title: Age-related changes in corneal pulsation: ocular dicrotism.
abstract: OBJECTIVE
  To evaluate age-related changes in the shape of corneal indentation pulse (CIP) in relation to simultaneously registered blood pulsation (BPL) and electrocardiogram (ECG) signals in healthy subjects.
  
  
  METHODS
  Seventy-seven subjects were recruited for the study, including 36 young subjects (aged 23 to 32 years) and 41 older subjects (aged 44 to 72 years) with no reported ocular and cardiovascular abnormalities and free of any systemic diseases. Corneal indentation pulse was measured with a noninvasive ultrasonic distance sensor. Simultaneously, BPL and ECG were acquired with a pulse oximeter placed on the earlobe and Eindhoven triangle setup, respectively. Correlation analysis was applied to identify the interactions between the parameters of the averaged signals, estimated with dedicated signal processing algorithms, for all subject measurements and separately for both considered groups.
  
  
  RESULTS
  Twenty-nine out of 41 older subjects showed evidence of a double peak-shaped CIP waveform that could be interpreted as ocular pulse dicrotism. None of the young subjects exhibited this phenomenon. For the young group, significant correlations (p < 0.05) were found between the CIP crest time of a single peak-shaped CIP waveform and the other shape parameters of the CIP, BPL, and ECG signals. Similarly, for the older group of subjects, significant corresponding correlations were only found between the preliminary crest time of a double peak-shaped CIP waveform.
  
  
  CONCLUSIONS
  Using noninvasive corneal indentation pulse measurement revealed, for the first time, an ocular pulse dicrotism. This might be a natural sign of aging or an early indication of hemodynamic aspects of cardiovascular diseases.
authors.affiliation: *MSc †PhD, DSc ‡MD, PhD Institute of Physics, Wroclaw University of Technology, Wroclaw, Poland (MED); Institute of Biomedical Engineering and Instrumentation, Wroclaw University of Technology, Wroclaw, Poland (DRI); and Department of Ophthalmology, Wroclaw Medical University, Wroclaw, Poland (PK-B).
authors.forename: Monika E
authors.initials: ME
authors.lastname: Danielewska
authors.forename: D Robert
authors.initials: DR
authors.lastname: Iskander
authors.forename: Patrycja
authors.initials: P
authors.lastname: Krzyżanowska-Berkowska
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D003315:Cornea / Q000000981:diagnostic imaging / Q000502:physiology*; D004562:Electrocardiography; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D010092:Oximetry; D010100:Oxygen / Q000097:blood; D014463:Ultrasonography; D055815:Young Adult
chemical_list: D010100:Oxygen