title: Disruption of emmetropization and high susceptibility to deprivation myopia in albino guinea pigs.
abstract: OBJECTIVE
  To compare emmetropization in albino and pigmented guinea pigs.
  
  
  METHODS
  Distributions of refractive state were examined in 214 albino and 234 pigmented guinea pigs. Albino (A) and pigmented (P) guinea pigs were divided into two groups, hyperopic (H) and myopic (M). Eye development was separately followed in 10 randomly selected animals from each group (AH, AM, PH, PM) from 2 to 10 weeks of age. In addition, deprivation myopia was induced in 36 age-matched albino (18 AH and 18 AM) and 36 pigmented (18 PH and 18 PM) guinea pigs by diffusers that were worn from 2 to 6 weeks of age. Finally, sclera fibril diameters were measured using transmission electron microscopy.
  
  
  RESULTS
  Strikingly, the distributions of refractive errors were bimodal at 2 weeks of age, both in albino and pigmented animals, with clearly different averages (-2.86 ± 5.60 diopters [D] vs. 2.13 ± 5.27 D respectively; t = 9.712; P < 0.001). Spontaneous myopia was more common in albino animals: 70.1% were myopic (AM) and 29.9% hyperopic (AH), whereas only 28.6% were myopic (PM) and 71.4% hyperopic (PH) in pigmented guinea pigs. Different from PM and AM did not show any recovery from myopia. With diffusers, AH became more myopic (-7.61 ± 2.71 D and -11.17 ± 2.55 D) than PH (-4.48 ± 1.46 D and -8.28 ± 2.13 D) after 2 and 4 weeks, respectively. Deprivation myopia could still be induced in PM (-1.64 ± 1.44 D and -5.17 ± 1.88 D after 2 and 4 weeks, respectively; P < 0.01) but not in AM. Scleral fibril diameters were smaller in myopic animals, both albino and pigmented.
  
  
  CONCLUSIONS
  Deprivation myopia could not be induced in spontaneously myopic but only in hyperopic albino guinea pigs, where it was even higher than in pigmented animals. The distinct effects of albinism on emmetropization will help to elucidate the mechanisms underlying the emmetropization.
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: Keli
authors.initials: K
authors.lastname: Long
authors.forename: Frank
authors.initials: F
authors.lastname: Schaeffel
authors.forename: Sen
authors.initials: S
authors.lastname: Zhang
authors.forename: Xiangtian
authors.initials: X
authors.lastname: Zhou
authors.forename: Fan
authors.initials: F
authors.lastname: Lu
authors.forename: Jia
authors.initials: J
authors.lastname: Qu
mesh_terms: D016115:Albinism, Oculocutaneous / Q000235:genetics / Q000503:physiopathology*; D000818:Animals; D058453:Emmetropia / Q000502:physiology*; D006168:Guinea Pigs; D006956:Hyperopia / Q000235:genetics / Q000503:physiopathology*; D008137:Longitudinal Studies; D008543:Melanins; D009216:Myopia / Q000235:genetics / Q000503:physiopathology*; D012590:Sclera / Q000648:ultrastructure; D012683:Sensory Deprivation
chemical_list: D008543:Melanins