Neurovascular retinal impairment in early-treated adults with phenylketonuria

Abstract

Purpose: To compare radial peripapillary capillary (RPC) vascular plexus parameters and peripapillary retinal nerve fiber layer (pRNFL) thickness between Early-Treated Adults with Phenylketonuria (ETPKU) and controls.

Methods: This observational study was a monocentric, case control study including 36 eyes of 36 participants. Among these, 18 were early-treated PKU (ETPKU) and 18 were controls. A SD-OCTA (XR Avanti AngioVue OCTA; Optovue Inc., Fremont, CA) was employed to assess the OCT and OCTA parameters of all the participants. The main outcome measures were the RPC vessels density (VD) %, and the pRNFL thickness.

Results: The average pRNFL thickness was significantly reduced in ETPKU (110.78 ± 12.48 μm) compared to controls (113.22 ± 13.95 μm), p = 0.046. The mean VD% of the small vessels of the RPC plexus was 52.31 ± 2.2 in ETPKU and 50.71 ± 3.2 in controls (p = 0.049), while the VD% of all the radial peripapillary capillary plexus (RPCP) was 58.5 ± 2.2 in ETPKU and 55.08 ± 3.4 in controls (p < 0.001). By contrast, there were no differences in age, sex, and IOP between the two groups.

Conclusion: Through structural OCT and OCTA, we observed thinning of the nerve fibers accompanied by an increase in perfusion of the RPC plexus. Thus, our conclusions suggest that OCTA may serve as a noninvasive method to identify novel retinal biomarkers in ETPKU.

Keywords: OCTA; early-treated adults with phenylketonuria; pRNFL; phenylketonuria; radial peripapillary capillary plexus; retinal imaging.

Figure 1

Representation of peripapillary OCT angiography in ETPKU patient. OCTA scan 4.5 × 4.5 mm centered on ONH. (A) Color-coded density maps and automatized vessel density measurements of the RPC. (B) RPC vascular density image.

Figure 2

Box and whisker plots showing radial peripapillary capillary plexus vessels density % of the small vessels, of all the plexus and the retinal nerve fiber layer thickness (μm). Each box displays mean (cross within the box), median (central horizontal line) and interquartile range (horizontal extremes of the box) values for each metric. The ends of the whiskers illustrate the minimum and maximum values. Outliers are visualized as dots not included in whiskers. Each graph reports comparisons between the groups for a specific metric (p = 0.049, p < 0.001, and p = 0.046, respectively).