Ambulatory blood pressure monitoring in glaucoma. The nocturnal dip.

PURPOSE: Hypoperfusion of the optic nerve head may be among the significant factors relating to glaucoma damage. The physiologic nocturnal blood pressure "dip" may be exaggerated in some patients and may compromise local vascular supply. METHODS: Twenty-four-hour ambulatory blood pressure recording was performed on 38 patients with normal-tension glaucoma and on 46 with primary open-angle glaucoma. Eleven control subjects of similar age also were tested. The means of the systolic and diastolic blood pressures, mean arterial pressure, and pulse pressure for 24 hours, taken during the daytime (6 AM-10 PM) and night (10 PM-6 AM) periods were determined. The percentage nocturnal dip for each patient was calculated. A masked assessment of Humphrey visual fields for progression or stability was done on those 52 patients who had numerous fields plotted for more than 2 years. RESULTS: The results of the control subjects confirmed that the authors' technique produces values similar to cardiologic studies from large healthy populations. The mean results from all the authors' patients with glaucoma were within the ranges reported for control subjects in the literature. The blood pressure parameters of the normal-tension glaucoma and primary open-angle glaucoma groups did not differ significantly. All nocturnal pressure parameters (except pulse pressure) were lower in the 37 patients with progressive field defects compared with the 15 patients whose pressure parameters were stable, whereas the systolic, diastolic, and mean arterial pressure dips were significantly larger (systolic dip, P = 0.001). CONCLUSION: The nocturnal reduction in blood pressure may be an additional risk factor in patients with glaucoma.

Correlation between the optic disc and results obtained with conventional, high-pass resolution and pattern discrimination perimetry in glaucoma.

The purpose of this study was to determine whether results obtained with two new techniques, high-pass resolution perimetry and pattern discrimination perimetry, correlated better to the appearance of the optic disc than results obtained with conventional automated perimetry in patients with open-angle glaucoma. Our sample consisted of 28 eyes of 28 patients with early glaucomatous field damage who are part of a prospective follow-up study. We used the second of two sets of baseline perimetric examinations separated by 1 week in the analysis. Neuroretinal rim area was calculated by planimetry of stereophotographs of the disc and was correlated to the visual field sensitivity measured with each of the techniques. We found a poor correlation between the disc and field measurements (correlation coefficients; -0.048 for conventional perimetry, 0.111 for high-pass resolution perimetry and -0.315 for pattern discrimination perimetry). Although the correlation appeared to be higher with the newer techniques, the differences were not statistically significant.

Reproducibility of topographic parameters obtained with the heidelberg retina tomograph.

The Heidelberg retina tomograph is a confocal scanning laser ophthalmoscope that permits recording of topographic information related to the optic nerve and retina. We studied the reproducibility of the topographic parameters obtained by recording five times sequentially the images obtained from one eye of five healthy people and five glaucoma patients. The reproducibility coefficients ranged from 60.5 to 99.4%. The results indicate that, for the parameters examined, the instrument has a high level of reproducibility.

Effect of the number of threshold determinations on short-term fluctuation in automated perimetry.

The authors studied the effect of multiple threshold determinations on local and global (root-mean-square) short-term fluctuation in 30 subjects (10 controls, 10 glaucoma suspects, and 10 glaucoma patients) with a mean age of 56.70 years. Five custom programs were designed on the Octopus perimeter in which the total number of threshold determinations was equal but in which thresholds at 2 principal locations were determined between 2 and 15 times. One randomly selected eye of each subject was first tested with the standard Octopus programs G1 and 31 followed by the custom programs. Local fluctuation initially increased with the number of threshold determinations and then stabilized after five determinations. Global fluctuation was not influenced by the number of determinations and the values obtained by the shorter custom programs were not significantly different from those obtained by the standard programs. Programs that determine thresholds only twice at a given location may underestimate local fluctuation. Furthermore, local fluctuation is de-emphasized by the "watering-down" effect of estimating global fluctuation.

Correlation of retinal nerve-fiber-layer loss, changes at the optic nerve head and various psychophysical criteria in glaucoma.

In 61 eyes of 61 patients with glaucoma, semiquantitative assessment of retinal nerve-fiber-layer (RNFL) loss and neuroretinal rim measurement of the optic nerve head by means of the Optic Nerve Head Analyzer were correlated to the outcomes of automated light-sense, flicker and resolution perimetry and the Farnsworth-Munsell (FM) 100-Hue test. A significant influence of age on total RNFL and total diffuse RNFL scores was found, but there was no measurable effect of age on neuroretinal rim area. Total RNFL and total diffuse RNFL scores showed a good correlation to the various visual field indices: total RNFL score vs mean flicker frequency as determined by flicker perimetry, r = -0.606, P less than 0.0001; total RNFL score vs mean sensitivity as determined by light-sense perimetry, r = -0.385, P = 0.002; and total RNFL score vs mean ring score as determined by resolution perimetry, r = 0.341, P = 0.007. There was no significant correlation between RNFL scores and the FM 100-Hue score. Correlation between the neuroretinal rim area and the various psychophysical indices was poor and mostly not statistically significant. The high correlation of flicker scores with RNFL loss provides interest for future applications of this perimetric technique.

Adrenergic and adrenolytic effects on intraocular pressure.

We compared the pressure-lowering effects of timolol, pindolol, epinephrine and the mixture of timolol and epinephrine with that of placebo over a 12-h period. All agents reduced the pressure significantly but with varying time courses. The mixture of timolol and epinephrine reduced the pressure significantly more than did timolol or epinephrine alone, especially at 12 h after the last administration of the drops.

Lens opacity as a predictor of visual field impairment due to cataract.

The contribution of cataract to the decrease of visual field in patients with glaucoma is difficult to ascertain. To attempt to quantitate the change in visual field due to cataract, we examined 27 eyes of 26 patients before and after cataract extraction. The examination consisted of measurement of best refraction with visual acuity, visual field testing with the pupil dilated, measurement of lens opacity, determination of the intraocular pressure, and evaluation of the character of the cataract before surgery and of the posterior capsule after surgery. The results reaffirmed the detrimental effect that cataract may have on the visual field but also showed that the heterogeneity of cataracts limits the usefulness of the lens opacity meter in quantitating the extent of visual field loss due to cataract.

Possible significance of cilioretinal arteries in low-tension glaucoma.

Cilioretinal arteries arise from the short posterior ciliary artery circulation or directly from the choroidal circulation. The presence of a cilioretinal artery may in compromised discs steal flow from the peripapillary circulation and account for worsening glaucoma damage. We reviewed the records of 33 patients with unilateral cilioretinal arteries admitted for investigation of low-tension glaucoma. We looked for absolute difference between the affected and unaffected eyes as well as percent difference relative to the mean value for the two eyes and to the value for the unaffected eye in the following variables: mean defect, corrected loss variance or corrected pattern standard deviation, and adjusted neuroretinal rim area. No statistically significant differences were found. The mean disc area for the eyes with cilioretinal arteries was significantly larger than that previously reported for normal eyes. The results suggest that if vascular steal exists because of the presence of this artery, it is not of major clinical importance.

The effect of refractive blur on the visual field using the ring perimeter.

To determine the effect of optically induced blur on the visual field measured with high pass spatially filtered targets, 10 normal subjects had field examinations with 0 diopter + 1.00 diopter or + 2.00 diopter of overcorrection in the cyclopleged state. All subjects showed a significant loss of sensitivity when defocussed, but not with pupil dilation. Mean thresholds for the central field rose from 4.79 +/- 0.68 dB (Mean +/- SD) with the image focussed and pupil dilated, to 7.16 +/- 0.72 dB with two diopters of image blur (P less than 0.001). The effects of defocussing did not differ significantly between the central and peripheral parts of the field. The great influence of defocussing the image on sensitivity should be considered during clinical perimetry as the 2.37 dB decline shown would place the group's mean sensitivity below the fifth percentile for age corrected normals.

A comparative evaluation of three methods of analyzing optic disc topography.

Topographical evaluations of the optic discs of 17 eyes obtained using a clinical planimeter, the Rodenstock video-ophthalmograph, and the IS 2000 image analyzer were compared. The parameters studied were vertical and horizontal cup-to-disc ratios, cup volumes, rim areas, disc areas, and rim area-to-disc area ratios. There was good correlation between the measurements obtained by the three methods (correlation coefficients ranged from 0.46 to 0.88). For various parameters, the correlations between clinical planimetry and image analysis were higher than either those between image analysis and video-ophthalmography, or those between clinical planimetry and video-ophthalmography. The mean horizontal cup-to-disc ratios and rim areas as measured by clinical planimetry were significantly higher than those measured by image analysis. Image analysis measured significantly higher disc area and rim areas and lower cup volumes than video-ophthalmography.

Effect of acute medical reduction of intraocular pressure on the visual field and optic disc in ocular hypertension.

The effect of acute reduction of intraocular pressure (IOP) through oral administration of glycerol was assessed in 15 eyes of 15 patients with ocular hypertension by means of automated perimetry, Farnsworth-Munsell 100 hue testing, measurement of spatial contrast sensitivity with a laser interferometer and automated optic disc analysis. There was no significant relation between the absolute or relative change in IOP and the corresponding changes in any of the visual field or optic disc indices studied. The colour vision score increased significantly as the IOP decreased (p = 0.03). There was a significant reduction in the logarithm of spatial contrast sensitivity at grating sizes of 3 (p = 0.007) and 7.5 (p = 0.05) cycles per degree as the IOP decreased.

Measurement of optic nerve head pallor with a video-ophthalmograph and with computerized boundary analysis.

Optic disc pallor was recorded in 53 eyes of 53 patients by means of global analysis with a video-ophthalmograph (Rodenstock Disk Analyzer) and computerized boundary analysis. The coefficients of correlation between the values obtained with the Rodenstock Disk Analyzer and those obtained with boundary analysis were r = 0.24 (p = 0.08) at the 0.29 cutoff level, r = 0.39 (p = 0.004) at the 0.39 level and r = 0.46 (p = 0.0005) at the 0.50 level. Although the correlation was significant, the correlation coefficients were not high. The Rodenstock Disk Analyzer uses global analysis, which does not take into account the spatial relationship of the pallor on the disc, whereas boundary analysis is sensitive to spatial relationship, which may account for the poor correlation.

Response of blood flow to warm and cold in normal and low-tension glaucoma patients.

We measured blood flow in the finger in 38 control subjects with normal ocular findings without migraine, 13 control subjects with normal ocular findings with classic migraine, 17 patients with low-tension glaucoma with classic migraine, and 29 patients with low-tension glaucoma without migraine. Three blood flow measurements were recorded: one at baseline, one after immersion in warm water (40 C), and one after ten seconds' exposure to cold water (4 C). The mean baseline flow and the mean flow after exposure to cold was lower in patients with low-tension glaucoma (P = .013 and P less than .001, respectively).

Reproducibility of computerized pallor measurements obtained with the Rodenstock Disk Analyzer.

Computerized pallor measurements of the optic nervehead were performed by global analysis with the Rodenstock Disk Analyzer. Total intervideographic and intravideographic variability was calculated. The coefficients of variation ranged from 8.3% to 20.08% for intervideographic variability of different pallor histogram values. The intravideographic variability for pallor histogram values ranged from 0.82% to 2.94%.

Short-term effect of intraocular pressure variation on differential light threshold and colour vision.

Laser trabeculoplasty was performed in one eye in each of 38 patients with uncontrolled chronic open-angle glaucoma (37 patients) or low-tension glaucoma (1). Topical therapy was stopped for 1 week before the procedure and for 1 week before reassessment 6 weeks later. Differential light threshold values were determined with an automatic perimeter four times throughout the study, and colour vision was tested twice. The patients were followed for 3 months. The rise and subsequent drop in intraocular pressure were not found to be correlated with differential light threshold or colour error scores.

Effects of laser trabeculoplasty on intraocular pressure in the medically untreated eye.

Laser trabeculoplasty was carried out in one eye in each of 38 patients, 37 with chronic open-angle glaucoma and 1 with low-tension glaucoma, whose visual fields were deteriorating. The patients were randomly assigned to receive 10, 50 or 100 burns. Topical therapy was stopped for 1 week before treatment and for 1 week before reassessment 6 weeks later. Patients who received 50 or 100 burns had significant pressure reduction (p = 0.000). The difference in mean reduction between these two groups was not significant. Ten burns occasionally produced a reduction in pressure. Some patients may need fewer laser burns than are currently given, but most require the current treatment schedules.

The detection of paracentral scotomas with varying grids in computed perimetry.

The ability to identify the physiologic blind spot was reviewed for programs 31 and 32 on the OCTOPUS 201 perimeter. One eye of 100 randomly selected patients suspected of having glaucoma were used in the study. OCTOPUS program 31 failed to identify the physiologic blind spot in 11 eyes (22%), while program 32 missed the blind spot in three eyes (6%). These findings suggest that a 6 degrees grid may not be adequate for identification of scotomas of the size and depth of the physiologic blind spot in the central field.

Comparison of visual field defects in normal-tension glaucoma and high-tension glaucoma.

In a prospective comparison of visual defects in 23 patients with normal-tension glaucoma and 23 with high-tension glaucoma, the groups were matched for equal involvement of the optic disk. F profiles on the Octopus 201 Perimeter were used to quantify thresholds at 1-degree intervals from fixation to define eccentricity, depth, and slope of the scotoma. The mean eccentricity of scotomas in the normal-tension group was 4.86 degrees from fixation; in the high-tension group it was 2.96 degrees. These differences were statistically significant (P less than .01). No statistically significant differences were found between the slopes of the scotomas or depths of the scotomas in the two groups.

The correlation between cup-disk ratio, neuroretinal rim area, and optic disk area measured by the video-ophthalmograph (Rodenstock analyzer) and clinical measurement.

The video-ophthalmograph (Rodenstock analyzer) records the topography of the optic disk via simultaneous stereoscopic video images which are stored and analyzed with the help of a microcomputer. We performed a prospective study of 49 eyes of 49 patients to compare the vertical cup-disk ratio, the horizontal cup-disk ratio, the neuroretinal rim area, and the optic disk area obtained with the video-ophthalmograph with those obtained with manual analysis of black-and-white stereoscopic photographs. The correlation coefficients were 0.67, for vertical cup-disk ratio (P = .0000), 0.63 for horizontal cup-disk ratio (P = .0000), 0.72 for neuroretinal rim area (P = .0000), and 0.89 for optic disk area (P = .0000).

The correlation between optic disk topography measured by the video-ophthalmograph (Rodenstock analyzer) and clinical measurement.

The video-ophthalmograph (Rodenstock analyzer) records the topography of the optic disk via simultaneous stereoscopic images, which are stored and analyzed with the help of a microcomputer. We performed a prospective study on 68 eyes of 68 patients to compare the vertical cup-disk ratio obtained with the video-ophthalmograph to that obtained with manual analysis of black-and-white stereoscopic photographs. The correlation coefficient was 0.61, highly significant at P = .0000.