title: Biometry and refractive outcome of eyes filled with silicone oil by standardized echography and partial coherence interferometry.
abstract: BACKGROUND
  We evaluated the validity of calculations for refractive outcome in cataract surgery in silicone oil-filled eyes. The retrosilicone space (RSS) was included in these calculations.
  
  
  METHODS
  In a prospective study the axial length (AL) of silicone oil-filled eyes was measured. with standardized A-scan echography (SAE) and partial coherence interferometry (PCI). Meldrum's formula was used to transform the velocity of ultrasound within the vitreous cavity. To investigate whether refractive outcome can be calculated accurately, we assessed the difference between precalculated and final refractive outcome. Furthermore, we determined the advantages and disadvantages of SAE and PCI. A minor aim was to assess whether the AL of the two eyes differed significantly.
  
  
  RESULTS
  In 85% of 117 eyes the difference between precalculated and postsurgical refraction was smaller than 1 diopter spherical and statistically not significant (p>0.2). The mean AL was 24.1 mm (range 20.0-31.4 mm). The difference in outcome between the two methods was without statistical significance: the AL difference was 0.4 (+/-2.6) mm on measurement with SAE and 0.04 (+/-0.46) mm with PCI. PCI has the advantage that it can be performed more easily, without contact, while echography is advantageous in the presence of advanced cataracts. In supine position an oil-free fluid space behind the silicone oil was detected with echography. The mean dimension of this space was 1.9 (+/-0.67) mm and it was taken into consideration for IOL calculation. The mean AL difference between the two eyes was 0.4 mm, but the difference was greater than 1 mm in 26% of the patients.
  
  
  CONCLUSIONS
  The AL of eyes filled with silicone oil can be measured reliably with SAE and PCI. In supine position the RSS has to be considered to obtain more accurate IOL calculations.
authors.affiliation: Department of Ophthalmology, Medical University of Vienna, Waehringer Gürtel 18-20, 1090, Vienna, Austria. johannes.nepp@meduniwien.ac.at
authors.forename: Johannes
authors.initials: J
authors.lastname: Nepp
authors.forename: Katharina
authors.initials: K
authors.lastname: Krepler
authors.forename: Kerstin
authors.initials: K
authors.lastname: Jandrasits
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hauff
authors.forename: Georg
authors.initials: G
authors.lastname: Hanselmayer
authors.forename: Michaela
authors.initials: M
authors.lastname: Velikay-Parel
authors.forename: Karl C
authors.initials: KC
authors.lastname: Ossoinig
authors.forename: Andreas
authors.initials: A
authors.lastname: Wedrich
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001699:Biometry / Q000379:methods*; D002648:Child; D005123:Eye / Q000000981:diagnostic imaging*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007267:Injections; D007368:Interferometry / Q000379:methods; D019654:Lens Implantation, Intraocular / Q000379:methods; D008297:Male; D008875:Middle Aged; D018918:Phacoemulsification; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology*; D012827:Silicone Oils / Q000008:administration & dosage*; D016896:Treatment Outcome; D014463:Ultrasonography; D014822:Vitreous Body
chemical_list: D012827:Silicone Oils