P. Garcia

Acircularity index and axis ratio of the foveal avascular zone in diabetic eyes and healthy controls measured by optical coherence tomography angiography

&NA; Given the complexity of the current system used to stage diabetic retinopathy (DR) and the risks and limitations associated with intravenous fluorescein angiography (IVFA), noninvasive quantification of DR severity is desirable. We examined the utility of acircularity index and axis ratio of the foveal avascular zone (FAZ), metrics that can noninvasively quantify the severity of diabetic retinopathy without the need for axial length to correct for individual retinal magnification. A retrospective review was performed of type 2 diabetics and age‐matched controls imaged with optical coherence tomography angiography (OCTA). Diabetic eyes were divided into three groups according to clinical features: No clinically observable diabetic retinopathy (NoDR), nonproliferative diabetic retinopathy (NPDR), and proliferative diabetic retinopathy (PDR). OCTAs of the superficial and deep vascular layers centered at the fovea were superimposed to form a full vascular layer on which the FAZ was manually traced. Acircularity index and axis ratio were calculated for each FAZ. Significant differences in acircularity index were observed between all groups except for controls vs. NoDR. Similar results were found for axis ratio, although there was no significant difference observed between NPDR and PDR. We demonstrate that acircularity index and axis ratio can be used to help noninvasively stage DR using OCTA, and show promise as methods to monitor disease progression and detect response to treatment. HighlightsAcircularity index and axis ratio can quantify FAZ abnormalities in diabetics.They do not require axial length measurement.They can be used to noninvasively stage severity of diabetic retinopathy using OCTA.These metrics show promise as methods to monitor disease over time.

Ultrahigh-Resolution Combined Coronal Optical Coherence Tomography Confocal Scanning Ophthalmoscope (OCT/SLO): A pilot study

SummaryOBJECTIVE: To evaluate clinical images from a prototype ultrahigh resolution (UHR) combined coronal optical coherence tomography/confocal scanning ophthalmoscope (OCT/SLO) and to compare them to standard-resolution OCT/SLO images on the same patients. DESIGN: Cross-sectional pilot-study. PARTICIPANTS: Sixty-six eyes of 42 patients with various macular pathologies, such as age-related macular degeneration, macular edema, macular hole, central serous retinopathy, epiretinal membrane and posterior vitreous traction syndrome. METHODS: Each subject was first scanned with a standard-resolution OCT/SLO that has an axial resolution of ∼10 micron. Immediately following, patients were scanned with the prototype UHR OCT/SLO device. The UHR system employs a compact super luminescent diode (SLD) with a 150 nm bandwidth centered at 890 nm, which allows imaging of the retina with an axial resolution of 3 microns. Both coronal and longitudinal OCT scans were acquired with each system, and compared side-by-side. Scan quality was assessed for the observers ability to visualize the vitreo-retinal interface and retinal layers – in particular of the outer retina/RPE/choroidal interface, increased discrimination of pathological changes, and better signal intensity. MAIN OUTCOME MEASURES: Ultrahigh and standard-resolution coronal and longitudinal OCT/SLO images of macular pathologies. RESULTS: In the side-by-side comparison with the commercial standard-resolution OCT/SLO images, the scans in the Ultrahigh resolution OCT/SLO images were superior in 85% of cases. Relatively poor quality images were attributed to lower signal-to-noise ratio, limited focusing, or media opacities. Several images that had a better signal intensity in the standard-resolution OCT/SLO system were found to show more retinal detail in the UHR system. In general, intraretinal layers in the UHR OCT/SLO images were better delineated in both coronal and longitudinal scans. Enhanced details were also seen in the outer retina/RPE/choroidal complex. The UHR OCT/SLO system produced better definition of morphological changes in several macular pathologies. CONCLUSIONS: Broadband SLD-based UHR OCT/SLO offers a compact, efficient, and economic enhancement to the currently available clinical OCT imaging systems. UHR OCT/SLO imaging enhanced the quality of the OCT C-scans, facilitated appreciation of vitreo-retinal pathologies, and improved sensitivity to small changes in the retina, and the outer retina/RPE/choroidal interface.

Progress in the en-face optical coherence tomography applied to eye imaging

A review is presented of the research on high resolution imaging of the eye based on en-face OCT. This can provide a dual display of images with different depth resolutions, where the two images are OCT and the other confocal. Two applications are presented: (i) OCT/ICG systems where the confocal channel is tuned to the fluorescence of indocyanine green and (ii) aberration corrections in both OCT and confocal channels using closed loop adaptive optics for enhanced contrast and transversal resolution.