Oxygen metabolic retinal function in choroideremia and retinitis pigmentosa

Abstract

Purpose : To measure the retinal oxygen metabolic function with retinal oximetry (RO) in patients with choroideremia (CMH) and compare these findings with retinitis pigmentosa (RP) and controls. Also, to test correlations between RO and parameters of retinal and choroidal structure in CHM patients.

Methods : Prospective observational study including 18 eyes of 9 molecularly confirmed CHM patients (9♂; 40.2 ± 21.2 years), 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). Secondary outcomes were choroidal thickness and retinal thickness measured with Spectralis OCT (Heidelberg Engineering, Germany) on the central subfield 1 mm as defined by the Early Treatment Diabetic Retinopathy Study. Statistics were performed with linear mixed-effects models analysis calculated with SPSS^®.

Results : Eyes suffering from CHM (Figure 1a) differed significantly from both RP (Figure 1b) and control eyes, when the retinal oxygen metabolic parameters were taken into account. While RP is known to show significantly higher A-SO₂ and V-SO₂ values when compared to controls, CHM showed opposite findings with significantly lower values when compared to RP and controls (P< 0.001). The A-V SO₂, which represents the retinal oxygen metabolic consumption, showed significantly lower values compared to both RP and controls (P< 0.05). Choroidal thickness was positively correlated with A-SO₂ and A-V SO₂ in CHM patients (P< 0.05).

Conclusions : RO revealed differences in retinal oxygen metabolic function in CMH when compared to RP and controls by not only showing significantly different oxygen metabolic parameters when compared to controls but also opposing findings to those that were so far known for RP. Thus, by providing new insights into the retinal oxygen metabolic mechanisms RO helps to understand the underlying pathophysiology of CHM and RP. These findings may also be relevant when considering oxidative stress-targeted therapies in inherited retinal dystrophies.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Figure 1. Retinal oximetry in CHM and RP. Retinal oximetry images of the right eye of a patient with CHM (a) and with USH2A-associated RP (b). The colour scale in the center shows oxygen saturation.