# Retinal oxygen metabolic function in choroideremia and retinitis pigmentosa

## TL;DR

This study shows that retinal oxygen levels are significantly lower in choroideremia compared to retinitis pigmentosa and healthy controls, suggesting a hypoxic environment in choroideremia.

## Contribution

The study reveals that choroideremia has opposite retinal oxygen metabolic patterns compared to retinitis pigmentosa, offering new insights into its pathophysiology.

## Key findings

- CHM patients showed significantly lower arterial and venular oxygen saturation compared to RP and controls.
- Retinal oxygen consumption (A-V SO2) was significantly reduced in CHM compared to controls.
- The hypoxic environment in CHM may be due to choroidal degeneration affecting oxygen supply to the retina.

## Abstract

To measure the retinal oxygen metabolic function with retinal oximetry (RO) in patients with choroideremia (CHM) and compare these findings with retinitis pigmentosa (RP) patients and controls.

Prospective observational study including 18 eyes of 9 molecularly confirmed CHM patients (9♂; 40.2 ± 21.2 years (mean ± SD), 77 eyes from 39 patients with RP (15♀ 24♂; 45.6 ± 14.7 years) and 100 eyes from 53 controls (31♀ 22♂; 40.2 ± 13.4 years). Main outcome parameters were the mean arterial (A-SO2; %), venular (V-SO2; %) oxygen saturation, and their difference (A-V SO2; %) recorded with the oxygen saturation tool of the Retinal Vessel Analyzer (IMEDOS Systems UG, Germany). Statistical analyses were performed with linear mixed-effects models.

Eyes suffering from CHM differed significantly from both RP and control eyes, when the retinal oxygen metabolic parameters were taken into account. While RP showed significantly higher A-SO2 and V-SO2 values when compared to controls, CHM showed opposite findings with significantly lower values when compared to both RP and controls (P < 0.001). The A-V SO2, which represents the retinal oxygen metabolic consumption, showed significantly lower values in CHM compared to controls.

The retina in CHM is a relatively hypoxic environment. The decrease in oxygen levels may be due to the profound choroidal degeneration, leading to decreased oxygen flux to the retina. RO measurements may help understand the pathogenesis of CHM and RP. These findings may provide useful details to inform the planning of clinical trials of emerging therapies for CHM.

What was known before?
Retinal oxygen metabolic function measured with retinal oximetry (RO) shows significant alterations in patients with retinitis pigmentosa.

Retinal oxygen metabolic function measured with retinal oximetry (RO) shows significant alterations in patients with retinitis pigmentosa.

What this study adds:
RO function in choroideremia is significantly altered when compared to controls.Furthermore, RO in choroideremia shows opposing findings within different oxygen metabolic parameters to those that were so far known for retinitis pigmentosa.By providing insights into the retinal oxygen metabolic mechanisms, RO can help understand the underlying pathophysiology in choroideremia.

RO function in choroideremia is significantly altered when compared to controls.

Furthermore, RO in choroideremia shows opposing findings within different oxygen metabolic parameters to those that were so far known for retinitis pigmentosa.

By providing insights into the retinal oxygen metabolic mechanisms, RO can help understand the underlying pathophysiology in choroideremia.

The online version contains supplementary material available at 10.1007/s00417-024-06659-8.