Abstract
Purpose: :
To characterize the 24-hour pattern of intraocular pressure (IOP) in a group of untreated ocular hypertension (OHTN) patients compared to two age-matched patient groups with either healthy eyes or primary open-angle glaucoma.
Methods: :
Measurements of IOP were taken every 2 hours during a 24-hour period from a group of 13 untreated patients with OHTN. These patients showed no visual field loss or glaucomatous optic nerve damage, but had IOP > 21 mmHg based on all the documented records. In the sleep laboratory, IOP measurements were taken in the sitting and supine positions during the 16-hour diurnal/wake period and in the supine position during the 8-hour nocturnal/sleep period. Mean diurnal sitting, diurnal supine, and nocturnal supine IOP levels in the OHTN group were compared with data obtained from 24 individuals with healthy eyes (control group) and 24 patients presenting early glaucomatous signs of visual field loss and/or optic nerve damage using ANOVA with post-hoc Bonferroni t-tests.
Results: :
Mean age was 57.8 ± 10.5 (OHTN), 55.6 ± 8.5 (control), and 59.2 ± 12.3 (glaucoma) years. There was no statistically significant difference in the central corneal thickness among the groups; 585 ± 26 µm (OHTN); 543 ± 46 µm (control); and 556 ± 52 µm (glaucoma). Compared to the control group, mean diurnal IOP, either sitting or supine, was significantly higher in the OHTN group and in the glaucoma group (p<0.05) while the nocturnal supine showed no statistical difference. For all three groups, the mean nocturnal supine IOP was higher than the diurnal sitting IOP (paired t test p<0.05). However, the diurnal-to-nocturnal increase in IOP in the habitual position was significantly smaller in the glaucoma group, not in the OHTN group, compared to the control group (p<0.05). The diurnal-to-nocturnal change in the supine IOP was also significantly different only between the glaucoma group and the control group (p<0.05).
Conclusions: :
The general pattern of 24-hour IOP in this group of OHTN patients is similar to the 24-hour IOP pattern in a group of patients who present with early glaucoma. However, the magnitudes of IOP change from the diurnal to the nocturnal periods are different between the glaucoma group and the control group, but not different between the OHTN group and the control group.
Keywords: circadian rhythms • intraocular pressure