title: Variations in corneal asphericity (Q value) between African-Americans and whites.
abstract: OBJECTIVE
  To search for differences in corneal asphericity on the basis of ethnicity between African-American and white populations.
  
  
  METHODS
  A prospective cohort design was used to analyze corneal asphericity (Q value) data obtained by Pentacam HR (Oculus, Wetzlar, Germany) on right eyes from African-American (n = 80) and white (n = 80). Subjects were stratified by ethnicity, age, and spherical equivalent (SE) refractive error. Q values were obtained from each quadrant (superior, nasal, inferior, and temporal) and two meridians (horizontal and vertical).
  
  
  RESULTS
  The mean Q values were African-Americans -0.26 ± 0.19 and whites -0.20 ± 0.12, indicating that the eyes of African-Americans were significantly more prolate (p = 0.003) than those of whites. There was a significant difference between mean Q values for ethnic groups only in the 30- to 39-year olds (p = 0.01) and there was a lack of correlation with age in both ethnic groups. Q value contrasts by gender were only significant between males (p = 0.01). There was a lack of correlation between Q value and SE for either ethnic group. Age group contrasts between ethnic groups found significant differences for those with SE greater than 0.00 D to -3.00 D (p = 0.05) and greater than 0.00 D to +3.00 D (p = 0.05). Comparison of mean Q values in opposing meridians within and across ethnic groups were significant, although neither group showed significant differences between horizontal and vertical meridians.
  
  
  CONCLUSIONS
  Corneal asphericity as represented by mean Q value varies significantly between African-Americans and whites. The greatest differences are evident in opposing quadrants and appear to be little influenced by age, gender, or SE.
authors.affiliation: Cornea Contact Lens Service, The Eye Center, Southern College of Optometry, Memphis, TN 38104, USA. dfuller@sco.edu
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Fuller
authors.forename: Danielle
authors.initials: D
authors.lastname: Alperin
mesh_terms: D000328:Adult; D001741:Black or African American / Q000208:ethnology*; D000368:Aged; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000208:ethnology* / Q000503:physiopathology*; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D044465:White People / Q000208:ethnology*; D055815:Young Adult