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Biomedical subjects

M Abrahamsson

Publications and source records attributed to M Abrahamsson.

49 records · Page 3Linked to original sources
PubMed1988

Contrast sensitivity and acuity relationship in strabismic and anisometropic amblyopia.

The contrast sensitivity function (CSF) and visual acuity were determined in children and adults with unilateral amblyopia due to strabismus or anisometropia with central fixation. The preschool children were examined repeatedly during occlusion treatment. All amblyopes had CSF deficits. The CSF was characterised by its peak value (the maximal sensitivity, Smax, and the spatial frequency at which Smax occurs, Frmax) calculated by a single peak least-square regression method. The two amblyopic groups showed discrepancies in relationship of both Smax and Frmax versus visual acuity both initially and during treatment. The strabismic cases had a more marked visual acuity deficit in relation to the contrast sensitivity losses, whereas these parameters are affected similarly in anisometropic amblyopes. The relationship between recovery of visual acuity and CSF during the initial month of occlusion treatment was of prognostic significance for the outcome of visual acuity improvement.

Adolescent↗
PubMed1988

Changes in astigmatism between the ages of 1 and 4 years: a longitudinal study.

Changes in astigmatism during development were studied in 299 infants with astigmatism as they grew from 1 to 4 years of age. All consecutive cases of 1-year-old infants with an astigmatism of 1.0 D or more in at least one eye found at an ophthalmic screening survey were selected for follow-up. The cycloplegic refraction was longitudinally followed at yearly intervals. During development there was no decrease in the degree of hypermetropia, but there was a significant decrease in the incidence and amount of astigmatism during the test period. The most pronounced decrease in magnitude and incidence of astigmatism occurred between the first and second year of life. The majority of astigmatic eyes of the 1-year-old infants had a horizontal curvature greater than the vertical (plus cylinder axis of 180 degrees), and no changes of the axis of the astigmatism were noted during the following years.

Aging↗
PubMed1986

Determination of a prodrug of tranexamic acid in whole blood by reversed-phase liquid chromatography after pre-column derivatization with fluorescamine.

A sensitive high-performance liquid chromatographic (HPLC) method for a prodrug of tranexamic acid (KABI 2161) in whole blood is described. Since KABI 2161 is rapidly hydrolysed in whole blood the samples are collected directly into the extraction tubes and extracted immediately. After pre-column derivatization with fluorescamine the derivatives are analysed by reversed-phase liquid chromatography on a C(8)-Nucleosil column using an eluent mixture of phosphate buffer and acetonitrile (pH 3). The eluent is monitored by a fluorescence detector. Determinations as low as 10 ng ml(-1) of KABI 2161 in whole blood can be made when 0.5 ml blood is analysed. The precision of the method is 4.1% (RSD) at the 300 ng ml(-1) level and 6.9% (RSD) at the 50 ng ml(-1) level.

Journal Article↗
PubMed1986

Photorefraction: a useful tool to detect small angle strabismus.

Forty patients with small angle strabismus and 30 straight eyed controls were examined by photorefraction in order to establish the validity of this method to detect strabismus. The sensitivity of the method was based on detection of asymmetry of the corneal light and/or fundus reflexes. All cases with a deviation of 2 degrees or more were detected, and 2 controls were falsely considered to be strabismic patients. The sensitivity of the method decreased when the patient wore optimal correction. Photorefraction therefore is considered to be a reliable, simple, and cheap tool with high sensitivity and specificity in screening for strabismus as well as refractive errors.

Adolescent↗
PubMed1986

Impairment of contrast sensitivity function (CSF) as a measure of disability glare.

A method for quantitative measurements of disability glare in clinical practice is presented. Glare is induced by a circular fluorescent tube which surrounds a sinusoidal grating displayed on a monitor. The threshold contrast that is needed for detection of the grating is measured with and without presence of the glare light. This is repeated for several different spatial frequencies. The discrepancy between the contrast sensitivity function (CSF) obtained with and without glare light was used to calculate the glare score (n) as a measure of disability glare. This was done for normals and cataract patients. The results show that an increasing glare score is related to an increase in turbidity of the optic media, while visual acuity had a weak correlation to the glare score. We also studied the relation glare score versus luminance and found that normals had a glare score that was almost independent of luminance level, while the cataract patients had a marked decrease in glare sensitivity when the luminance decreased. Most patients had a glare score that corresponded to their glare problems. These findings indicate a potential for using this psychophysical disability glare test method in industry, transport, and clinical ophthalmology. Some sources of methodological error inherent in the test method are evaluated and discussed.

Adult↗
PubMed1985

A comparison of the changes in suprathreshold apparent contrast in acute and simulated optic neuritis.

A thin PVC film was used as a diffusion filter together with glass lenses in order to induce a unilateral artificial contrast sensitivity depression in controls. These artificially depressed contrast sensitivity functions were made comparable to those assessed in patients during the recovery phase of their acute unilateral optic neuritis. A technique of subjective suprathreshold contrast matching was used to determine the suprathreshold apparent contrast in patients and controls with acute and simulated optic neuritis respectively. The results showed that differences in apparent contrast between the eyes is proportional to the discrepancy in threshold contrast for high and intermediate spatial frequencies in patients with optic neuritis. For low frequencies the apparent contrast difference was independent of threshold differences. Contrast vision of controls with simulated optic neuritis did not show this frequency dependency. There was also a discrepancy in visual acuity between the two groups. Generally the control with artificially depressed contrast sensitivity functions has a letter acuity value lower than that of the optic neuritis patient with a corresponding CSF depression.

Adult↗
PubMed1983

Photorefraction: A useful tool to detect refraction errors.

A simple photorefraction method using simultaneous photography of corneal and fundus reflexes have been used to screen 239 children aged 10 to 15 months for significant refraction errors. The photorefraction results were calibrated to those of cycloplegic retinoscopy. A good agreement was found between the 2 sets of values. The frequency distribution of refraction errors were similar to those presented by Ingram (1979). The aim to detect hyperopia greater than or equal to +2 or myopia greater than or equal to -4 diopters together with significant anisometropia or astigmatism was fulfilled with high reliability. Low degrees of hyperopia, myopia and astigmatism might be missed. Photorefraction therefore is considered to be a reliable, simple and cheap tool with high sensitivity and specificity in screening small children for significant refraction errors.

Astigmatism↗
PubMed1983

Malignant melanoma of the choroid and the ciliary body 1956-1975 in Halland and Gothenburg. Incidence, histopathology and prognosis.

All the 91 cases of enucleated malignant melanoma of the choroid and ciliary body in an area of the Swedish west coast (630 000 inhabitants) during the period 1956-1975 are analysed. The incidence was 0.72/100 000 inhabitants and year, which means that there was no increase lately corresponding to the increase described for cutaneous melanoma. Distribution according to age, sex and cell-type corresponded to other materials. 86 tumours were choroidal, 5 were located in the ciliary body. The mortality after 15 years was 50%. Tumours of the epitheloid type showed a surprisingly low mortality (29%). In only one case, with a 10 years survival, metastases were found at the time of primary diagnosis. The possibilities for early detection of metastases were, however, small. In 11 cases a period of delay and/or other treatment had preceded enucleation. The prognosis for these cases was not worse than for those who underwent immediate enucleation.

Adult↗
PubMed1982

Suprathreshold vision in acute optic neuritis.

The perception of contrast was measured in patients with acute unilateral optic neuritis by a technique of subjective suprathreshold contrast matching, and was compared with contrast sensitivity as defined by threshold measurements. The suprathreshold apparent contrast and threshold contrast sensitivity was repeatedly assessed during the recovery phase. Generally, an attenuation of suprathreshold apparent contrast was found for high and intermediate spatial frequencies in the eye with optic neuritis. At a low spatial frequency, however, the suprathreshold contrast vision was spared. The threshold contrast sensitivity was not however, spared at low spatial frequencies. During recovery this frequency-specific loss in suprathreshold apparent contrast diminished and finally a "normal" suprathreshold contrast vision was observed in all affected eyes reaching a visual acuity of 1.0 or better. In these cases also subjectively normal vision was reported in site of a persisting abnormality in threshold contrast sensitivity.

Acute Disease↗
PubMedDate not supplied

Prevention of amblyopia and the concept of cure.

Amblyopia is used as a comprehensive term for unexplained reduction of visual acuity, usually unilateral. As long as the visual deficit is monocular the visual loss is more of a potential problem than an actual handicap. Amblyopia is one of the most common causes of visual deficit in childhood, and since it is treatable, at least in children, considerable efforts have been made to detect it as early in life as possible. Screening programmes for amblyopia among preschool and school children have been widely organized throughout the world, although questions remain about their utility. This study evaluated amblyopia screening, focussing on some essential points that need thorough consideration before a screening programme is started. We also try to demonstrate some of the pros and cons of a screening system.

Amblyopia↗