IOP Measurements during Day and Night Time in Glaucoma Patients and Healthy Controls by Goldmann and Perkins Applanation Tonometry

Abstract

Abstract: : Purpose: It is well known that many glaucoma patients show circadianic variations of intraocular pressure. Aim of our study was to evaluate IOP levels in glaucoma patients and healthy controls during day and night time while measuring in an upright as well as in a supine position. Measurements were taken every 4 hours by using Goldmann and Perkins tonometry. Methods: 18 glaucoma patients and 15 healthy controls were included in this prospective clinical study. In each of them IOP measurements were taken every 4 hours during day and nighttime starting at 8 a.m. For the measurements at 12 a.m. and at midnight both methods were used to evaluate IOP while the patient was sitting followed by a measurement in a supine position. At 8 a.m. and 4 p.m. (upright position) as well as at 4 a.m. (supine position) the patients were measured just by means of Perkins tonometry. At 8 p.m. both methods were used while the patient was sitting. For statistical analysis ANOVA was used to evaluate IOP variations between upright and supine position and between healthy controls and POAG patients. In addition intraocular pressure values measured by Perkins and Goldmann tonometry were compared. Results: Comparing IOP values evaluated by both methods in an upright position mean intraocular pressure was 1.1 mmHg (12 a.m.) to 1.2 mmHg (8 p.m.) lower in Perkins tonometry measurements than in those taken by Goldmann tonometry which was statistically significant (p=0.002; p=0.004). There was no difference between the two patient groups. In a supine position intraocular pressure measured by Perkins tonometry was higher than in an upright position. At 12 a.m. the difference was 1.3 mmHg ± 2.6 mmHg in healthy subjects and 1.9 ± 1.9 mmHg in POAG patients. This increase of IOP was statistically significant only in the glaucoma patients group (p=0.001). At 12 p.m. the increase of intraocular pressure in the supine position was even more pronounced: it was 2.6 ± 3.4 mmHg in healthy subjects and 4.5 ± 3.8 mmHg in POAG patients. Both results were statistically significant (p=0.004; p=0.0001). Conclusion: During diurnal measurements of intraocular pressure in an upright position there were no statistically significant differences in IOP change between both groups. However, in a supine position the intraocular pressure was significantly higher than in the sitting position and increased more in the glaucoma patients than in healthy controls. This observation might be due to a faulty regulation of the fluid shift in glaucoma patients and might be a cause for progression of glaucomatous damage.

Keywords: intraocular pressure • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials