (RAL) was measured as the geodesic distance from the optic nerve to the vascular border. The area of vascularized retina (AVR) was estimated using the spherical cap formula, mean-RAL, and measured axial length.

Analysis of variance and generalized estimating equations to compare OCT-derived eye-level measurements with demographics and clinical diagnosis of zone as determined by clinical assessment of en face UWF-OCT images. Area under the receiver operating characteristic curve (AUROC) for RAL compared with zone and all biomarkers at first examination as predictors of future treatment.

Eighty-five eyes from 52 patients met inclusion criteria. Retinal arclength and AVR were both associated with clinical diagnosis of zone and ranged from 7.2 to 17.3 mm and 40.3 to 213.1 mm2, respectively (P < 0.001 for both). The mean difference between zone I and zone II of 4.5 mm (95% confidence interval [CI]: 4.0–5.1) for mean-RAL (P < 0.001) and 80.9 mm2 (95% CI: 71.6–90.2) for AVR (P < 0.001). Posterior zone II was intermediate for all measurements. All measures of length and area had an AUROC >0.97 for diagnosis of zone I ROP.

We present a framework for objective measurement of zone in ROP using UWF-OCT. This work complements prior work leveraging advances in imaging technology to bring quantitative and objective approaches to the diagnosis and classification of ROP.

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.