Objective area measurement technique for choroidal neovascularization from fluorescein angiography

Abstract

The purpose of this study was to develop a non-biased method of quantitatively measuring choroidal neovascularization (CNV) areas based on late-phase fluorescein angiography (FA) images. Experimental CNV was induced in Long Evans rats by laser disruption of the Bruch’s membrane. FA was performed weekly for 5 weeks. Multi-Otsu thresholding (MOT) was used to quantify CNV in late-phase FA images from both experimental rodent CNV and wet age-related macular degeneration patients (wAMD). Images were automatically thresholded into three levels based on the image histogram, with the highest level containing CNV. To determine the technique’s ability to quantify CNV areas, rats were given either triamcinolone acetonide or dexamethasone sodium phosphate to treat CNV and compared to untreated rats. The rat CNV lesion areas measured from 5-week histology sections from each treatment group were compared to areas measured from the corresponding FA images. MOT was able to detect statistical decreases in rodent CNV area in the treatment groups versus control from weeks 3 through 5. The ratio of CNV area measured from histology to area measured from FA images was not statistically different between groups. Finally, to determine the usefulness of MOT on pathological morphologies of CNV, MOT was performed on late-phase FA images from patients with classic and diffuse CNV. The technique was able to segment classical CNV in wAMD patients, but performed poorly with diffuse CNV. MOT provides a robust, objective, and quantifiable area measurement of CNV lesion area in both experimentally-induced and pathological CNV. The results indicate that MOT could be a useful research tool in helping evaluate the effects of therapeutics on CNV growth.

In vivo analysis of the time and spatial activation pattern of microglia in the retina following laser-induced choroidal neovascularization

“…The peak of activation was detected at D4 after laser treatment which decreased at D7 and was sustained at D14. Astonishingly, the majority of activated cells was found in the inner retina whereas the laser scar is located at the outer retina (Guthrie et al, 2014). Most of the cells counted at D1 were found surrounding the scar.…”

Neuropilin 1 Involvement in Choroidal and Retinal Neovascularisation

“…Although, each of the three methods assess slightly different aspects of CNV, all of them showed a clear effect caused by Nrp1 depletion. Postmortem histological analysis has the advantage that vascular elements and invading inflammatory cells can be identified separately and volume measurement of the CNV lesions can be obtained with high precision using confocal microscopy [38]. However, dissection and fixation artefacts might introduce noise into those volume measurements.…”

Intravitreal Stanniocalcin-1 Enhances New Blood Vessel Growth in a Rat Model of Laser-Induced Choroidal Neovascularization

“… 44 In the present study, the increase in fluorescence area and intensity was used as an index for vascular leakage based on the grading system described previously. 31 We found that 52% of all laser-induced CNV lesions showed significant elevation of fluorescein signal (grade 3) in the eyes treated with STC-1 compared with 25% in the control eyes ( Fig. 2 ).…”

“…Late-phase images were chosen for analysis of fluorescein leakage to correspond with the clearance time of fluorescein from the vasculature and to avoid interference with the observation of hyperfluorescence from CNV. 31 FFA was graded by two masked investigators. When the two grades for a lesion did not match, the two investigators discussed the lesion grades and agreed on the final grade together.…”