Accurate segmentation of retinal blood vessels is of great significance for diagnosing, preventing and detecting eye diseases. In recent years, the U-Net network and its various variants have reached advanced level in the field of medical image segmentation. Most of these networks choose to use simple max pooling to down-sample the intermediate feature layer of the image, which is easy to lose part of the information, so this study proposes a simple and effective new down-sampling method Pixel Fusion-pooling (PF-pooling), which can well fuse the adjacent pixel information of the image. The down-sampling method proposed in this study is a lightweight general module that can be effectively integrated into various network architectures based on convolutional operations. The experimental results on the DRIVE and STARE datasets show that the F₁-score index of the U-Net model using PF-pooling on the STARE dataset improved by 1.98%. The accuracy rate is increased by 0.2%, and the sensitivity is increased by 3.88%. And the generalization of the proposed module is verified by replacing different algorithm models. The results show that PF-pooling has achieved performance improvement in both Dense-UNet and Res-UNet models, and has good universality.
Algorithms ; Retinal Vessels ; Image Processing, Computer-Assisted

OBJECTIVE: We wanted to investigate the radial peripapillary capillary (RPC) network in patients with Bietti crystalline dystrophy (BCD). METHODS: We compared RPC densities in the disk and different peripapillary regions, obtained using optical coherence tomography angiography in 22 patients with BCD (37 eyes) and 22 healthy subjects (37 eyes). The BCD group was then divided into Stage 2 and Stage 3 subgroups based on Yuzawa staging, comparing the RPC densities of the two. RESULTS: The disk area RPC density was 38.8% ± 6.3% in the BCD group and 49.2% ± 6.1% in the control group ( P < 0.001), and peripapillary region RPC density was significantly lower in the BCD group than in the control group (49.1% ± 4.7% and 54.1% ± 3.0%, respectively, P < 0.001). There were no significant RPC density differences between the tempo quadrant and inside disk of Stages 2 and 3 subgroups; the other areas showed a significantly lower RPC density in Stage 3 than in Stage 2 BCD. CONCLUSION The BCD group RPC density was significantly lower than the control group. The reduction of RPC density in the tempo quadrant occurred mainly in the Stage 1 BCD. In contrast, the reduction of RPC density in superior, inferior, and nasal quadrants occurred mainly in Stage 2.
Adult ; Aged ; Angiography ; Corneal Dystrophies, Hereditary/physiopathology* ; Female ; Humans ; Male ; Microvascular Density ; Microvessels/physiopathology* ; Middle Aged ; Retinal Diseases/physiopathology* ; Retinal Vessels/physiopathology* ; Tomography, Optical Coherence

The existing retinal vessels segmentation algorithms have various problems that the end of main vessels are easy to break, and the central macula and the optic disc boundary are likely to be mistakenly segmented. To solve the above problems, a novel retinal vessels segmentation algorithm is proposed in this paper. The algorithm merged together vessels contour information and conditional generative adversarial nets. Firstly, non-uniform light removal and principal component analysis were used to process the fundus images. Therefore, it enhanced the contrast between the blood vessels and the background, and obtained the single-scale gray images with rich feature information. Secondly, the dense blocks integrated with the deep separable convolution with offset and squeeze-and-exception (SE) block were applied to the encoder and decoder to alleviate the gradient disappearance or explosion. Simultaneously, the network focused on the feature information of the learning target. Thirdly, the contour loss function was added to improve the identification ability of the blood vessels information and contour information of the network. Finally, experiments were carried out on the DRIVE and STARE datasets respectively. The value of area under the receiver operating characteristic reached 0.982 5 and 0.987 4, respectively, and the accuracy reached 0.967 7 and 0.975 6, respectively. Experimental results show that the algorithm can accurately distinguish contours and blood vessels, and reduce blood vessel rupture. The algorithm has certain application value in the diagnosis of clinical ophthalmic diseases.
Algorithms ; Fundus Oculi ; Optic Disk ; ROC Curve ; Retinal Vessels/diagnostic imaging*

In robot-assisted eye surgery, such as retinal vascular bypass surgery, precise positioning of operating points is required. In this study, a binocular vision-based 3D reconstruction method is proposed to locate the incision points on retinal vessels. Vessels in the image were extracted by CLAHE algorithm to remove the influence of background, then stereo matching was performed. Finally, the retinal vessel image was reconstructed by using the principle of parallax in binocular vision. Experimental results show that this method can accurately locate the incision points on retinal vessels and meet the requirements of ophthalmic surgery.
Algorithms ; Humans ; Imaging, Three-Dimensional ; Ophthalmologic Surgical Procedures ; Retinal Vessels/diagnostic imaging* ; Robotic Surgical Procedures ; Vision, Binocular

Retinal vascular function is complex, morphological structure varies from person to person, and is susceptible to vascular diseases and systemic vascular diseases. Its accurate segmentation is of great significance for disease diagnosis and identification. In this paper, a multi-scale matching filtering algorithm is proposed for the uneven size of retinal blood vessels. On the basis of the traditional singlescale Gaussian matching filter, multiscale Gaussian matched filters with two sizes are used to enhance grayscale images. Enhancement is performed, and the superimposed image is binarized using a twodimensional maximum entropy threshold segmentation algorithm. The algorithm is tested in the DRIVE database with sensitivity, specificity and accuracy of 0.803, 0.959, 0.981, respectively. Comparing with the traditional algorithm, the algorithm has high sensitivity, fast running speed and rich details of segmentation results.
Algorithms ; Entropy ; Humans ; Image Processing, Computer-Assisted ; Retinal Vessels/diagnostic imaging*

PURPOSE: To report a case of retinal toxicity after an intravitreal ganciclovir injection to treat acute retinal necrosis in an eye filled with silicone oil.CASE SUMMARY: A 56-year-old male presented with ocular pain and visual loss in his right eye. His best-corrected visual acuity was 20/25, inflammatory cells in the anterior chamber, multiple retinitis lesions and retinal vessel occlusions in the peripheral retina and vitreous opacity were showed. Acute retinal necrosis was suspected, anterior chamber polymerase chain reaction (PCR) test was done. Aciclovir 2,400 mg/day intravenously and ganciclovir 2.0 mg were administered by intravitreal injection. After 4 days, retinitis was worsened and PCR test was positive for varicella zoster virus. Ganciclovir intravitreal injections were increased twice a week. After 16 days, retinal detachment occurred, so scleral encircling, vitrectomy, laser photocoagulation, and silicone oil tamponade were conducted. Ganciclovir 1.0 mg was injected at the end of surgery. The patient's visual acuity decreased to hand motion, and multiple crystal deposits with multiple retinal hemorrhages were observed in the right eye the next day. Visual acuity did not recover and optical coherent tomography showed that the macula was thinned.CONCLUSIONS: Visual loss seemed to be related with the retinal toxicity of ganciclovir. The increased local concentration due to the silicone oil tamponade is thought to have caused the toxicity.
Acyclovir ; Anterior Chamber ; Ganciclovir ; Hand ; Herpesvirus 3, Human ; Humans ; Intravitreal Injections ; Light Coagulation ; Male ; Middle Aged ; Polymerase Chain Reaction ; Retina ; Retinal Detachment ; Retinal Hemorrhage ; Retinal Necrosis Syndrome, Acute ; Retinal Vessels ; Retinaldehyde ; Retinitis ; Silicon ; Silicones ; Visual Acuity ; Vitrectomy

Hyperhomocysteinemia (Hhcy) is an independent risk factor for Alzheimer's disease (AD). Visual dysfunction is commonly found and is positively correlated with the severity of cognitive defects in AD patients. Our previous study demonstrated that Hhcy induces memory deficits with AD-like tau and amyloid-β (Aβ) pathologies in the hippocampus, and supplementation with folate and vitamin B12 (FB) prevents the Hhcy-induced AD-like pathologies in the hippocampus. Here, we investigated whether Hhcy also induces AD-like pathologies in the retina and the effects of FB. An Hhcy rat model was produced by vena caudalis injection of homocysteine for 14 days, and the effects of FB were assessed by simultaneous supplementation with FB in drinking water. We found that Hhcy induced vessel damage with Aβ and tau pathologies in the retina, while simultaneous supplementation with FB remarkably attenuated the Hhcy-induced tau hyperphosphorylation at multiple AD-related sites and Aβ accumulation in the retina. The mechanisms involved downregulation of amyloid precursor protein (APP), presenilin-1, beta-site APP-cleaving enzyme 1, and protein phosphatase-2A. Our data suggest that the retina may serve as a window for evaluating the effects of FB on hyperhomocysteinemia-induced Alzheimer-like pathologies.
Alzheimer Disease ; etiology ; metabolism ; pathology ; therapy ; Amyloid beta-Peptides ; metabolism ; Animals ; Dietary Supplements ; Disease Models, Animal ; Folic Acid ; therapeutic use ; Homocysteine ; Hyperhomocysteinemia ; complications ; metabolism ; pathology ; therapy ; Male ; Rats, Sprague-Dawley ; Retina ; metabolism ; pathology ; Retinal Vessels ; metabolism ; pathology ; Vitamin B 12 ; therapeutic use ; tau Proteins ; metabolism

PURPOSE: We investigated structural changes in the retina by using optical coherence tomography (OCT) in a feline model of retinal degeneration using iodoacetic acid (IAA).METHODS: We examined 22 eyes of 11 felines over 2 years of age. The felines had fasted for 12 hours and were intravenously injected with IAA 20 mg/kg of body weight. OCT (Spectralis OCT) was performed at the point where the ends of the retinal vessels collected in the lateral direction from the optic nerve head and area centralis. Similarly, OCT was performed four times at 1-week intervals following injections, at which point the felines were sacrificed and histologic examinations were performed. Using OCT, the thickness of each layer of the retina was measured.RESULTS: The average body weight of the three male and eight female felines investigated in this study was 1.61 ± 0.19 kg. The mean total retinal thickness of the felines before injection was 221.32 ± 9.82 µm, with a significant decrease in the retinal thickness at 2, 3, and 4 weeks following injections of 186.41 ± 35.42, 174.56 ± 31.94, and 175.35 ± 33.84 µm, respectively (p = 0.028, 0.027, and 0.027, respectively). The thickness of the outer nuclear layer was 57.49 ± 8.03 µm before injection and 29.26 ± 17.87, 25.62 ± 13.88, and 31.60 ± 18.38 µm at 2, 3, and 4 weeks, respectively, after injection (p = 0.028, 0.028, 0.046, respectively).CONCLUSIONS: In a feline model of retinal degeneration using IAA, the total retinal thickness and the thickness of the outer nuclear layer were shown to decrease significantly on OCT.
Angiography ; Body Weight ; Female ; Humans ; Iodoacetic Acid ; Male ; Optic Disk ; Photoreceptor Cells, Vertebrate ; Retina ; Retinal Degeneration ; Retinal Vessels ; Retinaldehyde ; Tomography, Optical Coherence

BACKGROUND: To evaluate the association between retinal artery occlusion (RAO) and subclinical coronary artery disease (CAD). METHODS: We studied 41 patients with non-arteritic RAO without any history or symptoms of CAD, who had undergone coronary computed tomographic angiography (CCTA) for systemic atherosclerotic evaluation between 2007 and 2012. The age- and gender-matched control group comprised 4-fold subjects who were randomly selected from asymptomatic subjects who underwent CCTA during general health evaluation. Medical records and CCTA findings were compared between RAO patients and control groups. Multiple logistic regression analysis was carried out to assess the risk factors associated with CAD. RESULTS: Cardiovascular risk factors were not significantly different between RAO patients and control groups. RAO patients showed higher coronary artery calcium score than did control subjects (267.9 ± 674.9 vs. 120.2 ± 289.5). On CCTA, the prevalence of obstructive CAD (diameter stenosis ≥ 50%) in RAO patients was significantly higher than that in controls (29% vs. 15%; odds ratio [OR], 3.0). RAO patients demonstrated a significantly higher segment-involvement score (SIS) (2.6 ± 3.0 vs. 1.6 ± 2.4) and segment-stenosis score (SSS) (3.6 ± 4.8 vs. 2.0 ± 3.3) than did controls. After adjustment of associated factors, RAO showed significant association (OR, 3.0) with obstructive CAD and extensive CAD (SIS > 4: OR, 2.8; SSS > 8: OR, 3.4). CONCLUSION: Patients with RAO had a higher prevalence of subclinical obstructive CAD with a more extensive and heavier burden of coronary artery plaques than did age- and gender-matched controls. Physicians should understand the potential risk of CAD in RAO patients.
Angiography ; Atherosclerosis ; Calcium ; Constriction, Pathologic ; Coronary Artery Disease ; Coronary Vessels ; Humans ; Logistic Models ; Medical Records ; Odds Ratio ; Prevalence ; Retinal Artery Occlusion ; Retinal Artery ; Retinaldehyde ; Risk Factors

PURPOSE: To describe a patient who presented with central serous chorioretinopathy after 2 months of tadalafil administration without any other underlying disease or medication. CASE SUMMARY: A 49-year-old male patient was transferred from a local clinic with metamorphopsia and decreased visual acuity in the right eye. His visual acuity was 6/20 in the right eye and 18/20 in the left eye. The fundus examination showed a large serous detachment between the superior and inferior blood vessel arcades in the right retina. In his medical history, he used tadalafil three times a week for 2 months. His medication was then stopped, and a follow-up examination was scheduled. After 2 months, a fundus examination showed resolution of the subretinal fluid, and his corrected visual acuity recovered to 20/20. CONCLUSIONS: Tadalafil (Cialis®) is a phosphodiesterase (PDE)-5 inhibitor and predominantly prescribed for the treatment of erectile dysfunction. PDE–5 inhibitors may be potent vasodilators in the retina and choroid, and may induce choroidal vessel engorgement leading to leakage across the retinal pigment epithelium and accumulation of subretinal fluid in selected patients. When making a diagnosis as central serous chorioretinopathy, the physician should confirm the causative drugs that are easy to miss, by performing a thorough review of the patient's medical history and promptly terminating the causative drugs.
Blood Vessels ; Central Serous Chorioretinopathy ; Choroid ; Diagnosis ; Erectile Dysfunction ; Follow-Up Studies ; Humans ; Male ; Middle Aged ; Retina ; Retinal Pigment Epithelium ; Subretinal Fluid ; Tadalafil ; Vasodilator Agents ; Vision Disorders ; Visual Acuity