title: Axial length measurement in eyes with diabetic macular edema: a-scan ultrasound versus IOLMaster.
abstract: OBJECTIVE
  To compare axial length (AL) measurements obtained with ultrasound (US) and IOLMaster (software version 3.01.0294; Carl Zeiss Meditec, Jena, Germany) in eyes with diabetic clinically significant macular edema (CSME) and to examine the correlation between measurement difference and foveal thickness.
  
  
  METHODS
  Prospective nonrandomized clinical study.
  
  
  METHODS
  Twenty-three healthy eyes of 23 participants and 21 eyes with CSME of 21 diabetic outpatients.
  
  
  METHODS
  The authors prospectively measured AL using US and IOLMaster in eyes of both groups. Foveal thickness was measured with optical coherence tomography. The difference between both methods was assessed using the t test, and its correlation to foveal thickness was evaluated by Pearson coefficient.
  
  
  METHODS
  Difference in AL measurements between IOLMaster and US.
  
  
  RESULTS
  Mean+/-standard deviation foveal thickness in healthy and CSME eyes was 201+/-26 microm (range, 156-240) and 475+/-106 microm (range, 331-758), respectively. Mean AL by US and IOLMaster in healthy eyes was 23.17+/-1.07 mm (range, 21.17-25.18) and 23.25+/-1.10 mm (range, 21.17-25.26), respectively (P = 0.51); in CSME eyes, it was 23.02+/-0.97 mm (range, 21.53-24.81) and 23.27+/-0.924 mm (range, 21.9-25.13), respectively (P<0.001). Correlation between AL difference and foveal thickness was poor in both healthy (r = 0.18, P = 0.40) and CSME (r = 0.02, P = 0.93) eyes.
  
  
  CONCLUSIONS
  Axial length measurements using applanation A-scan US and IOLMaster in eyes with CSME differ statistically and clinically significantly. This is likely a result of the fundamentally different methodology of the 2 methods in measuring eyes with a pathologically thickened retina. A conversion formula based on foveal thickness can not be provided at present.
authors.affiliation: Department of Ophthalmology, Assaf Harofeh Medical Center, Zerifin, Israel.
authors.forename: Liat
authors.initials: L
authors.lastname: Attas-Fox
authors.forename: David
authors.initials: D
authors.lastname: Zadok
authors.forename: Yariv
authors.initials: Y
authors.lastname: Gerber
authors.forename: Yair
authors.initials: Y
authors.lastname: Morad
authors.forename: Eva
authors.initials: E
authors.lastname: Eting
authors.forename: Nathanael
authors.initials: N
authors.lastname: Benamou
authors.forename: Eran
authors.initials: E
authors.lastname: Pras
authors.forename: Ori
authors.initials: O
authors.lastname: Segal
authors.forename: Isaac
authors.initials: I
authors.lastname: Avni
authors.forename: Yaniv
authors.initials: Y
authors.lastname: Barkana
mesh_terms: D000328:Adult; D000368:Aged; D001837:Body Weights and Measures; D003930:Diabetic Retinopathy / Q000150:complications*; D003941:Diagnostic Techniques, Ophthalmological; D005123:Eye / Q000000981:diagnostic imaging* / Q000473:pathology*; D005584:Fovea Centralis / Q000000981:diagnostic imaging / Q000473:pathology; D006801:Humans; D007368:Interferometry / Q000379:methods; D008027:Light; D008269:Macular Edema / Q000150:complications*; D008875:Middle Aged; D011446:Prospective Studies; D014463:Ultrasonography / Q000379:methods