Biomedical subjects

F K Horn

Publications and source records attributed to F K Horn.

At least 19 recordsLinked to original sources

PubMed2006

[Flicker provocation with LED full-field stimulation in normals and glaucoma patients].

BACKGROUND: Flicker light is an easy method to test sensory function after stress. The aim of this study was to determine the influence of flicker stress on temporal contrast sensitivity in healthy controls and patients with glaucomatous alteration of the optic disk. METHODS: A commercially available full-field stimulator (Retiport, Roland Consult) equipped with white LEDs was modified to perform psychophysical tests. The patients underwent measurements of the recovery time interval from cessation of flicker stress until recognition of a pregiven flicker contrast after photo stress. In addition, we studied contrast sensitivity with a continuous flickering target and with a flicker burst protocol avoiding adaptation to prevailing flicker. All tests were performed at a constant retinal illumination and at a frequency of 37 Hz for provocation as well as for contrast sensitivity tests. SUBJECTS: Normal healthy controls (40), "preperimetric" (62), and "perimetric" (52) open-angle glaucoma patients were studied. Exclusion criteria were age lower than 31 years, visual acuity under 0.6, and perimetric mean defect more than 9.5 dB. RESULTS: Recovery time after flicker stress was significantly longer in patients than in normals and longer in perimetric than in preperimetric patients. Analysis in perimetric patients revealed a larger area under ROC for the provocation test (0.95) than in contrast sensitivity tests (continuous flicker method: 0.90, flicker burst mode: 0.84). CONCLUSION: High-power LEDs which are installed in modern full-field devices can be used as a helpful tool to study psychophysical properties. In the present study it could be shown that threshold, adaptation, and recovery of temporal transfer characteristics are impaired in many patients with glaucoma.

Contrast Sensitivity↗

PubMed2004

[Digital planimetry for long-term follow-up of glaucomatous optic disk injuries in patients with normal pressure glaucoma].

BACKGROUND: Aim of the study was to evaluate the validity of quantitative planimetry of the optic disc with a new digital method and to assess the correlation of the measurements with morphological changes in eyes with low tension glaucoma. MATERIAL AND METHODS: The study included 40 eyes from 40 patients (age 61+/-12 years) with low tension glaucoma with a mean follow-up of 4.9+/-2.1 (range 3-9) years. All patients underwent annually complete ophthalmological examination including 15 degrees color optic disc photographs and automated white-white visual fields. RESULTS: Out of 40 eyes morphological examination showed signs of progression in 18 eyes and in 22 eyes no morphological changes of the optic disc were detected The digital planimetrically measured optic disc area did not vary between the first and the last photos. The mean differences between measured values for optic disc area between two examinations were 0.027+/-0.071 mm(2) and the reliability coefficient (Cronbachs alpha) was 0.99. Neuroretinal rim area decreased statistically highly significantly in eyes with morphological progression, and in eyes without morphological changes decreased only slightly. CONCLUSIONS: The variation of measurements of the optic disc area can be minimized by consideration and adjustment of the individual image magnification of the photos using digital planimetry. This method allows the quantitative assessment even of slight changes of the neuroretinal rim area and is a useful examination for follow-up of glaucoma patients.

Disease Progression↗

PubMed2003

[Multifocal steady-state pattern-reversal electroretinography in glaucoma patients].

AIM: This study was designed to answer the question of whether multifocal steady-state pattern-reversal electroretinography (ERG) is capable of detecting glaucomatous visual field defects. METHOD: Sixteen patients (28 eyes) and ten normal subjects (20 eyes) were examined. Multifocal pattern ERGs were recorded with the RETIscan system and DTL electrodes. We stimulated with a steady-state checkerboard pattern reversal (three reversals during 171 ms sweep length, congruent with 17.5 reversals/s). The multifocal pattern ERG amplitudes were evaluated using discrete Fourier transformation (DFT) across three reversals. In cases of advanced glaucoma, the DFT-calculated amplitudes were combined in hemispheres and checked for correlations with corresponding visual field defects. In all binocularly examined persons, side comparisons ("worse" eye vs "better" eye), and interindividual comparisons (glaucoma vs normal) were carried out. RESULTS: In interindividual comparisons and interocular side comparisons, significant amplitude reductions of the "worse" eyes were seen in the foveal records. No topographical correlation between multifocal pattern ERG amplitudes and visual field defects could be found. CONCLUSIONS: In glaucomatous visual field defects, multifocal steady-state pattern-reversal ERG using the present stimulation was significantly reduced in its foveal records but seems to be incapable of detecting them topographically.

Adult↗

PubMed2002

Retinal nerve fiber layer measurements using laser scanning polarimetry in different stages of glaucomatous optic nerve damage.

PURPOSE: To evaluate the diagnostic value of polarimetric measurements of the retinal nerve fiber layer (RNFL) thickness in different stages of glaucomatous optic nerve damage. METHODS: The study included 92 eyes of 46 controls (age 41.0+/-13.7 years) and a heterogeneous group of 232 eyes of 135 patients with different stages of glaucomatous optic nerve damage (age 54.0+/-10.2 years; 68 patients with primary open-angle glaucoma, 56 with normal-pressure glaucoma and 11 patients with secondary glaucoma due to primary dispersion syndrome or pseudoexfoliation syndrome). All control subjects and patients underwent complete ophthalmological examinations including scanning laser polarimetry of the RNFL using the GDx (Laser Diagnostic Technologies, San Diego, Calif.) and 15 degrees color stereo optic disc photographs. Only subjects and patients with disc area less than 3.4 mm(2) were included in the study. The total glaucoma group were divided into four subgroups according to the morphological criteria of the neuroretinal rim. RESULTS: The stage of morphological glaucomatous optic nerve damage was classified as follows: stage 0: n=92, stage 1: n=103, stage 2: n=65, stage 3: n=40, and stage 4: n=19. Differences in mean polarimetric retardation between controls and eyes with glaucoma were significant for all parameters except the variable symmetry. The most significant differences between controls and eyes with glaucomatous optic nerve damage were found with the "number" variable assigned by the neural network analysis ( P<0.001). With increasing stage of glaucomatous optic nerve damage, separation of the variable "the number" increased significantly. At a predetermined specificity of 90% the sensitivity of the groups with different stages of morphological glaucomatous optic nerve damage increased from 32% for stage 1 to 90% for stage 4. CONCLUSION: Polarimetric measurement of the RNFL thickness is significantly associated with morphological glaucomatous optic nerve damage. The fast performance, easy handling, and low cost of RNFL polarimetry mean that it can be included in the routine examination of glaucoma patients. Further study and refinement of this technique are indicated to improve its usefulness in both clinical diagnosis and in population-based case identification.

Adult↗

PubMed2002

[Multifocal ERG with 30 Hz flicker stimulation in glaucoma patients and normal probands].

BACKGROUND: It was the aim of the present study to investigate the value of multifocal ERG with 30 Hz flicker stimulation for glaucoma diagnosis. METHODS: Multifocal ERGs with 30 Hz flicker stimulation were recorded with a mean luminance of 50 cd/m2 and a contrast of 99% from the central 60 degrees of the retina which were stimulated by 61 hexagons. From 30 patients with primary and secondary open-angle and low-tension glaucomas with reproducible visual field losses and glaucomatous optic disc atrophy and 21 normal subjects, one eye was included in the study. The first harmonic wave, the basewave and the ratio of these two parameters were ana-lysed. The responses of seven neighbouring hexagons were averaged for the intraocular comparison between areas with and without perimetric defects and for the comparison between glaucomas and normal subjects. RESULTS: In the glaucoma group, the ratio of the first harmonic wave and the basewave was significantly lower in an area within a perimetric defect than outside the defect (p < 0.001) when compared intraocularly. The extent of ERG changes however did not correlate with the extent of perimetric defects. Comparing the glaucoma with the normal group, the ratio of the first harmonic and the basewave was significantly lower in an area within the perimetric defect in the glaucoma group than in corresponding areas of the normal group (p = 0.002). The first harmonic and the basewave did not differ significantly. DISCUSSION: These results show that the method is not appropriate to objectively indicate visual field losses although it statistically separates glaucomas from normal subjects.

Adult↗

PubMed2001

Two methods of lens opacity measurements in glaucomas.

PURPOSE: Determination of lens opacity is important in aging glaucoma patients, because sensory testing may be influenced by increasing lens opacity. Purpose of this study was to measure lens opacity in normals and glaucoma patients using two different techniques, to compare both methods, and to correlate the results with contrast sensitivity testing. METHODS: 94 glaucomatous eyes, 47 ocular hypertensive eyes, and 79 control eyes were studied using the following devices: opacity lens meter (OLM, objective back scatter method), stray light meter (SLM, subjective forward scatter using flicker light), and temporal contrast sensitivity (full-field flicker test). SLM results were separately analyzed at the lower and upper flicker disappearance. All subjects were younger than 66 years and had no significant cataracts. RESULTS: In patients and in normal subjects OLM readings and SLM findings elicited at the upper disappearance point are significantly correlated with age and with each other (R >0.45, P<0.001), while SLM at the lower disappearance point shows no such correlation. In normals, but not in patients, SLM at the lower disappearance point is significantly correlated with temporal contrast sensitivity. CONCLUSIONS: Both devices can be used for quantifying lens opacity in glaucoma. SLM readings with increasing light intensity at the lower disappearance point seems to be more influenced by the individual flicker sensitivity than determination of the upper flicker disappearance. Therefore, using the SLM in glaucoma patients, the threshold measurements based on the upper disappearance of the flicker should be used instead of the suggested mean threshold measurements.

Adolescent↗

PubMed2001

The negative response of the flash electroretinogram in glaucoma.

The existence of a negative ERG component following the b-wave has been known for a long time. Recently, in unilateral macaque experimental glaucoma, a negative response in flash electroretinograms under scotopic as well as photopic conditions has been shown to be greatly reduced or absent compared to the healthy fellow eye. The aim of this pilot study was to test whether a late negative electroretinogram component is reduced also in human glaucoma patients under different stimulus conditions. Dark-adapted ganzfeld flash electroretinograms were recorded after 30 min of dark using two test conditions, obtained as optimal in pilot studies on controls. Under the scotopic condition I white Xenon-flashes of intensity 0.53 Log photopic Td s were presented on a low white background of 1.38 Log scotopic Td. Under the more photopic condition II orange flashes of intensity -0.37 Log photopic Td s were presented on a blue-adapting background of 2.5 Log scotopic Td. Nine controls and 18 patients with advanced glaucoma were analyzed. The amplitude of the negative response was not significantly reduced in glaucoma patients (condition I: -28.5+/-23.7 microV; condition II: -25.2+/-19.7 microV) compared to controls (condition I: -41.4+/-36.6 microV; condition II: -31.3+/-26.2 microV). The peak latency of the responses under condition I and II did not differ significantly between patients and controls. Thus, the late negative electroretinogram component in ganzfeld flash electroretinograms obtained under scotopic and more photopic conditions does not seem to distinguish as easy between human controls and glaucoma patients as animal experiments suggest.

Dark Adaptation↗

PubMed2001

[Conventional versus digital planimetry of optic disc photograph: a clinical comparative study].

BACKGROUND: The optic disc size is an important parameter for the diagnosis of glaucomatous and non-glaucomatous optic nerve damage. The aim of this study was to compare quantitative measurements of the optic disc with the established conventional planimetry and a new digital method using Soft imaging system analySIS(tm) for Ophthalmology and to determine the reproducibility of this new method. PATIENTS AND METHODS: Fifty color stereo optic disc photographs of 50 patients (mean age 41.7 +/- 13.4 y) were included in the retrospective, comparative study. Conventional and digital planimetry was taken from one skilled examiner in a masked fashion. According to patient's number measurement values obtained with both methods were matched. Digital planimetric measurements of 10 optic disc photographs were repeated on day 7 and day 14. Statistical analysis was done using linear regression analysis, reliability coefficient and U-test. RESULTS: The planimetric values did not vary significantly between the two methods for optic disc area (3.19 +/- 0.65 mm(2) vs. 3.03 +/- 0.64 mm(2), p=0.96), for cup area (1.36 +/- 0.62 mm(2) vs. 1.21 +/- 0.63 mm(2), p=0.96) or for neuroretinal rim area (1.83 +/- 0.39 vs. 1.82 +/- 0.41 mm(2), p=0.98). There was also no significant difference of horizontal and vertical diameter of optic disc and cup as well as the diameter of the superior temporal and inferior temporal retinal artery and vein at the optic disc border between both methods (p < 0.5). Differences between measured values for optic disc, optic cup area and neuroretinal rim area obtained with both methods were 0.16 +/- 0.10 mm(2) (range - 0.05 to 0.24), 0.15 +/- 0.10 mm(2) (range - 0.12 to 0.26) and 0.014 +/- 0.11 mm(2) (range - 0.26 to 0.26). A high correlation of all planimetric values was observed between both methods (r=0.9, p < 0.0001). Using digital planimetry differences between day 1, day 7 and day 14 were 0.05 +/- 0.03 (range 0.02 to 0.10 mm(2)) for optic disc, 0.05 +/- 0.04 (range 0.0 to 0.13 mm(2)) for optic cup area and 0.05 +/- 0.05 (range 0.01 to 0.14 mm(2)) for the neuroretinal rim area. The reliability coefficient of digital planimetry was 0.9 for optic disc parameters. CONCLUSIONS: The comparable results between both methods and a high reproducibility suggest that the digital planimetry could be used either for clinical routine or scientific evaluation of the optic nerve.

Adult↗

PubMed2001

The a-wave of the dark adapted electroretinogram in glaucomas: are photoreceptors affected?

AIMS: To evaluate whether the a-wave of the dark adapted flash electroretinogram (ERG) is affected by glaucomatous damage. METHODS: ERGs were recorded in 20 patients (age 33-65 years) with advanced glaucomas (primary and secondary open angle and low tension glaucomas) and 20 normals using a ganzfeld stimulus. After 30 minutes of dark adaptation and pupil dilatation to at least 7.5 mm in diameter, luminance response functions were obtained presenting white flashes of increasing scotopic luminance (the highest flash intensity being 9.4 cd/s/m2, the lowest being 5.75 log units below it) with an interflash interval of 5 seconds. For each scotopic luminance, the responses of four flashes were averaged. The a-wave's amplitude was measured at 10, 11, and 12 ms. Within the glaucoma group, correlations between the interocular differences of the a-wave's amplitude and the mean deviation of a static perimetry (Octopus 500 perimeter, program G1) were computed for all flash intensities. Between normals and glaucomas, the a-wave's amplitude was compared for all flash intensities (paired t test). RESULTS: Within the glaucoma group, the interocular differences of the a-wave's amplitudes correlated significantly with the differences of the MD for flash intensities of 9.4, 5.3, 1.7, and 0.5 cd/s/m2. The a-wave's amplitude was significantly lower in the glaucoma compared with the normal group (p <0.005) for flash intensities of 9.4 and 5.3 cd/s/m2. CONCLUSION: These electrophysiological results imply that also the outer retinal structures, especially the photoreceptors, may be affected by glaucomatous damage.

Adaptation, Ocular↗

PubMed2001

The b-wave of the dark adapted flash electroretinogram in patients with advanced asymmetrical glaucoma and normal subjects.

AIMS: To evaluate whether the b-wave of the dark adapted flash electroretinogram (ERG) is affected by glaucomatous damage. METHODS: ERGs were recorded in 35 patients aged 33-65 years with advanced asymmetrical glaucomas (interocular difference of perimetric defects (mean deviation) >2 dB between the two fellow eyes of the glaucoma patients, primary and secondary open angle and low tension glaucomas) and 17 normal subjects matched for age and sex using white flashes of a xenon discharge tube in a Ganzfeld stimulator. After 30 minutes of dark adaptation luminance response functions were obtained using flashes of increasing scotopic luminance (highest 9.4 cd/s/m2, lowest 5.5 log units below it). The parameters Vmax, n, and K of the Naka-Rushton equation were computed from the measurement values based on the usual fitting procedure. These parameters, together with b-wave amplitudes and implicit times for all flash intensities, were compared interocularly and between the normal subjects and those with glaucoma. Correlations were computed between interocular differences of the mean deviation and interocular differences of Vmax, n, K, b-wave amplitudes, and implicit times between the two fellow eyes of the patients with asymmetrical glaucomatous damage. RESULTS: Implicit times were significantly longer (p<0.005) in the glaucoma patients than in the normal group for flash intensities of 9.4, 5.3, 1.7, 0.53, and 0.17 cd/s/m2. b-Wave amplitudes did not differ significantly between the two study groups. Comparing the two fellow eyes of each patient with glaucoma, Vmax was significantly higher in the less damaged eye than in the more damaged eye. The interocular differences in the mean deviation correlated significantly with the interocular differences in the b-wave amplitudes, implicit times, and Vmax. CONCLUSIONS: These results suggest that glaucomas can lead to electrophysiologically measurable damage of the inner nuclear layer.

Adaptation, Ocular↗

PubMed2000

The full-field temporal contrast sensitivity test for glaucoma: influence of cataract.

PURPOSE: To determine the influence of lens opacities on temporal contrast sensitivity, measured by the full-field flicker test ("Erlangen flicker test"). METHODS: Thirty-six consecutive patients (mean age 71.1+/-11.6 years, 12 male, 24 female, refractive error -1.5+/-3.8 dpt) with cataract (visual acuity 0.21+/-0.16, retinal acuity 0.56+/-0.32, no glaucoma) were studied. Temporal contrast sensitivity (full-field flicker test, 37.1 Hz) and lens opacity (back scatter Lens Opacity Meter, Interzeag) were measured preoperatively and on the 3rd postoperative day. STATISTICS: nonparametric tests (Wilcoxon-test, Spearman correlation coefficient, Mann-Whitney U-test). RESULTS: No significant difference was seen in temporal contrast sensitivity pre- and postoperatively, but there was a significant difference in lens opacity measurements pre- and postoperatively. No significant correlation was found between temporal contrast sensitivity and lens opacity values preoperatively and postoperatively. CONCLUSION: The temporal contrast sensitivity, measured by the full-field flicker test, seems to be independent of lens opacity due to the range of cataract included in this study. The data indicate that the full-field flicker test is useful for early glaucoma detection even in patients with cataract formations.

Aged↗

PubMed2000

[Central corneal thickness in normal eyes, patients with ocular hypertension, normal-pressure and open-angle glaucomas--a clinical study].

BACKGROUND: The relation between Goldmann applanation tonometry and central corneal thickness (CCT) was investigated in several studies during the last thirty years. It was the aim of the present study to evaluate CCT in normals, patients with ocular hypertension, low-tension, and open-angle glaucomas. PATIENTS AND METHODS: CCT was measured in 135 normal eyes, 137 with ocular hypertension, 65 with low-tension, and 94 with primary and secondary open-angle glaucomas using the AL-11000-pachymeter (Tomey). The results were compared using the unpaired t-test. RESULTS: CCT was significantly higher in the patients with ocular hypertension (586 +/- 43 microns) than in the normal group (566 +/- 37 microns, p < 0.0001), in low-tension glaucomas (555 +/- 46 microns, p < 0.0001), and in open-angle glaucomas (558 +/- 31 microns, p < 0.0001). The latter three groups did not differ significantly. There was no significant correlation between CCT and age, the actually measured IOP, the highest IOP in the patient's history, or the spherical equivalent. CONCLUSIONS: Only patients with ocular hypertension showed a significant difference in CCT compared with normals. Pachymetry thus should be conducted in those patients to avoid overestimation of the IOP by applanation tonometry. In most of the patients with low-tension and open-angle glaucomas however, CCT regarded without other parameters (e.g. corneal or scleral rigidity) plays a minor role in detection of elevated IOP according to the results of this study.

Adolescent↗

PubMed2000

[Synopsis of various electrophysiological tests in early glaucoma diagnosis--temporal and spatiotemporal contrast sensitivity, light- and color-contrast pattern-reversal electroretinogram, blue-yellow VEP].

BACKGROUND: Of the three glaucoma-defining criteria intraocular pressure, optic-nerve damage, and visual field damage, the latter is a late symptom. Therefore, in order to improve an early sensory diagnosis, new tests are necessary. It is the aim of the present paper to test new sensory methods, to rank them in an order of sensitivity, and to base them on possible pathophysiological mechanisms. PATIENTS AND METHODS: The tests were carried out in subjects of the Erlangen Glaucoma registry: Normals, patients with ocular hypertension, and patients with open-angle glaucoma without or with field defects. The tests are designed to preferentially probe the function of different groups of ganglion cells. Psychophysical methods: Temporal contrast sensitivity in a ganzfeld as "Erlangen flicker test" and spatio-temporal contrast sensitivity to test Magno-cell function. Electrophysiological methods: Pattern-reversal electroretinogram with a luminance-contrast pattern to test Magno-cell function, color-contrast pattern electroretinogram for Parvo-cell function, and blue-on-yellow visual evoked potential to test the "blue-sensitive" pathway. RESULTS: The most sensitive test is the temp.CS, it is significantly reduced in OHT (p < 0.01). The spatio-temp.CS is reduced in perimetric stages (p < 0.01). The BY-VEP is altered in the preperimetric stage (p < 0.01), the PR-ERG in perimetric stages (p < 0.01). The CC-ERG is reduced in even later stages. These results are in agreement with the hypothesis that tests selective for non-redundant neurons are of early diagnostic value. Multivariate analyses increase the early diagnostic value when different functions are tested in combination. CONCLUSIONS: When a particular test is taylored to the the special needs of certain groups of ganglion cells sensory defects can be observed before the occurrence of optic-nerve damage (OHT). The most sensitive psychophysical test is the "Erlangen flicker test" which is a screening test selective for M cells. The most sensitive electrophysiological test is the BY-VEP testing the blue-sensitive ganglion cells.

Color Perception↗

PubMed2000

Visual evoked potentials under luminance contrast and color contrast stimulation in glaucoma diagnosis.

PURPOSE: To evaluate the diagnostic value of visual evoked potential (VEP) assessment with luminance-contrast and color-contrast stimulation in the detection of glaucoma. PATIENTS AND METHODS: The study included 59 patients (96 eyes) with glaucomatous changes of the optic disc and visual field defects and 58 control eyes of 29 healthy patients. Four types of pattern VEP stimulation (0.9 cycle/degree) were performed in all patients: achromatic, alternating sine-wave stripe pattern: 6 reversals per second, contrast of 10% (activation of predominantly the magnocellular pathway); isoluminant, red-green stripe pattern: 83.3 milliseconds onset, 83.3 milliseconds offset, contrast of 30% and 80% (activation of predominantly the parvocellular pathway); and blue grating with yellow background adaptation: 200 milliseconds onset, 500 milliseconds offset (activation of the blue-sensitive pathway). RESULTS: The glaucoma group and the control group differed significantly (P < 0.01) in the peak times of all chromatic VEP responses and to a lesser degree in the achromatic VEP. Considering the amplitudes, only the low-contrast red-green stimulus showed a statistically significant reduction in glaucoma. At a predefined specificity of 90%, in separating patients with glaucoma from healthy control subjects, the peak time of the blue-yellow VEP had a high sensitivity (90%), whereas the sensitivity of the achromatic VEP was low (31%). The red-green VEP showed a sensitivity of 73% using low contrast and 71% using high contrast. In a paired correlation analysis with visual field defects, all stimulations showed significant (P < 0.05) results. Correlation coefficients were highest (R = 0.79, P < 0.01) for the peak time of the blue-yellow VEP. CONCLUSIONS: VEP measurements with presumable stimulation of single neuronal pathways can detect glaucomatous optic nerve damage in a considerable fraction of patients with visual field loss. Occipital responses to chromatic stimulation seem to be more sensitive to glaucoma damages than do responses to achromatic pattern reversal stimulation.

Chronic Disease↗

PubMed1999

The full-field flicker test in glaucomas: influence of intraocular pressure and pattern of visual field losses.

BACKGROUND: The purpose of this study was to evaluate how temporal contrast sensitivity (TCS) determined with full-field flicker stimuli is influenced by intraocular pressure and whether TCS is reduced in glaucoma patients with diffuse perimetric losses as well as in patients with localized visual field deficits. METHODS: TCS was determined with sinusoidally flickering light (37.1 Hz) in a full-field bowl. Perimetric mean defect (MD) and cumulative defect curves (Octopus G1) were used to distinguish between patients with localized and diffuse field deficits. Normal subjects (296), low-tension glaucoma patients (98) and open-angle glaucoma patients with previously elevated intraocular pressure (541) were classified into five subgroups taking into account the depth of their visual field losses. RESULTS: No significant correlation between full-field flicker sensitivity and prevailing intraocular pressure was found in normals (Y=1.36+0.006 X) or in patients (Y=0.95-0.0002 X). Analyses of validity at a predefined specificity of 90% reveal a reduction of TCS in patients with early (MD<5 dB) diffuse perimetric losses (sensitivity 69%) as well as in those showing localized visual field defects (sensitivity 65%). Sensitivity was 87% in patients with diffuse perimetric defects (MD 5-10 dB), 93% in a group of patients with both types of losses, and 100% in advanced glaucomas (MD>20 dB). The lack of TCS is similar in open-angle glaucomas and in field-loss-matched normal-tension glaucoma patients. CONCLUSIONS: Significantly reduced TCS in patients with early diffuse perimetric losses as well as in those showing localized visual field defects indicates that localized damages can be associated with general deterioration of the ability to perceive flickering stimuli. Thus, this flicker test can be performed in a full-field bowl with no need for fixation. Considering its other clinical qualities (photopic conditions, low influence of prevailing intraocular pressure and media opacity) the test may be a useful, convenient supplementary procedure in glaucoma screening.

Chronic Disease↗

PubMed1999

Temporal contrast sensitivity with peripheral and central stimulation in glaucoma diagnosis.

AIMS: To evaluate temporal contrast sensitivity with full field, peripheral, and central stimulation and to determine the most sensitive corresponding retinal area for glaucoma damage. METHODS: Temporal contrast sensitivity was determined either with a full field, a peripheral annular area from 30 degrees to 90 degrees, or a central area from 0 degree to 30 degrees at a frequency of 37.1 Hz. 232 eyes of 232 subjects were included. They were classified into four groups: eyes with ocular hypertension (OHT, n = 54), "preperimetric" glaucomas (n = 73) with glaucomatous optic disc abnormalities but no visual field loss, "perimetric" glaucomas (n = 53) with visual field loss, and 52 normals. RESULTS: In all four groups, temporal contrast sensitivity was almost equal with full field and peripheral, but significantly higher than with central stimulation (p < 0.001). With regard to the diagnostic power of the three different stimulus areas, OHTs and glaucomas were found to be best discriminated from normals by peripheral stimulation. CONCLUSIONS: According to these results, temporal contrast sensitivity seems to be determined by peripheral retinal areas. As the diagnostic power of the three different stimulus areas was best with the peripheral stimulation, this condition should be used for early glaucoma diagnosis.

Adult↗

PubMed1999

Preperimetric glaucoma diagnosis by confocal scanning laser tomography of the optic disc.

AIM: To evaluate the ability of confocal scanning laser tomography of the optic nerve head to detect glaucomatous optic nerve damage in ocular hypertensive eyes without visual field defects. METHODS: The study included 50 normal subjects, 61 glaucoma patients with glaucomatous changes in the optic disc and visual field, and 102 "preperimetric" patients with increased intraocular pressure, normal visual fields, and glaucomatous appearance of the optic disc as evaluated on colour stereo optic disc photographs. For all individuals, confocal scanning laser tomographs of the optic nerve head were taken using the Heidelberg retina tomograph (HRT; software 2.01). RESULTS: Almost all investigated HRT variables varied significantly (p < 0.05) between the normal eyes and preperimetric glaucoma eyes with pronounced overlap between the two study groups. Corresponding to the overlap, sensitivity and specificity values were relatively low when HRT variables were taken to differentiate between normal and preperimetric glaucoma eyes. At a given specificity of 95% highest sensitivities were found for the variables "rim area in the superior disc sector" (24.8%), "nerve fibre layer thickness in the inferior disc sector" (26.5%), and "rim volume in the superior disc sector" (25.5%). A multivariate approach increased sensitivity to 42.2% at a given specificity of 95%. For the glaucoma group highest sensitivity values were reached by rim volume in the superior disc sector (73.8%) and rim area (72.1%); the multivariate approach reached 83.6%. CONCLUSIONS: Owing to pronounced overlapping between the groups, confocal scanning laser tomography of the optic nerve head has relatively low diagnostic power to differentiate between normal eyes and preperimetric glaucoma eyes. One of the reasons may be the biological interindividual variability of quantitative optic disc variables.

Adult↗

PubMed1999

Polarimetric measurement of retinal nerve fiber layer thickness in glaucoma diagnosis.

PURPOSE: To evaluate reliability and diagnostic value of polarimetric measurements of the retinal nerve fiber layer (RNFL) thickness in the diagnosis of glaucoma. METHODS: The study included 81 eyes with perimetric glaucoma with glaucomatous changes of the optic disc and visual field defects; 52 eyes with preperimetric glaucoma with glaucomatous optic disc abnormalities and normal achromatic visual fields; and 70 normal eyes. For determination of reliability, four examiners repeated polarimetric measurements five times in ten normal subjects. RESULTS: The polarimetric variables were significantly correlated with increasing mean visual field defect and decreasing neuroretinal rim area. In correlation analyses with visual field defects, correlation coefficients were highest for the variable "superior/nasal ratio" and "the Number," a variable calculated by the neural network of the device. In correlations with neuroretinal rim area, correlation coefficients were highest for measurements of the inferior nerve fiber layer thickness. The preperimetric glaucoma group and the control group differed significantly in the variables "superior/nasal ratio" and "the Number" and, to a smaller degree, in the variables "superior/temporal ratio" and "superior/inferior ratio." The Number variable had a sensitivity of 82% and 58% at a predefined specificity of 80% in separating perimetric glaucoma patients and preperimetric glaucoma patients, respectively, from control subjects. Reproducibility of the polarimetric measurements ranged between 70% and 89%. CONCLUSION: Polarimetric measurements of the RNFL thickness can detect glaucomatous optic nerve damage in patients with visual field loss, and in some patients with preperimetric glaucomatous optic nerve damage. Considering the fast performance, easy handling, and low maintenance costs, RNFL polarimetry may be helpful in glaucoma diagnosis.

Adult↗