Does aqueous humor secretion decrease with age?

Abstract

Aqueous humor flow was calculated during day-time in 148 healthy volunteers and 75 older patients using the Fluorotron Master II anterior chamber protocol (Coherent, Palo Alto, USA). Healthy volunteers as well as patients had no history of ocular pathology, surgery or laser treatment. Slitlamp examination revealed no ocular pathology. Hypertension, diabetes, local and systemic drug therapy, neoplasia, kidney or liver disease, contact lens and ocular trauma were excluded. Mean age of volunteers was 26.5±3.8 years; age of patients: 65.5±10.5 years. Aqueous humor flow during day-time in healthy volunteers in the OD: (mean± s.d.) 2.26±1.0μl/min, in the OS: 2.17±1.0μl/min. Correlation coefficient: r=0.8. The mean aqueous humor flow in the older patients during day-time: OD: 1.91±1.1 μl/min, OS: 1.86±1.1 μl/min. Correlation coefficient: r=0.54. The Mann-Whitney-U-test revealed a significant difference when comparing the right eyes of healthy volunteers with the right eyes of patients (p<0.01). When comparing all left eyes the difference is also significant (p=0.01). The results of the study underline, that the mean aqueous humor secretion does significantly decrease with age. However, the data show that there is only a slight decrease of flow of approximately 2.5% per decade. From the clinical point of view it should be concluded, that although the aqueous humor secretion does decrease with age, this is not of clinical importance, even in cases of glaucoma surgery. Afterall we still don't know, whether this decrease of aqueous humor flow is caused by a decrease of the pigmented and non-pigmented epithelium cells, or via a decrease of outflow facility, or via a decrease of CNS-stimulation.