title: The effect of age on ocular blood supply determined by pulsatile ocular blood flow and color Doppler ultrasonography.
abstract: OBJECTIVE
  Pulsatile ocular blood flow (POBF) assessment measures the choroidal circulation and provides diagnostic value to certain ocular diseases such as glaucoma. This technique assumes a constant ocular rigidity and is influenced by axial length, diurnal variation, and age. This study investigated the effect of age on POBF, with consideration of the above factors. Ocular blood supply in the ophthalmic artery was also determined using color Doppler ultrasonography.
  
  
  METHODS
  A total of 118 healthy subjects aged 19 to 75 years were recruited. They were divided into five groups (below age 30, 30 to 39, 40 to 49, 50 to 59, and 60 or above) of at least 20 subjects each. Only one eye of each subject, with axial length <24.5 mm, was considered. The subject's supine POBF was determined followed by a measurement of the blood flow velocity in the ophthalmic artery using color Doppler ultrasonography. All the measurements were at around the same time of day to eliminate any effect from diurnal variation. The scleral rigidity was measured using a Schiotz tonometer with 5.5- and 7.5-g weights.
  
  
  RESULTS
  Linear regression analysis demonstrated a significant increase of scleral rigidity with age (Pearson correlation coefficient r = 0.26, p < 0.01) and a significant decrease of POBF with age (r = -0.35, p < 0.01). The reduction in peak systolic velocity in the ophthalmic artery with age was significant (r = -0.28, p < 0.01). Both the systolic and diastolic brachial pressure showed significant increase with age (r = 0.55, p < 0.01; r = 0.40, p < 0.01, respectively). Using multiple regression analysis, POBF showed a significant correlation with age (partial correlation r = -0.36, p < 0.01), but not with scleral rigidity or systolic or diastolic brachial pressure. The peak systolic velocity in the ophthalmic artery also showed significant correlation with age (partial correlation r = -0.29, p < 0.01).
  
  
  CONCLUSIONS
  The reduction in POBF with age was significant. Although aging affects scleral rigidity and systemic blood pressure, multiple regression analysis indicates that the most influential factor affecting POBF is aging. The peak systolic velocity in the ophthalmic artery also decreased with age, indicating reduced ocular blood supply.
authors.affiliation: Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong SAR, China. orkclam@polyu.edu.hk
authors.forename: Andrew K C
authors.initials: AK
authors.lastname: Lam
authors.forename: Suk-Tak
authors.initials: ST
authors.lastname: Chan
authors.forename: Henry
authors.initials: H
authors.lastname: Chan
authors.forename: Ben
authors.initials: B
authors.lastname: Chan
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001783:Blood Flow Velocity; D001794:Blood Pressure; D002829:Choroid / Q000098:blood supply*; D006801:Humans; D007429:Intraocular Pressure; D008875:Middle Aged; D009880:Ophthalmic Artery / Q000000981:diagnostic imaging / Q000502:physiology*; D011673:Pulsatile Flow; D012590:Sclera / Q000502:physiology; D018615:Ultrasonography, Doppler, Color