Effects of changing the direction of gravity on sector pupil dilations.

Publications // Yanjun Chen // Aug 01 2004

PubMed ID: 15300122

Author(s): Chen Y, Wyatt HJ. Effects of changing the direction of gravity on sector pupil dilations. Optom Vis Sci. 2004 Aug;81(8):629-35. PMID 15300122

Journal: Optometry And Vision Science : Official Publication Of The American Academy Of Optometry, Volume 81, Issue 8, Aug 2004

PURPOSE To study anterior segment aqueous humor kinetics by using sector pupil dilations with different directions of gravity to change the direction of convectional flow in the anterior chamber.

METHODS Sector pupil dilations were elicited using focal applications of phenylephrine at the limbus. To vary the direction of gravity (and hence the direction of convectional flow) relative to the eye, subjects’ heads were tilted left side down or right side down with gaze horizontal. Pupil elongation and pupil center displacement were measured as functions of time.

RESULTS Early stages of pupil dilation were dominated by pupil elongation toward the site of drug application. Amplitude of elongation was about the same for all the application points, but center displacement depended on the application point. Later stages of pupil dilation showed an interaction between the site of drug application and the direction of gravity.

CONCLUSIONS The results are interpreted in terms of anterior chamber convectional flow and its interaction with transpupillary aqueous flow and diffusion. Early distribution in the anterior segment of a substance applied to the limbus appears to be determined primarily by local diffusion, whereas later distribution is affected by movement of the drug in convectional and transpupillary flow.