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Biomedical subjects

S Harrer

Publications and source records attributed to S Harrer.

At least 19 recordsLinked to original sources
PubMed1988

[Activation-induced changes in visual functions].

Visual functions were tested in 18 healthy male medical students on a control day and on the day of an oral examination. Stress induced impairment was observed in binocular tests measuring accommodation, convergence or their mutual relationship (near points of accommodation and convergence, Maddox-wing). Results of tests in which fusion operates as stabilizing factor (slightly dissociating test: Polatest) or of tests designed for far distance vision (synoptophore, Maddox-cross, Pola-cross) did not show significant impairment under examination stress. In slightly dissociating tests an activity-dependent improvement in stereoscopic vision became evident. Flicker fusion frequency values increased under stress. Colour vision analysis by means of the Nagel anomaloscope revealed that the absolute matching range remained unchanged, whereas the relative matching range broadened on the day of examination. The results indicate activity-dependence of binocular vision, with an improvement in central nervous functions on the one hand and an impairment of peripheral accommodative components on the other hand. Furthermore, it may be concluded that binocular coordination is achieved independently from accommodation dependent focusing of the image and is apparently processed separately and parallel to monocular image components.

Accommodation, Ocular↗
PubMed1988

[Color vision in cataract, aphakia and pseudophakia].

Color vision examinations were performed using a clinical test battery and two spectral laboratory methods. With aphakia and iris-clip lenses (ICL) there were slight acquired blue-yellow defects six months to three years after surgery, especially when the more sensitive laboratory methods were used. They were possibly caused by photochemical damage to the retina or by a barrier deprivation syndrome. Color vision with posterior chamber lenses (PCL) was superior to that with ICL, and in aphakic subjects it was quite normal. In the clinical tests no differences could be found between PCLs of clear PMMA material and those with UV absorbing properties. Slight acquired blue-yellow defects in the immediate postoperative phase after implantation of PCLs can be attributed to postoperative irritation and are reversible. Lasting and severe blue-yellow defects indicate inflammation or macular edema.

Adult↗
PubMed1987

[Modification of visual perception by vision training].

The course of the visual pathway as far as the sulcus temporalis superior is described and the change in the shape of the receptive fields is pointed out. The transformation of action potentials into conscious perception is interpreted as it was by Eccles. A connection is made between the problem of learning and the plasticity of the spine synapses, the capacity of which can be considerably increased. In conclusion, it is pointed out that in cases of macular disease it is possible to stimulate peripheral areas of the visual field by special training and thus to help the visual field by special training and thus to help the patient.

Aged↗
PubMed1986

Oestrogen modulates dopamine-controlled behaviours in the male ferret.

Oestradiol (100 micrograms/kg) was administered to male ferrets on three successive days. Two and three days after the last oestradiol injection the effects of apomorphine (0.5 mg/kg) on stereotyped, predatory and scent marking behaviour were intensified. Thus, three days of oestradiol administration produced a supersensitive dopaminergic system two days after the last oestradiol injection. However, no initial antidopaminergic effect of oestradiol could be demonstrated one day after the last oestradiol injection.

Animals↗
PubMed1986

Annual rhythm and hormonal control of predatory behavior in female ferrets.

The predatory behavior of female ferrets shows seasonal fluctuations which appear to be affected by estradiol. Under natural lighting conditions in the laboratory the annual rhythm of the behavior was observed during anestrus, estrus, pregnancy, pseudopregnancy and lactating period. Females in heat failed to show predatory behavior whereas females in anestrus killed their prey. Exposure of anestrous ferrets to a prolonged illumination (LD 16:8) during winter induced an estrus which inhibited predatory behavior. When estrus was terminated with human chorionic gonadotropin (HCG), predatory behavior did not further regress as it did in control runs. Thus, during the period of estrus, when estrogen levels are presumably high, predatory behavior was inhibited. To prove a possible interdependency of estrogen and predatory behavior, estradiol-17 beta-valerat was chronically administered. This treatment induced the estrous cycle one day after the first injection. Inhibition of predatory behavior occurred following a delay of 28 days. Thus, fluctuations of estradiol levels are a factor which may affect fluctuations of predatory behavior in female ferrets.

Animals↗
PubMed1986

[Significance of aniseikonia following implantation of posterior chamber lenses].

Posterior chamber lenses with angled haptics were implanted in one eye of each of 53 patients with senile cataract. Dioptric aniseikonia was calculated between 1 month and 24 months after surgery (with Gruber's and Huber's computer program) on the basis of most recently obtained values (bulb axis length, depth of the anterior chamber, lens thickness, necessary refraction), and compared with subjective measurements taken with the phase difference haploscope. The agreement between the calculated and subjective aniseikonia was greatest when tested in a vertical meridian. However, it was not possible to predict any correlation between dioptric and subjective aniseikonia with confidence. On the basis of the test results it seems justified to aim for a minimal refractive error in the pseudophakic eye of about +/- 0.5 D in patients with hypermetropia or myopia up to 4 D, even if subjective aniseikonias of over 10% can be proved. The latter manifest great meridional differences and hardly interfere with binocular single vision.

Adult↗
PubMed1985

[Diagnosis and therapy of optic neuritis].

Time-consuming and complicated electrophysiological methods need only be applied in unclear cases of optic neuritis. In the majority of patients it is possible to demonstrate opticus conduction disturbance with exact clinical subjective and objective tests. Some neuroophthalmological investigations that are well-suited for routine use are described more closely. Our own investigations of 190 patients demonstrated - in accordance with the modern medical literature - that the nowadays usual therapeutic measures do not influence the course of an optic neuritis essentially.

Color Vision Defects↗
PubMed1985

[Central corneal endothelial changes in contact lens wearers].

Report on the appearance of opacities in the central area of the cornea after long-term wearing of HEMA lenses. These changes are at first small curved spots and can develop into marked reticulate opacities at a late stage. All of the patients were long-term contact lens wearers and all used cleaning solutions containing chlorhexidine. Since early symptoms such as 'red eye' or 'blurred vision' are absent in most of the cases the patients fail to consult their doctors in time. The damage appears to be irreversible and early diagnosis is therefore important.

Adult↗
PubMed1985

[Differential diagnosis and therapy of gigantopapillary conjunctivitis].

If wearers of contact lenses present with secretion and incompatibility of the contact lens, simple ectropionation of the upper eyelids often is sufficient to diagnose a giant papillary conjunctivitis as the cause. This form of papillary hypertrophy affecting wearers of both hard and soft contact lenses is morphologically similar to vernal conjunctivitis, which should be considered in cases of corneal ulceration resistant to therapy. The histological difference between the two forms of papillary hypertrophy is that contact lens-induced giant papillary conjunctivitis shows remarkably less eosinophilic infiltration of the papillary stroma. Both forms of papillary hypertrophy seem to be based on a complex immunologic reaction.

Adult↗
PubMed1985

[Binocular vision following posterior chamber lens implantation].

Binocular vision was tested in 106 pseudophakic patients 1 week after unilateral implantation of a Simcoe posterior chamber lens with 10 degrees angled haptics. Binocular functions are resumed immediately after surgery. Visual acuity, or rather the difference in visual acuity between the right and left eyes is mainly responsible for the quality of binocular vision. Heterophoria, anisometropia, and aniseikonia are less important.

Aged↗
PubMed1985

[Topographic-anatomic position of the posterior chamber lens].

The present paper reports on a macroscopic and scanning electron microscope examination of a human cadaver eye with implanted posterior chamber lens (Simcoe type). The actual position of the lens haptics after planned sulcus ciliaris fixation is illustrated.

Aged↗
PubMed1985

[Disorders of binocular vision in amblyopic patients working at computer terminals].

For the first time two cases are described with disturbances of binocular vision caused by subjective perception of positive scotomata in the amblyopic eye. The visual strain of working at a terminal leads to a slight increase in the squint angle; as a result, a paracentral scotoma may shift into the middle of the binocular visual field and impair the image quality of the fixing eye. Amblyopic subjects presenting with these symptoms are disqualified from working at VDUs. However, not every amblyopic is affected.

Adult↗
PubMed1983

[Convergent strabismus with eccentric fixation in a case of persistent pupillary membrane].

Case report of a now 9-year-old boy with a pronounced persistent pupillary membrane in both eyes combined with amblyopia and eccentric fixation in the right eye and a convergent squint. After surgery removing the persistent pupillary membrane in both eyes at the age of 4 years, pleoptics and orthoptics were applied. Visual acuity and eccentric fixation did not improve. Strabismic surgery was carried out with good cosmetic result. Aetiologically, one can assume a deprivation by the persisting pupillary membrane.

Amblyopia↗
PubMed1982

[Limbal and perilimbal changes in wearers of HEMA lenses].

Incompatibility of HEMA contact lenses leads to changes in the conjunctiva and cornea which frequently appear in the region of the corneal limbus. From the limbus toward the sclera one can differentiate four stages according to the clinical picture: (1) enlargement of the pericorneal capillary network; (2) pronounced pericorneal injection right to the rim of the contact lens; (3) border-like edema in the area actually in contact with the lens; (4) additional haemorrhage in this area. From the limbus toward the cornea three typical changes occur: (1) peripheral edema of the cornea; (2) neovascularization of the cornea; (3) pannus formation.

Conjunctival Diseases↗
PubMed1982

[Corneal changes due to HEMA lenses].

The topic of this paper is the appearance of palisade-shaped, soft, gray opacities of the corneal epithelium in wearers of HEMA lenses. The opacity emanates from the limbus and is located under the upper eyelid. The paper also deals with the formation of folds in Bowman's membrane. They are approximately horizontal, are usually located within the lid-fissure and occur in combination with large-scale opacity of the corneal epithelium in the upper third of the cornea. The differential diagnosis of well-known corneal changes is also discussed.

Contact Lenses, Hydrophilic↗
PubMed1981

[Differential diagnosis of corneal changes in wearers of Hema lenses (author's transl)].

The authors report on a disease of the cornea resembling keratitis nummularis developed by patients wearing Hema lenses. The large disk-shaped subepithelial opacities are accompanied by pathologic changes in the endothelium of the peripheral parts of the cornea. Etiologically, it is believed that there is an immunologic process acting on components of the lenses and the solutions they are cleaned with and kept in. The differential diagnosis between Dimmer's nummular keratitis, epidemic keratoconjunctivitis and herpetic corneal diseases in discussed.

Contact Lenses, Hydrophilic↗