One hundred twenty-eight patients with glaucoma were examined; however, two had noninducible venous pulsation and so were excluded. The remaining 126 patients and 40 normal subjects were examined, and their respective ages, IOPs, blood pressures, and sternal notch measurements are described in
Table 1 . The average mean deviation in right glaucomatous eyes was −13.6 ± 0.93 dB (SE) and in left glaucomatous eyes was −11.8 ± 0.72 dB. There was no significant difference in the age, IOP, sternal notch measurement, or sex ratios between groups. The pulse blood pressure and mean blood pressure were significantly lower in the glaucoma group than in the normal group.
Only 43% of patients with glaucoma had spontaneous venous pulsation in the right eye, whereas it was observed in 97% of normal right eyes. This difference in proportions was statistically significant (χ2 with Yates correction, 28.1, df = 1, P < 0.001). The mean ODF in the patients with glaucoma was 18.4 ± 21.1 g (SD; n = 47) in the right eye and 13.5 ± 18.2 g, n = 50) in the left eye. Only one normal right eye did not have spontaneous venous pulsation, with an ODF of 8 g, whereas only two left eyes did not (mean ODF, 11 g).
Eleven pairs of hemivein ODF measurements, from 11 patients, were repeated nine times, with a mean SD of 2.4 (mean ODF, 17.4) and a mean coefficient of variation of 21% ± 11.5% (SD). Twenty-one eyes of 21 individuals were examined on two separate occasions, with mean hemivein ODF of 7.8 g (n = 84). The mean difference between initial and second ODF measurements was 4.1 ± 4.9 g.
When data from both eyes were examined in the mixed linear regression model, gender, age, and sternal notch measurement were not independently associated with ODF. Mean deviation was shown to be the most statistically significant predictor of ODF (
P < 0.0001,
Table 2 ). Pulse blood pressure was the other significant predictor (
P < 0.0001). A lower-pulse blood pressure was associated with a greater ODF. A greater mean blood pressure tended to be associated with greater ODF, but this relationship did not reach formal statistical significance (
P = 0.08). In addition, a lower IOP tended to be associated with a greater ODF but again did not reach formal statistical significance (
P = 0.08). When blood pressure and pulse blood pressure were excluded from the linear model, lower age was found to be significantly associated with an increased ODF (
P = 0.03). There was a significant linear correlation between age and mean blood pressure (
r = 0.3,
P < 0.0001), so that, with increasing age, there tended to be an increased mean blood pressure. In addition, age was even more strongly associated with pulse blood pressure (
r = 0.45,
P < 0.0001), and thus an increased age was associated with an increased pulse pressure. The intereye correlation with the original linear mixed model was 0.25 ± 0.20 (SE).
Of the 126 patients with glaucoma examined, 83 had no spontaneous pulsation in one or both eyes. When no spontaneous pulsation was present in both eyes, only data from the right eye were analyzed. A direct correlation of ODF and mean deviation demonstrated a Spearman rank correlation coefficient of −0.475 (
P < 0.0001).
Figure 2demonstrates the relationship between visual field severity and ODF in the patients with glaucoma.
Of the 83 patients with glaucoma with no spontaneous venous pulsation, 3 had induced pulsation in the central retinal vein and were excluded from subsequent analysis. The remaining 80 subjects had separate induced pulsation in each hemivein.
Figure 3demonstrates the relationship between the hemivein ODF difference and hemifield difference. The
y-axis is the upper hemifield sensitivity loss minus the lower hemifield sensitivity loss. A positive value reflects a worse lower visual field. Data to the right of the
x-axis indicate that greater force was needed to induce pulsation in the upper hemivein than in the lower hemivein. Spearman’s rank correlation coefficient was 0.369 (
P < 0.0001). Both linear (adjusted
r = 0.26,
df = 2) and spline curve fit (adjusted
r = 0.46, estimated
df = 4.4,
P < 0.0001) models were applied, with the spline curve being a significantly better fit than the linear model (
P = 0.001).
A semiparametric multiple regression model, combining linear parametric and smoothing spline terms, was used to model the effect of key variables on the hemifield difference. The results for the parametric terms in the model are described in
Table 3 . The only parametric term found to be significantly associated with the difference between hemifield sensitivities was the difference in hemivein ODF (
P < 0.0001). In addition, a spline function in dODF (difference between upper and lower hemivein ODF) was significant (χ
2 = 11.585; estimated
df = 1,
P = 0.0011).
When multiple linear regression was performed modeling the effect of upper hemivein ODF, lower hemivein ODF, age, sex, IOP, and mean and pulse BP on upper hemifield loss, lower hemivein ODF was found to be independently associated with upper hemifield loss (P = 0.004). Upper hemivein ODF, sex, IOP, and mean and pulse blood pressure were not associated with upper field loss. Similarly, when the effect of upper hemivein ODF was modeled, lower hemivein ODF, age, sex, IOP, and mean and pulse BP on lower hemifield loss, upper hemivein ODF was found to be independently associated (P < 0.0001). Sex was associated with lower hemifield loss (P = 0.001), and males were more likely to have a worse inferior hemifield. Pulse and mean BP, IOP, and lower hemivein ODF were not associated with lower hemifield loss. Increasing age was found to be significantly associated with both upper (P = 0.001) and lower (P = 0.02) hemifield loss.