Matthias Korth

Migraine and tension headache in high-pressure and normal-pressure glaucoma

PURPOSE To analyze the association of normal-pressure glaucoma and migraine. METHODS In a prospective study, 154 patients with glaucoma (56 normal-pressure subgroup and 98 high-pressure glaucoma subgroup), 55 patients with ocular hypertension, and 75 control subjects were analyzed by means of a standardized questionnaire based on International Headache Society criteria. RESULTS According to the questionnaire, 46 patients (17%) were classified as suffering from migraine and 20 (7%) from tension headache (episodic and chronic). The prevalence of headache, migraine, and tension headache did not vary significantly among control subjects, patients with ocular hypertension, and patients with glaucoma, but migraine was significantly more common in patients with normal-pressure glaucoma (28%) compared with control subjects (12%; P<.05) and patients with high-pressure glaucoma (10%; P<.01). CONCLUSION The results suggest an association of normal-pressure glaucoma and migraine and a potential, common vascular etiology of both diseases.

The pattern-evoked electroretinogram (PERG): age-related alterations and changes in glaucoma.

Pattern-onset electroretinograms (PERGs) were studied in 147 normal subjects of different ages (14–79 years) and in 110 eyes of 65 patients with glaucoma or ocular hypertension. The responses showed an increase (P < 0.001) in peak latency with increasing age and a decrease (P < 0.001) in amplitude which approximately parallels the loss of ganglion cells estimated by other authors. Many glaucoma eyes showed a loss of the normally present spatial tuning. In the age group above 50 years 50% of the onset responses were significantly diminished and the peak latencies were not significantly different. A negative correlation (P < 0.001) was found between the size of the PERG and the cup/disc ratio and a positive correlation (P < 0.001) with the area of the neuroretinal rim of the optic disc. The PERG decreased (P < 0.01) with increasing visual field losses.

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.

Spatial and spatiotemporal contrast sensitivity of normal and glaucoma eyes

The spatial contrast sensitivity (CS) to static patterns was tested in the central retina of 156 normal subjects. It showed a decrease above 50 years of age at all spatial frequencies tested which was slightly more pronounced in females than in males. The spatial CS was also studied in 32 glaucoma eyes: Small reductions were found only in the group below 50 but not in eyes of patients above 50. The spatiotemporal CS to phase-reversing patterns was tested in four retinal quadrants of 99 normal subjects. It showed no age dependence in males whereas in females it decreased significantly beyond 50 years at all spatial frequencies tested. The spatiotemporal CS was studied also in 21 glaucoma eyes: Strong losses were again noted only in patients below 50. Spatiotemporal CS losses and perimetric losses were also compared in the four quadrants: For both measures the severest losses were found in the lower nasal and the mildest in the upper temporal quadrant. The spatiotemporal CS test of the peripheral retina seems to be a more powerful tool in glaucoma research than the spatial CS test of the central retina; however, effects of age and gender have to be considered.

Luminance-contrast evoked responses and color-contrast evoked responses in the human electroretinogram

Pattern electroretinograms to onset-offset stimuli were studied in response to luminance-contrast (e.g. red-black or green-black) and color-contrast (e.g. red-green) stripe patterns of equal luminance. Onset responses to color-contrast patterns show no spatial selectivity and a constant peak latency at all spatial frequencies, a behavior different from that of luminance-contrast evoked responses (spatial selectivity and increasing peak latency with spatial frequency). These results are tentatively related to the physiology of tonic and phasic primate retinal ganglion cells and to the spatially selective and non-selective human contrast sensitivity to respectively luminance-contrast and color-contrast gratings.

Quick full-field flicker test in glaucoma diagnosis: correlations with perimetry and papillometry.

The value of a full-field flicker stimulus in glaucoma diagnosis was tested. In 69 normals, 60 ocular hypertension, and 50 manifest primary openangle glaucoma patients, the temporal contrast (flicker) thresholds were tested with a sinusoidally flickering white light of constant mean photopic luminance (10 candela/m) presented in a full-field bowl. A modulatable xenon-arc lamp was used, and only one frequency (37.1 Hz) was tested. Luminances were corrected according to pupil widths. No significant age relationships of flicker thresholds were found in normal eyes. Forty (80%) of glaucoma eyes were recognized as pathologic at a specificity of 93%. In the glaucoma group, significant correlations of flicker thresholds were found with measurements of neuroretinal rim areas of the optic disc (linear r = -0.61, nonparametric r = -0.59, p = 0.001) and with perimetric mean defects (linear r = 0.74, nonparametric r = 0.66, p = 0.0001). Because of its high sensitivity and the significant correlation with perimetric losses and neuroretinal rim areas, the full-field flicker test can be used as a quick (5 min per eye) additional examination in the diagnosis of glaucoma.

Human fast retinal potentials and the spatial properties of a visual stimulus

Abstract Alternating square wave stripe and checkerboard patterns of different spatial frequencies were used in order to study the wavelets of the human ERG. With increasing spatial frequency the b-wave obtained with both types of pattern showed a monotonic decrease in amplitude and an increase in peak time, indicating the action of retinal summation elements detecting local luminance changes. The shape of the wavelets changed in a characteristic way with varying spatial frequency. The summed amplitude of all wavelets observed with the stripe pattern decreased with increasing spatial frequency up to 1 c/deg; around 3 c/deg however it showed an increase, indicating the lateral inhibitory action of center-surround elements. A similar, although less pronounced behaviour was observed with the checkerboard pattern.

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.

Changes in spatial selectivity of pattern-ERG components with stimulus contrast

Electrical mass responses of the visual system to stripe patterns of varying fineness (spatial frequency) can show either an amplitude maximum at a medium spatial frequency, a behavior termed “spatial selectivity,” or a monotonic decrease in amplitude with increasing spatial frequency. The former behavior is probably mediated by neurons having a center-surround receptive field structure and the latter by neurons lacking this antagonism. The pattern-evoked human electroretinogram was studied in this report using different spatial frequencies and pattern contrasts. The positive component of the response showed a spatial selectivity only at low contrast but was not spatially selective at the highest contrast. The negative component showed a spatial selectivity at all contrast levels. The data indicate that if pattern-related responses activated by antagonistic receptive fields are to be studied, low contrast values should be employed and attention should be paid to the negative component of the response.

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° to 90°, or a central area from 0° to 30° 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 senstitivity 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.