Evaluation of Automated Measurement of Macular Ischemic Changes in Retinal Vein Occlusion With Optical Coherence Tomography Angiography.

OBJECTIVE: The foveal avascular zone (FAZ) is altered in patients with retinal vein occlusion (RVO) and correlates inversely with visual acuity. Optical coherence tomography angiography (OCTA) is an imaging tool to visualize FAZ safely and easily. Automated measurements can facilitate interpretation of OCTA images. In this comparative cross-sectional study, we compare the results of manual measurement of the FAZ with automated measurement by built-in application (Metrix). METHODS: The study included patients with RVO who underwent OCTA. Manual measurement was compared with automated evaluation by Metrix in 3 mm x 3 mm and 6 mm x 6 mm scan sizes and correlations of the circularity, circumference, and size of the FAZ were calculated. RESULTS: Forty-seven eyes were included in the study. A reliable measurement result in both Metrix 3 mm x 3 mm and 6 mm x 6 mm was found in only 25 of 47 eyes. The mean FAZ in these eyes by manual measurement was 0.50 mm2 compared with 0.20 mm2 and 0.24 mm2, respectively, by automated measurement. A statistically significant inverse correlation was found in both the automated 3 mm x 3 mm and 6 mm x 6 mm measurements for FAZ circumference with FAZ circularity but not FAZ area. CONCLUSION: The two automated measurements showed no significant bias regarding the size of the FAZ, but the plausibility of the data should be checked on a case-by-case basis. The manual measurements were higher, indicating limited agreement of manual and automated measurements. The information on circularity can point to ischemic maculopathy early in the course of the disease. [Ophthalmic Surg Lasers Imaging Retina 2023;54:462-469.].

NOVEL TECHNIQUE FOR INTRAOCULAR FOREIGN BODY REMOVAL: Magnetized Disposable Microforceps. A Systematic Approach and First Clinical Result.

PURPOSE: To verify whether disposable microforceps can be magnetized to atraumatically attract and then grasp intraocular foreign bodies. An effective magnetization protocol was developed. The clinical relevance was tested, and a first practical application was performed. METHODS: The magnetic flux density (MFD) of a bar magnet and an electromagnet was measured. Steel screws were used to determine the magnetization protocol. Disposable microforceps was magnetized, MFD generated at the tip was measured, and the weight that can be lifted was tested. Foreign body removal with such forceps was performed. RESULTS: The electromagnet MFD was much higher than the bar magnet. The most effective magnetization protocol was to pass the screw from the end along the shaft and back over the electromagnet. Magnetized microforceps had a 7.12 mT change in MFD at the tip. Steel balls up to 87 mg could be lifted in buffered saline solution. In clinical use, the intraocular foreign body could be attracted and grasped safely. CONCLUSION: Disposable microforceps can be easily and inexpensively magnetized. The achievable MFD is clinically relevant to attract typical intraocular foreign bodies. An electromagnet is best suited for this purpose. With such prepared forceps, foreign bodies can be attracted atraumatically and grasped securely.

Optical Coherence Tomography Angiography Findings in Proliferative Diabetic Retinopathy.

PURPOSE: To characterize preretinal neovascularizations (NV) and their corresponding branching routes in proliferative diabetic retinopathy (PDR) with optical coherence tomography angiography (OCTA) and compare the findings with fluorescein angiography (FA). METHODS: In patients with PDR, angiograms were acquired with spectral-domain OCTA (CIRRUS 5000, OCTA AngioPlexTMCarl Zeiss Meditec, Inc.) and FA (Zeiss FF450PlusIR fundus camera or Spectralis HRA-OCT SLO, Heidelberg Engineering Inc.) and were consecutively evaluated. Neovascularization of the disc (NVD) and neovascularization elsewhere (NVE) were analyzed with 6 × 6 and 8 × 8 mm OCTA flow images and B-scans with flow registration. Segmentations of the vitreoretinal interface (VRI) and superficial retina were performed for analysis. Two independent investigators examined OCTA findings and compared them to corresponding FA. RESULTS: Forty-two eyes of 30 patients with PDR were analyzed. A total of 76 NV with their corresponding proliferation routes were visualized and characterized, with 55 (72.4%) proliferating along the posterior hyaloid membrane (PHM), 14 (18.4%) along the epiretinal membrane, and 7 (9.2%) along the fibrovascular membrane. The posterior vitreous was partially detached in 37 of 42 eyes (88.1%), completely detached in 1 of 42 eyes (2.4%), and adherent in 1 of 42 eyes (2.4%). In 38 of 42 cases, OCTA was superior (n = 23) or equivalent (n = 15) to FA in detecting NV and provided a more detailed information of the neovascular vessels. In 4 of 42 study eyes, OCTA was inferior to FA. CONCLUSIONS: OCTA is a useful tool to detect NV in PDR. In comparison to FA, OCTA has the advantages that it is noninvasive and the image capture takes only seconds. We were able to identify all NV and characterize their corresponding proliferation routes in the VRI, the superficial retina slab, or the B-scan with flow registration. Through evading the masking effect of dye leakage in FA, OCTA is capable of better visualization of NV. FA, however, remains essential for the detection of all NV, since OCTA supplies a smaller detection field. Additionally, we identified the PHM as the main proliferating route of diabetic NV (72.4%), marking it as an important structure for sprouting vessels in neoangiogenesis in PDR.

Quantity and quality of image artifacts in optical coherence tomography angiography.

OBJECTIVE: To analyze quality and frequency of OCTA artifacts and to evaluate their impact on the interpretability of OCTA images. DESIGN: 75 patients with diabetic retinopathy (DR), retinal artery occlusion (RAO), retinal vein occlusion (RVO), or neovascular age-related macular degeneration (nAMD) and healthy controls were enrolled in this cross-sectional study in the outpatient department of a tertiary eye care center. METHODS: All participants underwent an OCTA examination (spectral domain OCT Cirrus 5000 equipped with the AngioPlex module). OCTA scans were analyzed independently by two experienced ophthalmologists. Frequency of various artifacts for the entire OCTA scan and for different segmentation layers and the grading of OCTA interpretability were investigated. RESULTS: The analysis of 75 eyes of 38 women and 37 men between 24 and 94 years were included. Six eyes had no retinal disease, 19 eyes had nAMD, 16 had DR, 19 eyes had RVO, and 15 eyes showed RAO. A macular edema (ME) was present in 40 of the diseased eyes. Projection artifacts occurred in all eyes in any structure below the superficial retinal vessel layer, segmentation and motion artifacts were found in 55% (41/75) and 49% (37/75) of eyes, respectively. Other artifacts occurred less frequently. Segmentation artifacts were significantly more frequent in diseased than in healthy eyes (p<0.01). Qualitative assessment of OCTA images was graded as excellent in 65% and sufficient in 25% of cases, adding up to 91% images deemed acceptable for examination. Presence of ME was associated with a significantly poorer interpretability (p<0.01). CONCLUSION AND RELEVANCE: Various artifacts appear at different frequencies in OCTA images. Nevertheless, a qualitative assessment of the OCTA images is almost always possible. Good knowledge of possible artifacts and critical analysis of the complete OCTA dataset are essential for correct clinical interpretation and determining a precise clinical diagnosis.

Advanced Non-Destructive Ocular Visualization Methods by Improved X-Ray Imaging Techniques.

Due to limited X-ray contrast, the use of micro-CT in histology is so far not as widespread as predicted. While specific staining procedures-mostly using iodine-address this shortcoming, long diffusion times restrict its use in the often time-constrained daily routine. Recently, a novel staining protocol has been proposed using a biochemical preconditioning step, which increases the permeability of the cells for the staining agent. This could enable the imaging of entire organs of small mammals at a yet unmatched image quality with reasonable preparation and scan times. We here propose an adaptation of this technique for virtual ophthalmology and histology by volumetrically assessing both human and porcine eyes. Hereby, we demonstrate that (contrast-enhanced) micro-CT can outperform conventional histology in the assessment of tumor entities, as well as functioning as a supplementary tool for surgeons in the positioning of intraocular implants in-vitro and as a general assessment tool for ophthalmologic specimens.