title: Light-Induced Thickening of Photoreceptor Outer Segment Layer Detected by Ultra-High Resolution OCT Imaging.
abstract: We examined if light induces changes in the retinal structure that can be observed using optical coherence tomography (OCT).
  
  
  
  Normal C57BL/6J mice (age 3-6 months) adapted to either room light (15 minutes to ∼5 hours, 50-500 lux) or darkness (overnight) were imaged using a Bioptigen UHR-OCT system. Confocal histologic images were obtained from mice killed under light- or dark-adapted conditions.
  
  
  
  The OCT image of eyes adapted to room light exhibited significant increases (6.1 ± 0.8 μm, n = 13) in total retina thickness compared to the same eyes after overnight dark adaptation. These light-adapted retinal thickness changes occurred mainly in the outer retina, with the development of a hyporeflective band between the RPE and photoreceptor-tip layers. Histologic analysis revealed a light-evoked elongation between the outer limiting membrane and Bruch's membrane from 45.8 ± 1.7 μm in the dark (n = 5) to 52.1 ± 3.7 μm (n = 5) in the light. Light-adapted retinas showed an increase of actin staining in RPE apical microvilli at the same location as the hyporeflective band observed in OCT images. Elongation of the outer retina could be detected even with brief light exposures, increasing 2.1 ± 0.3 μm after 15 minutes (n = 9), and 4.1 ± 1.0 μm after 2 hours (n = 6). Conversely, dark-adaptation caused outer retinal shortening of 1.4 ± 0.4 μm (n = 7) and 3.0 ± 0.5 μm (n = 8) after 15 minutes and 2 hours, respectively.
  
  
  
  Light-adaption induces an increase in the thickness of the outer retina and the appearance of a hyporeflective band in the OCT image. This is consistent with previous reports of light-induced fluid accumulation in the subretinal space.
authors.affiliation: Visual Function Core National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors.forename: Yichao
authors.initials: Y
authors.lastname: Li
authors.affiliation: Biological Imaging Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors.forename: Robert N
authors.initials: RN
authors.lastname: Fariss
authors.affiliation: College of Arts & Sciences, University of Virginia, Charlottesville, Virginia, United States.
authors.forename: Jennifer W
authors.initials: JW
authors.lastname: Qian
authors.affiliation: Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland, United States.
authors.forename: Ethan D
authors.initials: ED
authors.lastname: Cohen
authors.affiliation: Visual Function Core National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States.
authors.forename: Haohua
authors.initials: H
authors.lastname: Qian
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D007089:Image Enhancement / Q000379:methods*; D008027:Light / Q000009:adverse effects*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012164:Retinal Diseases / Q000175:diagnosis* / Q000209:etiology; D012165:Retinal Ganglion Cells / Q000473:pathology; D055214:Retinal Photoreceptor Cell Outer Segment / Q000473:pathology* / Q000528:radiation effects; D041623:Tomography, Optical Coherence / Q000379:methods*