Biomedical subjects

J L Hougaard

Publications and source records attributed to J L Hougaard.

4 recordsLinked to original sources

PubMed2005

Enhanced optical coherence tomography imaging by multiple scan averaging.

AIMS: To describe a method for computerised alignment and averaging of sequences in optical coherence tomography (OCT) B-scans and to present selected clinical observations based on the resulting improvement in retinal imaging. METHODS: A methodological study and retrospective investigation of selected cases. Five human subjects were included, one healthy subject, two patients with central serous chorioretinopathy, one patient with branch retinal vein occlusion, and one patient with cilioretinal artery pseudo-occlusion. Based on computerised alignment of sets of B-scans obtained at identical retinal locations, average OCT images were produced and displayed in false colour or grayscale. These enhanced tomograms were compared with other morphological and functional characteristics. RESULTS: Improved retinal imaging enabled assignment of the OCT image to retinal anatomy particularly at the outer layer of the photoreceptors and the retinal pigment epithelium, both in the healthy eye and in pathology. Identification of both post-oedematous structural disorganisation as well as post-ischaemic attenuation of the inner retina was superior to standard OCT images. CONCLUSIONS: Averaging of multiple OCT B-scans enhances the quality of retinal imaging sufficiently to reveal new details of retinal pathophysiology. Using the technique on OCT3 scans enables visualisation of details comparable with the results obtained using ultra high resolution OCT.

Adult↗

PubMed2004

On the possibility of a bridge between CBA and CEA: comments on a paper by Dolan and Edlin.

In a recent work by Dolan and Edlin, it is concluded that no link can be established between cost-benefit analysis (CBA) and cost-effectiveness analysis (CEA). However, the conclusion seems to depend rather heavily on what is understood by a link between CBA and CEA as well as on the exact meaning of the latter two terms. We argue that there is at least one approach to CBA and CEA in which the two are very intimately linked. On the other hand, the limitations in the access to preference information has consequences for the kind of questions that can be meaningfully addressed in both CBA and CEA.

Attitude to Health↗

PubMed2002

Lens ageing as an indicator of tissue damage associated with smoking and non-enzymatic glycation--a twin study.

AIMS/HYPOTHESIS: With ageing the long-lived proteins of the human lens undergo denaturation by non-enzymatic glycation. The denaturated proteins are fluorescent, a property that can be assessed in vivo by fluorometry. Our aim was to examine the relative contribution of hereditary and environmental effects on the accumulation of fluorescent compounds in the lens. METHODS: We examined 59 monozygotic and 55 dizygotic healthy twin pairs recruited from a population-based register of twins. Lens autofluorescence was measured on the undilated eye. All subjects underwent an OGTT and information on smoking habits was obtained. The genetic and environmental effects were estimated by structural equation modelling. RESULTS: Lens autofluorescence was related to age (R(2)=53%), current glucose homeostasis (R(2)=10%) and smoking habits (R(2)=10%). After adjusting for these factors, interindividual variation in lens autofluorescence was statistically attributable to hereditary factors by approximately 28% as well as shared environment by 58% and non-shared environment by 14%. The hereditary factor seems not to be linked to a genetic predisposition to diabetes. CONCLUSION/INTERPRETATION: The correlation in lens fluorescence was greater in monozygotic twins than dizygotic twins indicating a genetically predetermined susceptibility for the accumulation of fluorophores in the lens, the relative importance of which was found to increase with age. Since fluorophore formation in the lens is attributable to non-enzymatic glycation our results support that genetic characteristics to some degree determine the susceptibility to glycation related diabetes complications and ageing processes.

Adult↗

PubMed2001

Effects of pseudophakic lens capsule opacification on optical coherence tomography of the macula.

PURPOSE: To report observations on the influence of posterior lens capsule opacification on optical coherence tomographic imaging quality and measurements of macular thickness. METHODS: The retrospective study included 13 eyes in 12 patients of which 2 eyes had a healthy macula and 11 eyes had maculopathy. In all eyes posterior lens capsule fibrosis was present. A clinical examination including biomicroscopy of the macula and an in-vivo macular optical coherence tomography (OCT) before and after YAG-laser membranotomy had been performed. RESULTS: Foveal retinal thickness before and after membranotomy were highly correlated (R = 0.98), and no systematic difference was found between values obtained before vs. after membranotomy (mean thickness 318.7 +/- 92.7 microm vs. 322.2 +/- 97.4 microm; p = 0.221). The signal-to-noise ratio increased in 11 out of 13 eyes after membranotomy (mean signal-to-noise ratio before 47.1 +/- 6.6 dB vs. 52.6 +/- 4.0 dB after; p = 0.004, the change ranging from -1.5 dB to 17 dB). CONCLUSIONS: The qualitative effect of the posterior lens capsule opacification on the OCT-scan consists primarily of a loss of signal and consequently of intraretinal detail, whereas total foveal retinal thickness seems to be reliably assessed even when posterior lens capsule opacification interfering with the biomicroscopic evaluation of retinal edema are present. YAG-laser membranotomy results in a measurable improvement in the OCT signal-to-noise ratio, but OCT seems to yield reliable measurements of foveal retinal thickness before treatment. Consequently the OCT seems to reliably diagnose a macular thickening although not the type of this until after removal of the posterior lens capsule opacification.

Adult↗