title: Posterior Segment Distortion in Ultra-Widefield Imaging Compared to Conventional Modalities.
abstract: To describe posterior segment distortions in Optos ultra-widefield images (Optos 200TX; Optos, Dunfermline, United Kingdom) compared to Topcon retinal camera images (Topcon, Tokyo, Japan) using optic disc dimensions and exploring a proposed method for correcting these distortions.
  
  
  
  Comparative image analysis study on 20 eyes with color fundus images from Optos and Topcon. A model eye with vertical and horizontal grids imaged with Optos in the conventional position and rotated 90° was analyzed.
  
  
  
  Mean vertical-to-horizontal disc diameter ratios were 0.956 [95% CI, 0.919-0.993] for Optos and 1.083 [95% CI, 1.045-1.121] for Topcon (P < .001). This was 0.910 in the conventional position and 1.072 with the object rotated 90° for the model eye with Optos and 1.008 and 0.999, respectively, using Topcon. The average of the measurements taken using both images from Optos yielded a ratio of 0.987.
  
  
  
  Optos incorporates a consistent horizontal stretch to images. Combining images taken at right angles reduces the distortion. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:644-651.].
authors.forename: Luke
authors.initials: L
authors.lastname: Nicholson
authors.forename: Li Yen
authors.initials: LY
authors.lastname: Goh
authors.forename: Elena
authors.initials: E
authors.lastname: Marshall
authors.forename: Clara
authors.initials: C
authors.lastname: Vazquez-Alfageme
authors.forename: Irini
authors.initials: I
authors.lastname: Chatziralli
authors.forename: Monica
authors.initials: M
authors.lastname: Clemo
authors.forename: Philip G
authors.initials: PG
authors.lastname: Hykin
authors.forename: Sobha
authors.initials: S
authors.lastname: Sivaprasad
mesh_terms: D005260:Female; D005451:Fluorescein Angiography / Q000379:methods*; D005654:Fundus Oculi; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods*; D057972:Posterior Eye Segment / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results