Automated Image Alignment for Comparing Microvascular Changes Detected by Fluorescein Angiography and Optical Coherence Tomography Angiography in Diabetic Retinopathy

ABSTRACT

PURPOSE

To quantitatively compare microvascular features in the macula of patients with diabetic retinopathy (DR) using fluorescein angiography (FA) and optical coherence tomography angiography (OCTA).

METHODS

Patients with DR were recruited from the Cairo University Hospital. FA was performed using a Topcon TRC-50DX or Heidelberg Spectralis HRA+OCT. OCTA was performed using an Optovue RTVue-XR Avanti. FA images were cropped and aligned to the corresponding OCTA images using i2k Align Retina software. The foveal avascular zone (FAZ), area of ischemia, and microaneurysms (MAs) were manually quantified using ImageJ. The fractal dimension (FD) was calculated from each skeletonized image using the FracLac plugin of ImageJ after retinal vascular segmentation.

RESULTS

Twenty-four eyes of 17 patients were evaluated, but only 18 eyes were successfully aligned. There was no difference in FAZ area measured for FA and OCTA images. Compared with OCTA images, FD was significantly less for FA images (1.66 ± 0.048 versus 1.72 ± 0.023, p < .001). Significantly more MAs were identified on FA images (102 ± 27.5) compared with OCTA (47.5 ± 11.7, p < .0001). The number of MAs on FA correlated with decreasing best corrected visual acuity (r² = 0.315, p = .015) and increasing central macular thickness (r² = 0.492, p = .001). No such associations were found with MAs detected on OCTA. Nevertheless, the area of ischemia in the FA images (8.5 ± 4.1%) was significantly smaller compared with the area measured in both the superficial (30.7 ± 9.5%) and deep capillary plexus (21.6 ± 10.9%) of the OCTA (p < .001). Interestingly, number of MAs in the FA images correlated with increasing area of ischemia in the FA (r² = 0.568, p < .001) but only the superficial segment of the depth-resolved OCTA scans (r² = 0.539, p < .001).

CONCLUSIONS

OCTA is a non-invasive tool capable of resolving the retinal vasculature in greater detail when compared with FA but detects significantly fewer MAs. Automatic alignment facilitates quantitative comparison of the microvascular features in DR.

KEYWORDS:

• Automated image alignment
• Diabetic macular ischemia
• Fluorescein angiography
• Fractal analysis
• Optical coherence tomography angiography

Acknowledgments

Interim findings were presented at the 2019 Annual Meeting of the Association for Research in Vision and Ophthalmology in Vancouver, Canada. The poster’s abstract was published in ‘Poster Abstracts’ in the meeting program (A0378).

The authors thank Dr. Jeffrey L. Marx, Dr. Paul R. Cotran, Dr. Karim A. Raafat, Dr. Charles Stewart (Rensselaer Polytechnic Institute and DualAlign LLC [Founder and Chief Scientist]), Dr. Arthur L. Licht, Dr. Noreen Shaikh, David H. Pfennighaus, and Christine Gould, as well as Carol Spencer, Lahey Hospital Librarian, for research support. D.J. Ramsey is the Harry N. Lee Family Chair in Innovation at the Lahey Hospital & Medical Center, Beth Israel Lahey Health.

Declarations

No conflicting relationship exists for any of the authors.

Ethical approval

This study was approved by Cairo University Research Ethics Committee and followed the tenets of the Declaration of Helsinki.

Financial support

DJR: Supported by the Myles and Gertrude Hanson Foundation, Providence, RI., and the Harry N. Lee Family Chair in Innovation, Lahey Hospital & Medical Center, Beth Israel Lahey Health, Peabody, MA.

Abbreviations

BCVA: best corrected visual acuity;

CMT: central macular thickness;

DCP: deep capillary plexus;

DM: diabetes mellitus;

DME: diabetic macular edema;

DMI: diabetic macular ischemia;

DR: diabetic retinopathy;

FA: fluorescein angiography;

FAZ: foveal avascular zone;

FD: fractal dimension;

MA: microaneurysms;

OCT: optical coherence tomography;

OCTA: optical coherence tomography angiography;

SCP: superficial capillary plexus;

TCP: total capillary plexus