[Physiologic aging in aqueous humor minute volume of the human eye]

In 148 healthy volunteers and 75 older patients the physiological aqueous humor secretion was calculated during the afternoon hours (13.00 to 20.00 hours) using the anterior chamber protocol of Fluorotron Master II (Coherent, Palo Alto, USA). Fluorescein eye drops were applied topically to each eye five times, 5 h before measurements. Healthy volunteers as well as patients had no history of ocular pathology, surgery or laser treatment. Further exclusion criteria were hypertension, diabetes, local and systemic drug therapy, neoplasia, kidney or liver diseases, contact lens, ocular trauma. Mean age of volunteers was 26.5 +/- 3.8 years; mean age of patients was 65.5 +/- 10.5 years. The aqueous humor flow in healthy volunteers (mean +/- standard deviation) was 2.26 +/- 1.0 microliters/min and in the older patients 1.91 +/- 1.1 microliters/min. Correlation coefficient between right and left eyes in the younger volunteers: r = 0.8; in the older patients: r = 0.54. The Mann-Whitney-U-test revealed a significant difference comparing mean aqueous humor flow in healthy volunteers with the mean aqueous humor flow in older patients (P < 0.01). The results in our study underline that the mean aqueous secretion does decrease with age of about 2.5% per decade. However, to date we do not know whether eyes with primary open-angle glaucoma or ocular hypertension show such a decrease in aqueous humor flow with age or whether there is an autoregulation mechanism in eyes with primary open-angle glaucoma that decreases aqueous humor secretion in relation to an increase of outflow facility.