Diagnostic accuracy of the Retinal Thickness Analyser: differentiation between normal eyes and eyes with glaucoma or macular pathologies

Background The Retinal Thickness Analyser (RTA) is intended to detect glaucomatous changes as well as macular pathologies at the posterior pole. We determined the diagnostic accuracy for eyes with manifest glaucoma or macular diseases.Methods We examined 71 eyes with long-term, established eye conditions. Included were 28 eyes with glaucoma, 21 with different macular diseases and 22 normal eyes. All examinations were evaluated in a blind-test by RTA experts without any clinical information on the patients. After comparison of the RTA interpretation with the clinical diagnosis, we determined sensitivity, specificity, positive and negative predictive values.Results Of 71 examinations, 15 (21%) were not interpretable. If these results are excluded, the following diagnostic accuracy values were calculated for glaucoma and macular disorders respectively: sensitivity 75 and 59%, specificity 55 and 97%, positive predictive value 48 and 90% and negative predictive value 80 and 84%. These values were not significantly different when both eyes of each patient were included in the final analysis (n=133).Conclusion The diagnostic values of the RTA determined in this case control study were not satisfactory. However, no clinical information was used in the assessment. The extent to which additional clinical information increases the diagnostic value remains to be determined.     

Effects of acute administration of d-amphetamine and haloperidol on procedural learning in man

The effects of an indirect dopamine-agonist, d-amphetamine, and a non-selective dopamine receptor antagonist, haloperidol, were investigated in normal male volunteers using a between-subjects double-blind design in a procedural learning task, thought mainly to involve unconscious/automatic learning. The results showed: (1) d-amphetamine facilitated response speed, whereas haloperidol inhibited it, in comparison to placebo; (2) the linear increase in procedural learning corresponded with pharmacological manipulation of degree of dopaminergic activity, i.e. subjects given haloperidol showed the least, and subjects given d-amphetamine the greatest, procedural learning. The implications of these findings are discussed in relation to investigation of abnormalities of procedural learning processes in schizophrenia. Received: 28 June 1996/Final version: 2 October 1996     

Ineffectiveness of organic calcium channel blockers in antagonizing long-term potentiation

Evidence has accumulated suggesting that the presence of calcium is critical for development of hippocampal long-term potentiation (LTP). However, there is a paucity of information about whether calcium's role in LTP is pre- or postsynaptic. In the present study, we examined the effectiveness of nitrendipine, verapamil, flunarizine and the benzodiazepine diazepam in: blocking voltage-dependent calcium channels; blocking synaptic transmission; and preventing development of LTP. Using the in vitro slice preparation, we obtained intracellular and extracellular recordings from guinea pig hippocampal CA1 pyramidal cells. At the cellular level, all 4 drugs were ineffective in blocking voltage-dependent calcium spikes (TTX resistant) and the calcium-dependent afterhyperpolarization. Verapamil and diazepam appeared to antagonize synaptic transmission, as reflected in smaller population spike amplitudes. Development of long-term potentiation was not affected by the presence of verapamil, flunarizine and diazepam. Nitrendipine appeared to reduce the percentage of slices exhibiting LTP; however, ethanol, the vehicle used to dissolve nitrendipine, was shown in separate experiments to reduce the percentage of slices exhibiting LTP. These results suggest that neither the organic calcium channel blockers--nitrendipine, verapamil, and flunarizine--nor micromolar concentrations of diazepam are potent blockers of extrasynaptic voltage-sensitive calcium channels in hippocampus. They thus cannot be used to demonstrate a specific pre- or postsynaptic calcium role in LTP.