Biomedical subjects

Paul H Artes

Publications and source records attributed to Paul H Artes.

9 recordsLinked to original sources

PubMed2005

Longitudinal changes in the visual field and optic disc in glaucoma.

The nature and mode of functional and structural progression in open-angle glaucoma is a subject of considerable debate in the literature. While there is a traditionally held viewpoint that optic disc and/or nerve fibre layer changes precede visual field changes, there is surprisingly little published evidence from well-controlled prospective studies in this area, specifically with modern perimetric and imaging techniques. In this paper, we report on clinical data from both glaucoma patients and normal controls collected prospectively over several years, to address the relationship between visual field and optic disc changes in glaucoma using standard automated perimetry (SAP), high-pass resolution perimetry (HRP) and confocal scanning laser tomography (CSLT). We use several methods of analysis of longitudinal data and describe a new technique called "evidence of change" analysis which facilitates comparison between different tests. We demonstrate that current clinical indicators of visual function (SAP and HRP) and measures of optic disc structure (CSLT) provide largely independent measures of progression. We discuss the reasons for these findings as well as several methodological issues that pose challenges to elucidating the true structure-function relationship in glaucoma.

Adult↗

PubMed2004

Factors associated with optic disc hemorrhages in glaucoma.

PURPOSE: To evaluate factors associated with optic disc hemorrhages (ODHs) in patients with open-angle glaucoma. DESIGN: Cohort study. PARTICIPANTS: One hundred thirty-seven patients with open-angle glaucoma, with an initial mean age of 60.0 years (standard deviation [SD], 11.0 years) followed up for a mean of 9.5 years (SD, 5.0 years). METHODS: The association between ODHs and various patient-related variables (diabetes, systemic hypertension, heart disease, hypercholesterolemia, migraine, hypothyroidism, use of platelet antiaggregant agents) and eye-related variables (mean and range of intraocular pressure, refractive error, and severity of disease) was investigated using multivariate time-to-event analyses in patients with open-angle glaucoma. To determine the influence of the level of intraocular pressure (IOP) on the occurrence of ODHs, we compared the IOP at the time the first ODH was noted with the mean IOP of the previous 3 visits. As a control, a similar analysis was performed on the same eyes using a randomly selected visit before the occurrence of the first ODH. MAIN OUTCOME MEASUREMENTS: Patient-related and eye-related variables associated with ODHs and the comparative level of IOP in which these ODHs were observed. RESULTS: Fifty eyes of 38 patients (28%) had 1 or more ODHs during the follow-up period. The ODHs were associated with presence of diabetes (hazard ratio, 4.43; 95% confidence interval [CI], 1.8-10.50; P = 0.001) and use of aspirin (hazard ratio, 2.30; 95% CI, 1.2-4.6; P = 0.019). The IOP at the time of the first ODH was, on average, 1.4 mmHg lower than the mean IOP of the 3 previous visits (95% CI, -2.2 to -0.6 mmHg; P<0.001), whereas in the control analysis, the respective value was 0.3 mmHg lower (95% CI, -1.0 to 0.5; P = 0.410). CONCLUSIONS: Optic disc hemorrhages were associated with diabetes and aspirin use and were observed at relatively lower IOP during follow-up.

Adult↗

PubMed2003

Comparison of data analysis tools for detection of glaucoma with the Heidelberg Retina Tomograph.

PURPOSE: To evaluate the performance of three linear discriminant functions (LDFs) and the Moorfields Regression Analysis (MRA) in classifying optic disc topography images obtained with the Heidelberg Retina Tomograph (HRT) from patients with open-angle glaucoma and normal controls. Furthermore, to investigate whether the classification of glaucomatous eyes is related to the severity of visual field loss or to optic disc size. DESIGN: Prospective comparative observational case series. PARTICIPANTS: One eye of 104 patients with a diagnosis of open-angle glaucoma (mean age, 63.2; range, 30-88 years) and 48 normal controls (mean age, 52.4; range, 33-75 years). TESTING: Subjects were examined with the HRT. MAIN OUTCOME MEASURES: Diagnostic performance was calculated for the LDFs published by Mikelberg et al (LDF1), Burk (LDF2), and Bathija et al (LDF3) and for the MRA. RESULTS: Large differences in sensitivity and specificity were found among the different analyses when using the originally suggested cutoff criteria. When specificity was equalized to 90%, the sensitivities were more similar (LDF1, 55%; LDF2, 61%; and LDF3, 67%). At 95% specificity, the sensitivities decreased further (LDF1, 39%; LDF2, 55%; LDF3, 44%). When treating the "borderline" outcomes as test positives, MRA sensitivity and specificity were 78% and 81%, respectively. When treating the "borderline" outcomes as test negatives, the MRA gave a sensitivity of 58%, with a specificity of 96%. In glaucoma patients, the correlation between the severity of visual field damage, as measured by the mean deviation index, and the outcome of the classification systems was low to moderate (Spearman's r between 0.26 and 0.39). When the entire sample was stratified into equal thirds on the basis of optic disc size, large discs (area > 2.10 mm(2)) tended to be classified with a higher sensitivity but lower specificity than small discs (area < 1.73 mm(2)) with all methods except LDF3. Using a multiple regression model controlling for mean deviation, LDF1, and LDF2, but not LDF3, were significantly influenced by disc size. CONCLUSIONS: The 4 methods of analysis had similar sensitivities once their specificities were equalized. In this sample, the LDFs and MRA generally did not discriminate between glaucoma patients and controls as well as reported in the original respective studies that described the methods.

Adult↗

PubMed2003

Retinal arterial diameter changes in progressive and nonprogressive glaucoma.

PURPOSE: To determine if the degree of retinal arterial diameter change is different between patients with progressive and nonprogressive open-angle glaucoma. MATERIAL AND METHODS: In this prospective cohort study, 44 eyes of 44 open-angle glaucoma patients (mean age, 67.5 years; age range, 52-84 years; mean follow-up period, 4.9 years; follow-up range, 1.3-7.5 years) were included. The change in arterial diameter between the baseline and the most recent follow-up optic disc photograph was determined. The diameter of the 4 major arteries was measured at the optic disc margin and at the thinnest and broadest locations within 1 optic disc diameter from the disc margin. Patients were stratified into progressing and nonprogressing groups according to visual field and optic disc criteria. RESULTS: Visual field progression was observed in 13 (30%) patients and optic disc progression in 24 (55%) patients. On average, the arterial diameters at the edge of the optic disc decreased significantly by 2.37% (95% CI, -3.31% to -1.41%) per year of follow-up (P<0.001). No significant difference in generalized or focal arterial narrowing was observed between progressive and nonprogressive groups regardless of the criterion used (P>0.462). With this sample, the power to detect a 10% difference in arterial narrowing between the 2 groups was 66%. There was no relationship between the rates of visual field progression and arterial diameter change in the whole group (P = 0.171) or in groups segregated into progressing and nonprogressing patients (P>0.104). CONCLUSION: Arterial diameters decreased in both progressive and nonprogressive glaucoma. In this study, there was little evidence that arterial narrowing was more pronounced in progressive disease.

Aged↗

PubMed2003

Effects of blur and repeated testing on sensitivity estimates with frequency doubling perimetry.

PURPOSE: To investigate the effect of blur and repeated testing on sensitivity with frequency doubling technology (FDT) perimetry. METHODS: One eye of 12 patients with glaucoma (mean deviation [MD] mean, -2.5 dB, range +0.5 to -4.3 dB) and 11 normal control subjects underwent six consecutive tests with the FDT N30 threshold program in each of two sessions. In session 1, blur was induced by trial lenses (-6.00, -3.00, 0.00, +3.00, and +6.00 D, in random order). In session 2, only the effects of repeated testing were evaluated. The MD and pattern standard deviation (PSD) indices were evaluated as functions of blur and of test order. By correcting the data of session 1 for the reduction of sensitivity with repeated testing (session 2), the effect of blur on FDT sensitivities was established, and its clinical consequences evaluated on total- and pattern-deviation probability maps. RESULTS: FDT sensitivities decreased with blur (by <0.5 dB/D) and with repeated testing (by approximately 2 dB between the first and sixth tests). Blur and repeated testing independently led to larger numbers of locations with significant total and pattern deviation. Sensitivity reductions were similar in normal control subjects and patients with glaucoma, at central and peripheral test locations and at locations with high and low sensitivities. However, patients with glaucoma showed larger deterioration in the total-deviation-probability maps. CONCLUSIONS: To optimize the performance of the device, refractive errors should be corrected and immediate retesting avoided. Further research is needed to establish the cause of sensitivity loss with repeated FDT testing.

Adult↗

PubMed2003

Multisampling suprathreshold perimetry: a comparison with conventional suprathreshold and full-threshold strategies by computer simulation.

PURPOSE: To compare a multisampling suprathreshold strategy with conventional suprathreshold and full-threshold strategies in detecting localized visual field defects and in quantifying the area of loss. METHODS: Probability theory was applied to examine various suprathreshold pass criteria (i.e., the number of stimuli that have to be seen for a test location to be classified as normal). A suprathreshold strategy that requires three seen or three missed stimuli per test location (multisampling suprathreshold) was selected for further investigation. Simulation was used to determine how the multisampling suprathreshold, conventional suprathreshold, and full-threshold strategies detect localized field loss. To determine the systematic error and variability in estimates of loss area, artificial fields were generated with clustered defects (0-25 field locations with 8- and 16-dB loss) and, for each condition, the number of test locations classified as defective (suprathreshold strategies) and with pattern deviation probability less than 5% (full-threshold strategy), was derived from 1000 simulated test results. RESULTS: The full-threshold and multisampling suprathreshold strategies had similar sensitivity to field loss. Both detected defects earlier than the conventional suprathreshold strategy. The pattern deviation probability analyses of full-threshold results underestimated the area of field loss. The conventional suprathreshold perimetry also underestimated the defect area. With multisampling suprathreshold perimetry, the estimates of defect area were less variable and exhibited lower systematic error. CONCLUSIONS: Multisampling suprathreshold paradigms may be a powerful alternative to other strategies of visual field testing. Clinical trials are needed to verify these findings.

Computer Simulation↗

PubMed2002

New developments in supra-threshold perimetry.

PURPOSE: To describe a series of recent enhancements to supra-threshold perimetry. METHODS: Computer simulations were used to develop an improved algorithm (HEART) for the setting of the supra-threshold test intensity at the beginning of a field test, and to evaluate the relationship between various pass/fail criteria and the test's performance (sensitivity and specificity) and how they compare with modern threshold perimetry. Data were collected in optometric practices to evaluate HEART and to assess how the patient's response times can be analysed to detect false positive response errors in visual field test results. RESULTS: The HEART algorithm shows improved performance (reduced between-eye differences) over current algorithms. A pass/fail criterion of '3 stimuli seen of 3-5 presentations' at each test location reduces test/retest variability and combines high sensitivity and specificity. A large percentage of false positive responses can be detected by comparing their latencies to the average response time of a patient. CONCLUSIONS: Optimised supra-threshold visual field tests can perform as well as modern threshold techniques. Such tests may be easier to perform for novice patients, compared with the more demanding threshold tests.

Aged↗

PubMed2002

Response time as a discriminator between true- and false-positive responses in suprathreshold perimetry.

PURPOSE: To report on differences between the latency distributions of responses to stimuli and to false-positive catch trials in suprathreshold perimetry. To describe an algorithm for defining response time windows and to report on its performance in discriminating between true- and false-positive responses on the basis of response time (RT). METHODS: A sample of 435 largely inexperienced patients underwent suprathreshold visual field examination on a perimeter that was modified to record RTs. Data were analyzed from 60,500 responses to suprathreshold stimuli and from 523 false-positive responses to catch trials. RESULTS: False-positive responses had much more variable latencies than responses to suprathreshold stimuli. An algorithm defining RT windows on the basis of z-transformed individual latency samples correctly identified more than 70% of false-positive responses to catch trials, whereas fewer than 3% of responses to suprathreshold stimuli were classified as false-positive responses. CONCLUSIONS: Latency analysis can be used to detect a substantial proportion of false-positive responses in suprathreshold perimetry. Rejection of such responses may increase the reliability of visual field screening by reducing variability and bias in a small but clinically important proportion of patients.

Adolescent↗

PubMed2002

Properties of perimetric threshold estimates from Full Threshold, SITA Standard, and SITA Fast strategies.

PURPOSE: To investigate the distributions of threshold estimates with the Swedish Interactive Threshold Algorithms (SITA) Standard, SITA Fast, and the Full Threshold algorithm (Humphrey Field Analyzer; Zeiss-Humphrey Instruments, Dublin, CA) and to compare the pointwise test-retest variability of these strategies. METHODS: One eye of 49 patients (mean age, 61.6 years; range, 22-81) with glaucoma (Mean Deviation mean, -7.13 dB; range, +1.8 to -23.9 dB) was examined four times with each of the three strategies. The mean and median SITA Standard and SITA Fast threshold estimates were compared with a "best available" estimate of sensitivity (mean results of three Full Threshold tests). Pointwise 90% retest limits (5th and 95th percentiles of retest thresholds) were derived to assess the reproducibility of individual threshold estimates. RESULTS: The differences between the threshold estimates of the SITA and Full Threshold strategies were largest ( approximately 3 dB) for midrange sensitivities ( approximately 15 dB). The threshold distributions of SITA were considerably different from those of the Full Threshold strategy. The differences remained of similar magnitude when the analysis was repeated on a subset of 20 locations that are examined early during the course of a Full Threshold examination. With sensitivities above 25 dB, both SITA strategies exhibited lower test-retest variability than the Full Threshold strategy. Below 25 dB, the retest intervals of SITA Standard were slightly smaller than those of the Full Threshold strategy, whereas those of SITA Fast were larger. CONCLUSIONS: SITA Standard may be superior to the Full Threshold strategy for monitoring patients with visual field loss. The greater test-retest variability of SITA Fast in areas of low sensitivity is likely to offset the benefit of even shorter test durations with this strategy. The sensitivity differences between the SITA and Full Threshold strategies may relate to factors other than reduced fatigue. They are, however, small in comparison to the test-retest variability.

Adult↗