[Effect of change in refraction by increasing intraocular pressure with the suction cup method on pattern reversal VECP]. / Einfluss der Refraktionsänderung bei Erhöhung des Augeninnendruckes mit der Saugnapfmethode auf das Pattern-reversal-VECP.

When IOP is increased by the suction cup method, refraction changes will occur, depending on the shape of the cup and the height of the IOP increase. Similar refraction changes were simulated in six healthy volunteers by employing spherical and cylindrical glasses during pattern-reversal visual evoked cortical potential (VECP) with various check sizes and amount of contrast. While the pattern-reversal VECP latencies were not influenced, the amplitudes were reduced considerably. By using contact lenses and a suitably shaped suction cup, refraction changes could be compensated for. In 22 healthy volunteers pattern-reversal VECPs were derived with and without the application of contact lenses with artificially raised IOP. A comparison showed that the amplitudes differed significantly. Without contact lenses a negative pressure of more than 40 mmHg resulted in a drop in the amplitudes with a plateau formed between 80 and 120 mmHg. With compensation by contact lenses the amplitudes are found to be unaltered or even slightly increased until a negative pressure of 120 mmHg is reached in the suction cup, after which they drop. Plotting the pattern-reversal VECP amplitudes (obtained with refraction changes being compensated for by contact lenses) against ciliary perfusion pressure, one finds the characteristic curve described by Ulrich et al., suggesting an autoregulative capacity between 15 and 20 mmHg in healthy persons. The latencies, which remain uninfluenced by refraction changes, are also not altered within an IOP increase of 15-20 mmHg.

Refraction changes during elevation of intraocular pressure by suction cup, their reflection in the pattern visual evoked cortical potential and their compensation.

Visual evoked cortical potential studies using pattern stimuli with the intraocular pressure raised artificially by the suction cup method have been reported. Possible changes in the refraction of the eye due to the method employed and their influence on the pattern visual evoked cortical potential have not been considered. Changes in the refraction of the eye during artificial intraocular pressure elevation and the influence of such changes on pattern visual evoked cortical potentials were studied. The refraction changes were found to depend on the shape of the suction cup. They could be compensated for by employing properly shaped suction cups and contact lenses. The behavior of amplitude and latency of the pattern visual evoked cortical potential at artificially elevated intraocular pressure with compensation for refraction changes has been studied and found to depend in a characteristic manner on ocular perfusion pressure.

[Effect of welding arcs on the eyes of patients with contact lenses (literature study)]. / Wirkung von Schweisslichtbögen auf die Augen von Kontaktlinsenträgern (Literaturstudie).

Two accidents had been reported from abroad, within which contact lense users grew blind after staying quite near at electrical arcs. It is supposed that the contact lenses had been "welded" with the cornea by influence of the electromagnetic radiation. Removal of lenses shall have caused the cornea "ablation" and thus the subjects permanent blindness. Nilsson et al. (1, 2, 5) performed intensive animal tests which proved, that contact lenses get hot in special spectral ranges thus underlying a certain drying up. The "welding" between contact lenses and the cornea could not be confirmed by test animals, but partial glueing of contact lenses and cornea and surface lesions of the epithelium as well in some cases. Hüer and Conrads (3, 4) experimenting on enucleated pigs' eyes, reported on similar results.