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Biomedical subjects

P Niesel

Publications and source records attributed to P Niesel.

16 recordsLinked to original sources
PubMed1978

[Retinal circulation time in diabetic retinopathy treated with photocoagulation (author's transl)].

A preliminary report is given on studies of the retinal circulation in diabetic retinopathy before and after photocoagulation treatment. The local retinal circulation time RCT of selected retinal areas was calculated by means of a fluorescein long-term infusion technique. In 7 eyes with diabetic retinopathy (DR) the mean RCT was significantly higher (2.0 +/- 0.58 sec. range 1.27-2.6) than in 15 control eyes (1.11 +/- 0.34 sec, range 0.50-1.82, Niesel 1976). Assuming an increase of blood flow in DR (L'Esperance 1971, Kohner 1975) the increase of RCT by a factor 2 would imply an increase of the vascular volume by a factor hardly less than 3 indicating the marked impairment of retinal hemodynamics in DR. After photocoagulation, the mean RCT was significantly shortened only in eyes with preoperative RCT values above 2 sec. The reduction of local RCT correlated with the extent of treated retinal areas. The cross-sectional area of the retinal veins measured near the optic disc was generally reduced independently of the extent of coagulation treatment. Taking also the obvious postoperative reduction of the total retinal vascular volume into account, photocoagulation resulted in a marked decrease of blood flow not only in extensively treated but also in areas with little coagulation effects. In DR the disturbed retinal circulation in general tends to normalize following extensive photocoagulation.

Blood Volume↗
PubMed1978

[The effect of lens opacities on the visual field (author's transl)].

The stray light effect on the visual field was quantitatively studied in normal subjects under experimental conditions. Stray light comparable to that caused by lens opacities was produced by means of selective occluders or diascleral illumination. The results derived from this model were compared with the statistical evaluation of the visual fields of 123 eyes with glaucoma followed for a minimum of 10 years. As expected lens opacities resulted in a concentric constriction of the peripheral fields and a loss of the inner isopters. The light difference sensitivity as determined by static perimetry was generally reduced preferentially in the central fields. These calculations provide a measure to anticipate the degree of lens opacifications from a depressed visual without knowledge of the visual acuity.

Adult↗
PubMed1978

[The random dot test as a screening method for the visual acuity in children (author's transl)].

The Random Dot Test was used for a screening of the visual acuity of children of 6 to 10 years of age. The testing time is reduced by 50% as compared with the examination by means of illiterate E images on cardboard charts. Children with refractive errors of up to 3 delta but normal visual acuity after correction are not detected at the examination distance of 1.30 m used in this study. None out of 672 children with severe eye diseases gave false negative results with the Random Dot Test. Disturbances of the binocular vision could also be detected with the Random Dot Test.

Child↗
PubMed1978

[Haemodynamics in retinal branch vein obstruction (author's transl)].

A branch vein obstruction in a 44-years-old woman recovered with in 7 months without any clinical residuals. The evaluation of fluorescein angiograms performed during thrombosis and after recovery showed significantly reduced retinal circulation times in around the thrombosis. The results indicate an increased blood flow ranging between 50 and 200% around the obstructed area of the retina. The haemodynamic situation of the retinal circulation during branch vein obstruction and its therapeutic consequences (photocoagulation) are discussed.

Adult↗
PubMed1977

[Th clinical picture of retinal thrombosis (author's transl)].

Besides the acute arterial occlusion and simple venous thrombosis, the clinical symptomatology may include signs of chronic arterial insufficiency, i.e. progressive blurring of vision, absolute visual field defects, cotton wool exudates, capillary occlusion and increased retinal circulation time. The poor visual prognosis is caused by progressive macular degeneration. In the case of acute arterial thrombosis, fragmentation of the blood column and absence of arterial pulsation are indicative of pronounced retinal ischemia. The ophthalmoscopic aspect of a visible embolus may be a hint for the prognosis of eventual recanalisation.

Fluorescein Angiography↗
PubMed1976

[The disjunction zone in the slit-image-photograph of the human aging lens (author's transl)].

Standardised slit-image-photographs of 178 clear lenses were evaluated by microdensitometry. The mean distance of the disjunction zone from the anterior capsule and the density of the disjunction zone remain constant during life. Its thickness will be reduced and its extension into deeper layers increases with age. In contrast to these findings the thickness of the whole lens according to the increasing thickness of the cortex increases with age. Its density increases too in a not linear manner probably on behalf of the increasing number of reflecting zones (Alterskernstreifen). The density of the nucleus of the lens increases with age, whereas its densitometrically defined thickness remains constant during life. The disjunction zone behaves independently from age in contrast to other parts of the lens.

Adolescent↗
PubMed1976

[The disjunction zone in the slit-image-photograph of the human lens in eye diseases (author's transl)].

Standardised slit-image-photographs of the clear human lens in 78 eyes with wide angle glaucoma, 29 eyes with uveitis and 35 eyes after an operation of a retinal detachment were evaluated by microdensitometry and compared with clear lenses of 178 eyes without eye diseases. Most significant alterations were observed in the anterior disjunction zone. Its thickness was increased in all these diseases with the exception of the glaucoma eyes treated with derivates of phenylephrine and/or cholinesteraseinhibitors. Under these conditions the disjunction zone disappeared. The alterations of the lens cortex and of the nucleus of the lens with respect to the thickness and its density were mostly accelerations of the normal aging process and only glaucoma eyes were partly in contrast to this process. Thickening of the anterior disjunction zone may be combined with a thickening of the whole lens and vice versa.

Adolescent↗
PubMed1975

Quantification of retinal lesions in diabetic retinopathy.

A method of quantitative evaluation of the number of microaneurysms is described for clinical research in the therapy of early stages of diabetic retinopathy. In a double-blind study it can be demonstrated that the described method quantifies the progression of retinopathy statistically during only one year of observation in 32 resp. 40 patients. The difficulties of quantification are due to interpretation problems of the photographic documentation and the learning problem of the observer.

Analysis of Variance↗