title: Effects of Intraframe Distortion on Measures of Cone Mosaic Geometry from Adaptive Optics Scanning Light Ophthalmoscopy.
abstract: OBJECTIVE
  To characterize the effects of intraframe distortion due to involuntary eye motion on measures of cone mosaic geometry derived from adaptive optics scanning light ophthalmoscope (AOSLO) images.
  
  
  METHODS
  We acquired AOSLO image sequences from 20 subjects at 1.0, 2.0, and 5.0° temporal from fixation. An expert grader manually selected 10 minimally distorted reference frames from each 150-frame sequence for subsequent registration. Cone mosaic geometry was measured in all registered images (n= 600) using multiple metrics, and the repeatability of these metrics was used to assess the impact of the distortions from each reference frame. In nine additional subjects, we compared AOSLO-derived measurements to those from adaptive optics (AO)-fundus images, which do not contain system-imposed intraframe distortions.
  
  
  RESULTS
  We observed substantial variation across subjects in the repeatability of density (1.2%-8.7%), inter-cell distance (0.8%-4.6%), percentage of six-sided Voronoi cells (0.8%-10.6%), and Voronoi cell area regularity (VCAR) (1.2%-13.2%). The average of all metrics extracted from AOSLO images (with the exception of VCAR) was not significantly different than those derived from AO-fundus images, though there was variability between individual images.
  
  
  CONCLUSIONS
  Our data demonstrate that the intraframe distortion found in AOSLO images can affect the accuracy and repeatability of cone mosaic metrics. It may be possible to use multiple images from the same retinal area to approximate a "distortionless" image, though more work is needed to evaluate the feasibility of this approach.
  
  
  CONCLUSIONS
  Even in subjects with good fixation, images from AOSLOs contain intraframe distortions due to eye motion during scanning. The existence of these artifacts emphasizes the need for caution when interpreting results derived from scanning instruments.
authors.affiliation: Biomedical Engineering, Marquette University, Milwaukee, WI, USA.
authors.forename: Robert F
authors.initials: RF
authors.lastname: Cooper
authors.affiliation: Ophthalmology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Yusufu N
authors.initials: YN
authors.lastname: Sulai
authors.affiliation: Institute of Ophthalmology, University College London, London, UK ; Moorfields Eye Hospital, London, UK.
authors.forename: Adam M
authors.initials: AM
authors.lastname: Dubis
authors.affiliation: New York Eye and Ear Infirmary of Mount Sinai, New York, NY, USA ; Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Toco Y
authors.initials: TY
authors.lastname: Chui
authors.affiliation: New York Eye and Ear Infirmary of Mount Sinai, New York, NY, USA ; Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Rosen
authors.affiliation: Institute of Ophthalmology, University College London, London, UK ; Moorfields Eye Hospital, London, UK.
authors.forename: Michel
authors.initials: M
authors.lastname: Michaelides
authors.affiliation: Biomedical Engineering, Marquette University, Milwaukee, WI, USA ; Ophthalmology, Medical College of Wisconsin, Milwaukee, WI, USA ; Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA ; Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Dubra
authors.affiliation: Biomedical Engineering, Marquette University, Milwaukee, WI, USA ; Ophthalmology, Medical College of Wisconsin, Milwaukee, WI, USA ; Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA ; Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Carroll
keywords: adaptive optics; image analysis; image processing; photoreceptors