In a long-term study with 3% guanethidine and 0.5% adrenaline in one eye drop (GA) the combined results of patients with primary open angle glaucoma (POAG) and glaucoma suspects showed a biphasic response in intraocular pressure (IOP). The hypertensive phase peaked 3 hrs after administration (at noon) and reached a maximum of 3.5 mm Hg (p '~ 0.005) above the hypotensive phase. It is reported in the literature that during office hours untreated glaucoma patients show a peak near noon, suggesting that the initial increase in IOP may be the normal IOP pattern.
When the data of untreated patients with POAG and glaucoma suspects were separated, an increase in IOP around noon in the first group and a decrease around noon in the glaucoma suspects was found. However, during GA-treatment both groups showed a hypertensive response at noon (3 hrs). In addition, the highest IOP's in daycurves were timed during and without GA. It was shown that during GA there was a shift in the incidence of the highest IOP's towards noon (from 8.3% to 73.2% for patients with suspected glaucoma and from 32% to 63.6% for those with POAG).
It was therefore concluded that GA induces a characteristic biphasic IOP pattern in patients with POAG as well as in glaucoma suspects. Also, glaucoma suspects may have higher peak pressures more frequently than POAG patients. Furthermore, the study showed that during office hours untreated glaucoma suspects have daycurves with higher pressures in the morning while patients with POAG have higher pressures near noon.