Abstract
Purpose: :
To evaluate symmetry of diurnal IOP fluctuation between fellow eyes.
Methods: :
100 normal subjects were enrolled without previous ocular disease and lesion possible to affect the IOP. Diurnal IOP measurements were performed with Goldman applanation tonometer every 2 hours from 9 AM to 11 PM. Repeated measure ANOVA was conducted for symmetry of IOP between the fellow eyes with time. Pearson correlation coefficient of IOP between the fellow eyes at each time points, peak, trough, range and mean. Absolute differences of IOP and changes in IOP at given time intervals between the fellow eyes and their proportion exceeding 2mmHg, 10% and 15% were calculated. Biometry, demographic features and individual factors were obtained for the correlation with IOP profiles.
Results: :
The diurnal curve of both eyes showed symmetry between both eyes according to repeated measure ANOVA (p=0.687, between subjects effect) and high Pearson correlation coefficient ranging from 0.594 to 0.896. The mean absolute differences between the fellow eyes ranged from 0.78 to 1.19 mmHg and their proportion at each given cut off value were 18.2 - 31.2% at 10%, 9.1 - 22.1% at 15% and 3.9 % - 6.5% at 2mmHg. The mean absolute differences of changes in IOP at various time intervals ranged from 0.63 to 1.14 mmHg and the proportion were 18.18 - 44.16% at 10% ,15.58 - 28.57% at 15%, and 3.90 - 7.79% at 2mmHg. The value of biometry, demographic features and individual factors had no association with IOP profiles except two significant results including significant higher mean absolute differences between the fellow eyes in male and height greater than 160cm.
Conclusions: :
The diurnal IOP of normal individuals fluctuates symmetrically between the fellow eyes. Although asymmetric IOP and its fluctuation existed at any given cut off values, the overall amount of difference in IOP profiles was 1 mmHg which has been recognized as acceptable error by Goldman applanation tonometer from previous studies. The significant association of absolute IOP differences between fellow eyes with male sex and greater height may be due to the differences in cooperation and posture stability at the IOP measurements.
Keywords: intraocular pressure