title: Changes in corneal hysteresis after clear corneal cataract surgery.
abstract: OBJECTIVE
  To assess the changes in corneal hysteresis (CH) as measured by the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments, Buffalo, New York, USA) to describe the influence of clear corneal cataract surgery on corneal viscoelastic properties and intraocular pressure (IOP) measured by noncontact tonometry (NCT) and Goldmann applanation tonometry (GAT).
  
  
  METHODS
  Retrospective, interventional, comparative study.
  
  
  METHODS
  One hundred and one eyes of 101 consecutive patients who underwent routine clear corneal cataract surgery were evaluated. CH, NCT, and central corneal thickness (CCT) were measured by ORA before surgery and at postoperative day 1. A control group of 48 pseudophakic eyes (surgery >3 months previously) was included.
  
  
  RESULTS
  CCT increased from 556.82 +/- 32.5 microm before surgery to 580.26 +/- 45.5 microm after surgery (P < .001; control, 555.16 +/- 42.33 microm). Mean CH decreased from 10.35 +/- 2.5 mm Hg before surgery to 9.20 +/- 1.9 mm Hg after surgery (P < .001; control, 10.47 +/- 1.63 mm Hg). NCT values rose from 17.85 +/- 3.8 mm Hg before surgery to 20.10 +/- 6.3 mm Hg after surgery. GAT values were 14.85 +/- 2.8 mm Hg before surgery and 15.24 +/- 4.1 mm Hg after surgery (P = .52). There was no significant difference of CCT or CH between the preoperative values and the values of the control group (CCT, P = .986; CH, P = .166), in contrast to the difference between postoperative values and the values of the control group (CCT, P = .005; CH, P = .031).
  
  
  CONCLUSIONS
  At day 1 after clear corneal cataract surgery, CH is diminished, whereas CCT is increased significantly. Postoperative corneal edema leads to a change of corneal viscoelastic properties, resulting in a lower damping capacity of the cornea. It is supposed that GAT and NCT measurements are significantly different because of postoperative changes in viscoelastic properties of the cornea.
authors.affiliation: Department of Ophthalmology, Asklepios Klinik Nord - Heidberg, Hamburg, Germany. anhager@gmx.de
authors.forename: Annette
authors.initials: A
authors.lastname: Hager
authors.forename: Kristina
authors.initials: K
authors.lastname: Loge
authors.forename: Marc-Oliver
authors.initials: MO
authors.lastname: Füllhas
authors.forename: Bernd
authors.initials: B
authors.lastname: Schroeder
authors.forename: Martin
authors.initials: M
authors.lastname: Grossherr
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wiegand
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002387:Cataract Extraction; D003187:Compliance; D003315:Cornea / Q000503:physiopathology* / Q000601:surgery*; D003941:Diagnostic Techniques, Ophthalmological; D004547:Elastic Tissue / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D019654:Lens Implantation, Intraocular; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014065:Tonometry, Ocular; D014792:Visual Acuity / Q000502:physiology