Circadian Intraocular Pressure in Healthy Young Adults' Usual Life

Abstract

Purpose:: To evaluate the 24-hour IOP curve of young healthy white spanish subjects.

Methods:: The study was designed to have the least possible influence in the usual lifestyle and schedules of the individuals studied. IOPs were meassured where the subjects of the study developed their regular activities. 20 eyes of 20 healthy volunteers with a regular daily sleep cycle (11.30-7.30 ±1h) were included (mean age: 30 SD 3,9 (25-38). Total liquid intake was restricted to1.5l (alcohol beverages not allowed). Patients recruited were all partners of ophthalmologists from our institution. Each ophthalmologist examined his/her partner. IOP was measured every 4 hours throughout a 24-hour period (8:00pm to 8:00pm ). All measurements were taken in both supine and sitting positions with a calibrated Perkins applanation tonometer (waiting time: 15 minutes). At daytime (8:00am, 12:00pm, 4:00pm, 8:00pm) IOP was measured first in the sitting position and then in supine and at night time IOP was taken first in supine (12:00am and 4:00am). For each time point and position, three measurements were taken and the mean IOP was considered . Paired t-test was used (95% Confidence interval of the difference; p<0.05) for the statistical analysis.

Results:: Sitting diurnal mean IOP (SitD-IOP): 13.06 SD3.08. Supine diurnal mean IOP (SupD-IOP): 14.1SD2.9. Supine nocturnal mean IOP (SupN-IOP): 12.9 SD 3.2. Sitting nocturnal mean IOP (SitN-IOP): 11.6 SD 3.2. Supine IOP was significantly higher than sitting IOP at all time points. Peak supine IOP: 8:00am (14.7SD2,5). Peak sitting IOP: 12.00pm (13.5SD3.1). Higher difference sitting-supine IOP: 8:00am ( 1.5SD1.7); minimum:12.00am (0.6SD0.9). Supine trough-peak difference: 4.1SD1.5. Sitting trough-peak difference: 3.9SD1.2. No diferences were found between SitD-IOP and SupN-IOP. SitD-IOP was higher than SitN-IOP.

Conclusions:: In this subset of spanish active individuals the lowest and highest IOPs occurred later than in other populations, which might be related to the spanish lifestyle.

Keywords: intraocular pressure • circadian rhythms • outflow: trabecular meshwork