Fig 1.
The selection method of patients based on more frequently visited session of time.
Intraocular pressure (IOP) was divided into morning session (9 am-12 pm) and afternoon session (1 pm-5 pm) values. We identified a session with more frequent visit for each patient during the follow-up period, either morning or afternoon. The IOP and standard deviation of IOP measured during the selected session was defined as ‘time adjusted IOP’ and ‘time adjusted IOP SD’, respectively.
Table 1.
Clinical factors of NTG patients with and without progression.
Fig 2.
Relationship between conventional and time adjusted intraocular pressure (IOP) standard deviations (SDs).
The two variables were significantly related to each other, but deviation from direct proportion is more common in non-progression group. The ratio between conventional IOP SD and time adjusted IOP SD was significantly smaller in progression group than non-progression group (P = 0.002).
Table 2.
Percentage of used values of intraocular pressure measurements according to more frequently visited session, morning or afternoon type.
Table 3.
Cox proportional hazards model of progression (univariate analysis).
Table 4.
Cox proportional hazards model of progression (multivariate analysis).
Fig 3.
Kaplan-Meier curve showing the cumulative probability of glaucoma progression in patients with NTG.
With conventional long-term IOP variation (CLT), no difference in the cumulative probability of glaucoma progression was detected between the groups with a standard deviation of IOP of >1.5 and <1.5 mmHg (P = 0.377, log-rank test).
Fig 4.
Kaplan-Meier curve showing the cumulative probability of glaucoma progression in patients with NTG.
With time adjusted long-term IOP variation (TALT), the group with long-term IOP fluctuation of >1.5 mmHg had a higher cumulative probability of glaucoma progression than the group with standard deviation of IOP < 1.5 mmHg (P = 0.005, log-rank test).
Fig 5.
An example demonstrating the effect of diurnal fluctuation on the overall standard deviation value of intraocular pressures (IOPs) during follow-up in an individual patient.
This patient was a 47-year-old male who was diagnosed as normal tension glaucoma for the both eyes. The graph demonstrates the IOPs of the right eye on his continuous follow-up. The distribution of this patient’s IOP in the whole follow-up period was 13.67 ± 2.16 mmHg. When the IOP distribution was calculated only for the morning session values the result was 13.87 ± 1.46 mmHg, which showed a lower standard deviation value. He showed no evidence of progression during the total follow-up period of 144 months.