A total of 48 subjects (23 males and 25 females) were recruited. The mean age was 56.87 ± 8.36 years in group A, 60.63 ± 6.81 years in group B and 58.25 ± 11.47 years in group C. The mean VEGF concentration of the three sub-groups in patients with AL ≤ 23.30 mm (A1, B1, C1) were 112.59 ± 30.43 pg/ml, 89.39 ± 16.36 pg/ml, 125.25 ± 44.75 pg/ml, respectively. Similarly, the mean VEGF values of the three sub-groups in patients with AL > 23.30 mm (A2, B2, C2) were 53.92 ± 17.3 pg/ml, 58.50 ± 17.16 pg/ml, 75.95 ± 32.6 pg/ml respectively. (Table 1)
Table 1
Axial lengths and corresponding aqueous VEGF levels of different groups and sub-groups.
Groups
|
Axial lenghth (mm)
|
VEGF level
(pg/ml)
|
P value
|
Mean ± SD
|
Range
|
Group A
|
23.64 ± 2.51
|
19.55–29.77
|
83.26 ± 38.60
|
A1
|
21.76 ± 1.23
|
19.55–22.95
|
112.59 ± 30.43
|
0.001
|
A2
|
25.52 ± 1.96.
|
24.10-29.77
|
53.92 ± 17.3
|
Group B
|
23.51 ± 1.45
|
21.68–27.18
|
73.95 ± 22.74
|
B1
|
22.54 ± 0.64
|
21.68–23.14
|
89.39 ± 16.36
|
0.002
|
B2
|
24.83 ± 1.39
|
23.33–27.18
|
58.50 ± 17.16
|
Group C
|
23.46 ± 1.15
|
22.01–26.51
|
100.61 ± 45.60
|
C1
|
22.65 ± 0.53
|
22.01–23.30
|
125.25 ± 44.75
|
0.025
|
C2
|
24.27 ± 1.02
|
23.47–26.51
|
75.95 ± 32.6
|
Legends: Group A: non-diabetic patients (A1 AL≤ 23.30 mm, A2 AL > 23.30 mm), Group B: diabetic patients without diabetic retinopathy (B1 AL≤ 23.30 mm, B2 AL > 23.30 mm), Group C: diabetic patients with treatment naive non-proliferative diabetic retinopathy (C1 AL≤ 23.30 mm, C2 AL > 23.30 mm)
AL- axial length, mm- millimeters, ml- milliliter, pg- picogram, SD- standard deviation, VEGF- vascular endothelial growth factor
p < 0.05 - statistically significant
In group A (non-diabetics), the mean AL was 23.64 ± 2.51 mm. The mean VEGF in this group was 83.26 ± 38.60 pg/ml. For every 1mm increase in axial length, the VEGF decreased by 12.04 pg/ml in this group. In group B (Diabetics without NPDR), the mean AL was 23.51 ± 1.45 mm. The mean VEGF in this group was 73.95 ± 22.74 pg/ml. For every 1mm increase in axial length in this group, there was a decrease in VEGF by 12.04 pg/ml. In group C (Diabetics with NPDR), the mean AL was 23.46 ± 1.15 mm. The mean VEGF in this group was 100.61 ± 45.60 pg/ml. There was a 13.45 pg/ml decrease in VEGF values for each mm increase in axial length in group C. Figure 2 depicts the scatter diagram correlating the aqueous humor VEGF concentration with the AL across various groups and subgroups.
In sub-group analysis, the mean AL in sub-groups A1 (AL ≤ 23.30 mm) and A2 (AL > 23.30 mm) were 21.76 ± 1.23 mm and 25.52 ± 1.96 mm respectively. The mean VEGF levels were 112.59 ± 30.43 pg/ml and 53.92 ± 17.3 pg/ml in sub-groups A1 and A2 respectively. The difference in VEGF levels was statistically significant ( p = 0.001). Similarly, the mean AL in sub-groups B1 (AL ≤ 23.30 mm) and B2 (AL > 23.30 mm) were 22.54 ± 0.64 mm and 24.83 ± 1.39 mm respectively. The mean VEGF levels were 89.39 ± 16.36 pg/ml and 58.50 ± 17.16 pg/ml in sub-groups B1 and B2 respectively ( p = 0.002). In group C, the mean AL in sub-groups C1 (AL ≤ 23.30 mm) and C2 (AL > 23.30 mm) were 22.65 ± 0.53 mm and 24.27 ± 1.02 mm respectively. The mean VEGF levels were 125.25 ± 44.75 pg/ml and 75.95 ± 32.6 pg/ml in sub-groups C1 and C2 respectively (p = 0.025) (Table 1).
In group C, out of 16 patients, 4 had mild NPDR, 7 had moderate NPDR and 5 had severe NPDR. The mean AL (mm) in patients with severe, moderate, and mild NPDR were 23.05 ± 0.84, 23.94 ± 1.30, and 23.14 ± 0.69 respectively. The mean VEGF levels (pg/ml) in eyes with severe, moderate, and mild NPDR were 140.06 ± 49.49, 81.85 ± 26.96, and 84.1 ± 25.08 respectively. Thus, patients with longer axial length had low VEGF levels and less severe form of DR. However, this observation was not statistically significant. (Table 2)
Table 2
Mean axial length and VEGF values in Group C (diabetics with diabetic retinopathy)
Group C
|
Number of patients
(Total 16)
|
Axial Length ( mm)
|
Mean VEGF levels
(pg/ml)
|
Mean ± SD
|
Range
|
Mild NPDR
|
4
|
23.14 ± 0.69
|
22.2–23.7
|
84.1 ± 25.08
|
Moderate NPDR
|
7
|
23.94 ± 1.30
|
22.17–26.51
|
81.85 ± 26.96
|
Severe NPDR
|
5
|
23.05 ± 0.84
|
22.01–24.35
|
140.07 ± 49.49
|
Legends: NPDR-Non proliferative diabetic retinopathy, VEGF- vascular endothelial growth factor