title: Chronic ocular lesions associated with bi-directional microbeam radiation therapy in an experimental rat study for therapy of C6 and F98 gliomas.
abstract: OBJECTIVE
  To describe the chronic ocular lesions associated with microbeam radiation therapy (MRT) in an experimental rat study.
  
  
  METHODS
  MRT was administered bi-directionally with a skin entry dose of 350 Gy. During laterally directed irradiation, the beam entered the head on the right with the center of the beam array 3 mm posterior to the center of the right eye. During irradiation in anterior-posterior direction, the right eye was almost completely in the path of the beam array. Twelve months after MRT ophthalmic examinations were completed on 37 treated (MRT+) and 16 control (MRT-) rats. Electroretinography (ERG) was completed in two MRT+ and one MRT- rat. Histopathology was performed on eyes of 16 MRT+ and 9 MRT- rats, and retinal and choroidal thicknesses were measured.
  
  
  RESULTS
  Biomicroscopic and indirect ophthalmoscopic examinations revealed fundus pallor and retinal vascular attenuation in 33 of 37 right and 2 of 37 left eyes of MRT+ rats. Cataracts were present in the right eyes of 12 of 37 MRT+ rats. ERG amplitudes were reduced in the eyes of MRT+ rats. Light microscopy revealed retinal lesions ranging in severity with loss of outer to inner retinal cell layers, in 16 of 16 right and of 8 of 16 left eyes MRT+ rats. The mean right retinal thickness of MRT+ rats was reduced.
  
  
  CONCLUSIONS
  Eyes within the field treated with MRT at a dose of 350 Gy develop retinal degeneration and occasionally, cataract.
authors.affiliation: Department of Small Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. lynne.sandmeyer@usask.ca
authors.forename: Lynne S
authors.initials: LS
authors.lastname: Sandmeyer
authors.forename: Amber
authors.initials: A
authors.lastname: Sheikh
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Schültke
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Shültke
authors.forename: Daryl
authors.initials: D
authors.lastname: Fourney
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Grahn
mesh_terms: D000818:Animals; D016022:Case-Control Studies; D002386:Cataract / Q000209:etiology / Q000662:veterinary; D003315:Cornea / Q000528:radiation effects; D004596:Electroretinography / Q000662:veterinary; D005131:Eye Injuries / Q000209:etiology / Q000662:veterinary*; D005134:Eye Neoplasms / Q000532:radiotherapy / Q000662:veterinary*; D005910:Glioma / Q000532:radiotherapy / Q000662:veterinary*; D008297:Male; D011833:Radiation Injuries, Experimental; D011878:Radiotherapy / Q000009:adverse effects / Q000379:methods / Q000662:veterinary*; D011879:Radiotherapy Dosage; D011897:Random Allocation; D051381:Rats; D011916:Rats, Inbred F344; D017208:Rats, Wistar; D012160:Retina / Q000528:radiation effects*