Biomedical subjects

K G Gundersen

Publications and source records attributed to K G Gundersen.

6 recordsLinked to original sources

PubMed2000

Comparability of three-dimensional optic disc imaging with different techniques. A study with confocal scanning laser tomography and raster tomography.

PURPOSE: We wanted to compare optic nerve head topography measurements and discrimination between normal and glaucomatous eyes with two entirely different three-dimensional optic disc imaging techniques, confocal scanning laser tomography (Heidelberg Retina Tomograph, Heidelberg Engineering) and raster tomography (Glaucoma-Scope, Ophthalmic Imaging Systems). METHODS: Both eyes of 225 normal subjects and 229 eyes of 166 patients with glaucoma at different stages were imaged with the Heidelberg Retina Tomograph and the Glaucoma-Scope. Optics discs were analysed in 15 degrees sectors around the circumference. Depth measurements were calibrated on objects with known dimensions. RESULTS: We observed no significant differences in absolute measurements of maximum cup depth and cup area between the two instruments. We observed small differences in absolute measurements of disc anti rim area between the two instruments. Discrimination between normal and glaucomatous eyes was close to identical for the two instruments. Both instruments had the same ability to distinguish glaucomatous regional alterations of optic nerve head topography from normal disc configuration. CONCLUSION: Both instruments while using entirely different principles for three-dimensional optic disc imaging gave very similar results. This correspondence of results implies that the same optic disc parameters can be analysed, and the results interpreted similarly for both methods, and probably with other three-dimensional imaging instruments. It may also indicate that results of studies with one of the instruments have general validity.

Adult↗

PubMed2000

Comparison of ranked segment analysis (RSA) and cup to disc ratio in computer-assisted optic disc evaluation.

PURPOSE: Ranked segment analysis is a new method for evaluation of optic nerve head topography with the Heidelberg Retina Tomograph. This analysis ranks sector measurements around the optic disc and compares these measurements with rank specific significance limits. We evaluated the diagnostic precision of the ranked segment analysis in a large clinical sample and compared with vertical cup/disc ratio measurements. Vertical cup/disc ratio measurements were not corrected for disc size. METHODS: We analysed optic disc images from 153 normal and 75 glaucomatous eyes using the Heidelberg Retina Tomograph (software version 2.01). Ranked segment analyses and vertical cup/disc ratio measurements were obtained from each optic disc image, and ROC curves were plotted. RESULTS: At the 95% specificity level, sensitivity was significantly lower for ranked segment analysis (70%) compared to vertical cup/disc ratio measurements (85%). Almost 30% of the discs in the glaucoma group were classified as normal using the ranked segment analysis. DISCUSSION: Ranked segment analysis yielded unacceptably poor discrimination, in fact, worse than cup/disc ratio with its known clinical limitations Glaucomatous disc damage typically occurs at the vertical poles of the disc. High rank measurements (low sector values) in normal eyes, on the other hand, are more common in the temporal disc sectors. Important spatial information is lost during the ranking procedure. This may partly explain the low sensitivity of the ranked segment analysis observed in our study. The results raise serious concerns regarding the clinical usefulness of ranked segment analysis.

Adult↗

PubMed1999

Optic nerve head sector analysis recognizes glaucoma most effectively around disc poles.

PURPOSE: To analyze the topography of normal and glaucomatous discs with the goal of developing improved strategies to discriminate between normal and glaucomatous eyes. SUBJECTS AND METHODS: Raster tomography was performed in both eyes of 225 healthy subjects and in 296 eyes of 214 glaucoma patients. Cup area, average cup radius, rim area and minimal rim width were measured in 24 sectors around the optic nerve head at nine different depths from the reference plane. Receiver Operating Curves (ROC) for numerous combinations of parameter, sector and depth were calculated and compared. RESULTS: Discrimination between glaucomatous and normal eyes varied widely between single sectors of the optic disc, and was best at the vertical poles of the disc, intermediate in nasal sectors and worst in temporal sectors. When single sectors or combinations of sectors at the superior pole were combined with their counterparts at the inferior pole of the optic nerve, the gain in sensitivity exceeded the loss in specificity, and discrimination improved. Separation declined dramatically if any of the 8 temporal sectors were involved in such analysis. Depth influenced discrimination only slightly. CONCLUSION: Single sectors located close to the vertical meridian yielded better discrimination than global measurements. When two or more sectors at the superior pole were combined with each other, as well as with their counterparts at the inferior pole, discrimination improved even further. Localized changes concurred frequently, but asymmetrically at both poles of the disc. The depth from reference plane used to define the cup was not critical for separation between normal and glaucomatous eyes.

Adult↗

PubMed1998

Age, gender, IOP, refraction and optic disc topography in normal eyes. A cross-sectional study using raster and scanning laser tomography.

PURPOSE: To study the influence of age, gender, intraocular pressure and refraction on optic disc topography in normal subjects. METHODS: We studied both eyes of 225 healthy subjects between 20 and 80 years of age using raster tomography (Glaucoma-Scope, Ophthalmic Imaging Systems, Sacramento CA, USA) and scanning laser tomography (Heidelberg Engineering, Heidelberg, Germany). We chose to study cup area and maximum cup depth, two variables that are minimally influenced by the operator. RESULTS: Raster and scanning laser tomography results were strongly correlated. Cup area was independent of age, gender and refraction. It was weakly associated with IOP, but this association was significant only when the cup area was measured with scanning laser tomography. Maximum cup depth was independent of age, gender and IOP. It was larger in hypermetropic eyes, although this trend was significant only when maximum cup depth was measured with raster tomography. CONCLUSION: Our results indicate that optic nerve head topography does not change significantly with age in normal subjects. This information has important implications for follow-up of pathological changes in optic nerve head topography.

Adult↗

PubMed1996

Sensitivity and specificity of structural optic disc parameters in chronic glaucoma.

We studied different structural optic disc parameters and their ability to discriminate between normal and glaucoma eyes using computerized raster tomography. Two hundred and seventy-six eyes of 138 normal subjects and 146 eyes of 102 glaucoma patients were examined with a raster tomographic imaging system (The Glaucoma-ScopeTM, Ophthalmic Imaging Systems, Sacramento, CA). Glaucoma eyes were classified into four groups according to their perimetric mean deviation values. Minimum rim width within the 60 degrees and 90 degrees sectors across the vertical meridian, vertical and horizontal cup-disc ratio, rim and cup area were calculated for each optic disc. Receiver operating characteristics curves were set up for comparisons of the different parameters. Representing localised changes of the optic disc, minimum rim width 60 degrees and 90 degrees showed the best separating characteristics with sensitivity values of 91% at a fixed specificity of 90%, followed by vertical cup-disc ratio. Global indices like cup and rim area and horizontal cup-disc ratio showed the poorest separation. These differences were particularly obvious in the group with mild to moderate glaucomatous visual field defects. Thus, global parameters were less likely to detect early focal glaucomatous optic nerve head changes, than parameters representing localised changes.

Aged↗

PubMed1989

[Retinopathy as a complication of acute pancreatitis].

We describe a case of acute, severe retinopathy in a patient with acute pancreatitis. The relative times of the organ manifestations, and comparisons with other published cases, strongly suggest that the pancreatitis was the cause of the retinal changes. This complication is unknown to most physicians, but ten to 12 cases have been published earlier. The pathogenesis is not known. We briefly discuss the significance of this complication and several possible pathogenetic mechanisms.

Acute Disease↗