Descriptive demographic variables
In total, 168 patients (133 men and 35 women) with mean age of 55.72 years, 89 left-side strokes and 79 right-side strokes were analysed in this study. Among these patients, 113 (67.3%) had ischemic strokes and 50 (29.8%) had haemorrhagic strokes. Smokers and drinkers in this analysis include both current and former status. A summary of the demographic variables is listed in Table 1. In general, there was no significant difference in demographics between the patients with stroke on the left side and the right side.
Table 1
Demographic data of patients with stroke in the left and right sides.
| Total (n = 168) | Left side (n = 89) | Right Side (n = 79) | p-Value |
Male (n/%) | 133 (79.2%) | 70 (78.7%) | 63 (79.7%) | .862 |
Age (mean ± SD) | 55.72 ± 10.89 | 56.61 ± 10.61 | 54.72 ± 11.18 | .264 |
BMI (mean ± SD) | 23.29 ± 2.80 | 23.27 ± 2.69 | 23.31 ± 2.94 | .930 |
Smoker (%) | 50 (29.7%) | 26 (29.2%) | 24 (30.4%) | .531 |
Drinker (%) | 31 (18.5%) | 15 (16.8%) | 16 (20.2%) | .845 |
Insomnia (%) | 56 (33.3%) | 28 (32.2%) | 28 (35.4%) | .926 |
Hypertension (%) | 135 (80.4%) | 73 (83.9%) | 62 (78.5%) | .370 |
Diabetes (%) | 55 (32.7%) | 27 (30.3%) | 28 (35.4%) | .481 |
Stroke Type | | | | |
Ischemic (%) | 113 (67.3%) | 57 (64.0%) | 56 (70.9%) | .139 |
Haemorrhagic (%) | 50 (29.8%) | 31 (34.8%) | 19 (24.1%) |
Both (%) | 5 (3.0%) | 1 (1.1%) | 4 (5.1%) |
*p-Value < 0.05. |
Univariate analysis of retinal characteristics
Table 2 summarizes the retinal characteristics of the left and right eyes of the patients. From the results of univariate analysis, only venous asymmetry (Vasymmetry) in the left eye showed a slight but significant decrease in left-side stroke with an odds ratio (OR) of 1.227 (95% CI, 1.053–1.431; P = 0.009). However, for other retinal characteristics, there was no significant difference between left-side and right-side strokes in either the left or right eye.
Table 2
Retinal characteristics of left and right eyes among patients with stroke in the left and right sides.
| Left Eye (Mean ± SD) | | Right Eye (Mean ± SD) | |
| Left side (n = 89) | Right side (n = 79) | p-Value | Left side (n = 89) | Right side (n = 79) | p-Value |
CRAE | 14.41 ± 1.68 | 14.61 ± 0.78 | .371 | 13.96 ± 0.58 | 14.00 ± 0.67 | .653 |
CRVE | 20.86 ± 2.32 | 21.12 ± 0.77 | .406 | 20.78 ± 0.68 | 20.84 ± 0.76 | .580 |
AVR | 0.69 ± 0.04 | 0.69 ± 0.02 | .581 | 0.67 ± 0.02 | 0.67 ± 0.02 | .992 |
BCV | 2.04 ± 7. 21 | 1.29 ± 0.02 | .660 | 1.34 ± 0.13 | 1.33 ± 0.12 | .613 |
BCA | 1.61 ± 0.16 | 1.64 ± 0.07 | .169 | 1.44 ± 0.47 | 1.51 ± 0.41 | .353 |
Venous Angle | 67.82 ± 7.62 | 68.53 ± 2.13 | .470 | 69.03 ± 2.36 | 69.01 ± 2.29 | .970 |
Artery Angle | 70.31 ± 7.75 | 71.49 ± 1.49 | .156 | 59.68 ± 25.45 | 62.57 ± 22.20 | .436 |
Vasymmetry | 0.76 ± 0.06 | 0.77 ± 0.02 | .009* | 0.78 ± 0.03 | 0.78 ± 0.02 | .392 |
Aasymmetry | 0.83 ± 0.06 | 0.83 ± 0.01 | .491 | 11.46 ± 24.76 | 8.60 ± 21.83 | .430 |
AVNicking | 0.31 ± 0.07 | 0.31 ± 0.08 | .932 | 0.27 ± 0.08 | 0.27 ± 0.09 | .697 |
Tortuosity | 0.39 ± 0.14 | 0.38 ± 0.06 | .520 | 0.36 ± 0.06 | 0.37 ± 0.07 | .298 |
Haemorrhage | 0.22 ± 0.06 | 0.22 ± 0.06 | .937 | 0.19 ± 0.07 | 0.20 ± 0.07 | .174 |
Arteriole occlusion | 0.09 ± 0.04 | 0.09 ± 0.03 | .414 | 0.14 ± 0.13 | 0.12 ± 0.07 | .174 |
FDa | 1.16 ± 0.17 | 1.18 ± 0.01 | .262 | 1.31 ± 1.22 | 1.18 ± 0.01 | .845 |
FDv | 1.18 ± 0.10 | 1.19 ± 0.01 | .632 | 2.52 ± 11.33 | 1.32 ± 1.26 | .544 |
*p-Value < 0.05. |
Abbreviations: |
CRAE, central retinal artery equivalent; CRVE, central retinal vein equivalent; AVR, Arteriole-to-venule diameter ratio; BCV, bifurcation coefficient of venules; BCA, bifurcation coefficient of arterioles; FDa, fractal dimension of arteriolar network; FDv, fractal dimension of venular network. |
Multivariable analysis of retinal characteristics
Using left-side stroke as the reference, the results from the multivariable logistic regression analysis of retinal characteristics are shown in Table 3. As shown in this table, two right-eye retinal characteristics and the retinal composite score were strongly associated with the stroke side. Patients with an increased bifurcation coefficient of arterioles in the right eye (RBCA) were at seven times higher risk of right-sided strokes, with an OR of 7.523 (95% CI, 1.823–31.044; P = 0.005). In addition, a higher value of bifurcation coefficient of venules in the right eye (RBCV) was also associated with a higher risk of right-side strokes, with an OR of 7.377 (95% CI, 1.771–30.724; P = 0.006). Furthermore, a retinal composite score including complex effects containing tortuosity, haemorrhage, and fractal dimension of the vessel network, were also positively associated with right-side stroke (OR, 4.955; 95% CI, 3.061–8.022; P < 0.001).
Table 3
Multivariable logistic regression for stroke sides.
| OR | 95% CI | p-Value |
RBCA | 7.523 | 1.823–31.044 | .005* |
RBCV | 7.377 | 1.771–30.724 | .006* |
Retinal Composite Score | 4.955 | 3.061–8.022 | < .001* |
*p-Value < 0.05. |
The area under the ROC curve was 0.842 (95% CI, 0.782–0.901) for the multivariate logistic regression with a sensitivity of 79.8% and specificity of 73.4% using a cutoff of 0.5 probability, indicating an excellent potential predictive ability. (Fig. 1)
Validation
The validation of the logistic model was performed via leave-one-out cross-validation. Using RBCA, RBCV, and retinal composite score, 76.2% of left-side strokes and 74.4% of right-side strokes were correctly classified with a total accuracy of 75.3%.