Biomedical subjects

Boel Bengtsson

Publications and source records attributed to Boel Bengtsson.

12 recordsLinked to original sources

PubMed2007

Trained artificial neural network for glaucoma diagnosis using visual field data: a comparison with conventional algorithms.

PURPOSE: To evaluate and confirm the performance of an artificial neural network (ANN) trained to recognize glaucomatous visual field defects, and compare its diagnostic accuracy with that of other algorithms proposed for the detection of visual field loss. METHODS: SITA Standard 30-2 visual fields, from 100 glaucoma patients and 116 healthy participants, formed the data set. Our ANN was a previously described fully trained network using scored pattern deviation probability maps as input data. Its diagnostic accuracy was compared to that of the Glaucoma Hemifield Test, the Pattern Standard Deviation index at the P<5% and <1%, and also to a technique based on the recognizing clusters of significantly depressed test points. RESULTS: The included tests had early to moderate visual field loss (median MD=-6.16 dB). ANN achieved a sensitivity of 93% at a specificity level of 94% with an area under the receiver operating characteristic curve of 0.984. Glaucoma Hemifield Test attained a sensitivity of 92% at 91% specificity. Pattern Standard Deviation, with a cut off level at P<5% had a sensitivity of 89% with a specificity of 93%, whereas at P<1% the sensitivity and specificity was 72% and 97%, respectively. The cluster algorithm yielded a sensitivity of 95% and a specificity of 82%. CONCLUSIONS: The high diagnostic performance of our ANN based on refined input visual field data was confirmed in this independent sample. Its diagnostic accuracy was slightly to considerably better than that of the compared algorithms. The results indicate the large potential for ANN as an important clinical glaucoma diagnostic tool.

Adult↗

PubMed2006

Fluctuation of intraocular pressure and glaucoma progression in the early manifest glaucoma trial.

PURPOSE: To investigate whether increased fluctuation of intraocular pressure (IOP) is an independent factor for glaucoma progression. DESIGN: A cohort of patients was followed up in a randomized clinical trial. PARTICIPANTS: Two hundred fifty-five glaucoma patients from the Early Manifest Glaucoma Trial (EMGT; 129 treated and 126 control patients). METHODS: Study visits, conducted every 3 months, included ophthalmologic examinations, IOP measurements, and standard automated perimetry, with fundus photography every 6 months. Intraocular pressure values were included only until the time of progression in those eyes that showed such progression. Individual mean follow-up IOP and IOP fluctuation, calculated as the standard deviation of IOP at applicable visits, were the variables of main interest. Cox regression with time-dependent variables was used to evaluate the association between IOP fluctuation and time to progression, both with and without IOP mean in the models. These analyses also controlled for other significant variables. MAIN OUTCOME MEASURES: Glaucoma progression, as defined by a predetermined visual field criterion, worsening of the disk, assessed by an independent disc reading center, or both. RESULTS: Median follow-up time was 8 years (range, 0.1-11.1 years). Sixty-eight percent of the patients progressed. When considering mean follow-up IOP and IOP fluctuation in the same time-dependent model, mean IOP was a significant risk factor for progression. The hazard ratio (HR) was 1.11 (95% confidence interval [CI], 1.06-1.17; P<0.0001). Intraocular pressure fluctuation was not related to progression, with an HR of 1.00 (95% CI, 0.81-1.24; P = 0.999). CONCLUSIONS: These results confirm our earlier finding that elevated IOP is a strong factor for glaucoma progression, with the HR increasing by 11% for every 1 mmHg of higher IOP. Intraocular pressure fluctuation was not an independent factor in our analyses, a finding that conflicts with some earlier reports. One explanation for the discrepancy is that our analyses did not include postprogression IOP values, which would be biased toward larger fluctuations because of more intensive treatment. In contrast, in this EMGT report, no changes in patient management occurred during the period analyzed.

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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↗

PubMed2006

Diagnostic sensitivity of fast blue-yellow and standard automated perimetry in early glaucoma: a comparison between different test programs.

PURPOSE: To compare the ability of Fast Swedish interactive threshold algorithm (SITA) short-wavelength automated perimetry (SWAP), lengthier full-threshold SWAP, and standard automated perimetry (SAP) using the SITA Fast program to detect early glaucomatous visual field loss. DESIGN: Cross-sectional prospective study of perimetric diagnostic sensitivity as defined by reference limits determined in the same healthy participants for all 3 test programs. PARTICIPANTS: One hundred one patients with ocular hypertension, or suspect or early manifest glaucoma. METHODS: One eye of each patient was tested with 2 blue-yellow perimetric programs: the SITA and full-threshold SWAP and the SAP SITA Fast program. MAIN OUTCOME MEASURES: Glaucomatous visual field loss, defined as number of significantly depressed test point locations or the number of clusters of such test points. RESULTS: No significant difference in number of significantly depressed test point locations between the 3 programs could be detected, neither at the P<5% limit nor at the P<2% limit. The difference in number of points depressed below the fifth percentile was 0.5 between full-threshold SWAP and SITA SWAP, 1.09 between full-threshold SWAP and SAP, and 1.04 between SITA SWAP and SAP. The number of eyes showing clusters of significantly depressed points also was similar with the 3 test programs: full-threshold SWAP identified clusters in 66 eyes, SITA SWAP identified clusters in 67 eyes, and SITA Fast SAP identified clusters in 65 eyes. Average test time was 12.0 minutes using full-threshold SWAP, 4.1 minutes with SITA SWAP, and 3.5 with SITA Fast. CONCLUSIONS: The SITA SWAP identified at least as much glaucomatous visual field loss as the older full-threshold SWAP, although test time was considerably reduced. Conventional SAP using SITA Fast was not significantly less sensitive than either of the 2 SWAP programs.

Adult↗

PubMed2005

Diurnal IOP fluctuation: not an independent risk factor for glaucomatous visual field loss in high-risk ocular hypertension.

PURPOSE: To establish whether intraocular pressure (IOP) fluctuations contribute to the risk of developing glaucoma in patients with high-risk ocular hypertension. METHODS: Ninety patients included in the Malmö Ocular Hypertension Study were examined every 3 months with office-hours diurnal tension curves and computerised perimetry. Patients were followed up prospectively for 10 years or until glaucomatous visual field loss could be demonstrated. Poststudy data were included in the analyses, extending maximum follow-up to 17 years. RESULTS: After 17 years, 37 patients had developed glaucomatous visual field defects. When applying univariate Cox regression analyses, mean IOP of all measurements during the prospective part of the study was a significant risk factor for developing glaucoma (95% confidence interval [CI] 1.08-1.39), while IOP fluctuations were almost significant (95% CI 0.98-1.93). When separating effects of mean IOP level and mean IOP fluctuation using Cox multiple regression analysis, only IOP level came out as significant (95% CI 1.09-1.38), and IOP fluctuations did not contribute to the risk (95% CI 0.80-1.60). IOP fluctuation depended linearly on IOP level (p<0.0001), i.e. IOP fluctuation was larger in eyes with higher IOP levels. CONCLUSION: IOP fluctuations were not an independent risk factor for the incidence of glaucomatous visual field loss in subjects with ocular hypertension.

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PubMed2005

A long-term prospective study of risk factors for glaucomatous visual field loss in patients with ocular hypertension.

PURPOSE: To evaluate the importance of baseline risk factors for development of glaucomatous visual field loss in patients with high-risk ocular hypertension. METHODS: In the Malmö Ocular Hypertension Study, 90 patients were randomized to topical timolol or placebo treatment and observed prospectively for up to 10 years. Patients with elevated intraocular pressure (IOP) and with open angles and normal visual fields, plus at least one extra risk factor, were eligible. Risk factors were suspect disc or known disc hemorrhage, positive family history of glaucoma, pseudoexfoliation or pigment dispersion syndrome, diabetes, and mean IOP on DTC > or = 27 mm Hg. These risk factors and also the mean baseline IOP and IOP fluctuation, sex, age, and blood pressure were evaluated as predictors for development of reproducible glaucomatous visual field loss. In addition to the prospective data, post-study data were retrieved from patients' records extending maximum follow-up to 17 years. RESULTS: Thirty-seven patients developed glaucomatous visual field loss. Of all factors included in the analysis, disc appearance, older age, and higher IOP came out as significant risks. Suspect disc appearance increased the risk approximately three times, with a hazard ratio of 2.90, and CI: 1.34-6.30, the hazard ratio was 1.05 and CI: 1.03-1.09 per year of age, while mean baseline IOP increased the risk with 14% per mm Hg (CI: 1.01-1.28). CONCLUSION: Patients with ocular hypertension were at higher risk for developing glaucomatous visual field loss if discs were suspect, if IOP was high, and if the patient was older in age.

Adult↗

PubMed2005

Effects of input data on the performance of a neural network in distinguishing normal and glaucomatous visual fields.

PURPOSE: To compare the performance of neural networks for perimetric glaucoma diagnosis when using different types of data inputs: numerical threshold sensitivities, Statpac Total Deviation and Pattern Deviation, and probability scores based on Total and Pattern Deviation probability maps (Carl Zeiss Meditec, Inc., Dublin, CA). METHODS: The results of SITA Standard visual field tests in 213 healthy subjects, 127 patients with glaucoma, 68 patients with concomitant glaucoma and cataract, and 41 patients with cataract only were included. The five different types of input data were entered into five identically designed artificial neural networks. Network thresholds were adjusted for each network. Receiver operating characteristic (ROC) curves were constructed to display the combinations of sensitivity and specificity. RESULTS: Input data in the form of Pattern Deviation probability scores gave the best results, with an area of 0.988 under the ROC curve, and were significantly better (P < 0.001) than threshold sensitivities and numerical Total Deviations and Total Deviation probability scores. The second best result was obtained with numerical Pattern Deviations with an area of 0.980. CONCLUSIONS: The choice of type of data input had important effects on the performance of the neural networks in glaucoma diagnosis. Refined input data, based on Pattern Deviations, resulted in higher sensitivity and specificity than did raw threshold values. Neural networks may have high potential in the production of useful clinical tools for the classification of visual field tests.

Adult↗

PubMed2003

Measuring visual field progression in the Early Manifest Glaucoma Trial.

AIMS: The Early Manifest Glaucoma Trial (EMGT) (316 eligible eyes) has used a new set of criteria to define visual field progression in glaucoma. This paper provides estimates of the amount of visual field worsening required to reach the EMGT definition of definite perimetric progression. METHODS: In the 148 eyes that reached definite progression, we first determined changes between baseline and the time of definite EMGT progression, both for mean deviation (MD) and for number of highly (p < 0.5%) significantly depressed test points in pattern deviation probability maps. Second, we studied whether such changes depended on baseline MD, intraocular pressure (IOP), age and time to progression, all of which are factors that affect the rate of field progression. RESULTS: In eyes reaching progression, the mean change in MD from baseline was -1.93 dB (SE +/- 0.20) and the mean change in number of significant points was +4.85 (SE +/- 0.35). These changes did not show linear dependency on baseline MD, IOP or time to progression. CONCLUSIONS: The average amount of field deterioration needed to reach EMGT visual field progression has been measured and expressed in more conventional units (i.e. a loss of about - 2dB in MD and an increase in about five highly significant points). These estimates will facilitate the clinical interpretation of the results of EMGT.

Aged↗

PubMed2003

A new rapid threshold algorithm for short-wavelength automated perimetry.

PURPOSE: To develop and test a short and reliable visual field threshold program for the early detection of glaucomatous visual field loss, by adapting the Swedish interactive test algorithm (SITA) to short-wavelength-automated-perimetry (SWAP). METHODS: Computer simulations were performed to test the accuracy of several versions of SITA SWAP, and to optimize speed versus reliability. The selected SITA SWAP version was evaluated and compared with the older Full Threshold SWAP and Fastpac SWAP programs in 41 patients with glaucoma and normal subjects. RESULTS: Average test time was 3.6 minutes for SITA SWAP, 11.8 minutes for Full Threshold SWAP, and 7.7 minutes for Fastpac SWAP, differences were significant at P < 0.0001. Mean threshold reproducibility, calculated as absolute difference between two tests, did not differ significantly between programs and was 2.4 dB for SITA, 2.3 dB for Full Threshold, and 2.4 dB for Fastpac SWAP. Simultaneous comparison showed significant differences in threshold sensitivity, P = 0.023: SITA SWAP showed highest sensitivity, 21.6 dB on average, compared with both Full Threshold SWAP and Fastpac SWAP with a mean sensitivity of 17.3 and 17.8 dB, respectively. CONCLUSIONS: SITA SWAP was much faster than the older SWAP strategies, and reproducibility did not differ. This implies that SITA SWAP could become a clinically useful method for the detection of early glaucoma. SWAP tests may also be applicable in larger groups of patients because of the increased dynamic range.

Adult↗

PubMed2003

Normal intersubject threshold variability and normal limits of the SITA SWAP and full threshold SWAP perimetric programs.

PURPOSE: To compare intersubject variability and normal limits of threshold values between the new Swedish interactive test algorithm short wavelength automated perimetry (SITA SWAP) and the older Full Threshold SWAP programs (Carl Zeiss Meditec, Dublin, CA). METHODS: Normal reduction of differential light sensitivity with age, age-corrected thresholds, intersubject variability, and normal limits of sensitivity were calculated from SITA SWAP and Full Threshold SWAP fields obtained in 53 normal subjects between 20 and 72 years of age. RESULTS: Age influence on threshold sensitivity was the same with the two SWAP programs. On average, sensitivity decreased by 0.13 dB per year of age. Age-corrected normal threshold sensitivity was significantly higher (P<0.0001) for SITA SWAP than for Full Threshold SWAP. The means for a subject 45.4 years of age were 28.8 dB with SITA SWAP and 24.4 dB with Full Threshold SWAP. Intersubject variance was 22% smaller with SITA SWAP than with Full Threshold SWAP. Normal limits at the P<5% significance level were, on average, 14% narrower with SITA SWAP than with Full Threshold SWAP using Total Deviations from age-corrected normal thresholds and 11% narrower when applying Pattern Deviation, which is intended to adjust for general depression or elevation of the field. CONCLUSIONS: SITA SWAP test results from normal eyes showed higher sensitivities than results from the older Full Threshold SWAP. This represents an increase of the dynamic range, which implies that more patients can be tested with SWAP. The smaller intersubject variability with SITA SWAP means narrower normal limits and may be associated with more sensitive probability maps.

Adult↗

PubMed2002

Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial.

OBJECTIVE: To provide the results of the Early Manifest Glaucoma Trial, which compared the effect of immediately lowering the intraocular pressure (IOP), vs no treatment or later treatment, on the progression of newly detected open-angle glaucoma. DESIGN: Randomized clinical trial. PARTICIPANTS: Two hundred fifty-five patients aged 50 to 80 years (median, 68 years) with early glaucoma, visual field defects (median mean deviation, -4 dB), and a median IOP of 20 mm Hg, mainly identified through a population screening. Patients with an IOP greater than 30 mm Hg or advanced visual field loss were ineligible. INTERVENTIONS: Patients were randomized to either laser trabeculoplasty plus topical betaxolol hydrochloride (n = 129) or no initial treatment (n = 126). Study visits included Humphrey Full Threshold 30-2 visual field tests and tonometry every 3 months, and optic disc photography every 6 months. Decisions regarding treatment were made jointly with the patient when progression occurred and thereafter. MAIN OUTCOME MEASURES: Glaucoma progression was defined by specific visual field and optic disc outcomes. Criteria for perimetric progression were computer based and defined as the same 3 or more test point locations showing significant deterioration from baseline in glaucoma change probability maps from 3 consecutive tests. Optic disc progression was determined by masked graders using flicker chronoscopy plus side-by-side photogradings. RESULTS: After a median follow-up period of 6 years (range, 51-102 months), retention was excellent, with only 6 patients lost to follow-up for reasons other than death. On average, treatment reduced the IOP by 5.1 mm Hg or 25%, a reduction maintained throughout follow-up. Progression was less frequent in the treatment group (58/129; 45%) than in controls (78/126; 62%) (P =.007) and occurred significantly later in treated patients. Treatment effects were also evident when stratifying patients by median IOP, mean deviation, and age as well as exfoliation status. Although patients reported few systemic or ocular conditions, increases in clinical nuclear lens opacity gradings were associated with treatment (P =.002). CONCLUSIONS: The Early Manifest Glaucoma Trial is the first adequately powered randomized trial with an untreated control arm to evaluate the effects of IOP reduction in patients with open-angle glaucoma who have elevated and normal IOP. Its intent-to-treat analysis showed considerable beneficial effects of treatment that significantly delayed progression. Whereas progression varied across patient categories, treatment effects were present in both older and younger patients, high- and normal-tension glaucoma, and eyes with less and greater visual field loss.

Adrenergic beta-Antagonists↗

PubMed2002

Evaluation of VEP perimetry in normal subjects and glaucoma patients.

PURPOSE: To estimate sensitivity to glaucomatous visual field loss using multifocal visual evoked potential (VEP) perimetry, to compare these findings to those of conventional achromatic perimetry and to determine specificity of VEP perimetry in normal subjects. METHODS: A total of 33 glaucoma patients with known visual field defects in at least one eye on standard computerized perimetry and 33 healthy subjects were tested with VEP perimetry. The glaucoma patients were also tested with standard computerized perimetry using the 30-2 SITA Fast program of the Humphrey Field Analyzer (HFA). Visual evoked potential perimetry classification and VEP probability maps were used to determine the sensitivity and specificity of the technique. RESULTS: Visual evoked potential perimetry classified 68% of all eyes in the glaucoma group (45/66) as pathological; sensitivity increased to 81% (38/47) when considering only those eyes with HFA field defects. It also identified more test locations with significant loss at the p < 5% level in both groups (48% and 37%, respectively) than did HFA, while HFA identified more loss at the higher significance levels p < 2%, and p < 1%. Visual evoked potential perimetry showed more significant loss in eyes with almost normal or slightly damaged standard fields, while HFA identified more significant field loss in eyes with severe conventional field damage. The mean VEP amplitude of the 66 glaucoma eyes was 1.46e(-7) V; it was 1.676e(-7) V for the 66 control eyes. This difference was significant (p = 0.0033), but the overlap between groups was large. Visual evoked potential perimetry classified 42% of the control eyes as 'outside normal limits', and VEP probability maps showed 30.0% of test segments as significantly depressed at the p < 5% level, 10.8% of sites at p < 2%, and 4.6% at the p < 1% level. CONCLUSION: Mean VEP amplitude differed significantly between normal and glaucoma eyes, but the overlap was considerable. Visual evoked potential perimetry falsely classified a large number of normal eyes as pathological and showed many more significantly depressed test locations than expected. Agreement between VEP and standard perimetry was relatively poor for the glaucoma group. Further refinements are needed before VEP perimetry can be regarded as a reliable clinical method of mapping glaucomatous visual fields.

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