Biomedical subjects

J Dobinson

Publications and source records attributed to J Dobinson.

3 recordsLinked to original sources

PubMed2000

A spatial frequency-doubling illusion-based pattern electroretinogram for glaucoma.

PURPOSE: A pattern electroretinogram (PERG) in which stimuli displaying the frequency-doubling (FD) illusion are presented simultaneously to multiple parts of the visual field was evaluated for its ability to diagnose glaucoma. This multiregion FD PERG is referred to in the current study as the MFP. METHODS: The nine stimulus regions were temporally modulated at incommensurate frequencies typically producing an FD percept. Two other spatial scales of the stimuli were also investigated. The sensitivity and specificity of MFP were examined using linear and quadratic discriminant methods. RESULTS: Even with the simpler linear discriminant classification, sensitivities and specificities of 100% were obtained in eyes with moderate to severe glaucoma. Of eyes with glaucoma strongly suspected, 67% were classified as being glaucomatous. Stimulus patterns having differing spatial scales produced different PERG visual field dependencies. CONCLUSIONS: The differing results for the 16-fold change in spatial scale may reflect the accessing of different mechanisms. The MFP method appears to have significant value for the diagnosis of glaucoma.

Electroretinography↗

PubMed2000

Comparing a parallel PERG, automated perimetry, and frequency-doubling thresholds.

PURPOSE: A pattern electroretinogram (PERG) simultaneously displaying the frequency-doubling (FD) illusion in nine parts of the visual field was compared with two other methods for ability to detect glaucoma. This multiregion FD PERG (MFP) was compared with results from achromatic automated perimetry and psychophysical tests using FD stimuli. METHODS: MFP data were compared with that from the Humphrey Field Analyser (HFA; Humphrey, San Leandro, CA) 24-2 program. Contrast thresholds were also determined in different visual field locations for FD stimuli. Thin-plate spline methods were used to derive comparisons from the tests, each of which sampled the visual field differently. RESULTS: Significant correlation with HFA could be obtained, providing seven to nine (of nine) MFP amplitudes were themselves significant. Evidence showed that both the psychophysical tests using FD stimuli and the MFP detect glaucomatous damage not detected by the HFA. CONCLUSIONS: The comparisons between HFA perimetry, the MFP, and FD thresholds indicate that both FD-based tests quantify a form of diffuse loss in early glaucoma as well as the scotomas of later glaucoma.

Electroretinography↗

PubMed1999

Testing for glaucoma with the spatial frequency doubling illusion.

We examined the performance of tests for glaucoma based on the spatial frequency doubling (FD) illusion. Contrast thresholds for seeing the FD illusion in four large visual field regions were measured from 340 subjects who were tested up to seven times over 2 years. Median sensitivities of 91% at specificities of 95% were obtained. Test-retest variability for the worst hemifield thresholds averaged 2.22 db +/- 0.09 S.E. for all tested groups, and significant progression was observed for glaucoma suspects over the seven visits, indicating that tests based on the FD illusion can detect diffuse early glaucomatous loss.

Adult↗