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Biomedical subjects

F Møller

Publications and source records attributed to F Møller.

17 recordsLinked to original sources
PubMed2005

Fixation topography in normal test persons.

BACKGROUND: The eye is moved so that the object of interest falls on the central fovea, where the spatial resolution is highest. In the present study we quantified eye movements of normal test persons during steady fixation and characterized the fixation using a 3D fixation plot (X horizontal eye position, Y vertical eye position, Z time in each eye position). METHOD: Fixation eye movements were quantified binocularly in ten normal test persons during a 40-s fixation task using an infrared recording technique. RESULTS: The fixation plot was characterized by a single preferred fixation locus in 17 eyes. One eye had two distinctly separated preferred fixation locations and in two eyes the configuration of fixation plot was flat with no single identifiable locus of fixation. The fixation plots were elliptical along the horizontal meridian in 9 eyes, elliptical along the vertical meridian in 8 eyes, and round in 3 eyes. The fixation area (RAF95) ranged between 1418 and 14182 arcmin(2), and a significant positive correlation was found between RAF95 and the mean microsaccadic amplitude (p<0.001). CONCLUSION: The fixation plots are often characterized by a single preferred fixation locus but may also be almost flat with no identifiable location of fixation. The individual fixations patterns resembles the cone density contour plots as found in histological studies, and it may be speculated, that the shape of the fixation plot is determined by the cone density topography.

Adult↗
PubMed2005

The contribution of microsaccades and drifts in the maintenance of binocular steady fixation.

BACKGROUND: The eye performs three types of eye movements during fixation: fast microsaccades are interrupted by slow drift movements, and tremor is superimposed on the drifts. The contribution of the microsaccades and drifts in maintaining fixation has been discussed since the late 1950s. Initially, microsaccades were thought to correct the misalignment from the optimal fixation locus induced by the drift movements, a theory still postulated in more recent work. The present study aimed to uncover to what extent each fixation movement contributes to maintain steady binocular fixation. METHOD: Binocular fixation during a 40-s fixation task was recorded using an infrared recording technique for ten normal test persons. Start and end point of each microsaccade and drift were superimposed on a fixation map, and the distance to the preferred retinal location of fixation (PRL) was measured. RESULTS: It was found that 32.6% of the microsaccades corrected the previous drift movement towards the PRL, whereas 53.1% of the drifts corrected the endpoint of the previous microsaccade towards the PRL. The overall mean post-microsaccadic and mean post-drift distance to the PRL for the ten normal test persons were 0.46 degrees and 0.41 degrees , respectively; the difference was not statistically significant. Interindividually, the mean post-microsaccadic distance to the PRL ranged between 0.21 degrees and 0.91 degrees and the mean post-drift distance to the PRL ranged between 0.20 degrees and 0.72 degrees . CONCLUSION: Neither the endpoints of the microsaccades nor the drifts bring the visual line to coincide with the centre of the PRL. Consequently, it must be the eye movements performed during the drifts ("slow control") that keep the visual line in the centre of the foveola.

Adult↗
PubMed2005

Binocular fixation topography in patients with diabetic macular oedema: possible implications for photocoagulation therapy (3rd revision).

BACKGROUND: During retinal photocoagulation for diabetic maculopathy, there is a potential risk of foveal burns, and laser scars may later enlarge to be sight-threatening when involving retinal areas previously used during fixation. Since the retinal area used during binocular steady fixation has been found to vary considerably in the normal test person and central fixation may be even further compromised in patients with diabetic maculopathy, the sight-threatening side effects could possibly be reduced by taking into account the fixation area individually. However, no study has described and quantified the retinal area of fixation binocularly in patients with clinically significant macular oedema (CSME). METHODS: Sixteen diabetic patients with CSME in one or both eyes were examined. Each examination included visual acuity testing (ETDRS charts), a standard eye examination, central retinal thickness assessment by optical coherent tomography, fluorescein angiography and binocular quantification of fixational eye movements using an infrared recording technique. RESULTS: A negative correlation was found between visual acuity and mean microsaccadic amplitude (R=0.48, p=0.009). The maximal retinal extension of the fixation area ranged between 1.0 degrees and 3.0 degrees , and in two eyes with CSME, this area was estimated to exceed 800 mum on the retinal plane. No correlation was found between retinal thickness and visual acuity, retinal area of fixation, maximal extension of the fixation area or mean microsaccadic amplitude. CONCLUSION: Large interindividual differences in quantitative measures of binocular fixational eye movements were found. The mean amplitude of fixational eye movements was not correlated to central retinal thickness, and fixation area could only partly be predicted by visual acuity. Two eyes with CSME had an estimated maximal extension of the fixation area exceeding the central 800 mum on the retinal plane; thus, the possible benefit of individualising central photocoagulation according to precise measures of fixation area needs to be investigated on a larger population.

Adult↗
PubMed2005

Adhesion of T and B lymphocytes to mouse atherosclerotic aortas: association with lesion topology and VCAM-1 expression.

OBJECTIVE: Although T and B lymphocytes accumulate in atherosclerotic lesions and play a key role in their growth, the mechanisms involved in the adhesion and recruitment of T and B lymphocytes by the lesions have not been resolved. The aim of this study was to compare T and B lymphocyte adhesion to atherosclerotic arteries and to test the role of VCAM-1 and ICAM-1. MATERIAL AND METHODS: T and B lymphocytes were labelled with red and green fluorescent dyes and incubated with freshly isolated aortas from apolipoprotein-E-deficient mice. In some experiments the aortas were pre-incubated with specific monoclonal antibodies. After washing, the adhering cells were detected by confocal laser scanning microscopy. RESULTS: The number of T and B lymphocytes that adhered to the aortic intimal surface was similar in both lesioned and non-lesioned areas and in the shoulder region of the lesions. However, the adhesion of T and B lymphocytes was significantly higher in the shoulder regions compared with the lesioned (p<0.0001) and non-lesioned areas of the aorta (p<0.0001). After pre-incubation of the aortas with antibodies against VCAM-1 or ICAM-1, the lymphocyte adhesions in lesioned areas were 42 % (p = 0.04) and 55 % (p = 0.17), respectively, of those in lesioned areas that had been pre-incubated with a control antibody. However, although VCAM-1 protein expression was most pronounced in the shoulder region, the lymphocyte adhesions in the shoulder region and in non-lesioned areas were unaffected by pre-incubation with VCAM-1 antibodies. CONCLUSIONS: The results suggest that adhesion of T and B lymphocytes to mouse aortic endothelium is similar, is affected by lesion topology and is dependent on VCAM-1 expression over the core of atherosclerotic lesions.

Animals↗
PubMed2004

Medical management of diabetic retinopathy.

Although current treatment and prevention of diabetic retinopathy with laser photocoagulation, and tight metabolic and blood pressure control has reduced the risk of visual loss, there is still a need for additional therapies. A literature review on medical therapies for diabetic retinopathy has been performed, and the following classes of drugs are discussed: blockers of the renin-angiotensin system, protein kinase C-beta inhibitors, glitazones, somatostatin analogues, lipid-lowering drugs and anti-inflammatory drugs. There is experimental and clinical data suggesting beneficial effect from several classes of drugs on diabetic retinopathy, and results from large clinical trials are awaited within the next 3-4 years.

Diabetic Retinopathy↗
PubMed2003

The relation between visual acuity, fixation stability, and the size and location of foveal hard exudates after photocoagulation for diabetic maculopathy: a 1-year follow-up study.

PURPOSE: To study the relation between changes in visual acuity, fixation stability and the retinal area covered by hard exudates 3, 6 and 12 months after laser photocoagulation for diabetic maculopathy. METHODS: Twenty-four eyes of 24 patients with diabetes mellitus were examined 3, 6 and 12 months after retinal photocoagulation for clinically significant macular oedema. Each examination included visual acuity testing (ETDRS charts), quantification of fixation stability using a scanning laser ophthalmoscope (Rodenstock 101) and fundus photography. The fundus photographs were digitised and the retinal area covered by hard exudates determined by image processing. RESULTS: The retinal area covered by hard exudates decreased significantly during the first 6 months after treatment ( P=0.05, paired t-test), but increased again between 6 and 12 months after treatment. The visual acuity showed an increase, albeit non-significant, during the first 6 months after treatment followed by a decrease between 6 and 12 months after treatment. Quantification of fixation stability showed that four patients with central exudates fixated at the border of these lesions, and in two of these patients the disappearance of the exudates resulted in increased visual acuity and a change in fixation to the former exudate area. CONCLUSIONS: The retinal area covered by hard exudates decreases during the first 6 months after central photocoagulation, but increases again between 6 and 12 months after the treatment. Hard exudates covering the foveal region contribute to disturbance of central vision.

Adult↗
PubMed2002

Binocular quantification and characterization of microsaccades.

BACKGROUND: The significance of microsaccades in the visual process has been discussed for more than 50 years. However, only a few studies have measured microsaccades binocularly, and detailed quantification and characterization of these small movements are needed in order to further understand their nature. METHOD: The amplitude, velocity, acceleration and direction of microsaccades were quantified binocularly in 10 normal test persons during a 40-s fixation task, using an infrared recording technique. RESULTS: All microsaccades for all test persons were performed simultaneously and individually with an almost identical amplitude in the right and left eye (a range of 0.003-0.042 deg between right and left eye mean values). The mean microsaccadic amplitude for the test persons was within a range of 0.223-1.079 deg. The directional difference between simultaneously-performed right and left eye microsaccades was less than 22.5 deg for 84.8% of the saccades, indicating that the majority of microsaccades are conjugated. Three different fixation patterns were identified and characterized: (1) a classic interplay between easily identified drifts and medium-sized microsaccades (mean amplitude range 0.328-0.413 deg); (2) long intersaccadic intervals (4-5 s) with almost absent drifts, followed by three or four large microsaccades (mean amplitude range 0.755-1.079 deg); and (3) low-amplitude drift movements interrupted by low-amplitude microsaccades (mean amplitude range 0.231-0.265 deg). CONCLUSION: Microsaccades are involuntary, predominantly conjugated, simultaneously performed, and of almost identical amplitude in the right and left eye, suggesting a central control mechanism for microsaccades at subcortical level.

Adult↗
PubMed2001

Changes in gene expression following induction of ischemic tolerance in rat brain: detection and verification.

Tolerance against ischemic insults can be elicited in the CA1 region of rat hippocampus by inducing a short ischemic period 2-3 days prior to the ischemic insult. To detect genes whose expression changes following induction of ischemic tolerance (IT), we applied a differential display technique called restriction fragment differential display-PCR (RFDD-PCR). RFDD-PCR displays the coding region of mRNA and allows detection of differentially expressed mRNA. Double-stranded cDNA generated using a T25V primer is digested by the endonuclease TaqI, and adapters are ligated onto the cDNA fragments. When amplifying the adapter-containing cDNA fragments under high-stringency conditions, reproducible PCR profiles are obtained. By comparing these profiles from naïve and ischemia-tolerant rat brains statistically, significant expression changes of 20 fragments were identified. To verify the observed changes, quantitative PCR and in situ hybridization were performed for three fragments representing proteins with quite different functions (GluR2-flop, SC1, and p68 RNA helicase). Quantitative PCR displayed the same degree of regulation as RFDD-PCR, but in situ hybridization did not display any regulation. As the applied PCR-based techniques detect only polyadenylated mRNA, whereas in situ hybridization detects both nonadenylated and adenylated mRNA, changes in the polyadenylation state of the mRNA, rather than inconsistent changes in the total amount of mRNA, probably explain this discrepancy. Thus, our results show that the expression of genes hitherto not related to IT changes with the induction of IT and that the degree of regulation displayed by RFDD-PCR can be verified by quantitative PCR.

Activated-Leukocyte Cell Adhesion Molecule↗
PubMed2001

Is the AMPA receptor subunit GluR2 mRNA an early indicator of cell fate after ischemia? A quantitative single cell RT-PCR study.

After a moderate global cerebral ischemia, two hypothetical populations of pyramidal neurons are present among the hippocampal CA1 pyramidal neurons: one that will die and another one that will survive. Prior analysis of dissected hippocampal CA1 regions has shown a reduction of the GluR1-3 mRNA following ischemia. In order to identify these changes in single neurons, quantitative single cell RT-PCR was used to analyze the expression of GluR1-4 mRNA in rats 24 h after ischemia and also in rats after tolerance inducing ischemia. Control CA1 cells had a median copy-number of 290, 247, 207 and 16 GluR1-4, respectively. The tolerant cells showed small significant up-regulations of GluR1, 3 and 4 mRNA, while the GluR2 mRNA showed a more than 4-fold up-regulation compared to control cells. All the cells from ischemic animals displayed down-regulations of GluR1-3 mRNA. The GluR4 mRNA was not detectable in the ischemic animals. Our results thus show that the CA1 neurons react uniformly 24 h after a moderate ischemia independent of the fate of the neuron: thus two neuron populations with different GluR2 profiles cannot be identified in post-ischemic animals at 24 h. It seems however that an increased level of GluR2 can be used as an indicator of tolerance to ischemia.

Animals↗
PubMed2001

GABAA receptor subunit interactions important for benzodiazepine and zinc modulation: a patch-clamp and single cell RT-PCR study.

The expression of mRNAs for the GABAA receptor subunits alpha1, alpha6, beta2, beta3, gamma2 and delta in single mouse cerebellar granule cells and cortical interneurons were analysed by RT-PCR and correlated to their midazolam and zinc modulation of agonist-induced receptor currents. The registration of molecular and electrophysiological data from each cell allowed us to estimate the significance of individual subunits and their two-factor interaction for modulation. The presence of alpha6 decreased midazolam modulation, but statistical analysis also suggested interactions of alpha6 with beta3 and gamma2 with respect to midazolam modulation. Zinc modulation was decreased by the presence of gamma2, and analysis points to an beta3 effect as well as an interaction between gamma2 and delta in zinc modulation. Thus, our model confirmed, in single native cells, the known effects of alpha6 in midazolam and gamma2 in zinc modulation, and additionally pointed to significant subunit interactions that need to be further tested in recombinant receptors. The present study offers a method to identify subunit interactions in heteromeric receptor complexes.

Animals↗
PubMed2001

Is one 60 degrees fundus photograph sufficient for screening of proliferative diabetic retinopathy?

OBJECTIVE: To compare one 60 degrees fundus photograph to seven field stereo fundus photographs in identifying proliferative diabetic retinopathy. RESEARCH DESIGN AND METHODS: A total of 44 eyes in 23 patients with moderate/severe nonproliferative diabetic retinopathy were included. Evaluation of each eye was based on one 60 degrees fundus photograph. Eyes were re-examined using seven field 30 degrees stereo fundus photographs according to the protocol of the Early Treatment Diabetic Retinopathy Study, and the photographs were examined independently by three ophthalmologists to identify retinal neovascular lesions. In addition, fluorescein angiography was performed in all patients to verify the presence of the lesions. RESULTS: In four eyes of three patients (11.1% of eyes) evaluated based on seven field stereo photographs, retinal neovascularization was found. This condition was not found on examination of 60 degrees fundus photographs. CONCLUSIONS: Examination of one 60 degrees fundus photograph was found to be insufficient as a screening procedure in patients with moderate/severe nonproliferative diabetic retinopathy.

Adult↗
PubMed2000

Lack of correlation between visual acuity and fixation stability after photocoagulation for diabetic maculopathy.

PURPOSE: To study the correlation between changes in visual acuity and changes in fixation stability after retinal photocoagulation for diabetic maculopathy. MATERIAL: Twenty-four patients with diabetic maculopathy and visual acuity (VA) ranging between 0.05-0.77 were studied at baseline and 1, 3, 6 and 12 months after retinal photocoagulation. Fixational eye movements were quantified from video recordings of the ocular fundus obtained with the Rodenstock scanning laser ophthalmoscope. RESULTS: No correlation was found between the changes in the quantitative measures of the fixational eye movements (amplitude and retinal area of fixation) and the changes in VA 12 months after retinal photocoagulation. Three patients all with VA<0.31 at baseline had the fixation centre located more than 3 deg from the centre of the foveal avascular zone (FAZ) at one or more of the follow-up examinations, and one of these patients used three different locations of fixations during the follow-up period. CONCLUSION: Changes in fixation stability after retinal photocoagulation are complex but not related to changes in visual acuity.

Adult↗
PubMed2000

Short term visual prognosis after retinal laser photocoagulation for diabetic maculopathy.

PURPOSE: Retinal photocoagulation can improve the visual prognosis of patients with diabetic maculopathy complicated with clinically significant macular oedema. However, this effect covers a wide variation of visual outcome with some patients improving and other patients worsening several visual acuity steps. Therefore, parameters are needed that can be used to ensure that treatment is modified or avoided in those patients who are at risk of experiencing visual loss. METHODS: The change in visual acuity shortly after laser photocoagulation for diabetic maculopathy was assessed in 95 eyes of 79 patients as a part of a routine quality assessment programme, and was compared to the age at onset of diabetes, the pre-treatment duration of diabetes, the number of retinopathy lesions and the number of laser applications given to treat the maculopathy. RESULTS: On average visual acuity was unchanged at the post treatment control (mean=-0.04, SD=0.15), however, with a wide variation (range: -0.44 to 0.33). There was no correlation between the change in visual acuity and any of the studied background parameters. CONCLUSIONS: It is concluded that the treatment intervention rather than the general disease state is the main determining factor for the visual prognosis after laser photocoagulation for diabetic maculopathy. Other parameters should be identified to act as a basis for differentiating and improving laser photocoagulation of diabetic maculopathy. One such possible parameter might be the distance of retinopathy lesions and laser applications from the retinal fixation area.

Adolescent↗
PubMed1998

The relation between visual acuity and the size of fixational eye movements in patients with diabetic and non-diabetic macular disease.

PURPOSE: To study fixational eye movements as a function of visual acuity (VA) in patients with diabetic maculopathy and in patients with non-diabetic macular disease. MATERIAL: Two groups of patients each with VA ranging between 0.05-0.77 were studied, i.e. 24 patients with diabetic maculopathy and 23 patients with non-diabetic macular lesions. Fixational eye movements were quantified from video recordings of the ocular fundus obtained with the Rodenstock scanning laser ophthalmoscope. RESULTS: Within both groups of patients we found a similar significantly negative relation between the amplitude of fast saccadic eye movements and the VA. Patients with VA > 0.20 showed a normal directional pattern with larger amplitudes of the fast saccadic movements in the horizontal than in the vertical plane, whereas for patients with VA < or = 0.20 the amplitudes of the saccadic movements in the vertical plane had enlarged to equal the saccadic amplitude in the horizontal plane. Four patients with VA < or = 0.10 had the fixation centre located more than three degrees (approximately 500 microns at the retinal plane) from the centre of the foveal avascular zone, whereas the fixation centre of the remaining 43 patients was within one degree of the centre of this zone. CONCLUSION: Patients with VA < or = 0.20 may have retinal areas of fixation located more than 500 microns from the fovea. This fact should be taken into account when planning retinal photocoagulation in macular disease.

Adolescent↗
PubMed1996

Quantitative assessment of fixational eye movements by scanning laser ophthalmoscopy.

A new method for quantifying fixational eye movements by scanning laser ophthalmoscopy was developed and the method was evaluated in ten normal persons. Video sequences of the ocular fundus obtained during fixation were recorded, and linear movements of the fovea between successive video frames were transformed to angular movements of the eye by an algorithm that takes into account the individual optical properties of the eye. A computer program was developed to automatically calculate the amplitude, the direction, and the duration of the angular movements together with the precision of each of these estimates. Two types of eye movements could be recognized in normal persons; a fast type (saccades) which was initiated and terminated within one video frame (20 msec), and a slow type (drifts) which lasted more than 8 video frames (160 msec). The mean amplitude of the fast movements (0.41 degrees) was significantly higher than the mean amplitude of the slow movements (0.31 degrees). The methods was found to be suitable for quantifying fixational eye movements in clinical trials while simultaneously visualizing the ocular fundus. However, by refining the determination of the foveal position on the SLO images the precision of the method can be further improved.

Adult↗
PubMed1985

A randomized trial of iohexol versus amidotrizoate in endoscopic retrograde pancreatography.

To evaluate whether a low-osmolar contrast medium could decrease hyperamylasemia after endoscopic retrograde pancreatography, a prospective randomized double-blind trial of 54 consecutive patients with suspected pancreatic disease referred for endoscopic retrograde pancreatography was performed. The low-osmolar contrast medium iohexol and high-osmolar amidotrizoate were used. No statistically significant differences with regard to rise in pancreatic-type amylase, pain reaction, or diagnostic information were found. No case of acute pancreatitis was observed.

Adult↗