The examined group consisted of 111 newly diagnosed POAG patients, including 43 female and 68 male with a mean age of 48.04 ± 14.14 years (22 - 82 years). Together, 215 eyes were examined (both eyes from 104 subjects and 7 eyes from 7 subjects). The mean follow-up time was 10.3 ± 7.02 months (1.15 - 41.57 months). Subjects had an average of 2.53 ± 1.42 (1-7) times of follow-up visits in the study. The mean axial length and corneal curvature of the total subjects were 25.6 ± 1.77 mm and 7.75 ± 0.24 mm, respectively (Table 1). A slight but statistically significant decrease in IOP (β=-0.0596, P=0.000047), bIOP (β=-0.0369, P=0.0029) and CCT (β=-0.6639, P<0.000001) was observed during the period of PGA usage (Table 2, Fig.1).
Table 1. Demographic, clinical and diagnostic characteristics of 111 newly diagnosed primary open angle glaucoma patients participating in the study.
Category
|
|
Age, years
|
48.04 ± 14.14 (22-82)
|
Gender
|
|
Female
|
43 (38.7%)
|
Male
|
68 (61.3%)
|
Follow-up period, months
|
10.3 ± 7.02 (1.15 - 41.57)
|
Follow-up times
|
2.53 ± 1.42 (1-7)
|
Diagnosis
|
|
High tension glaucoma (HTG)
|
43 (38.7%)
|
Normal tension glaucoma (NTG)
|
68 (61.3%)
|
Axial length, mm
|
25.6 ± 1.77
|
Corneal curvature, mm
|
7.75 ± 0.24
|
Table 2. The changes of IOP, bIOP and CCT in POAG patients under PGA treatment over time.
|
β
|
95% CI
|
P value
|
IOP
|
-0.0596
|
-0.0883 to -0.0309
|
0.000047
|
bIOP
|
-0.0369
|
-0.0612 to -0.0126
|
0.0029
|
CCT
|
-0.6639
|
-0.8048 to -0.5230
|
<0.000001
|
IOP: intraocular pressure; bIOP: biomechanically corrected intraocular pressure; CCT: central corneal thickness; POAG: primary open angle glaucoma; PGA: prostaglandin analogue
Generalized estimate equation model with an exchangeable correlation structure was used to observe the corneal biomechanical changes with PGA treatment over time. After adjusting for age, gender, axial length, corneal curvature, IOP and CCT, AT1 increased (β=0.0089, P<0.000001), whereas DA and AV1 decreased statistically significantly over time (β=-0.0015, P=0.016 for DA; β=-0.0004, P=0.00058 for AV1) (Table 3, Fig. 2). Other corneal biomechanical parameters showed no statistically significant changes over time (Table 3).
Table 3. The changes of corneal biomechanical parameters in POAG patients under PGA treatment over time with adjustment for age, gender, axial length, corneal curvature, IOP and CCT.
Corneal biomechanical
parameters
|
After adjustment
|
β
|
P value
|
DA
|
-0.0015
|
0.016
|
AT1
|
0.0089
|
<0.000001
|
AV1
|
-0.0004
|
0.00058
|
AT2
|
-0.0059
|
0.139
|
AV2
|
0.0003
|
0.364
|
HC-time
|
-0.0044
|
0.272
|
HC-PD
|
-0.0023
|
0.196
|
HC-radius
|
-0.0076
|
0.346
|
POAG: primary open angle glaucoma; PGA: prostaglandin analogue; IOP: intraocular pressure; CCT: central corneal thickness; DA: deformation amplitude; AT1: the first applanation time; AV1: the first applanation velocity; AT2: the second applanation time; AV2: the second applanation velocity; HC: the highest concavity; PD: peak distance
In addition, we analyzed the differences of corneal biomechanical parameters between NTG and HTG groups under PGA treatment over time. Among the 111 POAG patients, 68 were NTG patients and the other 43 were HTG (Table 1). There were no statistically significant differences in age, gender, axial length and corneal curvature between these two groups (all P>0.05, Table 4). IOP, bIOP and CCT of post-treatment of PGA in NTG group were all statistically significantly lower than those in HTG group (all P<0.0001, Table 4). After correcting for age, gender, axial length, corneal curvature, IOP and CCT, AT1 was lower (7.2950 ± 0.2707 in NTG and 7.5889 ± 0.2873 in HTG, P=0.00011, Fig. 3A) and AV1 was higher (0.1478 ± 0.0187 in NTG and 0.1314 ± 0.0191 in HTG, P=0.00002, Fig. 3B) in NTG group compared to that in HTG group with statistically significant differences (Table 5).
Table 4. Differences in demographic and clinical characteristics between NTG and HTG groups.
|
NTG (n=68)
|
HTG (n=43)
|
P value
|
Age (male)
|
49.15 ± 14.51
|
46.28 ± 13.50
|
0.292
|
Gender
|
41 (60.3%)
|
27 (62.8%)
|
0.843
|
Axial length
|
25.52 ± 1.81
|
25.74 ± 1.70
|
0.374
|
Corneal curvature
|
7.76 ± 0.22
|
7.75 ± 0.27
|
0.826
|
IOP
|
16.05 ± 2.36
|
18.47 ± 2.36
|
<0.0001
|
bIOP
|
15.37 ± 2.09
|
16.90 ± 2.10
|
<0.0001
|
CCT
|
537.44 ± 32.13
|
564.35 ± 27.96
|
<0.0001
|
|
|
|
|
|
|
NTG: normal tension glaucoma; HTG: high tension glaucoma; IOP: intraocular pressure; bIOP: biomechanically corrected intraocular pressure; CCT: central corneal thickness
Table 5. Differences in corneal biomechanical parameters between NTG and HTG groups under PGA treatment over time after adjusting for age, gender, axial length, corneal curvature, IOP and CCT.
|
NTG (n=68)
|
HTG (n=43)
|
P value
|
DA
|
1.1070 ± 0.1115
|
1.0425 ± 0.1248
|
0.681
|
AT1
|
7.2950 ± 0.2707
|
7.5889 ± 0.2873
|
0.00011
|
AV1
|
0.1478 ± 0.0187
|
0.1314 ± 0.0191
|
0.00002
|
AT2
|
21.8646 ± 0.6164
|
21.6138 ± 0.5827
|
0.173
|
AV2
|
-0.2682 ± 0.0580
|
-0.2551 ± 0.0426
|
0.709
|
HC-time
|
16.8531 ± 0.5389
|
16.8520 ± 0.8962
|
0.477
|
HC-PD
|
5.0539 ± 0.2704
|
4.8712 ± 0.3023
|
0.241
|
HC-radius
|
6.5643 ± 0.9992
|
6.8861 ± 2.5276
|
0.428
|
NTG: normal tension glaucoma; HTG: high tension glaucoma; PGA: prostaglandin analogue; IOP: intraocular pressure; CCT: central corneal thickness; DA: deformation amplitude; AT1: the first applanation time; AV1: the first applanation velocity; AT2: the second applanation time; AV2: the second applanation velocity; HC: the highest concavity; PD: peak distance