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Biomedical subjects

R D Fechtner

Publications and source records attributed to R D Fechtner.

At least 19 recordsLinked to original sources
PubMed2000

Diffuse and localized nerve fiber layer loss measured with a scanning laser polarimeter: sensitivity and specificity of detecting glaucoma.

PURPOSE: To differentiate normal from diseased retinal nerve fiber layers (NFL) using a new method of analyzing polarimetry data that specifically targets patterns of diffuse and localized NFL loss. METHODS: The NFL from a sample of 34 patients with primary open-angle glaucoma (POAG), 34 patients with ocular hypertension, and 34 normal subjects were imaged using a scanning laser polarimeter (GDx; Laser Diagnostic Technologies, Inc., San Diego, CA). Diffuse loss was defined as a reduction in the peak-to-trough amplitude of the double-hump NFL pattern, and localized loss was defined as a lowering of the correlation of thickness values between local regions shown previously to correspond in normal subjects. RESULTS: Significant differences were found between the groups of normal subjects, patients with hypertension, and patients for both the amplitude and the correlational measures. The sensitivity and specificity calculated using optimal criterion values were 94% and 91%, respectively. CONCLUSIONS: These results suggest that NFL analysis targeting specific patterns of loss may be beneficial for differentiating normal NFL patterns from diseased NFL patterns, as well as for identifying patients at high risk.

Adult↗
PubMed2000

Fourier analysis of nerve fiber layer measurements from scanning laser polarimetry in glaucoma: emphasizing shape characteristics of the 'double-hump' pattern.

PURPOSE: The pattern of the distribution of nerve fiber layer (NFL) thickness values across the retina may provide an early anatomic indication of glaucomatous disruption. We developed a method of analyzing polarimetry measurements that emphasizes the shape of the pattern of NFL thickness values. Sensitivity and specificity for detecting glaucoma was obtained for these measures and compared with those for conventional measures. METHODS: Nerve fiber thickness was inferred from retardation shift measured by a scanning laser polarimeter (Laser Diagnostic Technologies, Inc., San Diego, CA) in 34 healthy subjects (68 eyes) and 34 patients with glaucoma (68 eyes). Fourier analysis was performed on the polarimetry data to emphasize the shape in the evaluation of the distribution of thickness values around the optic disc (along a 1.7-disc diameter ring). This was computed separately on superior and inferior hemiretinas. RESULTS: Significant differences were found in the Fourier shape measures between healthy subjects and patients with glaucoma. The sensitivity and specificity using Fourier coefficients with this particular sample was 96% and 90%, respectively. CONCLUSION: The evaluation of NFL measurements with Fourier analysis to emphasize the holistic shape of the "double-hump" pattern was found to be a useful tool as an analysis strategy.

Adult↗
PubMed1999

Advances in optic nerve head analysis in glaucoma.

Assessment of the optic nerve head for structural changes is critical for the detection of glaucoma and for following progression in patients with established glaucoma. Qualitative optic nerve analysis can be obtained via methods such as disc drawings and stereo disc photography. However, these methods are limited by significant interobserver and intraobserver variability. Disc photographs can also vary greatly according to the camera angle, photographic technique, lighting, and magnification. The need for accurate, reproducible, and quantitative, cost-effective techniques of assessing the optic disc and appreciation of the limitations of subjective clinical observation stimulated the development of new technologies.

Diagnosis, Differential↗
PubMed1999

Interocular symmetry in nerve fiber layer thickness of normal eyes as determined by polarimetry.

PURPOSE: The existence of asymmetries between the two eyes in number and distribution of nerve fibers may provide an early anatomic indication of glaucomatous disruption if a symmetrical pattern of nerve fibers can be shown in normal eyes. Normal eyes were tested to determine whether a high degree of correspondence of regional nerve fiber layer thickness exists between fellow eyes. METHODS: Nerve fiber layer thickness was inferred from retardation shift measured by a scanning laser polarimeter (Laser Diagnostic Technologies, Inc.) in 40 volunteers without glaucoma or ocular disease (80 eyes). Total thickness and the pattern of nerve fiber thickness over 208 regions was compared between the paired eyes. RESULTS: Inferred nerve fiber layer thickness in companion eyes was highly correlated. Variation of the total nerve fiber thickness was much less between companion eyes than between eyes of different individuals. In terms of regional (i.e., local) interocular correspondence, the measurements in the inferior retina were observed to be highly similar in the two eyes, but a pronounced shift of the location of the superior peak (maximum thickness) in the left eye relative to the right was observed, as were differences between the two eyes in the thickness measurements at the nasal and temporal minima. CONCLUSION: Significant interocular asymmetries were detected in regions other than the interior hemiretina. These interocular asymmetries may reflect previously unrecognized anatomic nerve fiber differences or systematic angular bias in the instrument for one eye relative to the other. In contrast to the regional measures, the measures of total thickness were very similar between companion eyes, suggesting that the assessment of interocular asymmetries of total thickness determined by polarimetry may offer potential for detecting glaucoma.

Adult↗
PubMed1998

Anterior uveitis associated with latanoprost.

PURPOSE: To report the association of anterior uveitis with the use of latanoprost. METHODS: We studied four patients with complicated open-angle glaucoma who had anterior uveitis associated with the use of latanoprost. The uveitis was unilateral and occurred only in the eye receiving latanoprost in three patients. In one patient, latanoprost was used in both eyes, and the uveitis was bilateral. Four of five eyes had a history of prior inflammation and/or prior incisional surgery. All patients were rechallenged with the drug. RESULTS: The uveitis improved after cessation of latanoprost with or without topical corticosteroids. It recurred after rechallenging with latanoprost in all eyes. CONCLUSION: There is a possible association between latanoprost and anterior uveitis. Topical prostaglandin analogs may be relatively contraindicated in patients with a history of uveitis or prior ocular surgery. This association may also be possible in eyes that have not had previous uveitis or incisional surgery.

Administration, Topical↗
PubMed1996

Binocular function in early glaucoma.

PURPOSE: This study investigated whether certain binocular mechanisms are disrupted in early glaucoma. METHODS: Glaucoma patients, suspects, and normals were tested on a battery of psychophysical tests consisting of flicker sensitivity (5 and 34 Hz), temporal cut-off frequency (CFF), contrast sensitivity (Pelli-Robson chart), and stereoacuity. Monocular channels were evaluated with tests of monocular flicker performance and spatial contrast sensitivity. Binocular summation on spatial and temporal tests was used to reflect integrity of binocular neural interactions. Stereoacuity was taken as a measure of performance of disparity processing mechanisms. RESULTS: The groups differed in terms of binocular flicker sensitivity at both temporal rates, binocular and monocular peak contrast sensitivity, and stereoacuity. Binocular summation of both spatial and temporal sensitivity was normal. The glaucoma suspect group was distinguishable from the age-matched normal group on binocular contrast sensitivity and stereoacuity. CONCLUSIONS: The binocular mechanisms that mediate stereoacuity appear to be heavily disrupted, whereas the binocular mechanisms that mediate central neural interaction of monocular inputs are normal. Although monocular spatiotemporal abilities are disrupted, the binocular processes combine the monocular input normally. In addition, our results suggest a benefit of binocular testing for routine assessment of glaucoma patients. The profound disruption of stereoacuity appears to result from disorder in the spatial sampling array at the ganglion-cell level similar to the disorder reported in the normal periphery and the central retina of strabismic amblyopes. These and previous findings were reviewed to evaluate the supposition of preferential M-pathway disruption in early glaucoma. Such a model can not be reconciled with the present findings. We conclude that measurements of temporal modulation sensitivity fit well with such a model, but that the current evidence of spatiotemporal contrast sensitivity disruption is less supportive of such a model.

Analysis of Variance↗
PubMed1994

Interpretation of automated perimetry for glaucoma by neural network.

PURPOSE: Neural networks were trained to interpret the visual fields from an automated perimeter. The authors evaluated the reliability of the trained neural networks to discriminate between normal eyes and eyes with glaucoma. METHODS: Inclusion criteria for glaucomatous and normal eyes were the intraocular pressure and the appearance of the optic nerve; previous visual fields were not used. The authors compared the backpropagation learning method used by automated neural networks to those used by two specialists in glaucoma to classify the central 24 degrees automated perimetric visual fields from 60 normal and 60 glaucomatous eyes. RESULTS: The glaucoma experts and a trained two-layered network were each correct at approximately 67%. The average sensitivity of this test was 59% for the two glaucoma specialists and 65% for the two-layered network. The corresponding specificities were 74% and 71% for the specialists and the two-layered network, respectively. The experts and the network were in agreement about 74% of the time, which indicated no significant disagreement between the methods of testing. Feature analysis with a one-layered network determined the most important visual field positions. CONCLUSIONS: The authors conclude that a neural network can be taught to be as proficient as a trained reader in interpreting visual fields for glaucoma.

Adult↗