An electrophysiological technique for assessment of the development of spatial vision.

An objective visual evoked potential (VEP) technique was developed to evaluate spatial processing in humans over a wide range of ages. The constellation of stimulus conditions and analysis methods constitute a novel tool for the assessment of neural development. The key points that delineate this VEP technique are: (1) A brief, 6-s, swept-parameter stimulus with spatial frequency of square-wave grating patterns varied in octave steps, which facilitates correct accommodation and increases the likelihood of collecting uninterrupted, useable data; (2) data collection synchronous with stimulus presentation, which prevents contamination of the relevant frequency component from other frequency components in the response, thereby increasing the signal-to-noise ratio; (3) noise estimation at the response frequency of interest (second harmonic), based on a multivariate statistic (Tcirc2), which yields a realistic measure of signal-to-noise; (4) estimation of grating acuity from linear interpolation of the signal-to-noise measure; (5) monocular testing followed by multivariate statistical comparison of fellow eye data for each spatial frequency condition, which enables the determination of asymmetries within monocular neural pathways; (6) evaluation of maturation of the visual system based on vector-averaged amplitude and phase measures. Preliminary results indicate that reliable response functions are obtained from infants, children, and adults. Acuity estimates increased as a function of age. Phase values decreased consistently with increases in spatial frequency greater than 4 c/deg. Infants produced larger peak amplitude responses than did older observers, consistent with known developmental changes in cortical synaptic density. Phase data for the 2 c/deg condition provided additional evidence for the lack of maturity in the infant visual system as compared with that of older observers.

[Sweep-VEP: a new method for objective visual assessment in small children]. / Sweep-VEP: Eine neue Methode zur objektiven Visusprüfung bei Kleinkindern.

For visual acuity testing in small children Preferential Looking and registration of Visually Evoked Potentials (VEP) are used clinically. Both methods are dependent on good cooperation, since the presented patterns have to be fixated during several minutes by the children tested. In contrast the sweep-technique, described in 1985 by Norcia, allows VEPs to be measured in only a few seconds. As in conventional VEP-testing filtering and Fourier data analysis are performed. The short examination time guarantees in most cases no problems in maintaining attention and stable fixation, even when newborns or handicapped are tested. In several studies good reliability has been demonstrated. As an illustration results of sweep-VEP-testing of three months old twins are shown.

[Ocular vasospasm. 2: Diagnosis of vasospastic syndrome using nailfold capillary videomicroscopy]. / Okulärer Vasospasmus. Teil 2: Diagnose des vasospastischen Syndroms mit Hilfe der Nagelfalzkapillarvideomikroskopie.

Nailfold capillary videomicroscopy provides a very useful method to verify vasospastic disorders in ophthalmic patients. Capillary videomicroscopy at the nailfold in connection with a local cold exposure test are presented as a method with clinical applicability in vasospastic disease. This method allows not only differential diagnosis of Raynaud's phenomenon and evaluation of follow up but also to achieve pharmacological tests with different drugs which possess a specific action at the microvascular bed.

[Ocular vasospasm. 4: Clinical examples]. / Okulärer Vasospasmus. Teil 4: Klinische Beispiele.

The presumed ocular vasospasms provoke a variety of symptoms. Out of the large spectrum, two typical cases are described. The first case is a patient that developed visual field defect under psychological stress conditions. A drug therapy relieved the patient from the symptoms. The second case is a patient with a normal-tension-glaucoma. The treatment of the vasospasm improved the visual field markedly.

[Erythropsia following exposure to toluene]. / Erythropsie nach Toluolexposition.

A patient who had been exposed to toluol for ten years developed acute erythropsia. The examinations leading to the diagnosis and the possible differential diagnosis are discussed.