Possibilities of OCT Angiography for Diagnosis of Anterior Ischemic Optic Neuropathy: Parameters of the Ganglion Cell Complex, Optic Disc and Peripapillary Retina

Purpose. Study the thickness of periapillary retina, ganglion cell complex and optic disc parameters in patients with nonarteritised anterior ischemic optic neuropathy using the spectral OCT angiography. Material and Methods. We examined 17 people (17 eyes) with unilateral non-arteritised anterior ischemic optic neuropathy (no more than 30 days from the appearance of complaints), the average age was 64.1±8.1 years. The control group consisted of 37 volunteers. All the subjects were treated with spectral OCT angiography on RTVue XR Avanti device (Optovue Inc., USA). Results. In patients with non-arteritised anterior ischemic optic neuropathy, compared to the control group, there was a statistically significant increase in the average thickness of periapillary retina nerve fiber layer from 136 to 403 µm, an increase in optic disc area and neuroretinal belt (p < 0.0001) and the absence of cupping (Cup Volume = 0). A decrease in average thickness of ganglion cell complex was found in 8 out of 17 patients, while all patients showed increases in FLV (p=0.008) and GLV (p=0.036). A direct correlation relationship between FLV (r=0.64; p<0.05) and GLV (r=0.51; p<0.05) was found, as well as a moderate negative correlation relationship between uncorrected visual acuity (r=-0.58; p<0,05), moderate direct correlation relationship between average thickness of periapillary retina nerve fiber layer and thickness of ganglion cell complex (r=0.68; p<0,05), and high inverse correlation relationship between FLV (r=-0.77; p<0,05) and GLV (r=-0.76; p<0,05). Conclusion. A comprehensive analysis of thickness of periapillary retina nerve fiber layer and parameters of ganglion cell complex using spectral OCT angiography may allow for a more accurate detection of early retinal structural abnormalities and the timely commencement of conservative therapy to preserve functional parameters. Key words: spectral OCT angiography, anterior ischemic optic neuropathy, ganglion cell complex, optic disc.

Needle tip force estimation by deep learning from raw spectral OCT data

Purpose Needle placement is a challenging problem for applications such as biopsy or brachytherapy. Tip force sensing can provide valuable feedback for needle navigation inside the tissue. For this purpose, fiber-optical sensors can be directly integrated into the needle tip. Optical coherence tomography (OCT) can be used to image tissue. Here, we study how to calibrate OCT to sense forces, e.g., during robotic needle placement. Methods We investigate whether using raw spectral OCT data without a typical image reconstruction can improve a deep learning-based calibration between optical signal and forces. For this purpose, we consider three different needles with a new, more robust design which are calibrated using convolutional neural networks (CNNs). We compare training the CNNs with the raw OCT signal and the reconstructed depth profiles. Results We find that using raw data as an input for the largest CNN model outperforms the use of reconstructed data with a mean absolute error of 5.81 mN compared to 8.04 mN. Conclusions We find that deep learning with raw spectral OCT data can improve learning for the task of force estimation. Our needle design and calibration approach constitute a very accurate fiber-optical sensor for measuring forces at the needle tip.

Sensitivity and Specificity of Spectral Oct in Patients with Early Glaucoma

The study examines the sensitivity and specificity of spectral OCT in detecting early glaucoma. The aim was to evaluate data obtained by RNFL analysis in 4 observed quadrants and to compare it with the resulting diagnosis of glaucoma neuropathy determined subsequently on the basis of changes in the visual field. This concerns a retrospective study numbering 31 probands who underwent OCT examination at our centre in the period from 2008 to 2017. Test statistics demonstrated sensitivity of OCT examination (specific RNFL analysis) of 63.64% and specificity of 90%. The used ROC (receiver operating characteristic curve) test showed an AUC (area under curve) value of 0.734 on a statistically significant level of p = 0.0097. We therefore found that the instrument Spectral OCT SLO, with the aid of RNFL analysis, was effective in determining probands in whom development of glaucoma pathology was subsequently confirmed.

Evaluation of the Results of Glaucoma Surgery Using Optical Coherent Tomography (Literature Review)

Optical coherence tomography (OCT) is a noncontact method that provides two-dimensional (three-dimensional for some models) highresolution images of the anterior eye segment, with an axial resolution in the range from 3 to 20 µm. Two OCT diagnostics platforms are available: time-domain and spectral OCT. OCT provides a qualitative and quantitative assessment of the most important structures involved in the glaucoma pathogenesis: the state of the optic nerve head, the thickness of the nerve fiber layer, the anterior chamber angle and the trabecular apparatus. The OCT advantage is the ability to visualize surgically formed outflow tracts in the early postoperative period after antiglaucoma surgery. The OCT studies of the antiglaucomatous surgery zone are presented in detail in the literature, namely, the assessment of such biometric parameters of filtering bleb (FB) as wall thickness and reflectivity, radial length and height. According to the literature, the presence of a multi-layer filtration cushion 6 months after the operation indicates a favorable prognosis for the duration of the hypotensive effect of the operation. Such signs as low reflectivity of the filtration cushion wall and the presence of episcleral fluid are in most cases associated with a successful outcome of trabeculectomy. OCT studies of a filtration cushion after trabeculectomy make it much easier to choose an area for revision and nidling. In addition, OCT is used to assess anatomical features in the field of surgical intervention with drains and drainage devices. Currently OCT is widely implemented at the prehospital stage, however, engineers did not stop at the achieved level and carried out the integration of spectral OCT with an operating microscope. The possibilities of intraoperative imaging with cataract phacoemulsification (FEC) and trabeculectomy, implantation of the Ahmed valve, reconstruction of the anterior chamber angle, revision of the filtration bag and nidlinge are described in the literature. Conclusion. OCT is a very valuable method of intravital imaging of the antiglaucoma operation zone. It allows assessing the level of retention of intraocular fluid, determining the functional activity, the location of drains and drainage devices both in the early and late postoperative period.

Time-domain versus spectral-domain optical coherence tomography: Findings in acute central serous chorioretinopathy*

Aims: To evaluate the optic coherence tomographic (OCT) features in acute central serous chorioretinopathy (ACSC) with time-domain or spectral-domain OCT at Dokuz Eylul University, Department of Ophthalmology, Izmir, Turkey.Subjects and Methods: Clinical data from the Department of Ophthalmology (of Dokuz Eylul University) including fluorescein angiography (FA) and OCT findings of 39 eyes of 34 patients with ACSC were retrospectively analyzed. Eleven eyes (Ntd =11) were examined with time-domain (Stratus OCT 3, Version 4.0) and 28 eyes (Nsd =28) with spectral-domain OCT (Heidelberg HRA2 Spectralis).Results: Of the sample of 34, twenty-four patients (70.6%) were men and 10 women (29.4%). FA demonstrated smokestack type hyperfluorescence in five eyes (12.8%), a round ink blot type hyperfluorescence in 32 eyes (82.1%) and diffuse leak-age in two (5.1%) eyes. Twenty-five eyes (64.1%) had only one leakage site, five eyes (12.8%) hadtwo leakage sites and nine eyes (23.1%) had three or more leakage sites. Detachment of the neurosensory retina was detected in 37 eyes (94.9%, 11 eyes with Stratus OCT and 26 eyes with Spectral OCT). Pigment epithelial detachment (PED) was detected in nine eyes (23.1%, one eye with Stratus OCT and eight eyes with Spectral OCT). Protrusion of the RPE layer was detected in 10 eyes (25.6%, all eyes with Spectral OCT). Both fibrinous exudates and bridging between the neurosensory retina and PED was detected with Spectral OCT in four eyes (10.2%). Retinal dipping was detected with Spectral OCT in two eyes (5.1%).Conclusion: Spectral-domain OCT seems to yield more information and depicts RPE layer protrusion, fibrinous exudates and bridging better when compared to conventional time-domain OCT. (S Afr Optom 2012 71(4) 166-170)