title: Phacopower modulation and the risk for postoperative corneal decompensation: a randomized clinical trial.
abstract: OBJECTIVE
  In compromised corneas, eg, patients with Fuchs endothelial dystrophy (FED), it is of utmost importance to use a phacotechnique that is the least traumatic to the corneal endothelium. Furthermore, preoperative patient selection is crucial, because unexpected corneal decompensation leads to dissatisfied patients.
  
  
  OBJECTIVE
  To compare corneal thickness and corneal volume changes using torsional and longitudinal phacoemulsification in patients with Fuchs endothelial dystrophy (FED) and determine risk factors of postoperative corneal decompensation.
  
  
  METHODS
  Prospective randomized clinical trial of all patients diagnosed with FED and planning to undergo cataract surgery for visually significant cataract at a university medical center from November 2008 to May 2010.
  
  
  METHODS
  Fifty-two eyes with FED and visually significant cataract underwent torsional (n = 26) or longitudinal (n = 26) phacoemulsification. Patients were evaluated preoperatively and 1 day, 1 week, 1 month, 3 months, and 6 months postoperatively. Visits included best spectacle-corrected visual acuity, anterior segment optical coherence tomography evaluating central corneal thickness (CCT) and peripheral corneal thickness (PCT), and Scheimpflug imaging calculating corneal volume (CV). Randomization took place according to stage of FED, nucleus density grade, and age. Intraoperatively, ultrasonography time and cumulative dissipated energy were recorded.
  
  
  METHODS
  Central corneal thickness, PCT, and CV.
  
  
  RESULTS
  Ultrasonography time and cumulative dissipated energy were significantly lower in the torsional group for harder nucleus density grades compared with the longitudinal group (P = .009 and P = .002, respectively). Peripheral corneal thickness at the 6-o'clock position, CCT, and CV were significantly smaller in the torsional group 1 day postoperatively (P = .002; P = .03; and P = .004, respectively). Changes in PCT at the 12-o'clock position and best spectacle-corrected visual acuity were not significantly different between the 2 groups (P > .05). Preoperative CCT was the only significant predictor of corneal decompensation postoperatively (P < .001). Preoperative CCT of 620 µm corresponded to an odds ratio of 1, meaning no increased risk of developing corneal decompensation. For each 10-µm increase in preoperative CCT, the odds of developing corneal decompensation increased 1.7 times.
  
  
  CONCLUSIONS
  Torsional phacoemulsification effectively reduces ultrasonography time and cumulative dissipated energy compared with longitudinal phacoemulsification in patients with FED. However, there were only significant differences in corneal thickness and CV changes at 1 day postoperatively in favor of the torsional group. Central corneal thickness more than 620 µm, measured by noncontact pachymetry, leads to an increased risk for corneal decompensation after phacoemulsification in patients with FED.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT00781027.
authors.affiliation: University Eye Clinic Maastricht, Maastricht University Medical Center, Maastricht, the Netherlands.
authors.forename: Muriël
authors.initials: M
authors.lastname: Doors
authors.forename: Tos T J M
authors.initials: TT
authors.lastname: Berendschot
authors.forename: Wouter
authors.initials: W
authors.lastname: Touwslager
authors.forename: Carroll A
authors.initials: CA
authors.lastname: Webers
authors.forename: Rudy M M A
authors.initials: RM
authors.lastname: Nuijts
mesh_terms: D000368:Aged; D003315:Cornea / Q000473:pathology*; D015715:Corneal Edema / Q000175:diagnosis / Q000209:etiology*; D063171:Corneal Pachymetry; D057111:Descemet Stripping Endothelial Keratoplasty; D005260:Female; D005642:Fuchs' Endothelial Dystrophy / Q000150:complications* / Q000601:surgery; D006801:Humans; D019654:Lens Implantation, Intraocular; D008297:Male; D018918:Phacoemulsification / Q000379:methods*; D011183:Postoperative Complications; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D041623:Tomography, Optical Coherence; D014792:Visual Acuity