[Are diurnal and nocturnal intraocular pressure measurements over 48 h justified?].

Purpose: Diurnal intraocular pressure (IOP) measurements are recommended in cases of visual field deterioration in glaucoma patients. In this study the rationale of 24 h versus 48 h IOP measurements was investigated.

Patients And Methods: Mean IOP and maximum IOP values were obtained in 80 patients over a period of 48 h. The IOP measurements (Goldmann tonometry) of day 1 and 2 (taken every 4 h) were compared. To reduce interindividual and intraindividual differences of measurements the statistical calculation took a tolerance level of ± 2 mmHg and ± 1 mmHg into account.

Results: Maximum IOP measurements were found to differ between 37.5 % and 65.0% respectively for right eyes and 28.8 % and 47.5% respectively for left eyes depending on the measurement tolerance (±2 mmHg or ±1 mmHg) between day 1 and day 2. Mean IOP values were found to differ by 25 % and 51.3 % respectively for right eyes and 26.3 % and 46.3% respectively for left eyes (± 2 or ± 1 mmHg in) between day 1 and day 2. A time-related clustering of extreme deviations could not be found but the maximum values from all patients were found to be roughly equally distributed over daytime and nighttime hours.

Conclusions: Both maximum IOP and mean IOP measurements were found to differ by at least ± 2 or ± 1 mmHg between day 1 and 2 at a significant percentage and the maximum values did not peak at a predictable time point during the 48 h. Therefore, 48 h IOP measurements appear to be more reliable than 24 h measurements.