Neuroretinal Imaging Inflammatory Biomarkers Anticipating Radiation-Induced Macular Edema

RADIATION MACULOPATHY IS ANTICIPATED BY OCT HYPERREFLECTIVE RETINAL FOCI: A Large, Prospective, Confirmation Study

PURPOSE

To investigate, by means of spectral domain optical coherence tomography, retinal reflectivity changes as an early biomarker anticipating radiation-induced macular edema (ME) in patients treated by iodine-125 (I-125) brachytherapy.

METHODS

Thirty patients planned for I-125 brachytherapy because of uveal melanoma were prospectively included and followed every 4 months for five years. Reflectivity alterations, namely hyperreflective retinal foci, were characterized and counted by two independent masked examiners by means of spectral domain optical coherence tomography imaging. Hyperreflective retinal foci were defined as discrete intraretinal reflectivity changes ≤30 µm, with reflectivity similar to nerve fiber layer and without back shadowing.

RESULTS

Macular edema occurred in 17 patients (24.2 ±15.1 months) (group 1) after irradiation. Thirteen patients showed no signs of ME at the 5-year follow-up (group 2). The number of hyperreflective retinal foci was statistically higher in sequential visits until the evidence of ME in group 1 vs group 2 (P < 0.0001). In group 1, hyperreflective retinal foci at the follow-up before the evidence of ME were significantly related to the OCT central subfield thickness at ME appearance (P = 0.0002, r2=0.6129). The intergrader agreement was almost perfect (intraclass correlation coefficient = 0.80).

CONCLUSION

Hyperreflective retinal foci may be considered as an early in vivo imaging biomarker of retinal inflammatory response to ocular irradiation, anticipating the development of radiation maculopathy.

OCT Hyperreflective Retinal Foci in Diabetic Retinopathy: A Semi-Automatic Detection Comparative Study

Optical coherence tomography (OCT) allows us to identify, into retinal layers, new morphological entities, which can be considered clinical biomarkers of retinal diseases. According to the literature, solitary, small (<30 µm), medium level hyperreflective (similar to retinal fiber layer) retinal foci (HRF) may represent aggregates of activated microglial cells and an in vivo biomarker of retinal inflammation. The identification and quantification of this imaging biomarker allows for estimating the level and possibly the amount of intraretinal inflammation in major degenerative retinal disorders, whose inflammatory component has already been demonstrated (diabetic retinopathy, age-related macular degeneration, radiation retinopathy). Currently, diabetic retinopathy (DR) probably represents the best clinical model to apply this analysis in the definition of this clinical biomarker. However, the main limitation to the clinical use of HRF is related to the technical difficulty of counting them: a time-consuming methodology, which also needs trained examiners. To contribute to solve this limitation, we developed and validated a new method for the semi-automatic detection of HRF in OCT scans. OCT scans of patients affected by DR, were analyzed. HRF were manually counted in High Resolution spectral domain OCT images. Then, the same OCT scans underwent semi-automatic HRF counting, using an ImageJ software with four different settings profiles. Statistical analysis showed an excellent intraclass correlation coefficient (ICC) between the manual count and each of the four semi-automated methods. The use of the second setting profile allows to obtain at the Bland–Altman graph a bias of −0.2 foci and a limit of agreement of ±16.3 foci. This validation approach opens the way not only to the reliable and daily clinical applicable quantification of HRF, but also to a better knowledge of the inflammatory component—including its progression and regression changes—of diabetic retinopathy.