title: The Effects of Diabetic Retinopathy and Pan-Retinal Photocoagulation on Photoreceptor Cell Function as Assessed by Dark Adaptometry.
abstract: OBJECTIVE
  The pathophysiology of vision loss in persons with diabetic retinopathy (DR) is complex and incompletely defined. We hypothesized that retinal pigment epithelium (RPE) and rod and cone photoreceptor dysfunction, as measured by dark adaptometry, would increase with severity of DR, and that pan-retinal photocoagulation (PRP) would exacerbate this dysfunction.
  
  
  METHODS
  Dark adaptation (DA) was measured in subjects with diabetes mellitus and healthy controls. Dark adaptation was measured at 5° superior to the fovea following a flash bleach, and the data were analyzed to yield cone and rod sensitivity curves. Retinal layer thicknesses were quantified using spectral-domain optical coherence tomography (OCT).
  
  
  RESULTS
  The sample consisted of 23 controls and 73 diabetic subjects. Subjects with moderate nonproliferative diabetic retinopathy (NPDR) exhibited significant impairment of rod recovery rate compared with control subjects (P = 0.04). Cone sensitivity was impaired in subjects with proliferative diabetic retinopathy (PDR) (type 1 diabetes mellitus [T1DM]: P = 0.0047; type 2 diabetes mellitus [T2DM]: P < 0.001). Subjects with untreated PDR compared with subjects treated with PRP exhibited similar rod recovery rates and cone sensitivities. Thinner RPE as assessed by OCT was associated with slower rod recovery and lower cone sensitivity, and thinner photoreceptor inner segment/outer segment layer was associated with lower cone sensitivity.
  
  
  CONCLUSIONS
  The results suggest that RPE and photoreceptor cell dysfunction, as assessed by cone sensitivity level and rod- and RPE-mediated dark adaptation, progresses with worsening DR, and rod recovery dysfunction occurs earlier than cone dysfunction. Function was preserved following PRP. The findings suggest multiple defects in retinoid function and provide potential points to improve visual function in persons with PDR.
authors.affiliation: Department of Ophthalmology and Visual Sciences W. K. Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, Michigan, United States.
authors.forename: J Clay
authors.initials: JC
authors.lastname: Bavinger
authors.affiliation: Department of Ophthalmology and Visual Sciences W. K. Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, Michigan, United States.
authors.forename: Grace E
authors.initials: GE
authors.lastname: Dunbar
authors.affiliation: Department of Ophthalmology and Visual Sciences W. K. Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, Michigan, United States.
authors.forename: Maxwell S
authors.initials: MS
authors.lastname: Stem
authors.affiliation: Department of Ophthalmology and Visual Sciences W. K. Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, Michigan, United States.
authors.forename: Taylor S
authors.initials: TS
authors.lastname: Blachley
authors.affiliation: Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, United States.
authors.forename: Leon
authors.initials: L
authors.lastname: Kwark
authors.affiliation: Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, United States 3Department of Biomedical Engineering, Duke University, Durham, North Carolina, United States.
authors.forename: Sina
authors.initials: S
authors.lastname: Farsiu
authors.affiliation: MacuLogix, Inc., Hummelstown, Pennsylvania, United States.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Jackson
authors.affiliation: Department of Ophthalmology and Visual Sciences W. K. Kellogg Eye Center, University of Michigan Medical School, Ann Arbor, Michigan, United States.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Gardner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003623:Dark Adaptation / Q000502:physiology*; D003930:Diabetic Retinopathy / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D006801:Humans; D017075:Laser Coagulation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012160:Retina / Q000473:pathology / Q000503:physiopathology* / Q000601:surgery; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D041623:Tomography, Optical Coherence / Q000379:methods; D014792:Visual Acuity; D055815:Young Adult