Biomedical subjects
Publications and source records attributed to J Peregrin.
In a group of 57 patients with chronic terminal renal insufficiency, treated by haemodialyses a significantly reduced sensitivity to contrast was observed. Changes in the sensitivity to contrast do not correlate with the period of dialyzation treatment.
Stimulation by means of moving the structure in the visual field is used to produce visual evoked responses (VER) only rarely. The authors attempted to verify the fact how VER to the movement depended on some stimulation parameters and to compare them with VER to the most frequently used stimulation method, i. e. reversal. Horizontally moving black and white vertical stripes were used with special frequency 2.3 cycles/deg on the screen. It was found that at least 3s interval between two stimuli (between the end of the preceding and onset of the following movements) was necessary and sufficient period of the moving was about 100 ms. Resultant VER are then a reaction on the onset of the movement and are characterized mostly only by marked negative peak with latency being 140 to 200 ms. Opposite to reversal VER, those to the onset of the movement were obtained just in 87.5% of the persons examined (n = 40), in five cases, however, the response to the onset of the motion was higher than that to reversal VER amplitudes were in the latter case highest in the unipolar lead from the right occipital region with the rate of the structure movement being 42 to 84 mm/s.
The statistical evaluation of the visual acuity has to be based on the non-parametric test as the decimal scale of the visual acuity forms a serial scale and not the intervallic one. From the theoretic point of view, the most advantageous approach uses the paremetric statistical tests. Visual acuity is measured on optotypic tables with log gradiation of the optotype size. At present time optotypes of this kind are not available in Czechoslovakia.
The results of the present study show that the normal human visual acuity is not 1 (30 c/dg) but a remarkably higher value, about 1.73 (55 c/dg). Many authors, who studied the problem of objective determination of the visual acuity using visual evoked cortical potentials, corrected their results under the assumption that the objective method overestimates the real visual acuity. Now it is clear that the conventional determination of the visual acuity leads to serious underestimation of the real visual acuity. So, the way toward a more precise objective estimation of the human threshold visual acuity is now open.
In the sphere of dialysis treatment, the questions of adequacy of this form of treatment are receiving increasing attention. One of the criteria for the evaluation of this problem is no doubt the functional and anatomical state of the body. As the eye findings form an integral part of the entire clinical picture, the occurrence of pathological ophthalmologic lesions found after long term dialysis treatment (LTDT) can be used as a criterion of adequacy of the chosen treatment. Eye findings were evaluated in 12 patients with chronic renal insufficiency treated by haemodialysis for at least 10 years. On the external eye segment, most evident were degenerative changes of the pinguecula type, occurring in all patients. In all cases we also observed a massive disturbance of the retinal electrical activity (REA). In 58% of all examined patients we found a peculiar yellow-brownish pigmentation of the eye background. Greater or smaller alterations in the intra-ocular microcirculation in the chorioideal, retinal and papillary circulation regions were proven fluoroangiographically in all patients. In 5 eyes a marked disturbance of central vision was found as a result of pathological changes of the retinal centres or atrophy of the optic nerve. We may sum up that the haemodialysis treatment is yet not able to maintain all functions of the body at a satisfactory level.
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On examination, the central retinal areas of both eyes of a 44-year-old woman appeared symmetrical. So far only one other case with the same findings has been described in the literature; it was termed "cogwheel macular degeneration." Distinctive fluorescein angiographic and electrophysiological features indicate that the disease is dystrophic, primarily affecting the retinal pigment epithelium. Several criteria of the findings justify including this entity in the larger group of pattern dystrophies of the retina.
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Sixty-four amblyopic children (mean age 7.5 years, age range 4-12 years) were subjected to treatment using slowly rotating patterns of different spatial frequencies. In 20 amblyopes square-wave gratings (spatial frequencies 0.26-16.84 c/deg), in 44 checkerboard-patterned structures (spatial frequencies 0.04-5.2 c/deg) were used for stimulation. The mean improvement of the distance visual acuity was significantly higher in the checkerboard-stimulated group (3.59 equidistant optotype lines) than in the grating-stimulated group (2.71). As the highest spatial frequency of the checkerboards was substantially lower than of gratings, the results cannot be explained in terms of optical qualities of the stimulating patterns. Other factors, such as short-term occlusion, accomplishment of demanding visuomotor tasks and the quality of cooperation and attentiveness of the patients are considered to be more important for the success of treatment.