Vitreous Contents Research Articles

Refractive shift prediction of DNA supramolecular hydrogels as artificial vitreous substitutes

Vitreous substitutes are sufficient for tamponade after pars plana vitrectomy. However, these substitutes (silicone oil and gas) are weak in the refractive aspect. DNA supramolecular hydrogel, a novel vitreous substitute, exhibits good biocompatibility. This study calculated the theoretical refractive shifts after the DNA supramolecular hydrogels were tamponed in the vitreous cavity in schematic eyes. Navarro and Liou–Brennan schematic eyes with relaxed accommodation were modeled using ZEMAX software. The refractive index representing the vitreous contents was changed to simulate a DNA supramolecular hydrogel tamponade in the vitreous cavity. The results of the theoretical refraction and power of the required spectacles to correct refractive error were output by the software. The same procedures were performed for other commonly used vitreous substitutes. The theoretical refractions of DNA supramolecular hydrogels were 60.368 and 60.189 D in Navarro and Liou–Brennan schematic eyes, which were only 0.229 and 0.154 D lower than that of the natural vitreous body, respectively. The power of the corresponding spectacles was less than 0.25 D. The refractive property of DNA supramolecular hydrogels was confirmed to be similar to that of a natural vitreous body. Hence, it is considered a promising vitreous substitute.

Simultaneous injection\u2010aspiration technique of air/fluid exchange for in\u2010office treatment of post\u2010operative vitreous cavity hemorrhage

BackgroundPost-operative vitreous cavity hemorrhage following pars plana vitrectomy is common. In-office drainage of the hemorrhage may be an option for some patients.TechniqueA new method for office-based air fluid exchange is described. A 30-gauge needle with a 10-mm syringe filled with sterile air is inserted 3.5-mm posterior to the limbus in the superotemporal quadrant. A second 30-gauge needle is inserted 3.5 mm from the limbus at 6 o’clock and connected to an empty 10-mm syringe with intravenous catheter tubing. The plunger of the air-filled syringe is pushed while the plunger of the empty syringe is pulled, so that the rate of fluid aspiration matches the rate of air injection.DiscussionThe method approximates conditions in pars plana vitrectomy, with balanced infusion and aspiration. Displaced vitreous cavity contents are collected in the aspiration syringe. The procedure is also cost effective.ConclusionThe simultaneous syringe method is an easy, safe, and effective way of clearing post-operative vitreous cavity hemorrhage.

Negative effects of transthyretin in high myopic vitreous on diabetic retinopathy.

To analyze the relationship between vitreous transthyretin (TTR) levels, high myopia and diabetic retinopathy (DR). We selected 6722 individuals from the southern Jiangsu Province for diabetes and ophthalmic examinations. The TTR concentration in the vitreous of 50 patients with high myopia and diabetes, 50 patients with only DR, and 20 healthy controls were determined by ELISA. Key factors in Tie2 pathway in DR development including vascular endothecial growth factor (VEGF), Tie2, Angpt1, Angpt2, vascular endothelial growth factor receptor (VEGFR) 1 and VEGFR2 were also detected by ELISA. The prevalence of DR in patients with diabetes and myopia [<6.00 diopter (D)], diabetes and high myopia (>6.00 D), and diabetes without myopia were 11.1%, 2.5%, and 60.0%, respectively. The vitreous TTR concentration of patients with diabetes and high myopia was approximately 6.5- and 4.2-times higher than those of patients with DR and healthy controls, respectively (P<0.05). Following the vitreous TTR concentration, the levels of VEGF, Tie2, Angpt1, Angpt2, VEGFR1 and VEGFR2 in vitreous of diabetes and high myopia patients, DR patients and healthy controls were detected as dramatically fluctuated. The results suggest that TTR can affect the vitreous contents of key factors in Tie2 pathway for neovascularization, and there should be a protective association between abundant TTR levels in the vitreous of highly myopic patients and a decreased risk of DR.

Dependence of the origin of pain in the eyes with terminal stage of glaucoma from chemical composition of vitreous

AbstractPurpose To identify a possible link between the origin of hypertonic pain syndrome (HPS) in the eyes with terminal stage of glaucoma and the difference of the urea concentrations between vitreous contents and blood serum.Methods 31 patients (31 eyes) with refractory terminal glaucomas of different origins with IOP more 35 mm Hg were studied and operated on. The principle of surgery was drainage of the vitreous space for HPS elimination. Some vitreous contents and venous blood were taken during the surgery and researched for measuring urea concentrations. The samples were centrifuged then the blood serum and the supernatant of the vitreous contents were analyzed (SPOTCHEM‐EZ SP 4430). The patients were divided into 3 groups depending on the intensity of pain syndrome: 1st with strong pain; 2nd ‐ pain was present earlier; but it was absent before the surgery; 3d ‐ pain was never registered.Results A high concentration of urea in vitreous contents was found. Only in 6.45% the urea concentration in blood serum was higher then in vitreous. In 12.9% concentrations were near equal and in 80.64% the urea concentration in vitreous contents was higher than in blood serum. Pain existed in the cases when the difference (the negative gradient) of urea concentrations exceeded 6.1 mmol/L only.Conclusion High concentration of the osmoticaly active urea in the vitreous cavity can be the reason for increase of IOP in some cases of refractory glaucomas. If the negative gradient of the urea concentrations were higher than the critical level, it would be the reason for the development of HPS.

Elevated plasma CD105 and vitreous VEGF levels in diabetic retinopathy

Diabetic retinopathy is the leading cause of blindness in the industrialized world. Hyperglycaemia induces retinal hypoxia that upregulates a range of vasoactive factors which may lead to macular oedema and/or angiogenesis and hence potentially sight threatening retinopathy. In this study, we have focused on the association of CD105 and vascular endothelial growth factor (VEGF) with the development and progression of diabetic retinopathy by means of quantifying their expression in the plasma and vitreous of diabetic patients. CD105 levels were quantified in the plasma of 38 type I diabetic patients at various stages of retinopathy and 15 non-diabetic controls. In an additional cohort of 11 patients with advanced proliferative retinopathy and 23 control subjects, CD105 and VEGF were measured in the vitreous. The values were expressed as median (range) and statistical analysis was carried out using the non-parametric Mann-Whitney U test. Plasma CD105 levels were significantly increased in diabetic patients [1.8 (1.1-2.4) ng/ml] compared with non-diabetic controls [0.7 (0.3-1.8) ng/ml] (p<0.01). Plasma CD105 levels were elevated in diabetic patients with all stages of retinopathy, the highest level was observed in background retinopathy [2.3 (2.1-2.5) ng/ml] followed by proliferative retinopathy [2.1 (0.9-2.8) ng/ml] and advanced proliferative retinopathy [1.4 (0.6-1.8) ng/ml]. Vitreous contents of CD105 did not differ between controls and patients with advanced proliferative retinopathy, but vitreous levels of VEGF were elevated by approximately 3-fold in patients with advanced proliferative retinopathy [7.2 (1.90-15.60) ng/ml] compared with the control subjects [1.80 (1.10-2.210)] (p<0.01). These observations indicate that plasma levels of CD105 and vitreous levels of VEGF are associated with diabetic retinopathy, suggesting that CD105 and the angiogenic factor VEGF may play a critical role in the development and progression of diabetic retinopathy. Further studies are required to determine whether circulating CD105 levels could serve as a surrogate marker for early stage retinopathy and for monitoring disease progression.

A study on the effect of fine mineral powders with distinct vitreous contents on the fluidity and rheological properties of concrete

This paper presents an investigation on the effects of fine mineral powders on the fluidity and rheological properties of concrete. It was observed that the fluidity of concrete increased noticeably, and the plastic viscosity decreased, when vitreous powders were substituted partially for cement. It was found that vitreous powders have a strong dispersion effect on the fluidity and rheological properties of concrete, and this effect can be correlated with the vitreous content of the powders incorporated.

A Study Involving Venlafaxine Overdoses: Comparison of Fatal and Therapeutic Concentrations in Postmortem Specimens

The distribution and redistribution of venlafaxine were investigated in two overdoses and several cases involving the therapeutic use of venlafaxine. Blood, liver, bile vitreous humor, urine and gastric contents were analyzed using high performance liquid chromatography with ultraviolet detection. Blood concentrations of venlafaxine in the two overdose cases were 53 mg/L and 78 mg/L. Comparison of venlafaxine concentrations in blood samples taken at different times after death revealed increases in concentrations over time, suggesting the possible postmortem redistribution of venlafaxine.

Biodegradationin vitro and retention in the rabbit eye of crosslinked poly(1-vinyl-2-pyrrolidinone) hydrogel as a vitreous substitute

To elucidate the relatively short retention of crosslinked poly(1-vinyl-2-pyrrolidinone) hydrogels in the eye when used as potential vitreous substitutes, a 14C-labeled hydrogel was produced and subjected to both in vitro biodegradation assays and in vivo experiments. The polymer was synthesized by the free-radical copolymerization of 99% 1-vinyl-2-pyrrolidinone with 1% 14C-methyl methacrylate in the presence of ethylene glycol dimethacrylate (0.1%) as crosslinking agent. The in vitro protocol for assessing the biodegradation included the incubation of hydrogel with hydrolases (trypsin or collagenase), followed by examination of changes in its physical characteristics and by monitoring its residual radioactivity, as well as by detection of possible degradation products. Within the maximum duration of experiments (4 weeks), none of the procedures indicated biodegradation of polymer. The hydrogel was also injected into the vitreous humor of rabbits and followed up to 4 weeks. Residual radioactivity measurements of the vitreous contents indicated that 50% of the polymer was removed by the end of this period. Histopathologic examination revealed cell infiltrates of the mononuclear phagocyte system in both vitreous and retinal tissue. A possible phagocyte-mediated mechanism for the dissipation of hydrogel is discussed.