title: [A study on the effect of vitreous cavity length in primary ametropia].
abstract: OBJECTIVE
  To study the nature of primary ametropia and disclose the actions of ocular refractive components, especially the length of vitreous cavity, on primary ametropia.
  
  
  METHODS
  The refractive state, corneal refractive power (CP), anterior ocular segment length (ASL), vitreous length (VL) and ocular axial length (AL) were measured for 1 336 eyes, including 523 hyperopic eyes, 199 emmetropic eyes and 614 myopic eyes. The relationships of these elements were studied.
  
  
  RESULTS
  CP had no effect on the refractive state. There was no significant difference between CP of these three refractive groups (hyperopia vs. emmetropia and emmetropia vs. myopia) (P > 0.05). The test of normality showed that the distribution of CP was normal in each refractive state. Case control study of paired sample revealed that ASL did not change regularly with the change of refraction, while VL changed progressively with the change of refraction and there was significant difference between each pair of groups (F = 204.29, P < 0.01). The study of the relationship with matching t test between AL and VL showed that the change amount of AL and VL was nearly the same, that was, the growth of AL was about the same as the growth of VL (P > 0.05). Analysis of correlation and regression showed that these two elements were highly correlated, the coefficient of correlation being 0.879.
  
  
  CONCLUSIONS
  VL determines AL and finally determines refractive state. VL is the most important element in determining primary ametropia while the anterior eye segment has no significant contribution.
authors.affiliation: Department of Ophthalmology, Jin Shan Hospital, Shanghai Medical University, Shanghai 200540, China. juneleeok@163.net
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: F
authors.initials: F
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Ji
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012029:Refraction, Ocular; D012030:Refractive Errors / Q000209:etiology*; D014822:Vitreous Body / Q000033:anatomy & histology*