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Analyse morphométrique des vaisseaux rétiniens par optique adaptative chez des patients ayant été traités par protonthérapie pour mélanome choroïdien

Radiation therapy is a common treatment for ocular tumors but can cause potentially severe radiation retinopathy, whose mechanism remains unclear. Histopathological analysis shows early endothelial cell loss and capillary closure. Following the observation of occlusion of large retinal vessels in such patients, we explored by adaptive optics ophthalmoscopy (AOO) the morphometry of large retinal vessels in patients who underwent proton therapy for melanoma.

Adults with choroidal melanoma treated by proton therapy were longitudinally analyzed by AOO (rtx1, Imagine Eye, Orsay, France) to document the post-radiotherapy evolution of vascular diameters. Data were compared to that of fellow eyes and to healthy volunteers.

Thirteen eyes of thirteen patients (mean age 64.4 years) over a mean follow–up of 747 days (2.45 years) were analyzed. The mean post-proton delay was 2.79 years at first examination. The mean wall-to-lumen ratio was 0.262. Temporal evolution showed marked changes in arterial diameters, with variations from 10% to -25%. Segmental variations of vasomotricity were observed in arteries as well as veins. Occlusion of large arteries or veins occurred in 2 cases. These occlusive episodes were always preceded by vasoconstriction. These changes in vascular diameter were significantly higher than in control eyes. 

Radiation retinopathy leads to dramatic changes of vascular diameters with alternating episodes of dilation and constriction. The latter may lead to vascular occlusion. The combined effect of arterial and venous pathology may explain the severity and spatial extent of the disease. Indeed, proximal vasoconstriction may cause distal capillary damage.

Conclusion: Radiation retinopathy is associated with alteration of motricity of large retinal vessels, in arteries as well as veins. This vasomotor dysregulation may contribute to downstream capillary closure. Further studies are ongoing to document the link between large and small vessel pathology. Targeting vascular dysregulation may be a therapeutic target in the future for post-radiation tissue damage.