Retinal oxygen metabolic function in choroideremia and retinitis pigmentosa.

Abstract

Purpose: 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.

Methods: 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.

Results: 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.

Conclusion: 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.

Key messages: What was known before? 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.