title: Spontaneous axial myopia and emmetropization in a strain of wild-type guinea pig (Cavia porcellus).
abstract: OBJECTIVE
  To describe a wild-type guinea pig strain with an incidence of spontaneous axial myopia, minimal pupil responses, lack of accommodation, and apparently normal spatial vision. Such a strain is of interest because it may permit the exploration of defective emmetropization and mapping of the underlying quantitative trait loci.
  
  
  METHODS
  Twenty-eight guinea pigs were selected from 220 animals based on binocular myopia (exceeding -1.50 diopter [D]) or anisometropia (difference between both eyes exceeding 10 D) at 4 weeks of age. Refractions and pupil responses were measured with eccentric infrared photoretinoscopy, corneal curvature by modified conventional keratometer, and axial lengths by A-scan ultrasonography once a week. Twenty-one guinea pigs were raised under a normal 12-hour light/12-hour dark cycle. From a sample of 18 anisometropic guinea pigs, 11 were raised under normal light cycle and 7 were raised in the dark to determine the extent to which visual input guides emmetropization. Spatial vision was tested in an automated optomotor drum.
  
  
  RESULTS
  In 10 guinea pigs with myopia in both eyes, refractive errors ranged from -15.67 D to -1.50 D at 3 weeks with a high interocular correlation (R = 0.82); axial length and corneal curvature grew almost linearly over time. Strikingly, two patterns of recovery were observed in anisometropic guinea pigs: in 12 (67%) anisometropia persisted, and in 6 (33%) it declined over time. These ratios remained similar in dark-reared guinea pigs. Unlike published strains, all guinea pigs of this strain showed weak pupil responses and no signs of accommodation but up to 3 cyc/deg of spatial resolution.
  
  
  CONCLUSIONS
  This strain of guinea pigs has spontaneous axial refractive errors that may be genetically or epigenetically determined. Interestingly, it differs from other published strains that show no refractive errors, vivid accommodation, or pupil responses.
authors.affiliation: School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang, China.
authors.forename: Liqin
authors.initials: L
authors.lastname: Jiang
authors.forename: Frank
authors.initials: F
authors.lastname: Schaeffel
authors.forename: Xiangtian
authors.initials: X
authors.lastname: Zhou
authors.forename: Sen
authors.initials: S
authors.lastname: Zhang
authors.forename: Xi
authors.initials: X
authors.lastname: Jin
authors.forename: Miaozhen
authors.initials: M
authors.lastname: Pan
authors.forename: Lingying
authors.initials: L
authors.lastname: Ye
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Wu
authors.forename: Qinzhu
authors.initials: Q
authors.lastname: Huang
authors.forename: Fan
authors.initials: F
authors.lastname: Lu
authors.forename: Jia
authors.initials: J
authors.lastname: Qu
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000818:Animals; D015858:Anisometropia / Q000235:genetics / Q000503:physiopathology; D003315:Cornea / Q000473:pathology; D004195:Disease Models, Animal; D006168:Guinea Pigs; D009216:Myopia / Q000235:genetics* / Q000503:physiopathology; D011681:Pupil Disorders / Q000235:genetics* / Q000503:physiopathology; D012029:Refraction, Ocular / Q000502:physiology; D042262:Retinoscopy; D014792:Visual Acuity / Q000502:physiology