title: Healing of retinal photocoagulation lesions.
abstract: OBJECTIVE
  To systematically assess the changes in retinal morphology during the healing of retinal photocoagulation lesions of various clinical grades.
  
  
  METHODS
  Rabbits were irradiated with a 532-nm Nd:YAG laser with a beam diameter of 330 microm at the retinal surface, a power of 175 mW, and pulse durations between 5 and 100 ms. Retinal lesions were clinically graded 1 minute after placement as invisible, barely visible, light, moderate, intense, very intense, and rupture and were assessed histologically at six time points from 1 hour to 4 months.
  
  
  RESULTS
  At all pulse durations, the width of the retinal lesions decreased over time. At clinical grades of light and more severe (pulse durations, 10-100 ms), retinal scarring stabilized at 1 month at approximately 35% of the initial lesion diameter. Lesions clinically categorized as barely visible and invisible (pulse durations of 7 and 5 ms) exhibited coagulation of the photoreceptor layer but did not result in permanent scarring. In these lesions, photoreceptors completely filled in the damaged areas by 4 months.
  
  
  CONCLUSIONS
  The decreasing width of the retinal damage zone suggests that photoreceptors migrating from unaffected areas fill in the gap in the photoreceptor layer. Laser photocoagulation parameters can be specified to avoid not only the inner retinal damage, but also permanent disorganization and scarring in the photoreceptor layer. These data may facilitate studies to determine those aspects of laser treatment necessary for beneficial clinical response and those that result in extraneous retinal damage.
authors.affiliation: Department of Ophthalmology, Stanford University School of Medicine, Stanford, California 94305-5308, USA.
authors.forename: Yannis M
authors.initials: YM
authors.lastname: Paulus
authors.forename: Atul
authors.initials: A
authors.lastname: Jain
authors.forename: Ray F
authors.initials: RF
authors.lastname: Gariano
authors.forename: Boris V
authors.initials: BV
authors.lastname: Stanzel
authors.forename: Michael
authors.initials: M
authors.lastname: Marmor
authors.forename: Mark S
authors.initials: MS
authors.lastname: Blumenkranz
authors.forename: Daniel
authors.initials: D
authors.lastname: Palanker