Hagen Thieme

Vascular Endothelial Growth Factor in Ocular Fluid of Patients with Diabetic Retinopathy and Other Retinal Disorders

BACKGROUND Retinal ischemia induces intraocular neovascularization, which often leads to glaucoma, vitreous hemorrhage, and retinal detachment, presumably by stimulating the release of angiogenic molecules. Vascular endothelial growth factor (VEGF) is an endothelial-cell-specific angiogenic factor whose production is increased by hypoxia. METHODS We measured the concentration of VEGF in 210 specimens of ocular fluid obtained from 164 patients undergoing intraocular surgery, using both radioimmuno-assays and radioreceptor assays. Vitreous proliferative potential was measured with in vitro assays of the growth of retinal endothelial cells and with VEGF-neutralizing antibody. RESULTS VEGF was detected in 69 of 136 ocular-fluid samples from patients with diabetic retinopathy, 29 of 38 samples from patients with neovascularization of the iris, and 3 of 4 samples from patients with ischemic occlusion of the central retinal vein, as compared with 2 of 31 samples from patients with no neovascular disorders (P < 0.001, P < 0.001, and P = 0.006, respectively). The mean (+/- SD) VEGF concentration in 70 samples of ocular fluid from patients with active proliferative diabetic retinopathy (3.6 +/- 6.3 ng per milliliter) was higher than that in 25 samples from patients with nonproliferative diabetic retinopathy (0.1 +/- 0.1 ng per milliliter, P = 0.008), 41 samples from patients with quiescent proliferative diabetic retinopathy (0.2 +/- 0.6 ng per milliliter, P < 0.001), or 31 samples from nondiabetic patients (0.1 +/- 0.2 ng per milliliter, P = 0.003). Concentrations of VEGF in vitreous fluid (8.8 +/- 9.9 ng per milliliter) were higher than those in aqueous fluid (5.6 +/- 8.6 ng per milliliter, P = 0.033) in all 10 pairs of samples obtained simultaneously from the same patient; VEGF concentrations in vitreous fluid declined after successful laser photocoagulation. VEGF stimulated the growth of retinal endothelial cells in vitro, as did vitreous fluid containing measurable VEGF. Stimulation was inhibited by VEGF-neutralizing antibodies. CONCLUSIONS Our data suggest that VEGF plays a major part in mediating active intraocular neovascularization in patients with ischemic retinal diseases, such as diabetic retinopathy and retinal-vein occlusion.

The regulation of trabecular meshwork and ciliary muscle contractility.

Current models of aqueous humor outflow no longer treat trabecular meshwork (TM) as an inert tissue passively distended by the ciliary muscle (CM). Instead, ample evidence supports the theory that trabecular meshwork possess smooth muscle-like properties and is actively involved in the regulation of aqueous humor outflow and intraocular pressure. In this model, trabecular meshwork and ciliary muscle appear as functional antagonists, with ciliary muscle contraction leading to a distension of trabecular meshwork with subsequent reduction in outflow. and with trabecular meshwork contraction leading to the opposite effect. Smooth-muscle relaxing substances would therefore appear to be ideal candidates for glaucoma therapy with the dual goal of reducing intraocular pressure via the trabecular meshwork and of improving vascular perfusion of the optic nerve head. However, for such substances to effectively lower intraocular pressure, the effect on the ciliary muscle would have to he minimal. For this reason, more information is needed on the signalling processes involved in regulating trabecular meshwork and ciliary muscle contractility. This review attempts to outline current knowledge of signal transduction pathways leading to relaxation and contraction of ciliary muscle and trabecular meshwork. Pathways can be classified as involving or not involving changes of membrane voltage and of requiring or not requiring external calcium: possibly, other pathways exist. These different pathways involve different ion channels and isoforms of PKC and are expressed to a differing degree in ciliary muscle and trabecular meshwork, leading to differential responses when exposed to relaxing or contracting pharmacological agents. Some of these agents. like tyrosine kinase inhibitors and inhibitors of PKC. have been shown to relax trabecular meshwork while leaving ciliary muscle comparatively unaffected. This profile makes these substances appear as ideal drugs for simultaneously improving ocular outflow and retinal circulation, parameters that determine the time course of visual deterioration in glaucoma.

Comparative Analysis of Vascular Endothelial Growth Factor Receptors on Retinal and Aortic Vascular Endothelial Cells

Ischemic eye disease often results in ocular neovascularization, presumably due to the elaboration of growth factors. Diabetic retinopathy is a classic example in which dramatic retinal neovascularization arises after ischemic retinal damage. The characterization of vascular endothelial growth factor (VEGF) as an angiogenic molecule whose expression is markedly induced by hypoxia makes it a promising candidate for mediating ischemic retinal neovascularization. Thus, we have characterized the structure, binding, and regulation of VEGF receptors in bovine retinal (BREC) and aortic endothelial cells (BAEC). VEGF stimulated a 2.1-fold increase in BREC number and DNA content at 0.6 nmol/l VEGF (P < 1 × 10−7). Scatchard binding analysis demonstrated specific high-affinity VEGF receptors on BREC with a Kd of 4.9 ± 0.6 × 10−11 mmol/l, similar to that observed for BAEC at 5.1 ± 0.4 × 10−11 mmol/l. BREC, however, possess 1.5 × 105 high-affinity receptors/cell, threefold more than BAEC (P < 0.003) and more than any cell type reported previously. 125I-VEGF affinity cross-linking revealed complexes at 220 and 170 kDa in BREC, but only a 220-kDa band of lesser intensity in BAEC. Cross-linking was displaceable in a dose-dependent manner by VEGF (P < 0.01) but not by other hormones. Hypoxia increased VEGF receptor number 50% in BREC without altering affinity. Antiphosphotyrosine immunoblotting showed VEGF-stimulated tyrosine autophosphorylation of VEGF receptor bands at 225 and 220 kDa and another band at 80 kDa within 1 min. These findings suggest that VEGF may mediate retinal vascular proliferation through large numbers of high-affinity receptors on retinal vascular endothelial cells and suggest that VEGF may be an important mediator of neovascularization induced by ischemic retinopathies such as diabetes.

Contrast sensitivity after implantation of a spherical versus an aspherical intraocular lens in biaxial microincision cataract surgery

PURPOSE: To determine whether implantation of a microincision intraocular lens (IOL) with a modified anterior surface, designed to compensate for the positive spherical aberration of the cornea in eyes of cataract patients, results in improved pseudophakic quality of vision in pseudophakic eyes after biaxial microincision phacoemulsification. SETTING: Department of Ophthalmology, Johannes Gutenberg‐University, Mainz, Germany. METHODS: In a nonrandomized parallel cohort investigation, the visual performance of 52 eyes of 52 patients unilaterally implanted with the aspherical Acri.Smart 36 A IOL (Acri.Tec) were compared with those of 25 eyes of 25 age‐matched patients unilaterally implanted with the spherical Acri.Smart 46 S IOL (Acri.Tec). Eight weeks after surgery, the following parameters were assessed: uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), pupil size under various illumination conditions, high‐contrast and low‐contrast visual acuities, photopic and mesopic contrast sensitivities, capsulorhexis size, and wavefront aberration of the cornea and eye. The primary clinical endpoint of the comparison was defined as the area under the cycles per degree (cpd) curve of the contrast sensitivity profile. RESULTS: The aspherical IOL group and the spherical IOL group did not differ in baseline characteristics. The median age was 71 years and 68% were women in the aspherical group versus 69 years and 62% women in the spherical group. The preoperative median UCVA was 20/80 in both groups. The UCVA, BCVA, pupil size, and capsulorhexis size were not statistically different between the 2 groups. Furthermore, no clinically relevant or statistically significant between‐group differences were observed in the primary clinical endpoint. The median postoperative low mesopic contrast sensitivity without glare was 73 cpd in the aspherical group and 84 cpd in the spherical group (P = .624); a similar tendency was observed under high mesopic conditions (median 80 cpd and 83 cpd, respectively) (P = 1.000). Implantation of both IOL types resulted in a negative spherical aberration Z40, which was significantly different between the 2 groups (median −0.09 μm aspherical and −0.29 μm aspherical at a pupil size of 4.5 mm) (P<.001). CONCLUSIONS: No clinically relevant postoperative differences in contrast sensitivity were observed between the aspherical microincision IOL and the spherical equivalent model. The development of microincision IOLs, which fit through corneal incisions smaller than 2.0 mm and improve night‐driving conditions (eg, reduction of glare), could optimize modern biaxial cataract surgery.

Histopathologic findings in early encapsulated blebs of young patients treated with the ahmed glaucoma valve.

Objective/AimUncontrolled glaucoma presents a challenge for the ophthalmic surgeon especially in children and juvenile patients. For many patients who have undergone failed surgical procedures before, episcleral implants remain the last choice. Encapsulated blebs forming over antiglaucoma devices present a complication leading to malfunctioning or even failure with reincrease in intraocular pressure. We report our histopathologic findings of such blebs developing around the Ahmed glaucoma valve (AGV) after a short time period in young patients. Materials and MethodsNine young patients (2 to 17 y of age) with otherwise uncontrollable glaucoma were treated with AGV (models FP-7 and FP-8, silicone base plate) by 1 surgeon (H.T.). Four eyes needed surgical revision 2 to 6 months after initial implantation owing to encapsulated bleb development over the valve with total loss of function. The dense capsule around the device was surgically removed and investigated macroscopically, microscopically, and ultrastructurally. ResultsThe cystic wall of these encapsulated blebs had an overall thickness of 1.5 to 2 mm. Macroscopically, the tissue was split into 2 layers. Histopathologically, the smooth inner surface (facing the base plate of the AGV) consisted of compressed collagen fibers with signs of elastoid degeneration and with formation of a pseudoendothelium toward the base plate. There was a pronounced transformation of fibroblasts into myofibroblasts in this inner layer. The outer area was highly vascularized. In these vessels electron microscopy revealed thrombosis. Inflammatory responses were nearly absent in all areas of the excised material. Intraocular pressure could be controlled by removal of the encapsulated blebs in all 4 cases. ConclusionsEncapsulation of the AGV is an early complication in young patients, leading to inhibition of fluid exchange and failure of the procedure. The valve mechanism is blocked by contracted scar tissue, but the device itself is not affected by the encapsulation. Surgical excision of the capsule immediately leads to an aqueous flow and drop of intraocular pressure.

Surface Topographies of Glaucoma Drainage Devices and Their Influence on Human Tenon Fibroblast Adhesion

PURPOSE This study was performed to investigate the surface topography of different glaucoma drainage devices and to determine the effects of surface roughness on cell adhesion of cultured human tenon fibroblasts. METHODS The surface topography of four widely used devices (Ahmed FP7 and Ahmed S-2; New World Medical, Inc., Rancho Cucamonga, CA; Baerveldt BG101-350; Advanced Medical Optics, Irvine, CA; and Molteno S1; Molteno Ophthalmic Ltd., Dunedin, New Zealand) was investigated by scanning electron microscopy, and roughness was quantified by white-light confocal microscopy. Cells were grown for 72 hours on the surfaces of implants affixed to standard culture dishes. The cells were labeled with a fluorescent dye and detected by confocal laser scanning microscopy, while simultaneously imaging the surface reflectance. Collagen adsorption was quantified immunologically by using fluorescent beads coupled to a secondary antibody. RESULTS The root-mean-square roughness was 1.5 +/- 0.1 microm (mean +/- SE) for the silicone Ahmed model FP7 and 1.3 +/- 0.1 microm for the Ahmed with polypropylene base plate Ahmed model S-2. The Baerveldt was substantially smoother, with a mean roughness of 0.1 +/- 0.01 microm. The Molteno was the smoothest of all devices (0.07 +/- 0.01 microm). Cell adhesion was most prevalent on base plates with higher surface roughness, markedly less pronounced on the smoother base plates, and independent of collagen adsorption. CONCLUSIONS The most frequently implanted glaucoma drainage devices are of markedly different surface topography. Surface roughness appears to correlate with tenon fibroblast adhesion in vitro and also with the rate of occurrence of postimplantation hypertensive phase and failure due to fibrous encapsulation. Surface roughness may thus play a role in triggering excessive fibrovascular reactions. Smoother base plate surfaces may enhance the success rates of these devices.

Pharmacological and Functional Characterization of Endothelin Receptors in Bovine Trabecular Meshwork and Ciliary Muscle

To clarify the potential role of endothelin-1 (ET-1) in the pathogenesis of glaucoma, the endothelin receptors expressed in bovine trabecular meshwork (TM) and ciliary muscle (CM) were identified. TM and CM strips were subjected to ET-1 as well as to specific endothelin receptor antagonists. In both tissues BQ123, a specific ET-A receptor antagonist, substantially inhibited ET-1-induced contraction. BQ788, a specific ET-B receptor antagonist, showed only moderate effects. Both ET receptor types were detected in bovine TM and CM using Western blot analysis. ET-1 produced an increase in intracellular calcium in cultured TM cells. This effect was inhibited by BQ123, but not by BQ788. Thus, although both receptors are present, the ET-A receptor appears to play the predominant role in mediating contraction in both the TM and CM, while the ET-B receptor seems to contribute little to the overall ET-1 effect.

Effects of Unoprostone and Endothelin 1 on L-Type Channel Currents in Human Trabecular Meshwork Cells

Background: The trabecular meshwork (TM) is a smooth muscle-like tissue with contractile properties and by this mechanisms involved in the regulation of aqueous humor outflow. Isopropyl unoprostone (Rescula®, Novartis Ophthalmics), a synthetic docosanoid, reduces intraocular pressure in glaucoma patients and normal subjects. In isolated TM strips, unoprostone reduces TM contractility in the presence of endothelin 1 (ET-1). However, the signal transduction pathway of unoprostone still remains unclear. Since L-type channel currents are known to influence the contractility of TM, we examined the effects of unoprostone and ET-1 on L-type channel currents of TM cells. Methods: The effects of unoprostone, ET-1 and the tyrosine kinase inhibitor herbimycin A on L-type channel currents of cultured human TM cells were investigated using the perforated patch configuration of the patch-clamp technique. Results: Application of ET-1 had no effect on L-type channel currents. Unoprostone led to a dose-dependent reduction of control currents. The effect of unoprostone is independent of ET-1. After preincubation of cells with herbimycin A, unoprostone had no effect on the L-type channel current amplitude. Human TM cells preincubated with herbimycin A showed a reduced current density compared with control cells. Both substances, unoprostone and herbimycin A, increased the inactivation time constant of L-type channel currents. Conclusion: We conclude that unoprostone reduces the activity of L-type Ca2+ channels. This effect seems to be independent of ET-1. The signal transduction pathway seems to be mediated by tyrosine kinases.

A pedigree of Leber's hereditary optic neuropathy with visual loss in childhood, primarily in girls

Abstract · Background: Leber’s hereditary optic neuropathy (LHON) mostly affects young males. In patients carrying one of the primary mutations the risk to develop LHON is 50% for males and 10% for females. We report a family with predominantly young girls affected. · Methods: In a family with 14 known maternal relatives (11 females, 3 males) 9 patients in 4 generations developed LHON. Eight of the 9 patients were females. Three affected females could be examined and followed. · Results: The only affected male showed the typical course of LHON with acute visual loss in both eyes (20/400–20/800) within 6 weeks at 20 years of age. Eight of 9 females developed signs of LHON. In these females acute visual loss occurred at about 10 years of age. Final visual acuity was about 20/200. Central or paracentral scotomata, color vision defects and delayed P100 latencies in the VEP were seen. Ophthalmoscopy showed hyperemic discs in the acute stage and optic atrophy in later stages. Molecular genetic analysis revealed the presence of the mtDNA ND4/np11778 mutation in this family. Specific clinical or additional molecular genetic risk factors could not be detected. · Conclusion: Families with LHON may show considerable variations of the clinical course and the gender- or age-specific risk. We present a family with a high disease penetrance of 64% and a 2 times higher risk for young females than for males. Furthermore, early visual loss in this family is permanent.

Efficacy and Tolerability of Preservative-Free Eye Drops Containing a Fixed Combination of Dorzolamide and Timolol in Glaucoma Patients

PURPOSE To evaluate the efficacy and tolerability of preservative-free eye drops (dorzolamide/timolol) in routine management of preservative-sensitive glaucoma patients. METHODS Data from 2,298 glaucoma patients requiring intraocular pressure (IOP) reduction and suffering from intolerance to benzalkonium chloride or active agents of previously used eye drops were valid for baseline and safety analysis in this prospective, open, noncomparative, multicenter, noninterventional study. Patients were treated with preservative-free dorzolamide/timolol eye drops for 12 weeks. Main efficacy endpoint was IOP reduction after 12 weeks of treatment. Two thousand forty-nine patients were considered for efficacy analysis. Tolerability was assessed by evaluating adverse drug reactions. RESULTS Mean baseline IOP was 20.8 mmHg. Baseline IOP was reduced to 16.7 mmHg after 12 weeks of treatment corresponding to a mean absolute (percent) change of -4.1 mmHg (-17.3%). The proportion of patients with IOP ≤21 mmHg increased from 59.9% at baseline to 94.6% after 12 weeks. The most frequently reported ocular adverse drug reactions were burning eyes (2.4%) and hyperemia (0.9%). Local tolerability improved in 79.3% of patients compared to their previous glaucoma therapy. CONCLUSIONS This observational study confirms the IOP lowering effect of preservative-free eye drops containing the fixed combination of dorzolamide/timolol in a large patients population. The drug was well tolerated and improved the local tolerability in the vast majority of patients.