Abstract
Purpose: :
In this study the relationship between mean intraocular pressure (mIOP), ocular pulse amplitude (OPA) and diastolic blood pressure (DIA) was investigated in ocular hypertension (OHT) and primary open angle glaucoma (POAG) patients.
Methods: :
Patients without topical therapy for at least four weeks and healthy controls were recruited (aged 59.0 ± 8.9 years). There were 28 OHT, 37 POAG patients and 57 healthy controls. The eye with the highest average IOP or more advanced damage, respectively, was selected and OPA was recorded with Dynamic Contour Tonometry. Systemic blood pressure was assessed by automated non-invasive blood pressure oscillometry. Mean daily IOP was obtained by average diurnal Goldman applanation tonometry. In a one-way analysis of variance DIA, mIOP and OPA were compared between OHT, POAG and healthy controls. Correlation between blood pressure, mIOP and OPA was analyzed by Spearman ranking.
Results: :
OHT patients have significantly higher OPA than POAG patients(p=0.037, least significant difference test) and healthy controls (p=0.012). OHT patients also have significantly higher DIA (one-way ANOVA p=0.024). DIA correlated significantly (Spearman R=0.40, p=0.037, n=28) with mIOP only in OHT patients. Weak but significant correlation was demonstrated between OPA and mIOP (Spearman R=0.25, p=0.008, n=122).
Conclusions: :
On the average, OPA and DIA are higher in OHT patients. At least to some extent higher OPA is a result of higher mIOP in OHT. In contrast to classical view of increased aqueous outflow resistance, higher DIA might contribute to haemodynamic outflow resistance, thus increasing the blood volume present in the eye, and indeed be a part of the causal mechanism of ocular hypertension at least in our cohort of OHT patients. DIA did correlate significantly with mIOP only within the OHT group. It is plausible that such constellation, including the higher OPA, represents a protective mechanism against glaucomatous damage in patients with OHT.
Keywords: intraocular pressure • blood supply