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Background: Normal tension glaucoma is a major subtype of glaucoma, associated with intraocular pressures that are within the statistically normal range of the population. Monogenic forms following classical inheritance patterns are rare in this glaucoma subtype. Instead, multigenic inheritance is proposed for the majority of cases. The present study tested common sequence variants in candidate genes for association with normal tension glaucoma in the German population., Methods: Ninety-eight SNPs were selected to tag the common genetic variation in nine genes, namely OPTN (optineurin), RDX (radixin), SNX16 (sorting nexin 16), OPA1 (optic atrophy 1), MFN1 (mitofusin 1), MFN2 (mitofusin 2), PARL (presenilin associated, rhomboid-like), SOD2 (superoxide dismutase 2, mitochondrial) and CYP1B1 (cytochrome P450, family 1, subfamily B, polypeptide 1). These SNPs were genotyped in 285 cases and 282 fully evaluated matched controls. Statistical analyses comprised single polymorphism association as well as haplogroup based association testing., Results: Results suggested that genetic variation in five of the candidate genes (RDX, SNX16, OPA1, SOD2 and CYP1B1) is unlikely to confer major risk to develop normal tension glaucoma in the German population. In contrast, we observed a trend towards association of single SNPs in OPTN, MFN1, MFN2 and PARL. The SNPs of OPTN, MFN2 and PARL were further analysed by multimarker haplotype-based association testing. We identified a risk haplotype being more frequent in patients and a vice versa situation for the complementary protective haplotype in each of the three genes., Conclusion: Common variants of OPTN, PARL, MFN1 and MFN2 should be analysed in other cohorts to confirm their involvement in normal tension glaucoma.

Background: Protein kinase C (PKC) plays a key role in cell metabolism. Three subgroups and 12 isoforms have been isolated so far, catalysing specific functions in cell metabolism. The demonstration of PKC subtypes in corneal tissue has been inconsistent. The aim of this study was to verify the expression of several PKC subgroups and isoforms in human and bovine corneal epithelial and endothelial cells., Materials and Methods: PKC subgroups and isoforms were studied using polyclonal antibodies., Results: Antibodies to PKC-alpha, -delta, -epsilon and -zeta, representing all three PKC subgroups, bound in human and bovine corneal epithelium and endothelium. No binding was found for antibodies to PKC-beta2., Conclusions: For the first time the presence of all three PKC subgroups was demonstrated in human and bovine corneal epithelial and endothelial cells. Further studies are needed to show the role of these subgroups in cellular functions such as cell proliferation and differentiation.

Background: The measurement of corneal thickness plays an increasing role in glaucoma screening and diagnosis. The influence of a variety of drugs on corneal thickness is well established. Especially for antiglaucomateous drugs this effect seems to be important. However, little is known about the influence of beta receptor antagonists on corneal thickness. The aim of this study was to provide evidence of the effect of timolol on central corneal thickness and endothelial cell density., Materials and Methods: Ten healthy volunteers (five women and five men) with a mean age of 29 years (range 25 to 56 years) were examined in a double-blind, prospective and randomised pilot study. Intraocular pressure, corneal thickness and endothelial cell density was estimated before as well as fifteen minutes, 24, 48, 72 and 96 hours after application of timolol 0.5 % eye drops twice daily. The partner eye received sodium hyaluronate eye drops twice daily and served as a control., Results: The application of timolol showed a decrease of intraocular pressure from initially 12 mmHg to 9 mmHg after four days (p = 0,0188) as well as an increase of corneal thickness from 537 microm to 557 microm after four days (p = 0,0659). There was no change of intraocular pressure (p = 0,9935) or corneal thickness (p = 0,9998) in the control eyes. There was also no effect of timolol (p = 0,2782) or sodium hyaluronate (p = 0,1940) on endothelial cell density., Conclusions: The study provides evidence of the influence of beta receptor antagonists on corneal thickness. This effect may be caused by receptor mediated influences on corneal ion and fluid transport. Further studies are needed to show if the increase of corneal thickness after application of topical timolol has clinical importance.

Background: Muscarinic acetylcholine receptors are located throughout the body. The demonstration of muscarinic receptors in corneal tissue has been inconsistent. Using freshly fixed human corneal tissue, we show a complete profile of muscarinic receptor subtypes in human corneal epithelium and endothelium., Methods: Muscarinic receptor sites were studied using immunocytochemistry, immunofluorescence and immunoblotting., Results: Antibodies to M2, M4 and M5 muscarinic receptor subtypes bound in human corneal epithelium and endothelium. No binding was found for antibodies to M1 and M3 muscarinic receptor subtypes., Conclusions: Our studies indicate the presence of M2, M4 and M5 muscarinic acetylcholine receptor subtypes in human corneal epithelium and endothelium. These receptors may play a role in the regulation of corneal homeostasis, other functions, like wound healing, or the pathogenesis of corneal diseases.

Purpose: Monoamine receptors are found throughout the body. Reports about the presence of monoamine receptors in the human cornea are inconsistent., Methods: Immunohistochemistry, immunofluorescence and immunoblotting were used to localize monoamine receptor sites on human corneal epithelium and endothelium., Results: Antibodies to alpha-1, beta-1 and beta-2 adrenergic receptors and to D1-like and 5HT-7 receptors were bound in corneal epithelium. Antibodies to alpha-1, alpha-2A, beta-1 and beta-2 adrenergic receptors and to 5HT-7 receptors were bound in corneal endothelium., Conclusions: Our data demonstrate the presence of several monoamine receptors in the human cornea. These receptors may play a role in the regulation of fluid transport or corneal homeostasis.

Purpose: To analyze chloroquine-induced morphological changes in the retinal pigment epithelium (RPE) and Bruch's membrane (BM)., Methods: Retina-choroid complexes of chloroquine-treated Long-Evans rats were analyzed by electron microscopy., Results: Intercellular spaces between the RPE cells and BM were enlarged. Residual material from phagosomes was released into these enlarged spaces. Debris accumulated within BM and encircled choriocapillaris endothelial cells., Conclusion: There is a release of undegraded phagocytic material (rod outer segments) into the extracellular space between BM and RPE cells, following inhibition of lysosomal degradation. Electron-dense deposits in BM and choriocapillaris may lead to reduced oxygen and nutrition flow.

Purpose: To report three cases with breakage of a 20-gauge kryptonite forceps during vitreoretinal surgery., Design: Interventional case report., Methods: Pars plana vitrectomy that included a membrane peeling was performed in three patients through standard ports with 20-gauge vitrectomy systems. The peeling procedure was attempted with the end-gripping kryptonite forceps., Results: Intraoperatively, the branch/tip broke and dropped onto the posterior pole. Removal of the broken part was uncomplicated, and the subsequent clinical course was unremarkable. In one case, the handle and branch/tip part were exchanged inadvertently. In the other two cases, neither an exchange nor a maladaptation of the parts was noted., Conclusion: An exchange of the hand piece and gripping end may increase the risk of breakage and retinal damage. The delicate gripping tips, however, may break because of inadequate maintenance and/or aging of the material. Intraoperative visual and functional examination is recommended before intraocular use.