Study Sample

Inclusion criteria for this study included diabetic patients diagnosed with different stages of DR, ranging from minimal nonproliferative DR (NPDR) to high-risk and treated quiescent proliferative DR (PDR). We also included 1 eye from a healthy, age-matched individual with normal DCP perfusion for comparison with our study sample.

Exclusion criteria included patients with significant diabetic macular edema (DME), diagnosed either clinically or with SDOCT, that disrupted the contour of the segmentation on OCTA, or if the edema was diffuse and obscured the entire outer retinal changes in areas of nonperfusion. We defined DME as central subfield thickening of at least 250 μm (2 standard deviations above average normal thickness). Other exclusion criteria included eyes that had undergone surgical retinal repair or laser treatment within the past 5 years and/or any laser treatment in the area with outer retinal disruption as revealed on SDOCT, as well as eyes that had received intravitreal anti–vascular endothelial growth factor (anti-VEGF) or intravitreal corticosteroids. We also excluded patients with evidence of significant cataracts, graded above nuclear opalescence grade 3 or nuclear color grade 3, in order to avoid optical artifacts that may potentially compromise SDOCT image quality. We excluded eyes with other retinal disease that may contribute to retinal nonperfusion, including arterial branch occlusion of the retina. After image acquisition, we excluded eyes where the OCTA images had movement or shadow artifacts in the area of interest, OCTA signal strength score lower than 50, and eyes with previously undetected cystic changes and macular edema. The original study population included 28 eyes of 14 patients and, after applying the exclusion criteria, only 14 eyes of 10 patients from the original study population were found eligible and are included in the study, as well as 1 healthy (nondiabetic) control eye.

Study Procedures

To localize the level of capillary nonperfusion at the SCP or DCP, we used the XR Avanti Optical Coherence Tomography OCTA instrument (Optovue Inc, Fremont, California, USA) with split-spectrum amplitude-decorrelation angiography (SSADA) software. SDOCT images from the same OCTA device, in the same OCT volume, were used to study outer retinal disruption. This instrument has an A-scan rate of 70 000 scans per second and uses a light source centered on 840 nm and a bandwidth of 45 nm. A 3 × 3-mm scanning area, centered on the fovea and/or area corresponding to the outer retinal disruption on SDOCT, was obtained. Two consecutive B-scans (M-B frames), each containing 304 A-scans, were captured at each sampling location and SSADA was used to extract OCTA information. The OCT signal strength score is considered “unacceptable” if the score is less than 40, “acceptable” if the score is between 40 and 50, and “good” if the score is greater than 50. We only analyzed images with a score greater than 50. En face OCT angiograms were segmented to define the SCP, DCP, and choriocapillaris, using the segmentation algorithm by the built-in software.

Two independent masked graders (F.S. and A.A.F.), masked to any associated information, analyzed SDOCT and angiographic images from the OCTA device. The SDOCT scans for each patient were qualitatively evaluated as normal or as having thinning of the inner retina and/or outer retina. Outer retinal changes were defined as focal thinning of the outer nuclear layer (ONL), disruption of the external limiting membrane, disruption of the inner segment–outer segment (IS/OS) junction, or thinning/absence of the OS–retinal pigment epithelium (RPE) junction. Scans in which the presence of macular edema was noted were not considered for the analysis. The OCTA images were examined to define the presence and location of capillary nonperfusion areas and/or reduced capillary density either in the SCP or DCP, which appeared as areas of capillary nonperfusion (nonflow areas wider than 100 μm) on the OCTA.

Incidents of disagreement between graders (3 cases in SDOCT and 1 case in OCTA) were resolved by an open discussion and review of the data to reach consensus. Medical records were reviewed to gather information about systemic renal and hypertension status, visual acuity, data regarding slit-lamp biomicroscopy, and any history of retinal laser treatment or intravitreal injection or surgery.

Imaging Findings

OCTA in 8 eyes showed capillary derangements including an irregular and enlarged contour of FAZ along with reduced capillary density, appearing as areas of capillary nonperfusion (nonflow) of either SCP or DCP or both. Point-by-point correlation between areas of capillary nonperfusion on OCTA showed exact correspondence to outer retinal disruption on B-scan SDOCT.

Based on OCTA image analysis, the 8 eyes were divided into 2 groups. In the first group, 4 eyes of 3 patients ( Figures 2, 3, and 4 ) had mild reduced capillary density or areas of reduced flow intensity suggestive of low flow within the DCP. Group 2 comprised the remaining 4 eyes ( Figures 5 and 6, and Supplemental Figure ; Supplemental Material available at AJO.com ), which had larger zones of complete capillary nonflow at the level of the DCP.

Diabetic macular ischemia with flow abnormalities and mild decreased deep capillary density around the foveal avascular zone, Case 1 (right eye). Optical coherence tomography angiography (OCTA) of the superficial capillary plexus (SCP) (Top left), deep capillary plexus (DCP) (Top middle), and choriocapillaris (Top right). A shadow artifact from an overlying retinal exudate is seen in the choriocapillaris (yellow arrow). (Bottom left) Enlarged inset of DCP from Top middle (green box). Blue lines indicate location of B-scans and red lines highlight abnormalities in flow. OCTA reveals a slightly irregular contour of the foveal avascular zone with surrounding areas of deceased capillary density in both SCP and DCP, appearing as areas of nonflow significantly larger than 100 μm. (Bottom right) Optical coherence tomography (OCT) B-scans showing DCP segmentation boundaries (green lines). Top and bottom OCT B-scans show focally reduced reflectivity of the inner segment–outer segment and outer segment–retinal pigment epithelium junctions in areas corresponding to decreased capillary density (red lines). Bottom B-scan shows the retinal exudate causing a shadow artifact on the choriocapillaris (Top right) (yellow arrows), but note that no artifacts are seen in the DCP angiogram, since this exudate is casting a shadow below the DCP segmentation boundaries (green lines).

Reduced flow signal at the level of the deep capillary plexus (DCP) around the foveal avascular zone (FAZ), Case 2 (right eye). Optical coherence tomography angiography (OCTA) of the superficial capillary plexus (SCP) (Left) and DCP (Middle). Blue lines indicate locations of B-scans and red line highlights abnormalities in flow. OCTA of the DCP reveals an irregular contour of the FAZ with nonflow areas around the FAZ, with a relatively intact overlying SCP. Furthermore, low pixel intensity of capillaries compared to surround indicate reduced capillary flow signal at the level of the DCP (red circles). (Right) Optical coherence tomography B-scans (blue boxes) showing DCP segmentation boundaries (green lines). Red and green boxes indicate location of enlarged insets for top and bottom B-scan, respectively. Top B-scan shows lower reflectivity of the inner segment–outer segment and outer segment–retinal pigment epithelium junctions (OS/RPE) corresponding to zones of reduced capillary flow signal on OCTA (red lines). The bottom B-scan shows healthy photoreceptor lines corresponding to an area of normal DCP capillary perfusion on OCTA (bottom blue line). Inset B-scans: Orange arrows in enlarged insets point to location of OS/RPE. The top scan (red box) shows indistinct (hyporeflective) OS/RPE junction in an area of reduced capillary flow signal. Bottom scan (green box) shows the normally hyperreflective OS/RPE junction in an area of normal DCP perfusion.

Reduced flow signal around the foveal avascular zone (FAZ), Case 2 (left eye). Optical coherence tomography angiography (OCTA) of the superficial capillary plexus (SCP) (Top left), deep capillary plexus (DCP) (Top middle), and choriocapillaris (Top right). A large retinal vessel in the SCP produces a shadow artifact in the choriocapillaris (yellow arrows). A gap defect artifact related to eye movement produces a dark vertical line on the choriocapillaris (green arrow). (Bottom left) Enlarged inset of DCP from Top middle (green box). Blue lines indicate location of B-scans and red line highlights abnormalities in flow. Red circles highlight areas of decreased capillary flow signal. OCTA reveals an irregular contour of the FAZ, more pronounced in the DCP, with nonflow areas around the FAZ. Low pixel intensity of capillaries compared to surround indicate reduced capillary flow signal at the level of the DCP (red circles). (Bottom right) Optical coherence tomography B-scans showing DCP segmentation boundaries (green lines). Red and green boxes indicate location of enlarged insets for top and bottom B-scan, respectively. B-scans: Orange arrows in enlarged insets point to location of outer segment–retinal pigment epithelium (OS/RPE). The top scan (inset in red box) shows hyporeflectivity and shortening of the OS/RPE junction, as well as decreased reflectivity of the inner segment–outer segment (IS/OS) in an area of reduced capillary flow signal. Bottom scan (green box) shows the normal hyperreflectivity of the IS/OS and OS/RPE junctions in an area of normal DCP perfusion. In addition, comparing the insets side-by-side shows decreased distance between IS/OS and RPE lines, which suggests shortening of the photoreceptors in areas of DCP nonperfusion (red inset box).

Large zones of closure of the capillaries at the level of the deep capillary plexus (DCP), Case 4 (left eye). Optical coherence tomography angiography (OCTA) of the superficial capillary plexus (SCP) (Left) and DCP (Middle). Blue line indicates location of optical coherence tomography (OCT) B-scan and red lines highlight abnormalities in flow. OCTA reveals enlargement of the foveal avascular zone (FAZ), more pronounced at the level of the DCP. OCTA also shows reduced capillary density in both SCP and DCP, appearing as large areas of nonflow. (Right) OCT B-scan (blue box) showing DCP segmentation boundaries (green lines). Red box indicates location of enlarged inset below. B-scan shows reduced reflectivity of the inner segment–outer segment and outer segment–retinal pigment epithelium junctions in areas of decreased capillary density (red lines), with intervening areas of more distinct photoreceptor lines, overlying zones with relatively higher capillary density.

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Antiangiogenic or Corticosteroid Treatment in Patients With Radiation Maculopathy After Proton Beam Therapy for Uveal Melanoma
2. Comparison of Amniotic Membrane Transplantation and Umbilical Cord Serum in Acute Ocular Chemical Burns: A Randomized Controlled Trial
3. Comparison of Latanoprostene Bunod 0.024% and Timolol Maleate 0.5% in Open-Angle Glaucoma or Ocular Hypertension: The LUNAR Study
4. Reply

Stay updated, free articles. Join our Telegram channel

Join