[Usability testing of the canal expander - a new implant for canaloplasty]. / Gebrauchstauglichkeitstest des Kanal-Expander - ein neues Implantat für die Kanaloplastik.

BACKGROUND: Canaloplasty is a bleb-independent glaucoma surgery in which Schlemm's canal is dilated with a microcatheter and viscoelastic material, and stretched by a tensioning suture. The suture stent has numerous drawbacks such as the technical challenging implantation, deficient knowledge of proper suture tension, late loosening of the suture, or suture extrusion into the anterior chamber. The Stegmann Canal Expander (SCE) was developed to replace the suture stent and to make canaloplasty easier and more reproducible. The aim of this test was evaluate the usability regarding effectiveness, efficacy, and satisfaction of the implanting ophthalmologist (test person). METHODS: In an experimental setting, the test persons were asked to implant the SCE in human autopsy eyes with a surgically prepared Schlemm's canal by means of surgical instruments and an operating microscope. The standardised test was performed in terms of participant observation with a subsequent opinion survey based on checklist and photographic documentation. Data for a successful handling of the task and qualitative data from the experience of the test person with the product were anonymised, collected and registered in an assessment sheet. The evaluation comprised the aspects of instructions for use, packaging, identification, handling, and implantation of the SCE. RESULTS: The implantation took 2 to 5 min (mean: 3 min). All questions in the assessment sheet regarding effectiveness, efficacy, and satisfaction (n=35) were answered by all test persons (6/6) with the best category ("completely true"; or "no, no problem"). CONCLUSIONS: The usability of the SCE under standardised and experimental conditions regarding effectiveness, efficacy, and satisfaction has been rated as very positive, especially allowing for the fact that some of the ophthalmologists did not have experience in glaucoma surgery or only little experience in ophthalmic surgery.

Stimulation and inhibition of human platelet adenylylcyclase by thiophosphorylated transducin beta gamma-subunits.

The effect of beta gamma-dimers isolated from the retinal guanine nucleotide-binding protein (G protein) transducin eluted from illuminated bovine rod outer segment membranes with GTP, guanosine 5'-O-(beta, gamma-imino)triphosphate (Gpp(NH)p), or guanosine 5'-O-(gamma-thio)triphosphate (GTP gamma S) on basal and forskolin-stimulated adenylylcyclase activities in membranes of human platelets was studied. beta gamma-Subunits isolated from transducin eluted with GTP gamma S (TD beta gamma GTP gamma S) had a concentration-dependent stimulatory effect on basal adenylylcyclase activity. The stimulatory agonist prostaglandin E1 increased the potency and the maximum extent of stimulation due to TD beta gamma GTP gamma S). With a similar concentration dependence, TD beta gamma GTP gamma S exerted an inhibitory influence on forskolin-stimulated adenylylcyclase activity. At the same concentrations, beta gamma-dimers isolated with either GTP or Gpp(NH)p did not alter enzyme activities. The observed effects of TD beta gamma GTP gamma S were similar to those of directly added GTP gamma S with regard to maximum levels, time dependence, and persistence; however, TD beta gamma GTP gamma S was approximately 10-fold more potent than GTP gamma S. Treatment of TD beta gamma GTP gamma S, but not of free GTP gamma S, with hydroxylamine caused a loss of adenylylcyclase regulation by TD beta gamma GTP gamma S. The data presented indicated that TD beta gamma GTP gamma S potently and efficiently activates the stimulatory and inhibitory G proteins of adenylylcyclase in human platelet membranes. Furthermore, evidence is provided suggesting that the observed effects of TD beta gamma GTP gamma S, which can be thiophosphorylated by GTP gamma S at the beta-subunit (Wieland, T., Ulibarri, I., Gierschik, P., and Jakobs, K. H. (1991) Eur. J. Biochem. 196, 707-716), are due to formation of GTP gamma S at the G proteins.

Severe occlusive retinal periphlebitis with vitreous hemorrhage in multiple sclerosis.

Severe ocular complications in multiple sclerosis are rare. A 43-year-old patient had a history of diplopia episodes and optic neuritis in the right eye between 1979 and 1980. In 1984, multiple sclerosis had been diagnosed. The patient presented with visual deterioration in the right eye in 1992. Ophthalmoscopy and fluorescein angiography showed severe occlusive retinal periphlebitis with diffuse retinal hemorrhages and large areas of nonperfusion. At the time of presentation the patient was in general good health and presented no neurological sign. Examinations for other causes of periphlebitis were negative. Although treatment with laser therapy and corticosteroids was initiated, the patient developed recurrent vitreous hemorrhages that required pars plana vitrectomy. In 1993 the patient suffered from a general deterioration of the disease course and was treated with systemic immunosuppressive medication. Vitreous hemorrhage is a rare complication of multiple sclerosis.

Reproducibility of measurements with a new slit lamp-mounted ocular blood flow tonograph.

PURPOSE: To assess the reliability of measurements of intraocular pressure (i.o.p.), pulse amplitude (PA), and pulsatile ocular blood flow (POBF) and the validity of measurements of IOP with a new ocular blood flow tonograph. METHODS: Intraocular pressure pulse was assessed with pneumatic tonometry. In this study, we used the OBF Labs ocular blood flow tonograph with two different pneumatic probes, a modified Langham probe and a newly developed probe. One ophthalmologist compared two machines, first with the modified Langham probe and secondly with the newly developed probe (40 volunteers). Additionally, two ophthalmologists performed measurements on different days and in different sequence (34 volunteers). Furthermore, results of IOP measurements performed with this tonograph were compared to those of Goldmann applanation tonometry (213 volunteers). RESULTS: Using the modified Langham probe, POBF and PA were associated with the machine used for the test. However, using the newly developed pobe, no relevant or statistically significant differences were found for any variables, and reliability coefficients were between 0.70 and 0.90. Linear regression analysis of the Goldmann applanation tonometer on the measurements of IOP with the tonograph showed a regression coefficient of 0.765. CONCLUSIONS: Results of measurements performed with this ocular blood flow tonograph and the newly developed probe are expected to be reliable and comparable.

Urine saturation with calcium salts in normal subjects and idiopathic calcium stone-formers estimated by an improved computer model system.

The state of saturation of urine with calcium salts has been estimated by means of a computer model system whose accuracy has been improved by the use of stability constants of 31 complexes which were re-determined at 37 degrees C and at the actual ionic strength of urine. The experimental determination of the concentration solubility products of calcium oxalate monohydrate (CaOx) and of calcium hydrogen phosphate dihydrate (bsh) allows an expression of the saturation degree as free concentration product ratio beta CaOx and beta bsh. Morning urine samples from 50 healthy controls and 50 idiopathic calcium stone-formers and 24 h urines from 40 normal subjects and 192 stone-formers, taking normal diet were investigated by this technique. From our results urine supersaturation with calcium oxalate salts seems to play an important role in calcium stone disease. Hypercalciuria and hyperoxaluria seem to be the main pathological features in this regard. The data concerning beta bsh values have not confirmed previous reports in which this parameter was found to be increased in stone-formers.

Critical evaluation of various forms of therapy for idiopathic calcium stone disease.

The results are presented of the dietary management, alone or in association with thiazides and/or allopurinol, evaluated in 143 idiopathic calcium stone formers after a mean follow-up of 18 months. Diet alone proved to be effective in the prevention of stone relapses. The addition of thiazide and/or allopurinol provided mild improvements of urine environment but seemed to give no further clinical benefits irrespective of underlying metabolic abnormalities.