Search PubMed⌕ Search

Biomedical subjects

T Bek

Publications and source records attributed to T Bek.

At least 19 recordsLinked to original sources
PubMed1998

[Patient satisfaction with screening for diabetic retinopathy in a hospital setting].

The purpose of the study was to assess how patients appreciate the quality of screening examinations for diabetic retinopathy at the Department of Ophthalmology, Arhus University Hospital. A questionnaire was given to 500 consecutive patients who were examined between February and May 1996. Four hundred and twenty-nine patients (85.8%) answered and returned the questionnaire. Generally, there was satisfaction about the employed examination concept and the information and service provided during the examination. Patients in the age group between 26 and 35 years demanded more in order to achieve the same level of satisfaction as did patients from other age groups. One-third of the patients did not know that eye examination with fundus photography can detect diabetic retinopathy, but not all other eye diseases. Furthermore, the transport to the clinic was a greater problem than expected for patients living more than a few kilometers from the hospital. It can be concluded that in the planning of screening examinations for diabetic retinopathy, procedures should be designed so that the special expectations and needs of patients in the age group of 25-36 years are fulfilled. Patients should be informed that screening with fundus photography only detects retinal changes secondary to diabetes mellitus.

Adult↗
PubMed1998

[Organization of screening for diabetic retinopathy at a department of ophthalmology, Aarhus Municipal Hospital].

This article describes the organisation of screening for diabetic retinopathy at The Department of Ophthalmology, Arhus University Hospital, giving a descriptional analysis using Leavitt's organisational model. The employed organisational model is suitable for offering screening examinations for diabetic retinopathy in municipal diabetes teams. The experience gained to date at Arhus University Hospital shows that the severity of retinopathy of examined patients is similar to that found earlier in Danish diabetes clinics, and the frequency of newly diagnosed severe diabetic retinopathy is similar to that of findings from other centres.

Denmark↗
PubMed1998

24-h ambulatory blood pressure and retinopathy in normoalbuminuric IDDM patients.

The role of blood pressure elevation in the incidence and progression of diabetic retinopathy is not clearly established and results have been conflicting. Blood pressure and urinary albumin excretion (UAE) are closely related. In order to evaluate the independent relationship between retinopathy and blood pressure elevation, precise information on UAE is essential, as confounding by renal disease (incipient or overt), cannot otherwise be excluded. The aim of the present study was to evaluate the association between diabetic retinopathy and 24-h ambulatory blood pressure (AMBP) in a group of well-characterized normoalbuminuric IDDM patients. In 65 normoalbuminuric (UAE < 20 microg/min) IDDM patients we performed 24-h AMBP (Spacelabs 90207) with readings at 20-min intervals. Fundus photographs were graded independently by two experienced ophthalmologists. UAE was measured by RIA and expressed as geometric mean of three overnight collections made within 1 week. HbA1c was determined by HPLC. Tobacco use and level of physical activity were assessed by questionnaire. Fifteen patients had no detectable retinal changes [grade 1], 35 had grade 2 retinopathy; and 15 had more advanced retinopathy [grade 3-6]. Diastolic night blood pressure was significantly higher in patients with diabetic retinopathy compared to patients without retinopathy (68 +/- 8 mmHg [grade 3-6] and 65 +/- 6 mmHg [grade 2], compared to 61 +/- 4 mmHg [grade 1], p = 0.02). Diurnal blood pressure variation was significantly blunted in the patients with retinopathy as indicated by a higher night/day ratio of diastolic blood pressure (84.6% +/- 4 [grade 3-6], and 81.2% +/- 6 [grade 2] compared to 79.1% +/- 4 [grade 1], p = 0.01). Heart rate tended to be higher in patients in group 2 and 3-6 compared to patients without retinopathy with p values of 0.07 and 0.11 for day-time and 24 h values, respectively. Mean HbA1c increased significantly with increasing levels of retinopathy (p < 0.01). Patients were similar regarding sex, age, tobacco use, and level of physical activity. Notably, UAE was almost identical in the three groups (5.0 x /divided by 1.7 [grade 1], 3.9 x /divided by 1.8 [grade 2], and 5.1 x /divided by 1.6 microg/min [grade 3-6]). In conclusion, night blood pressure is higher and circadian blood pressure variation blunted in patients with retinopathy compared to patients without retinopathy despite strict normoalbuminuria and similar UAE levels in the groups compared. Our data suggest that the association between blood pressure and diabetic retinopathy is present also when coexisting renal disease is excluded. Disturbed diurnal variation of blood pressure is a pathophysiological feature related to the development of both retinopathy and nephropathy in IDDM patients.

Adult↗
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↗
PubMed1998

Capillary closure secondary to retinal vein occlusion. A morphological, histopathological, and immunohistochemical study.

BACKGROUND: The mechanisms underlying capillary closure leading to neovascularisation in retinal disease are unknown. In order to further characterize these mechanisms morphological, histopathological, and immunohistochemical changes in areas of capillary closure secondary to retinal vein occlusion were studied. MATERIAL: The retina from four eyes of two patients with evidence of previous retinal vein occlusion were cast for demonstrating the morphology of capillary closure. Subsequent histological sections through these areas were stained with periodic acid Schiff, Sirius red, and Alcian blue (basement membranes), and by immunohistochemistry to type IV collagen (basement membranes), von Willebrand factor (endothelial cells), glial fibrillary acid protein (GFAP) and vimentin (glial cells), S-100 protein (perivascular glial cells), carbonic anhydrase isoenzyme II (CAH-II) and CD-57 antigen (Müller cells), and CD-68 antigen (microglia). RESULTS: Retinal capillary closure was most prominent on the venous side of microvascular units. The material which was accumulated to occlude the lumen of retinal capillaries displayed immunoreactivity to GFAP, vimentin, CD-57 antigen, and CAH-II, but not to S-100 protein, suggesting that this material represents invaded Muller cells. The perivascular glial cells displayed continuous bands of immunoreactivity to S-100 protein corresponding to border zones of retinal areas affected by retinal vein occlusion, but this immunoreactivity was absent inside areas of capillary closure. The histopathological and immunohistochemical appearance of vascular basement membranes was similar in areas of capillary occlusion and outside these areas. CONCLUSIONS: The findings in areas of capillary closure secondary to retinal vein occlusion showed both similarities to and differences from capillary closure in other retinal disease such as diabetic retinopathy. This evidence may act as a basis for further elucidation of the pathophysiology of capillary closure in retinal disease.

Aged↗
PubMed1997

Corneal versus scleral tunnel incision in cataract surgery: a randomized study.

PURPOSE: To compare the induced regular and irregular astigmatism after scleral and corneal tunnel incision. SETTING: University hospital outpatient cataract clinic. METHODS: One hundred phacoemulsification patients with less than 1.0 diopter (D) of preoperative astigmatism were randomly assigned to have a clear corneal incision (50 patients) or a scleral tunnel incision (50 patients). All incisions were 3.5 to 4.0 mm wide and were made in the steepest axis of the corneal astigmatism. The surgically induced astigmatism was analyzed by vector analysis from keratometric data, as well as by Fourier harmonic series analysis of the topographic data. RESULTS: One day after surgery, the surgically induced astigmatism (vector analysis, keratometry) was 1.41 D +/- 0.66 (SD) and 0.55 +/- 0.31 D in the corneal incision group and the scleral incision group, respectively (P < .01). Six months after surgery, the induced astigmatism was 0.72 +/- 0.35 D and 0.36 +/- 0.21 D in the two groups, respectively (P < .01) The corneal topography data confirmed the regular astigmatism changes found by conventional keratometry. However, in addition, Fourier harmonic series analysis of the topography data showed significantly more irregular induced astigmatism with the corneal approach than with the scleral approach. CONCLUSION: The clear corneal incision induces significantly more regular as well as irregular astigmatism than the scleral tunnel incision.

Adult↗
PubMed1997

Immunohistochemical characterization of retinal glial cell changes in areas of vascular occlusion secondary to diabetic retinopathy.

PURPOSE: To study changes in retinal glial cell components in areas of vascular occlusion secondary to diabetic retinopathy. MATERIAL: The retina from ten eyes of six diabetic patients and from five eyes of five normal controls were studied for immunoreactivity to glial fibrillary acid protein and vimentin (glial cells), S-100 protein (perivascular glial cells), carbonic anhydrase isoenzyme II and CD-57 antigen (Müller cells), and CD-68 antigen (microglia). RESULTS: The study showed increased immunoreactivity to S-100 protein, corresponding to perivascularly located glial cells in the retina from diabetic patients, except for areas of vascular occlusion where this immunoreactivity was absent. Furthermore, the material invading the lumen of former retinal vessels in areas of vascular occlusion showed immunoreactivity to CAH-II and CD-57, suggesting that this material represents ingrowth of retinal Müller cells. CONCLUSIONS: The findings suggest that at least two types of changes in retinal glial cells are involved in the pathophysiology of diabetic retinopathy, i.e. 1) Reactive changes in the perivascular glial cells in the retina, and 2) Müller cell ingrowth into the former lumen of occluded retinal vessels.

Adult↗
PubMed1997

Glial cell involvement in vascular occlusion of diabetic retinopathy.

Twenty areas of retinal vascular occlusion from ten eyes of 6 diabetic patients were studied by immunohistochemistry to type IV collagen (basement membranes), von Willebrand factor (endothelial cells), and to glial fibrillary acid protein (glial cells) on serial sections. In all studied lesions immunoreactivity to type IV collagen and von Willebrand factor was confined to the retinal vascular walls whereas the material accumulated to occlude the vascular lumens centrally displayed immunoreactivity to glial fibrillary acid protein. All arterioles observed in the lesions were occluded. These arterioles had retained their circular shape, and the intravascular glial protein immunoreactivity communicated with the extravascular glial tissue through localised breaks in the vascular wall. The intravascular immunoreactivity was found to continue inside the arteriole along its successive diminishing to reach the capillary level. The venules were only occluded in less than half of the studied lesions. These venules were collapsed to assume a bean-like shape, and sequences with total obliteration of the vascular lumen alternated with sequences where a residual space corresponding to the former lumen displayed immunoreactivity to glial protein. The paper suggests that glial cell invasion, but not endothelial cells or basement membrane thickening, occludes the vascular lumen in areas of retinal non-perfusion secondary to diabetic retinopathy.

Aged↗
PubMed1996

Evaluating surgically induced astigmatism by Fourier analysis of corneal topography data.

PURPOSE: To evaluate surgically induced astigmatism using Fourier harmonic series analysis of corneal topography data. SETTING: Aarhus Kommunehospital, Aarhus University, Denmark. METHODS: We evaluated the results of 46 phacoemulsifications with a 4 or 6 mm scleral tunnel sutureless incision based on the axis of the steepest meridian. We performed conventional keratometry and corneal topography before and up to 1 month after surgery. Using Fourier analysis, the corneal topographic images were broken into spherical power, regular astigmatism, and nonregular astigmatism for individual or aggregate analysis of surgically induced astigmatism. The induced refractive change (average of the difference between preoperative and postoperative corneal topographies) was analyzed and normalized according to the surgical meridian and to right/left eye. RESULTS: Regular astigmatism calculated by Fourier analysis of mires from the keratometer zone correlated well with conventional keratometry readings. Surgery induced a localized flattening in the superior region and a with-the-rule regular astigmatism component in the central area. CONCLUSION: Surgically induced corneal topography changes can be analyzed by Fourier series harmonic analysis, allowing aggregate data to be broken into optically meaningful quantities.

Adult↗
PubMed1996

Vascular occlusion in diabetic retinopathy. A qualitative and quantitative histopathological study.

The retinal vessels from seven diabetic patients and from six age-matched normal controls were studied qualitatively and quantitatively using various histological staining techniques. In diabetic patients the walls of retinal arterioles and capillaries showed significantly more staining than normals for periodic acid Schiff (neutral glycoproteins), Sirius red (connective tissue), and for Alcian blue at pH 2.6, pH 5.8 and at pH 5.8 combined with MgCl22 in concentrations less than 0.9 M (acid mucopolysaccharides). In the retina from diabetic patients there was no difference between the number of capillaries staining with these dyes in areas of vascular occlusion, and in adjacent control areas. Furthermore, in areas of vascular occlusion, the material accumulated centrally to occlude the lumen of ghost vessels did not stain with any of the dyes used. A homogenous material, accumulated in the outer retina in areas of vascular occlusion in the retina from diabetic patients, only stained with Alcian blue at pH 5.8 combined with MgCl2 in concentrations less than 0.4 M, suggesting a different molecular composition from the Alcian blue material accumulated in the retinal vascular walls. The findings are in accordance with the knowledge that basement membranes of retinal vessels are thickened in diabetes mellitus. However, the findings also indicate that basement membrane thickening cannot fully account for vascular occlusion in diabetic retinopathy.

Aged↗
PubMed1996

Glycoprotein deposition in vascular walls of diabetic retinopathy. A histopathological and immunohistochemical study.

The association between periodic acid Schiff staining and immunoreactivity to laminin, fibronectin, vitronectin, and type VI collagen was studied qualitatively and quantitatively in the retinal vascular bed from 7 eyes of 5 diabetic patients and from 5 eyes of 5 normal persons. In the retina from diabetic patients the number of arterioles showing immunoreactivity to vitronectin, the number of venules showing immunoreactivity to type VI collagen, and the number of both arterioles and venules showing immunoreactivity to laminin and fibronectin, was higher than in normals. There was no difference between the number of capillaries showing periodic acid Schiff staining and immunoreactivity to laminin, fibronectin, and vitronectin when comparing areas of vascular occlusion with adjacent control areas. However, the number of capillaries displaying immunoreactivity to type VI collagen was higher in control areas than in areas of vascular occlusion in diabetic patients and in normal controls. Staining with periodic acid Schiff correlated topographically with immunoreactivity to laminin and fibronectin, but not with immunoreactivity to vitronectin and type VI collagen. In areas of vascular occlusion there was seen no immunoreactivity or histological staining corresponding to the material accumulated to occlude the ghost vessels.

Aged↗
PubMed1996

Precise correlation of histopathological and fluorescein angiographic morphology using retinal vascular casting.

The histopathology of three eyes obtained post mortem from 2 patients with age-related macular degeneration was correlated with the pre mortem fluorescein angiographic morphology. A precise point-by-point correlation between histopathology and the corresponding angiographic appearance was ensured by using the cast retinal vascular system as a pattern of reference. The study showed that both the photoreceptors, the pigment epithelium, and substances accumulated between the retinal and the choroidal vascular systems, may have a blocking effect on choroidal background fluorescence as seen on fluorescein angiograms. Furthermore, it is confirmed that fluorescein angiographic hyperfluorescence may be due to a lack of blocking of the choroidal fluorescence because of a window defect in the retinal photoreceptor layer and/or the pigment epithelium.

Aged↗
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↗
PubMed1995

Quantitative assessment of lateral interaction as determined by computerized quantitative layer-by-layer perimetry.

BACKGROUND: Quantitative layer-by-layer perimetry is a psychophysical technique which assesses lateral interaction in human vision. In prior designs of this technique the test procedure was time-consuming and quantitative assessment of the results was not possible. In order to shorten test duration and provide quantitative experimental data, a new computerized version of the technique has recently been developed. METHODS: A mathematical model for describing lateral interaction as assessed by computerized quantitative layer-by-layer perimetry was developed, and experimental data from the testing of 18 normal persons were fitted to the model. Two descriptive parameters of, respectively, lateral stimulation and lateral inhibition were for each test point related to the differential light sensitivity and to the eccentricity in the visual field. RESULTS: The two parameters describing lateral stimulation could not be reliably estimated. However, the two parameters describing lateral inhibition showed, respectively, a positive correlation with the differential light sensitivity in the visual field and a significant decline with increasing eccentricity in the visual field. CONCLUSION: The technique and the mathematical model employed are suitable for quantitative assessment of lateral inhibition in human vision.

Adult↗
PubMed1995

Clinical pathology and retinal vascular structure in the Bardet-Biedl syndrome.

A comparative study of clinical pathology and retinal vascular structure is described as studied by vascular casting in an eye of a patient with the Bardet-Biedl syndrome. At the time of examination the eye had been almost blind for at least 4 years. The histopathological examination showed a largely uniform loss of the outer retinal layers. The gross pathological examination of the cast ocular fundus showed three distinct zones, an inner zone inside the temporal vascular arcades where retinal vessels had been cast, a mid peripheral zone with bone spicules, and a peripheral zone with neither cast vessels nor bone spicules. The findings are discussed in relation to possible pathophysiological mechanisms involved in the development of retinal dystrophy in the Bardet-Biedl syndrome.

Female↗
PubMed1995

Fourier analysis of video-keratographic data. A tool for separation of spherical, regular astigmatic and irregular astigmatic corneal power components.

Topographic analysis of the cornea and computation of changes in corneal topography is difficult because of the lack of a standardized concept for analysing topographic information. We have used Fourier series harmonic analysis to decompose the often very complex information given in topographic images (TMS-1 video-keratograph). The polar data values arising from each mire were separated into spherical (average power), regular astigmatic (2' harmonic) and non-regular astigmatic components. The non-regular astigmatic components were further divided into a decentration component (1' harmonic) and a higher order irregular refractive component (root mean square (r.m.s.) of the residual between original data and the sum of spherical, 1' and 2' order components). Algorithms for utilizing the Fourier analysis technique on subjective refractive and on keratometric changes in regular astigmatism were also derived. Averages of the separate refractive components were calculated for groups of normal (right and left eye of 25 patients), keratoconic (13 eyes), and transplanted eyes (20 eyes), and average topographic maps were reconstructed and imaged. Changes in the separate topographic refractive components were compared with subjective refractive changes in eyes that had undergone combined myopic-astigmatic excimer laser ablation (8 eyes). Fourier series analysis was found superior to conventional keratometry in predicting spherical and regular astigmatic changes in subjective refraction. Fourier series analysis seems to be a powerful tool to decompose the information of complex topographic corneal images into rational optical components.

Algorithms↗