title: Light-induced retinopathy: comparing adult and juvenile rats.
abstract: OBJECTIVE
  To investigate the effect of chronic exposure to a bright, luminous environment, starting at the opening of the eyes, on the retinal structure and function of the suckling rat.
  
  
  METHODS
  Juvenile Sprague-Dawley rats were exposed to 10,000 lux, for varying lengths of time between postnatal day (P)14 and P34. Results were compared with those obtained from adult rats exposed to the same light intensity and for the same duration. Electroretinograms (ERGs) were recorded at 1 month and 2 months of age, after which the retinas were harvested for histologic analysis.
  
  
  RESULTS
  In juvenile rats, the severity of light-induced retinopathy (LIR) depended not only on the duration of the exposure but, more important, on the age of the rat at the onset of exposure. For example, in adult rats, 6-day exposure reduced the thickness of the outer nuclear layer (ONL) to less than 18% of normal, whereas in juvenile rats, 6-day exposure between P14 and P20 reduced it to 50% compared with 27% after exposure between P28 and P34. An adultlike effect could only be evidenced in rats exposed at the end of the first postnatal month (P28-P34). A similar age-dependent effect was also noted on the electroretinogram.
  
  
  CONCLUSIONS
  These results show that, compared with the mature retina, the developing retina appears to be relatively preserved from the devastating consequences of exposure to bright light. This window of resistance to light damage gradually weakens as the juvenile rat approaches its 1-month anniversary.
authors.affiliation: Department of Biological Sciences, University of Montreal, and Department of Ophthalmology, McGill University-Montreal Children's Hospital Research Institute, Quebec, Canada.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Joly
authors.forename: Vincent
authors.initials: V
authors.lastname: Pernet
authors.forename: Allison L
authors.initials: AL
authors.lastname: Dorfman
authors.forename: Sylvain
authors.initials: S
authors.lastname: Chemtob
authors.forename: Pierre
authors.initials: P
authors.lastname: Lachapelle
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D004596:Electroretinography; D005260:Female; D008027:Light / Q000009:adverse effects*; D011247:Pregnancy; D011833:Radiation Injuries, Experimental / Q000209:etiology / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012160:Retina / Q000503:physiopathology / Q000528:radiation effects*; D012162:Retinal Degeneration / Q000209:etiology / Q000503:physiopathology*; D013997:Time Factors