Assessment of Peritoneal Membrane Arteriolar Structure in Conjunction with Traditional Cardiovascular System Evaluation in Chronic Kidney Disease (CKD) Stage 5 Patients.

BACKGROUND/AIMS: Cardiovascular complications are responsible for increased mortality and morbidity in chronic kidney disease (CKD) patients. Functional and structural changes of peritoneal membrane are reported in CKD patients both on conservative treatment and on renal replacement therapy (RRT). The aim of the study was to assess the structure of peritoneal membrane small arteries (precapillary arterioles) in diabetic and non-diabetic CKD stage 5 patients before initiation of peritoneal dialysis (PD) and evaluate its relationship with heart and large arteries abnormalities and with selected biochemical parameters. METHODS: Evaluation of 42 CKD stage 5 patients before starting PD. Diabetic (n=26) and non-diabetic (n=16) patients were compared. Peritoneal membrane samples were taken during Tenckhoff catheter insertion. Histopathological evaluation of peritoneal precapillary arterioles (arteriolar evaluation) with measurement of wall thickness (WT) and calculation of lumen/vessel (L/V) ratio was performed in each patients. Echocardiography, intima media thickness (IMT), pulse wave velocity (PWV), ambulatory blood pressure monitoring (ABPM) and biochemical parameters assessment: serum albumin (SA), total cholesterol (TCH), hemoglobin (Hgb), parathormone (PTH), serum calcium (Ca), serum phosphorus (P), transferrin saturation (TSAT%), C-reactive protein (CRP) were performed in each participant. RESULTS: There were no statistically significant differences in peritoneal membrane arteriolar indices - wall thickness (WT) and L/V ratio between investigated groups. There was statistically significant higher PWV value in diabetic patients. There were no statistically significant differences in echocardiographic indices, IMT, laboratory data in analyzed groups. There were some linear correlations between: PWV vs IMT (R=0,84; p=0,0006); PWV vs PP (R=0,58; p=0,03) in non-diabetic and linear correlation between: PWV vs age (R=0,75; p=0,02); WT vs DP (R=-0,93; p=0,001); WT vs DBP ( R=0,64; p=0,04) in diabetic group. CONCLUSION: Peritoneal membrane arteriolar damage seems to be an integrated part of cardiovascular system damage in CKD stage 5 patients.

Blood flow dynamics in the snake spectacle.

The eyes of snakes are shielded beneath a layer of transparent integument referred to as the 'reptilian spectacle'. Well adapted to vision by virtue of its optical transparency, it nevertheless retains one characteristic of the integument that would otherwise prove detrimental to vision: its vascularity. Given the potential consequence of spectacle blood vessels on visual clarity, one might expect adaptations to have evolved that mitigate their negative impact. Earlier research demonstrated an adaptation to their spatial layout in only one species to reduce the vessels' density in the region serving the foveal and binocular visual fields. Here, we present a study of spectacle blood flow dynamics and provide evidence of a mechanism to mitigate the spectacle blood vessels' deleterious effect on vision by regulation of blood flow through them. It was found that when snakes are at rest and undisturbed, spectacle vessels undergo cycles of dilation and constriction, such that the majority of the time the vessels are fully constricted, effectively removing them from the visual field. When snakes are presented with a visual threat, spectacle vessels constrict and remain constricted for longer periods than occur during the resting cycles, thus guaranteeing the best possible visual capabilities in times of need. Finally, during the snakes' renewal phase when they are generating a new stratum corneum, the resting cycle is abolished, spectacle vessels remain dilated and blood flow remains strong and continuous. The significance of these findings in terms of the visual capabilities and physiology of snakes is discussed.

Genomewide molecular and biologic characterization of biomembrane formation adjacent to a methacrylate spacer in the rat femoral segmental defect model.

OBJECTIVES: This study focuses upon the morphologic and molecular features of the layer of cells, termed the "biomembrane," which forms around methacrylate spacers in bone segmental defects. The objective of this research was to assess the biomembrane formed in a novel rodent femoral segmental defect model at 4, 8, and 16 weeks with histologic and molecular studies. METHODS: Following Institutional Animal Care and Use Committee approval, a segmental defect was created in the rat femur and stabilized with the AO LockingRatNail and analyzed at 4, 8, and 16 weeks postsurgery using digital radiologic imaging, morphological and immunohistochemical studies, and genomewide gene expression studies employing microarray analysis. RESULTS: The biomembrane formed around the methacrylate spacer was rich in vasculature, which showed vascular endothelial growth factor immunolocalization. The biomembrane supported development of foci of bone and cartilage within it. Bone morphogenetic protein 2 immunolocalization and gene expression were positive within developing osseous and chondrocyte foci. Microarray analysis showed significant expression of key genes related to bone and cartilage formation and angiogenesis. CONCLUSIONS: This rat bone model was effective in creation of the biomembrane. Bone and cartilage foci were formed within the vascularized biomembrane with associated expression of genes critical for bone and cartilage development/formation and vascularization. The polymethyl methacrylate-induced biomembrane offers an exciting potential solution for segmental defects; the biomembrane, may act as a receptive bed and also serve as a source for mesenchymal stem cells, which could be recruited/directed for the healing process.

Morphological features and clinical significance of epidural membrane in the cervical spine.

STUDY DESIGN: A prospective clinical study. OBJECTIVE: To elucidate the histomorphological features and clinical significance of the epidural membrane (EM) in the cervical spine based on operative and histological findings. SUMMARY OF BACKGROUND DATA: The anatomical features of the EM have been mostly discussed on the basis of cadaver studies in the whole spine. However, the histomorphological features and clinical significance of the EM in the cervical spine based on operative findings have never been reported. METHODS: Eighty-seven patients with cervical spondylotic myelopathy who had undergone an expansive open-door laminoplasty under microscopy were evaluated with a more than 2-year follow-up period. The most damaged spinal segment was determined in each patient from the preoperative neurological and image findings along with the remaining symptoms at follow-up. The morphological features of the EM were observed and recorded in each patient during decompression. For histology, specimens of common and remarkable types of the EM obtained from 16 patients were examined. RESULTS: The age at surgery averaged 64.5 years; there were 58 men and 29 women. With regard to the most damaged spinal segment, there were 14 cases at the C3-C4 level, 37 at the C4-C5 level, 32 at the C5-C6 level, and 4 at the C6-C7 level. The EM was an adipo-fibro-vascular tissue with various histomorphologies, blending with the periradicular sheath. Some EMs showed notable findings: obstructing dural tube expansion (13 cases, 14.9%), compressing a nerve root or disturbing its mobility (4 cases, 4.6%), and the combined type (1 case, 1.1%). All of them were located at approximately the most damaged spinal segment. In addition, some EMs had interesting histological features, such as harboring many small arteries, calcified debris, and metaplastic bone fragments. CONCLUSION: The EM can develop into remarkable structures with spondylosis and aging in patients with cervical spondylotic myelopathy, affecting surgical outcomes as well as successful decompression procedures. A sound understanding of the histomorphological features of the EM is required to obtain satisfactory surgical outcomes in the limited field afforded by minimally invasive surgery.

Effects of bevacizumab on the neovascular membrane of proliferative diabetic retinopathy: reduction of endothelial cells and expressions of VEGF and HIF-1α.

PURPOSE: Anti-vascular endothelial growth factor (VEGF) agents have recently been used intravitreally during the perioperative period for proliferative diabetic retinopathy (PDR). However, the mechanism of theraputic effects of the agents remains unclear. This study aimed to investigate the effects of intravitreal bevacizumab (IVB) on retinal vascular endothelial cells and expressions of VEGF and hypoxia inducible factor-1α (HIF-1α) in PDR. METHODS: Twenty-four patients with PDR were enrolled and randomized to two groups. Twelve eyes of 12 patients of each group received either an intravitreal injection of 1.25 mg bevacizumab or a sham injection 6 days before vitrectomy. Neovascular membranes (NVMs) were collected during pars plana vitrectomy. The numbers of vascular endothelial cells in the NVMs were counted after staining with hematoxylin and eosin and von Willebrand. The expressions of VEGF and HIF-1α in the NVMs were detected through immunohistochemistry. Ten epiretinal membrane specimens from patients with proliferative vitreoretinopathy (PVR) without IVB treatment were set as an additional control. RESULTS: The number of vascular endothelial cells in NVMs of the IVB pretreated group was significantly lower than that of the sham group (21.5±3.94 versus 41.33±7.44, p=0.003). The IVB pretreated group also showed significantly lower levels of VEGF and HIF-1α in NVMs than those of the sham group (P(HIF-1α)=0.02, P(VEGF)<0.001). A stepwise regression analysis showed that IVB was a significant negative predictor for the numbers of vascular endothelial cells (ß=-0.89, p<0.001) and the expressions of VEGF (ß=-0.85, p<0.001) and HIF-1α (ß=-0.64, p=0.001) in PDR patients. Epiretinal membranes of the PVR group showed negative staining of VEGF and HIF-1α. CONCLUSIONS: Pretreatment with IVB in patients with PDR significantly decreased vascular endothelial cells and expressions of VEGF and HIF-1α, which further supports preoperative use of IVB in such patients.

Congenital fibrovascular pupillary membranes: clinical and histopathologic findings.

PURPOSE: To report the clinical and histopathologic findings associated with congenital fibrovascular pupillary membranes. DESIGN: Case series. PARTICIPANTS: Seven infants were included, 6 with a unilateral congenital pupillary membrane and 1 with classic persistent fetal vasculature (PFV). METHODS: Patients underwent a membranectomy, pupilloplasty, or lensectomy. Histopathologic examination was performed on the excised membranes. MAIN OUTCOME MEASURES: Visual acuity and pupil size. RESULTS: Four of the 6 patients with a unilateral congenital pupillary membrane had 1 or more recurrences after a membranectomy and pupilloplasty. The most recent pupil size ranged from 2 to 5 mm in the affected eye. When last tested, the vision in the affected eye was excellent in 4 of the 6 patients. The 2 patients without recurrences of the pupillary membranes underwent multiple iris sphincterotomies at the time of the initial surgery. Histopathologic examination of 2 primary pupillary membranes showed fibrovascular tissue that did not stain for neuron-specific enolase. Smooth muscle actin was only present in vascular walls. In contrast, histopathology of a recurrent pupillary membrane revealed collagenized fibrovascular tissue that was immunoreactive for smooth muscle actin. Finally, histopathology of the retrolenticular membrane excised from an infant with classic PFV was similar to the latter aside from hypercellularity. CONCLUSIONS: Congenital fibrovascular pupillary membranes in infants are likely a variant of PFV that may recur if incompletely excised. The risk of these membranes recurring may be reduced by excising as much as the membrane as possible and enlarging the pupil with iris sphincterotomies. A lensectomy should be avoided if possible.

Angiogenesis pattern of native and cross-linked collagen membranes: an immunohistochemical study in the rat.

The aim of the present study was to immunohistochemically evaluate angiogenesis pattern of native and cross-linked collagen membranes after subcutaneous implantation in rats. Five commercially available and three experimental membranes (VN) were included: (1) BioGide (BG), (2) BioMend (BM), (3) BioMend Extend (BME), (4) Ossix (OS), (5) TutoDent (TD), and (6-8) VN(1-3). Specimens were randomly allocated in unconnected subcutaneous pouches (n=4) separated surgically on the back of 40 wistar rats, which were divided into five groups (2, 4, 8, 16, and 24 weeks), including eight animals each. Pattern of angiogenesis was labelled using primary mouse monoclonal antibody to transglutaminase II. For each membrane, the period of time, needed for a complete and homogeneous transmembraneous vascularization, was assessed immunohistomorhometrically. Differences between the membranes were found regarding the initial pattern of transmembraneous angiogenesis, as evaluated 2 weeks following implantation. Mean cross- and longitudinal-sectional area of blood vessels (%) was highest for VN(3) (5.27+/-2.73), followed by BG (2.45+/-0.88), VN(1) (2.07+/-0.29), VN(2) (1.91+/-0.55), TD (1.44+/-0.53), BME (0.35+/-0.29) and BM (0.25+/-0.4). In contrast to BG and VN(1-3), BM, BME and TD exhibited a homogeneous transmembraneous formation of blood vessels merely 4-8 weeks following implantation. OS, however, exhibited no signs of angiogenesis throughout the whole study period. Within the limits of the present study, it may be concluded that pattern of transmembraneous angiogenesis markedly differs among the membranes investigated.

Effects of peritoneal dialysis on the vascular bed of peritoneal membrane.

The vascularization of the peritoneal membrane is a key factor in the effectiveness of peritoneal dialysis as a dialysis modality. Over the last years, our understanding of how the peritoneal vasculature reacts to instillation of peritoneal dialysate has substantially improved. The changes in the structure of the peritoneal function over time on peritoneal dialysis as found in functional tests has been confirmed in biopsy studies performed on patients. These show both neoangiogenesis and fibrosis as the underlying morphological changes contributing to these phenomena. A thorough understanding of the biological processes involved in these alterations will be the clue for improvement of the treatment and a key to develop strategies to avoid these deformations.

Hemodynamic effects of peritoneal dialysis solutions on the rat peritoneal membrane: role of acidity, buffer choice, glucose concentration, and glucose degradation products.

Conventional peritoneal dialysis fluids (PDF) are unphysiologic because of their hypertonicity, high glucose and lactate concentrations, acidic pH, and presence of glucose degradation products (GDP). Long-term exposure to conventional PDF may cause functional and structural alterations of the peritoneal membrane. New PDF have a neutral pH, a low GDP content, and contain bicarbonate or lactate as the buffer. Intravital microscopy was used to analyze the vasoactive effects of conventional and new PDF on the rat peritoneal membrane. A conventional, acidic pH, lactate-buffered 4.25% glucose PDF induced maximal vasodilation of mesenteric arteries, resulting in a doubling of the arteriolar flow and a 20% increase of the perfused capillary length per area. The hemodynamic effects of conventional PDF were similar after pH-adjustment with NaOH, indicating that acidity per se is not essential for the changes. Superfusion by a pH-neutral, lactate-buffered PDF with low GDP content caused only a transient arterial vasodilation despite continuous exposure, with a commensurate effect on arteriolar flow and capillary recruitment. Application of a pH-neutral, bicarbonate-buffered PDF with low GDP content did not affect the hemodynamic parameters. Resterilization of the bicarbonate solution increased GDP levels and completely restored the vasodilatory capacity. The corresponding 1.5% glucose PDF induced similar but less pronounced changes. Conventional PDF have important vasoactive effects on the peritoneal circulation, mainly because of the presence of GDP and transiently because of high lactate concentrations. Capillary recruitment may increase effective peritoneal vascular surface area. In addition, chronic vasodilation may induce structural adaptations in the blood vessel wall, contributing to vascular sclerosis. PDF with reduced GDP content induce no major hemodynamic effects and may thus have the potential to better preserve peritoneal vascular integrity.

Surgical removal of subfoveal choroidal neovascular membranes in high myopia.

BACKGROUND: A study was carried out to elucidate the anatomical and functional outcome after surgical excision of subfoveal choroidal neovascular membranes in high myopia. METHODS: Sixty-five patients with high myopia (> or =6 diopters), well-defined subfoveal neovascular membranes on fluorescein angiography and preoperative visual acuity < or =20/100 were selected for surgery. A standardized surgical technique was used in all cases, by a single surgeon. The main outcomes assessed were Snellen visual acuity, surgical retinal pigment epithelium defect and postoperative perfusion of the choriocapillaris. Multifactor analysis of variance and chi-square/Fisher's exact test statistics were used to assess the association between patients' pre- and postoperative characteristics and outcome measures. RESULTS: Follow-up ranged from 6 to 48 months (mean 16 months). Mean postoperative visual acuity (0.18) was significantly better than mean preoperative visual acuity (0.09). Visual acuity improved by at least two lines in 29 eyes (45%) and was unchanged in 24 (37%). Overall, 43 eyes (66%) had visual acuity of 20/200 or better and 15 (23%), 20/60 or better. Predictive factors with a significant effect on final visual acuity were mean visual acuity, preoperative status of retinal pigment epithelium and postoperative perfusion of the choriocapillaris. Postoperative perfusion was detected in 31 (48%) of the total 65 eyes and in 12 (67%) of the 18 eyes with normal retinal pigment epithelium at baseline. The mean postoperative retinal pigment epithelium defect was 4.6 times larger than the original neovascular membrane. In selected patients, SLO macular scotometry showed areas of retained retinal sensitivity within the atrophic scar. CONCLUSION: The natural history of subfoveal neovascularization in high myopia is rarely visually restorative. By contrast, surgical excision of the membranes is feasible and may restore visual acuity in selected patients. This therapeutic approach merits a formal multicenter clinical trial.

Aqueous vascular endothelial growth factor and basic fibroblast growth factor decrease during regression of rabbit pupillary membrane.

We studied the roles of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in the aqueous during regression of the pupillary membrane in rabbits. Aqueous samples were obtained using a 30-gauge needle passed through the limbus in newborn rabbits. The VEGF and bFGF levels were measured by a quantitative sandwich enzyme-linked immunosorbent assay. The aqueous VEGF levels at 60 days of age (29.0-351.9 with a median of 190.5 pg/mL) decreased significantly compared with those at 12 and 20 days of age (356.7-1148.3 with a median of 752.5 pg/mL at 12 days of age and 193.5-657.7 with a median of 425.6 pg/mL at 20 days of age, Mann-Whitney U Test, P < 0.0001 and P = 0.002, respectively). The aqueous bFGF levels at 60 days of age (0.0-126.2 with a median of 63.1 pg/mL) decreased significantly compared with those at 12 days of age (33.4-301.3 with a median of 167.4 pg/mL, P < 0.0001). Light microscopically, the pupillary membrane at 12 days of age was rich with capillaries that were subsequently closed at 20 days of age, and the membrane itself disappeared at 60 days of age. The aqueous VEGF and bFGF levels decreased in the process of regression of the pupillary membrane, suggesting that VEGF or bFGF played a role in eye development such as maintenance of the pupillary membrane.

Apoptosis in surgically excised choroidal neovascular membranes in age-related macular degeneration.

BACKGROUND: Choroidal neovascular membranes (CNVMs) in age-related macular degeneration show progressive histologic changes from active, cellular, highly vascularized membranes to inactive paucicellular scars. The purpose of this study was to determine whether apoptosis was involved in the evolution of these changes, what cell types are involved, and whether there was an association with the Fas antigen (Fas or CD95) and Fas ligand (FasL). METHODS: Serial frozen sections from 10 surgically excised CNVMs were stained by the TUNEL (terminal deoxynucleotidyl transferase-mediated biotin-deoxyuridine 5-triphosphate nick-end labeling) method for detection of DNA strand breaks and by propidium iodide staining for morphologic detection of apoptosis. Immunoperoxidase staining was used for detection of Fas, FasL, and cell-type specific antigens. RESULTS: Highly vascularized membranes contained cells with TUNEL-positive nuclei, particularly in the regions of neovascularization, while fibrotic membranes showed few, if any, TUNEL-positive cells. Many of the TUNEL-positive cells were stromal retinal pigment epithelial cells, although smaller numbers were identified as endothelial cells and macrophages. Confocal microscopy of propidium idoide-stained sections confirmed the presence of apoptotic nuclei. The extent of Fas antigen expression correlated with extent of apoptosis. FasL expression was found in all specimens but was most intense in the highly vascularized membranes. CONCLUSIONS: Highly vascularized CNVMs related to age-related macular degeneration show apoptosis in stromal retinal pigment epithelial cells, endothelial cells, and occasional macrophages. Apoptosis is associated with prominent Fas and FasL expression.

Quantitative kinetic analysis of blood vessels in the outer membranes of chronic subdural hematomas.

Dynamic biologic modeling was used to calculate the transfer rate constant for gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) and capillary permeability in the outer membrane of chronic subdural hematomas and effusions. Following intravenous Gd-DTPA injection, Gd concentrations in the subdural fluid and in timed arterial blood samples were measured by ion-coupled plasma emission spectrometry in 53 chronic subdural hematomas and 18 chronic subdural effusions. The capillary surface area in outer membrane was assessed morphometrically. Transfer rate constants for subdural hematomas and subdural effusions were 12.4 +/- 1.0 and 20.6 +/- 1.7 (x 10(-4)min-1, respectively. Capillary permeabilities for subdural hematomas and subdural effusions were 16 +/- 1.2 and 19 +/- 3.7 ml.min-1(mm2/mm3)-1, respectively. The capillary surface areas for subdural hematomas and subdural effusions were 48 +/- 3 and 77 +/- 10 mm2/mm3, respectively. The high degree of infiltration of Gd into subdural effusions reflects the high capillary surface area in the outer membrane rather than greater permeability of individual capillaries. The value of transfer rate constant was correlated inversely with the duration of the chronic subdural fluid collection. Immature outer membrane has a high transfer rate constant which allows extravasation of plasma components into the subdural space, resulting in increasing volume of the subdural effusion. Delayed magnetic resonance imaging following Gd administration may be clinically useful for estimating the age of chronic subdural fluid accumulations.

The dimensions and vascular anatomy of the cricothyroid membrane: relevance to emergent surgical airway access.

Following traumatic injury, rapid surgical access to the airway may be required, with surgical cricothyroidostomy the procedure of choice. Immediate complications of cricothyroidostomy include unsuccessful or incorrect site of tube placement and hemorrhage. Subglottic stenosis is the most common late complication. This project was undertaken to better define the dimensions and vasculature of the cricothyroid region. In 15 cadaveric specimens, cervical dissection revealed the average width of the cricothyroid membrane visible between cricothyroid muscles to be 8.2 mm, and the average height 10.4 mm. Latex injection of the carotid artery demonstrated a transverse cricothyroid artery arising from the superior thyroid artery in 93% of cases. The cricothyroid artery crossed the upper one-half of the cricothyroid membrane in all but one specimen. Branches of the cricothyroid artery penetrated the membrane and ascended along the undersurface of the thyroid cartilage. Unilateral superior thyroid artery injection demonstrated anastomoses between right and left cricothyroid arteries. In 54% of specimens, the superior thyroid artery coursed anterior to the sternothyroid muscle and then the lateral edge of the cricothyroid membrane. The membrane was also crossed by venous tributaries to the superior and inferior thyroid veins. To lessen the possibility of complications following cricothyroidostomy, a knowledge of the dimensions, relations, and vasculature of the cricothyroid membrane is of inestimable value.

The two- and three-dimensional structure of the microcirculation of the chick chorioallantoic membrane.

The chick chorioallantoic membrane (CAM) is a common model for studying biological processes, but descriptions of the CAM circulatory system and especially experimental preparations of the CAM in shell-less eggs are both scant and controversial. We studied the CAM structure and the three-dimensional spatial configuration of the CAM vessels using five methods: in vivo stereoscopic observations, whole-mount preparations, histological sections, corrosion cast microinjection techniques, and the reconstruction of a three-dimensional wax model. Our findings show that the CAM consists of a superficial two-dimensional layer composed of a network of a very dense capillary mesh, floating over and enclosing a deeper three-dimensional space in which medium and larger free-floating vessels are seen to supply and drain the superficial layer. It is interesting to note that no tips or sprouts of blood vessels were observed during the development of the CAM vessels. In a shell-less egg preparation, the capillaries were found in the mesoderm layer of the CAM and not in or superficial to the ectoderm as is the case in the CAM of the intact egg which adheres to the shell membrane.

Subretinal neovascular membranes associated with choroidal nonperfusion and retinal ischemia.

This is the first well-documented case of co-existent underlying choroidal nonperfusion in an eye with a subretinal neovascular membrane that was subsequently treated with krypton red laser photocoagulation by the senior author (LEM). The possible role of chronic macular ischemia secondary to choroidal circulatory impairment is discussed in relationship to other well-established risk factors. Perhaps treatment to improve macular oxygenation would be a reasonable alternative to eradication of the neovascularization by direct laser photocoagulation.

Vascularized vitreous membranes in congenital retinoschisis.

Congenital retinoschisis is a bilateral x-linked disease characterized by a stellate maculopathy and retinoschisis. The pathogenesis is unknown. This article describes a patient with congenital retinoschisis and documents the unique development of vascularized vitreous membranes. A posterior vitreous separation with subsequent vascularization of the posterior hyaloid face occurs early in the course of the disease process and is coincident with the development of maculopathy and schisis cavities. This process may represent an important element in the pathogenesis of the maculopathy and schisis cavities in congenital retinoschisis. With atrophy of the neovascular tissue, a membrane remains and consists of a thickened area of the posterior hyaloid face.

Hyaloid vascular pattern in the human fetus.

The hyaloid vascular system of developing human eyeballs is studied to elucidate the relationship to the retinal vascular patterns. The process of the regression of the hyaloid vascular system in fetuses consisted of gradual shrinkage of the wall of the vessels with lessening of the lumen and eventually, thread-like acellular strands that remained as a consequence. The intercapillary bridge in the retinal vessel appeared to be a remnant of the degenerated vessel as in the hyaloid vascular system. At the ninth month of intra-uterine life, the regression of the hyaloid vascular system was almost complete.