Biomedical subjects

Jesper Leth Hougaard

Publications and source records attributed to Jesper Leth Hougaard.

6 recordsLinked to original sources

PubMed2006

Modelling the normal retinal nerve fibre layer thickness as measured by Stratus optical coherence tomography.

BACKGROUND: The variation in retinal nerve fibre layer thickness (RNFLT) as measured by Stratus optical coherence tomography (OCT) in healthy subjects may be reduced when the effect on RNFLT measurements of factors other than disease is corrected for, and this may improve the diagnostic accuracy in glaucoma. With this perspective we evaluated the isolated and combined effects of factors potentially affecting the Stratus OCT RNFLT measurements in healthy subjects. METHODS: We included 178 healthy eyes of 178 subjects between 20 and 80 years of age. Participants underwent an extensive eye examination. Stratus OCT RNFLT was measured by three standard protocols, two with high and one with standard image resolution. Effects on RNFLT of age, gender, refractive error, axial length, lens nuclear colour and opalescence, intra-ocular pressure (IOP), and optic disc size were examined by univariate and multivariate analyses. RESULTS: Age, refractive error, axial length, and lens nuclear colour and opalescence affected RNFLT in univariate analyses, whereas gender, IOP, and optic disc size had no significant effect. In multivariate analyses only age in combination with refractive error, or with axial length, was significant and explained 14.7-17.6% (R2) of the total variation of RNFLT, approximately 50% more than age alone. RNFLT decreased by 2.6-2.9 microm per increasing decade of age and increased by 1.5-1.8 microm per more positive diopter of spherical equivalent using full-circle measurements of the three standard protocols. These effects varied between measurement sectors. CONCLUSIONS: RNFLT as measured by Stratus OCT standard protocols was significantly affected by age and refractive status. The effect on global RNFLT of a difference in refractive error of 10 diopters corresponded to the effect of a difference in age of 60 years. Theoretically, the effect of refractive status may be explained by artefacts of RNFLT measurement circle placement. The results suggest that the diagnostic accuracy of Stratus OCT may be improved by considering refractive status in addition to age when RNFLT is measured. For this purpose spherical equivalent seems as effective as axial length.

Adult↗

PubMed2004

The nerve fibre layer symmetry test: computerized evaluation of human retinal nerve fibre layer thickness as measured by optical coherence tomography.

PURPOSE: To present and test a new interpretative concept, the nerve fibre layer symmetry test (NST), for computerized evaluation of retinal nerve fibre layer thickness (RNFLT) as measured by optical coherence tomography (OCT) in glaucoma. METHODS: The NST concept was constructed and tested in a pilot study. A total of 32 healthy and 40 age-matched glaucomatous eyes were included and examined by OCT, computerized perimetry, RNFL/disc photography, tonometry and a general ophthalmologic examination. RESULTS: The observed NST sensitivity and specificity were high, at 38/40 eyes (95%) and 32/32 eyes (100%), respectively, and 40/40 eyes (100%), and 31/32 eyes (97%), respectively, when correcting the OCT RNFLT measurement for the influence of variability in image signal/quality. The NST sensitivity was 8-10% higher than the single most sensitive traditional OCT RNFLT parameter; this difference was not statistically significant in this small sample. CONCLUSION: The NST showed high specificity and sensitivity for detection of RNFLT attenuation indicating early to severe glaucoma. Although promising, the NST needs to be further developed and validated in larger study samples and in patients with various stages of glaucomatous damage.

Aged↗

PubMed2004

Visual acuity and refractive errors in a suburban Danish population: Inter99 Eye Study.

PURPOSE: The present study was performed as part of an epidemiological study, the Inter99 Eye Study. The aim of the study was to describe refractive errors and visual acuity (VA) in a suburban Danish population. METHODS: The Inter99 Eye Study comprised 970 subjects aged 30-60 years and included a random control group as well as groups at high risk for ischaemic heart disease and diabetes mellitus. The present study presents VAs and refractive data from the control group (n = 502). All subjects completed a detailed questionnaire and underwent a standardized general physical and ophthalmic examination including determination of best corrected VA and subjective refractioning. RESULTS: Visual acuity </= 0.05 was found in one eye of one subject and VA </= 0.3 in 11 eyes of 11 subjects. The main cause of reduced visual function was strabismic amblyopia. Myopia (</= - 0.5 D, spherical equivalent refraction) was present in 33.1% of right eyes of the total population but in 56.8% of subjects with a university degree. CONCLUSIONS: Strabismic amblyopia was a significant cause of unilateral visual impairment. Myopia was approximately twice as frequent in subjects with a university degree as in the remaining study population.

Adult↗

PubMed2003

[Optical coherence tomography].

Optical coherence tomography (OCT) is a novel technique for two and three-dimensional imaging of tissues at a histological level. The technique is based on optical technology and commercially available fiber-optic components that may be adapted for use in conventional endoscopes or intravascular catheters. OCT is a non-invasive technique, which does not utilize ionizing radiation, and it may within a few seconds provide in vivo images ("optical biopsies") of tissues in cases where excisional biopsy is hazardous or impossible, or when repeated examinations are required. OCT has numerous potential clinical applications, and the technique is currently used in ophthalmology, where it may improve diagnosis and therapeutic control of various eye diseases. Detection and characterization of skin tumors and other dermatological diseases is another area where OCT has tremendous clinical potential. In the field of cardiology, intravascular OCT may be capable to contribute to early diagnosis of vulnerable atherosclerotic lesions. The OCT technique is also being developed in other clinical areas and is expected to become integrated in a range of clinical situations in the future.

Coronary Disease↗

PubMed2003

Corneal fluorescence in relation to genetic and environmental factors: a twin study.

PURPOSE: Corneal fluorescence is believed to be caused by advanced glycation end products formed by non-enzymatic glycation on corneal proteins. The purpose of the present twin study was to examine whether the process is related to genetic or environmental factors. METHODS: Corneal fluorescence was measured in 59 monozygotic and 54 dizygotic twin pairs. The influences of genetic and environmental factors were estimated using structural equation modelling. RESULTS: Interindividual variation in corneal fluorescence was attributable to environmental factors, whereas the effect of genetic factors was of little or no significance. Corneal fluorescence correlated significantly with smoking habits (r = 0.38) and the 2-hour oral glucose tolerance test response (r = 0.27), and increased with age (p < 0.0001). CONCLUSION: Fluorophore accumulation in the cornea was attributable to age and environmental effects, of which smoking was the most conspicuous identifiable factor, although glucose was also of relevance. However, the greater part of interindividual variation in corneal fluorescence remains unexplained.

Adult↗

PubMed2003

Evaluation of heredity as a determinant of retinal nerve fiber layer thickness as measured by optical coherence tomography.

PURPOSE: To study to what extent genetic factors determine the retinal nerve fiber layer thickness (RNFLT) in healthy subjects. METHODS: In vivo peripapillary optical coherence tomography (OCT), clinical examination, lens fluorescence, and fundus photography were performed on both eyes of 25 monozygotic and 25 dizygotic same-sex pairs of twins. The cross-sectional study included twins aged from 20 to 45 years recruited from a population-based register. Only healthy eyes were included. MAIN OUTCOME VARIABLES: peripapillary OCT RNFLT, reproducibility, and heritability (the proportion of the total observed variance statistically attributable to genetic factors). RESULTS: The within-pair difference in RNFLT was 4.6% (0.7%-15.2%; median [range]) in monozygotic versus 7.3% (0.2%-20%) in dizygotic twins (P = 0.032, Mann-Whitney test). The RNFLT heritability was 66%. The RNFLT measurement was found to decrease 3.8 microm per decade (P = 0.003). The RNFLT heritability increased to 82%, when corrected for the effect of age and excluding within-pair refractive differences of 2 D or more. The signal-to-noise ratio correlated with lens transmittance (r = 0.25, P = 0.012), age (r = -0.29, P = 0.004), and RNFLT (r = 0.43, P < 0.001). Intravisit RNFLT reproducibility was 4.2%. CONCLUSIONS: Peripapillary RNFLT in healthy adults, as measured by OCT, was determined predominantly by genetic factors in this study population. Theoretically, these factors may involve variations in the number of ganglion cells and nerve fiber formations early in life and/or in the rate at which these structures are subsequently lost.

Adult↗