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Characteristics of radiation induced microangiopathy in the treatment of wet AMD

Session Details

Session Title: AMD II

Session Date/Time: Friday 27/09/2013 | 08:00-10:00

Paper Time: 08:32

Venue: Hall 3 (Level 0)

First Author: U.Chakravarthy UK

Co Author(s):    J. Slakter   D. Moshfeghi   T. Jackson   M. Shusterman     

Abstract Details

Purpose:

To describe the characteristic features of the microangiopathy seen after exposure to focal low energy ionizing radiation as treatment for persistent choroidal neovascularization due to age-related macular degeneration (AMD) in the INTREPID trial

Setting:

Multicenter randomized sham controlled clinical trial in 21 European centers

Methods:

Patients (n = 230) with active, neovascular AMD were entered into a double masked, sham controlled, randomized clinical trial. Of this group, 226 received the allocated treatments of 16 Gray (N=74), 24 Gray (N=73) or sham treatment (N=79) at the baseline visit. At subsequent visits, treatment with ranibizumab could be administered on fulfilling specific re-treatment criteria. Retinal imaging outputs (color, fluorescein angiography (FA) and optical coherence tomography (OCT) were graded by netWORC UK for nAMD activity and for the safety outcome of radiation induced retinopathy. To differentiate nAMD characteristics from radiation induced changes, the grading protocol pre-specified the following features on color (retinal hemorrhage, cotton wool spots, abnormally dilated microvessels) and FA (capillary dropout, intraretinal telangiectasia and intraretinal edema). If these changes were present either within the area occupied by the nAMD lesion or in a region uninvolved by the lesion, an ocular adverse event was triggered. The reading centre clinician (UC) and an independent observer (JS) both of whom were masked to the treatment status performed a repeat grading to classify any changes as radiation induced microangiopathy (RIM) or as microvascular abnormalities related to nAMD

Results:

At time of completion of this report, the reading center has identified 13 participants as exhibiting features suggestive of radiation retinopathy. Both experts were 100% concordant and assigned 6 of the 13 into the category of RIM. The most commonly encountered features were hemorrhage in the inner retinal layers and/or cotton wool spots on color grading. Microvascular narrowing and irregularity of the lumen and/or telangiectasia with capillary drop out were the commonest abnormalities noted on FA. In 2 of the 4 participants with RIM who completed 24 months of follow up resolution of CWS was noted but the FA characteristics remained unchanged. The mean area occupied by RIM measured on FA was 2.83 mm2. RIM was seen in 3 participants at month 12 (of which 2 were detected only on FA) , 2 at month 18 and one at month 24. OCT scans passing through the area of RIM were only available in 2 cases and the morphological changes were restricted to the inner retina, comprising of areas of perivascular hypo reflectivity indicating localization of the pathology to the retinal microvessels.

Conclusions:

Radiation induced microvascular changes in the retinal circulation were observed after focal low energy RT by month 12. The frequency of occurrence was low and the area of retinal involvement is limited. The characteristic lesions were a microangiopathy with the potential to resolve over time.

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