title: [The relations of corneal, lenticular and total astigmatism].
abstract: OBJECTIVE
  To determine the relations of corneal, lenticular and total astigmatism and the changes of the astigmatism with age.
  
  
  METHODS
  Out-patients with refractive errors were refracted with retinoscope after using cycloplegic drops and measured the radii of anterior corneal curvature.
  
  
  RESULTS
  One hundred and ninety-four cases (382 eyes) with refractive errors were studied. Of the eyes 67.9% had regular corneal astigmatism, 68.1% irregular lenticular astigmatism and 60.7% regular total astigmatism, 88.5% of the corneal astigmatism has the same quality as the total astigmatism. The total astigmatism in 46% of the eyes included the summation of corneal and lenticular astigmatism, but in 41.3% of the eyes irregular lenticular astigmatism corrected the regular corneal astigmatism. The astigmatism of cornea, lens and total astigmatism changed from regular to irregular with the increase of age. The linear correlation analysis showed a positive correlation between the power of horizontal corneal refraction and age, and a negative corrlation between the power of vertical corneal refraction and age.
  
  
  CONCLUSIONS
  The shape of cornea was the major cause of total astigmatism. The influence of lens on the total astigmatism was different. The reasons for the change of the total astigmatism from regular to irregular with the increase of age were the changes of the power of corneal refraction, particularly the increase of the power of horizontal corneal refraction and lenticular irregular astigmatism.
authors.affiliation: Zhongshan Ophthalmic Center, Sun Yat-sen University of Medical Sciences, Guangzhou, China.
authors.forename: D
authors.initials: D
authors.lastname: Liang
authors.forename: Z
authors.initials: Z
authors.lastname: Guan
authors.forename: J
authors.initials: J
authors.lastname: Lin
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001251:Astigmatism / Q000145:classification / Q000473:pathology / Q000503:physiopathology*; D002648:Child; D003315:Cornea / Q000473:pathology; D006801:Humans; D007908:Lens, Crystalline / Q000473:pathology; D008875:Middle Aged; D011446:Prospective Studies; D012029:Refraction, Ocular