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Stefan Koinzer, Marie Otto, Carola Hesse, Mark Saeger, Amke Caliebe, Johann Roider; Descriptive study of choroidal effects underneath retinal photocoagulation lesions by optical coherence tomography – a rabbit study.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5848.
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© ARVO (1962-2015); The Authors (2016-present)
Diabetic choroidopathy includes microvasculopathy, delayed filling in indocyaningreen-angiography and thickness modulations in enhanced depth imaging (EDI) optical coherence tomography (OCT). Hence, choroidal affection by retinal laser photocoagulation could play a role in the clinical efficacy of the treatment. In a rabbit study, we analyzed morphological choroidal changes after retinal photocoagulation in spectral domain OCT (SD-OCT) images.
We applied 1019 photocoagulation lesions with a 532 nm continuous wave photocoagulator (Zeiss Visulas) to 6 eyes of 3 rabbits. Exposure diameter was 133µm on the fundus and exposure times and powers variable. We recorded SD-OCT images 2 hrs., 1, 4 and 12 weeks after the treatment (Heidelberg Spectralis®). For every lesion, we analyzed retinal lesion intensity on the basis of a 6-step classification, the greatest linear diameter (GLD) of every lesion on a retinal (outer limiting membrane) and a choroidal level and choroidal thickness in the lesion center.
Choroidal GLD values (Y) were greater than retinal GLD values (X), with a linear correlation Y=178+0.8*X (R2=0.56). Choroidal GLD values increased with the retinal lesion intensity and shrunk over 12 weeks (p<0.001). Choroidal GLD after 2 hrs. (12 weeks) was 354±70µm (225±29µm, mean±SD) for the lowest intensity class and 457±70µm (303±61µm) for the highest intensity class (each p<0.001). Choroidal thickness at 4 consecutive timepoints was 156±19µm, 147±21µm, 146±19µm and 149±21µm.
Retinal photocoagulation produces distinct choroidal effects, and their diameter correlates positively to the retinal damage intensity. Choroidal thickness decreases over 4 weeks after treatment, but increases again from weeks 5-12. SD-OCT as used in this study does not give insight in choroidal hemodynamics, which could be elucidated by phase sensitive OCT. It is likely that the choroid plays an unknown, possibly important role in the mechanism of action of photocoagulation, which should be thoroughly discussed in the light of standard, mild or subvisible photocoagulation.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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