Florian M. Heussen

Retinal vessel diameter measurements by spectral domain optical coherence tomography

PurposeTo describe a spectral domain optical coherence (OCT)-assisted method of measuring retinal vessel diameters.MethodsAll Patients with an OCT circle scan centered at the optic nerve head using a Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) were retrospectively reviewed. Individual retinal vessels were identified on infrared reflectance (IR) images and given unique labels both on IR and spectral domain OCT (SD-OCT). Vessel width and vessel types obtained by IR were documented as ground truth. From OCT, measurements of each vessel, including horizontal vessel contour diameter, vertical vessel contour diameter, horizontal hyperreflective core diameter, and reflectance shadowing width, were assessed.ResultsA total of 220 vessels from 13 eyes of 12 patients were labeled, among which, 194 vessels (88 arteries and 65 veins confirmed from IR) larger than 40 microns were included in the study. The mean vessel width obtained from IR was 107.9 ± 36.1 microns. A mean vertical vessel contour diameter of 119.6 ± 29.9 microns and a mean horizontal vessel contour diameter of 124.1 ± 31.1 microns were measured by SD-OCT. Vertical vessel contour diameter did not differ from vessel width in all subgroup analysis. Horizontal vessel contour diameter was not significantly different from vessel width for arteries and had strong or very strong correlation with vessel width for veins.ConclusionIn our study, vertical vessel contour diameter measured by current commercially available SD-OCT was consistent with vessel width obtained by IR with good reproducibility. This SD-OCT based method could potentially be used as a standard measurement procedure to evaluate retinal vessel diameters and their changes in ocular and systemic disorders.

An easy method to differentiate retinal arteries from veins by spectral domain optical coherence tomography: retrospective, observational case series

BackgroundRecently it was shown that retinal vessel diameters could be measured using spectral domain optical coherence tomography (OCT). It has also been suggested that retinal vessels manifest different features on spectral domain OCT (SD-OCT) depending on whether they are arteries or veins. Our study was aimed to present a reliable SD-OCT assisted method of differentiating retinal arteries from veins.MethodsPatients who underwent circular OCT scans centred at the optic disc using a Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) were retrospectively reviewed. Individual retinal vessels were identified on infrared reflectance (IR) images and given unique labels for subsequent grading. Vessel types (artery, vein or uncertain) assessed by IR and/or fluorescein angiography (FA) were referenced as ground truth. From OCT, presence/absence of the hyperreflective lower border reflectivity feature was assessed. Presence of this feature was considered indicative for retinal arteries and compared with the ground truth.ResultsA total of 452 vessels from 26 eyes of 18 patients were labelled and 398 with documented vessel type (302 by IR and 96 by FA only) were included in the study. Using SD-OCT, 338 vessels were assigned a final grade, of which, 86.4% (292 vessels) were classified correctly. Forty three vessels (15 arteries and 28 veins) that IR failed to differentiate were correctly classified by SD-OCT. When using only IR based ground truth for vessel type the SD-OCT based classification approach reached a sensitivity of 0.8758/0.9297, and a specificity of 0.9297/0.8758 for arteries/veins, respectively.ConclusionOur method was able to classify retinal arteries and veins with a commercially available SD-OCT alone, and achieved high classification performance. Paired with OCT based vessel measurements, our study has expanded the potential clinical implication of SD-OCT in evaluation of a variety of retinal and systemic vascular diseases.

Optical coherence tomographic correlates of angiographic subtypes of occult choroidal neovascularization.

PURPOSE To compare the optical coherence tomographic (OCT) correlates of two previously described angiographic subtypes of occult choroidal neovascularization (CNV). METHODS We retrospectively analyzed 17 consecutive patients with previously untreated occult CNV who underwent both fluorescein angiography (FA) and volume spectral domain (SD)-OCT imaging on the same visit. Planimetric grading was performed on the FA images by certified reading center graders to precisely outline the boundaries of the fibrovascular pigment epithelial detachment (FVPED) and/or late leakage of undetermined source (LLUS) components of occult CNV for each case. In the SD-OCT images, the outer retinal pigment epithelial (RPE) and inner choroidal boundaries were manually segmented on all B-scans to generate a PED thickness map. Fluorescein angiography images were manually registered with the OCT fundus image, and the PED thickness was correlated with the angiographic lesion component present at each corresponding point in the fundus. RESULTS Point-to-point correlations revealed that PED thickness was significantly different in areas of FVPED versus areas of LLUS. Whereas the mean PED thickness in areas of FVPED was 196.1 ± 120.36 μm, it was only 38.42 ± 8.14 μm in areas of LLUS (P = 0.003). Normalized internal reflectivity in areas of FVPED was lower than in areas of LLUS (0.12 ± 0.11 vs. 0.24 ± 0.07; P = 0.03). The integrity or continuity of the overlying RPE band on OCT, however, did not appear to differ between areas of LLUS and FVPED (P = 0.33). CONCLUSIONS Although LLUS and FVPED appear to be distinct angiographic subtypes of CNV, the major difference between the two is the height of the RPE elevation and the internal reflectivity, with areas of LLUS representing much shallower RPE elevations with brighter mean internal reflectivity.

Evaluation of Cystoid Change Phenotypes in Ocular Toxoplasmosis Using Optical Coherence Tomography

Purpose To present unique cystoid changes occurring in patients with ocular toxoplasmosis observed in spectral domain optical coherence tomography (OCT). Methods Forty-six patients (80 eyes) with a diagnosis of ocular toxoplasmosis, who underwent volume OCT examination between January 2005 and October 2012, were retrospectively collected. Review of clinical examination findings, fundus photographs, fluorescein angiograms (FA) and OCT image sets obtained at initial visits and follow-up. Qualitative and quantitative analyses of cystoid space phenotypes visualized using OCT. Results Of the 80 eyes included, 17 eyes (15 patients) demonstrated cystoid changes in the macula on OCT. Six eyes (7.5%) had cystoid macular edema (CME), 2 eyes (2.5%) had huge outer retinal cystoid space (HORC), 12 eyes (15%) had cystoid degeneration and additional 3 eyes (3.75%) had outer retinal tubulation due to age related macular degeneration. In one eye with HORC, the lesion was seen in the photoreceptor outer segment, accompanied by photoreceptor elongation and splitting. Three eyes presented with paravascular cystoid degeneration in the inner retina without other macular OCT abnormality. Conclusions In this study, different phenotypes of cystoid spaces seen in eyes with ocular toxoplasmosis using spectral domain OCT (SD-OCT) were demonstrated. CME presented as an uncommon feature, consistently with previous findings. Identification of rare morphological cystoid features (HORC with/without photoreceptor enlongation or splitting) on clinical examination had provided evidence to previous experimental models, which may also expand the clinical spectrum of the disease. Cystoid degeneration in the inner retina next to the retinal vessels in otherwise “normal” looking macula was observed, which may suggest more often clinical evaluation for those patients. Further studies are needed to verify the relevance of cystoid features seen on SD-OCT in assisting with the diagnosis and management of ocular toxoplasmosis.

Subretinal Fluid in Eyes with Active Ocular Toxoplasmosis Observed Using Spectral Domain Optical Coherence Tomography

Purpose To describe the clinical finding of subretinal fluid (SRF) in the posterior pole by spectral domain optical coherence tomography (SD-OCT) in eyes with active ocular toxoplasmosis (OT). Design Retrospective case series. Participants Thirty-eight eyes from 39 patients with active OT. Methods Eyes with active OT which underwent SD-OCT were reviewed. SRFs in the posterior pole were further analyzed. Main Outcome Measures Presence of SRF; its accompanying features, e.g. retinal necrosis, cystoid macular edema (CME), choroidal neovascularization (CNV); and longitudinal changes of SRF, including maximum height and total volume before and after treatment. Results SRF presented in 45.5% (or 15/33) of eyes with typical active OT and in 51.3% (or 20/39) of eyes with active OT. The mean maximum height and total volume of SRF were 161.0 (range: 23–478) µm and 0.47 (range: 0.005–4.12) mm3, respectively. For 12 eyes with SRF related to active retinal necrosis, SRF was observed with complete absorption after conventional anti-toxoplasmosis treatment. The mean duration for observation of SRF clearance was 33.8 (range: 7–84) days. The mean rate of SRF clearance was 0.0128 (range: 0.0002–0.0665) mm3/day. Conclusions SRF (i.e., serous retinal detachment) is a common feature in patients with active OT when SD-OCT is performed. The majority of SRF was associated with retinal necrosis and reacted well to conventional therapy, regardless of total fluid volume. However, SRF accompanying with CME or CNV responded less favorably or remained refractory to conventional or combined intravitreal treatment, even when the SRF was small in size.