AIM: To summarize the clinical features of the 24h intraocular pressure data and the water drinking test(WDT)results in patients with primary open angle glaucoma(POAG)and ocular hypertension(OHT), and analyze the correlation.

METHODS: To collect the data of 87 cases(174 eyes)with POAG and OHT, who had completed 24h intraocular pressure(IOP)(measured every 2h)and WDT(drink 1 000mL water off within 5min and then measure every 15min within 1h)in the ophthalmology department of Shenzhen University General Hospital from December 2019 to March 2022. They were divided into three groups, with 33 cases(66 eyes)in high tension glaucoma(HTG)group, 28 cases(56 eyes)in normal tension glaucoma(NTG)group and 26 cases(52 eyes)in OHT group. The clinical features of 24h IOP and WDT among the patients in three groups were summarized, and Spearman correlation was used to analyze the peak and fluctuation values of IOP.

RESULTS: Clinical features among the patients in three groups:(1)the proportion of peak IOP of HTG, NTG and OHT group:(2:00-6:00 a.m.): 40.9%, 23.2% and 26.9%;(8:00-12:00 a.m.): 34.8%, 46.4% and 55.8%;(14:00-18:00 p.m.): 18.2%, 21.4% and 11.5%;(20:00-24:00 p.m.): 6.1%, 8.9% and 5.8%. Valley proportion among groups: early morning: 21.2%, 25.0% and 30.8%; morning: 22.7%, 10.7% and 13.5%; afternoon: 19.7%, 17.9% and 17.3%; evening: 36.4%, 46.4% and 38.5%. The proportion of 24h IOP fluctuation <6mmHg: 9.1%, 62.5% and 17.3%; 6-<8mmHg: 24.2%, 32.1% and 40.4%; ≥8mmHg: 66.7%, 5.4% and 42.3%.(2)WDT: The proportion of the three groups that could reach peak IOP within 30min was 81.8%, 76.8% and 80.8%, respectively. The proportion of IOP fluctuations in the three groups <6mmHg: 10.6%, 78.6% and 38.5%; 6-<8mmHg: 22.7%, 16.1% and 28.8%; ≥8mmHg: 66.7%, 5.4% and 32.7%.(3)the proportions of WDT peak higher than 24h peak IOP in the three groups were 80.3%, 80.4% and 80.8%. Correlation: the peak values of 24h IOP were positively correlated with the peak values of WDT(all P<0.01), the fluctuation of 24h IOP was positively correlated with the fluctuation of WDT in HTG and OHT group(P<0.01, P<0.05), while it showed no significant correlation in NTG group(P>0.05).

CONCLUSION: Diurnal measurements of IOP during office hours(08:00 a.m.-18:00 p.m.)may fail to capture the peak values and underestimate IOP fluctuations. The 24h IOP fluctuation ≥HTG group of 8mmHg>OHT group>NTG group. The peak WDT in over 75% patients could be achieved within 30min, and it was higher than 24h peak IOP of over 80% patients. There was a positive correlation between the 24h IOP fluctuations and the WDT fluctuations in HTG and OHT patients. Therefore, WDT has clinical significance in assessing fluctuations in patients' IOP.