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Biomedical subjects

G Lennerstrand

Publications and source records attributed to G Lennerstrand.

At least 73 records · Page 4Linked to original sources
PubMed1982

Delayed visual evoked cortical potentials in retinal disease.

Flash and pattern visual evoked potentials (VEPs) were recorded in 16 patients with macular disease and in 3 patients with retinitis pigmentosa. Pathological VEP latencies were seen in 14 of the patients with macular lesions and in one with retinitis pigmentosa. Most eyes with a visual acuity below 0.2 showed delayed pattern responses. However, patients with higher visual acuity also had delayed pattern VEPs. It is concluded that an increase in VEP latency is not a specific sign of optic nerve lesion but may also occur in retinal disease, affecting different parts of the sensory retina.

Adolescent↗
PubMed1982

EMG as an aid in the retrieval of disinserted extraocular muscle. A case report.

In a 57-year-old man the traumatically disinserted inferior rectus muscle was located in the orbit with the help of EMG, and the muscle was re-attached to the globe. Post-operatively good ocular motility and comfortable binocular vision was regained. This seems to be the first report of the use of EMG recordings for the retrieval of a lost extraocular muscle.

Electromyography↗
PubMed1982

Visual evoked potentials to binocular stimulation with disparate patterns.

Experiments with VEP to checkerboard stimulation in 4 subjects with normal stereoscopic vision showed that binocular interaction was the same for fused images and for linear pattern displacement induced by horizontal and vertical prisms, as long as the patterns were projected on the macular areas of both eyes. Also in a stereo-blind subject the impaired binocular VEP interaction remained unchanged during linear displacement of the patterns. Thus the previously reported differences in binocular VEP interaction between stereo-normal stereoblind subjects cannot be explained by binocular stimulation with unfused patterns in the latter group. With patterns displaced to different hemifields in the 2 eyes, no binocular interaction was recorded. Experiments with black-and-white gratings of different orientations to the 2 eyes showed that binocular VEP reactions remained the same even with patterns perpendicular to each other. However, the binocular interaction was disrupted when the subject viewed the perpendicular patterns through coloured filters.

Adolescent↗
PubMed1982

Adjustable sutures in strabismus surgery. A follow-up study.

Strabismus surgery with adjustable sutures of absorbable material was performed in 19 patients, aged 8-69 years, who had paralytic strabismus and/or were re-operated. The ocular alignment was assessed at 1 week and 3-12 months post-operatively. In 12 of the patients eye position was stable during that period. Eleven of them had good or moderate binocular vision. However, eye position changed over the follow-up period in about half of the patients with poor binocular vision. No evidence was found for any muscle repositioning by mechanical stress during suture absorption.

Adolescent↗
PubMed1982

Pattern VEP in two immunochemical subtypes of optic neuritis.

Visual functions and visual evoked potentials (VEP) were compared in 2 groups of patients with optic neuritis (ON). The subdivision was based on the occurrence of oligoclonal IgG in the cerebrospinal fluid in some patients [the ON (+) group] but not in others [the ON (-) group]. At the onset of ON there were no other signs of neurological disease in these patients. Later the majority of those in the ON (+) group had developed multiple sclerosis but only one patient in the ON (-) group. Recovery after the acute optic inflammation was the same in both groups with respect to visual acuity and fields, but better in the ON (-) than in the ON (+) group with respect to colour vision and pattern VEP. A closer correlation between colour vision defects and VEP latency changes was found for the ON (+) than the ON (-) group, suggesting demyelinating disease as a more probable cause of the optic nerve inflammation in the former than in the latter group.

Adolescent↗
PubMed1981

Effects of grating stimulation on visual acuity in amblyopia.

Thirty-one children with amblyopia were treated with CAM vision stimulation. Twenty-one of them had previously been treated with conventional methods but failed to improve further. The conventional therapy was continued during and after CAM. Grating stimulation was the first treatment attempted for the rest of the children. Most children in both groups showed improved distance visual acuity after CAM-treatment and no one suffered a loss. The average visual acuity improvement was the same in both groups of children and did not vary with age. The improvement amounted to about 50% of the visual acuity before CAM, irrespective of the pre-treatment acuity level. We conclude that CAM-stimulation can be useful in cases where occlusion or other amblyopia treatment has failed, but that some form of treatment must be continued if visual acuity is to be maintained after the CAM-treatment period.

Adolescent↗
PubMed1981

Picture simulation of contrast sensitivity in organic and functional amblyopia.

We have tried to illustrate some contrast sensitivity defects by picture simulation. We have used data obtained from 2 patients: a woman with optic nerve lesion (Snellen VA 0.5) and a 7.5-year-old boy with anisometropic amblyopia (VA 0.6). The optic nerve lesion was represented by profound contrast sensitivity loss for all spatial frequencies, while the anisometropic eye showed loss only at high spatial frequencies. A positive picture was decomposed into 1.25 X 10(6) pixels (picture elements), using a drum scanner. In a computer each spatial frequency component of the picture was multiplied by the ratio between the patient sensitivity value and that of an age-matched reference group and a modified image was processed. The pictures illustrate the poor image quality that is associated with general contrast sensitivity loss, even when Snellen visual acuity is only moderately impaired.

Amblyopia↗
PubMed1980

The postnatal development of the inferior oblique muscle of the cat. III. Fiber sizes and histochemical properties.

Transversal sections of the inferior oblique muscle from kittens of various ages and from adult cats were stained for myofibrillar ATP-ase at Ph 9.4 and 4.35, succinic dehydrogenase (SDH) and fat. The same muscles had previously been submitted to studies of contractional and fatigue properties. With ATPase the fibers could be differentiated into types I, II and II C. The percentages of each fiber type remained approximately the same from birth onwards. In the inner, global layer of the muscle, type I fibers showed a linear increase in size, but types II and IIC fibers an accelerated growth after age 20 weeks. In the outer, orbital layer, where no type I fibers were seen, type II and II C fibers showed the same growth pattern as in the global layer. The fiber content of SHD and fat was low at birth but increased after two weeks of age. Type I fibers were poor and type II C fibers rich in SDH and fat. Type II fibers showed varying amounts of these substances. Provided that type I fibers are slow, type II fast and type II C intermediate in speed of contraction, like in other muscles, the findings on fiber growth and SDH content seem to support the idea that slow, fatigue resistant components in eye muscles reach maturity earlier than fast components.

Adenosine Triphosphatases↗
PubMed1979

Contractile properties of extraocular muscle in cats reared with monocular lid closure and artificial squint.

Kittens were raised with amblyopia by monocular lid suture or esotropia by transection of extraocular muscles in one eye at the age of 2--3 weeks. Isometric contractions in the inferior oblique muscle were recorded at 20 weeks or at adult age, and the results were compared with those of similarly aged cats with normal visual development. The speed of contraction and the fatigue resistance was reduced in the lid sutured animals. In the esotropic cats studied, fatigue resistance was also reduced but the speed of contraction did not change much. It is suggested that the postnatal eye muscle development can be modified by manipulation of the visual input at an early age. Presumably the impaired binocular vision in the lid sutured and esotropic cats reduced the demand for fusion vergences, and this might be reflected in the changes of eye muscle properties. In monocularly lid sutured cats, eye muscle changes were the same on both sides, suggesting that amblyopia per se did not affect eye muscle development.

Age Factors↗
PubMed1979

Age variations in normal human contrast sensitivity.

The visual contrast sensitivity (the reciprocal of contrast threshold) was studied as a function of age. Psychophysical measurements of binocular and monocular contrast thresholds were made for 33 normal observers at spatial frequencies within the range 0.5 to 40 cycles/degree. The observers were divided into three different age groups: young, middle-aged, and old subjects with the age ranges 6--10 years, 20--40 years, and 60--70 years, respectively. All observers had healthy eyes, normal vision, and Snellen visual acuity of 1.0 or better in both eyes. In all groups, contrast sensitivity for binocular and monocular viewing peaked at a spatial frequency around 3--5 cycles/degree and showed the typical attenuation at low and high spatial frequencies. The binocular contrast sensitivity was higher than the monocular. There was no significant difference between young and middle-aged subjects with regard to contrast sensitivity. Subjects aged 60 years or more showed significantly lower contrast sensitivity than younger subjects for most spatial frequencies above 4 cycles/degree. We may thus conclude that both the binocular and monocular contrast sensitivity seemed independent of age within the range of 6 to 40 years. For higher ages studied (above 60 years), there was a loss of sensitivity in the middle and high frequency regions.

Adolescent↗
PubMed1979

Contractile properties of extraocular muscle in Siamese cat.

Siamese cats are albinos with poor visual resolution and severely impaired binocular vision. Eey muscle phyiology was studied in Siamese cats as a part of a more extensive project on eye muscle properties in cats with deficient binocular vision. Isometric contractions of the inferior oblique muscle were recorded in response to single and repetitive muscle nerve stimulation. Speed of contraction, measured as twitch contraction time, fusion frequency and rate of tetanic tension rise, was lower in Siamese than in normal cats. Eye muscles of Siamese cats fatiqued more easily to continuous activation than normal cat eye mucle. These functional changes have also been found in cats with binocular defects from monocular lid suture, but were much more marked in Siamese cats. It is suggested that the eye muscle changes represent muscular adaptations to genetically caused impairments of binocular vision and visual resolution in Siamese cats.

Albinism↗
PubMed1978

The postnatal development of the inferior oblique muscle of the cat. I. Isometric twitch and tetanic properties.

The postnatal development of the inferior oblique muscle in the cat has been studied with physiological and histochemical techniques. This paper describes the changes with age in isometric twitch and tetanic response characteristics. The twitch amplitude increased and the twitch contraction time (ct) and half-relaxation time (hrt) decreased almost linearly from birth to adulthood. The relation between the strength of nerve stimulation and twitch ct and hrt changed during development with a threshold slow response appearing at 10 weeks. Twitch responses in cats 6 weeks of age or older were of longer duration than in younger cats, in spite of the longer ct and hrt in young cats. Fusion frequency of the tetanic response reached a constant level in muscles 6 weeks or older. The maximum rate of tension rise remained the same from birth to 6 weeks of age and later increased markedly up to 20 weeks of age. The contracture induced by succinylcholine was the same in muscles of all ages. These data were related to previous findings on the postnatal development of fast and slow muscles and motor units in the hindlimb of the cat. A differentiation of the development of fast and slow eye muscle fibers is suggested. Slow fibres seemed to have completed their maturation at about ten weeks of age, while the development of fast fibre properties continued, probably up to the adult stage.

Age Factors↗
PubMed1978

The postnatal development of the inferior oblique muscle of the cat. II. Effects of repetitive stimulation on isometric tension responses.

The changes with postnatal age in post-tetanic potentiation (PTP) and fatigue of the inferior oblique muscle have been studied in the cat. PTP of the twitch amplitude increased steadily with age up to 20 weeks after birth. Twitch contraction time (ct) and half relaxation time (hrt) was not significantly changed. The potentiation of the tetanic response also became more prominent with age. The young muscles (10 weeks and below) were slightly more susceptible to fatigue than older muscles, but recovery was rapid in muscles of all ages. Intensive stimulation induced post-tetanic depression of twitch responses in muscles older than 1 week, but none in the muscles of new-born cats. Ct and hrt were greatly prolonged in muscles above six weeks of age. In these muscles, but never in the very youngest, repetitive firing could be observed in response to post-tetanic single nerve stimulation. The results are compared with those obtained in similar experiments on hind-limb muscles by other workers. They further support the idea, raised in a previous paper, that slow eye muscle fibres develop quicker and reach maturity earlier than fast fibres.

Age Factors↗