Purchase this article with an account.
P.A. Radenbaugh, N.C. McLaren, D.C. Musch, S.E. Moroi; Concordance of Aqueous Humor Flow Phenotypes Between Morning and Evening Measurements . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3675.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine whether individuals show concordance in their aqueous humor flow phenotype in the morning and evening. It is known that individuals show a circadian rhythm in aqueous humor flow, and that among a population of normal subjects the aqueous humor flow exhibits a Gaussian distribution in the morning and evening. We hypothesize that individual flow phenotypes show close concordance in the individual circadian rhythm of aqueous humor flow. Methods: Normal human subjects, who were between the ages 18–50 years, with healthy eyes and no evidence of glaucoma were asked to participate in a fluorophotometry protocol approved by the UM IRBMED. The circadian rhythm of aqueous humor flow was measured using the FluorotronTM Master Fluorophotometer (OcuMetrics, Mountain View, CA) in an inpatient setting at the Univ. Michigan’s General Clinical Research Center. Scanning took place in the morning between 8 am and 12 pm (noon) every one hour, and in the evening between 12 am (midnight) and 6 am every two hours. Results: To date 17 subjects (11 males, 8 females) have been studied with an average age of 28.7 years + 8.8 (SD), with a range of 18–44 years. Using one eye from each subject, the average morning flow between 8 am and 12 pm (noon) was 3.14 µl/min + 1.09, with a range of 5.10 to 0.98 µl/min. The average flow between 12 am (midnight) and 6 am was 1.63 µl/min + 0.57, with a range of 2.40 to 0.94 µl/min. This expected difference between the morning and evening flows is due to circadian rhythm and was statistically significantly (P<0.0001, Student’s paired t test). Inspection of a scatter plot of AM and PM flows indicated a strong linear association (r=0.85). Upon categorizing AM and PM flow rates into low, medium, or high values, the AM flow rates were in agreement with PM rates for 76.5% (13/17) of the subjects. Conclusions: Our preliminary data indicate that flow phenotypes show close concordance whereby an individual will show a "high flow" in both the morning and evening, and similar for the "medium flow" and "low flow" phenotypes. Additional subjects will be studied for an adequately powered sample size to test this hypothesis. Our long–term goal will be to identify some genetic markers that are associated with this physiological trait.
This PDF is available to Subscribers Only