title: Response of corneal hysteresis and central corneal thickness following clear corneal cataract surgery.
abstract: OBJECTIVE
  To evaluate the effect of routine phacoemulsification in corneal viscoelastic properties determined by corneal hysteresis (CH) and central corneal thickness (CCT) and to explore the impact of phaco energy on the above parameters.
  
  
  METHODS
  Forty-one eyes of 41 patients undergoing cataract surgery were enrolled in this prospective study. CH and CCT were measured preoperatively, 1 day and 1 week postoperatively. CCT measurement was performed using a non-contact optical pachymeter followed by ocular response analyzer (ORA) examination. Intraoperatively ultrasound time, average phaco power and effective phaco time (EPT) were recorded.
  
  
  RESULTS
  Mean CH was 10.05±1.86 mmHg preoperatively, 8.25±1.85 mmHg 1 day and 9.12±1.37 mmHg 1 week postoperatively (p<0.001). The mean CCT was 534±37.33 μm preoperatively, 592.22±46.34 μm 1 day and 563.21±49.84 μm 1 week postoperatively (p<0.001). CCT and CH were statistically significantly correlated preoperatively (p=0.01, r=0.396). This correlation was not sustained on the first postoperative day (p=0.094, r=0.265) and was re-established 1 week postoperatively (p=0.002, r=0.568). On the first postoperative day, the CCT increase was positively correlated with EPT (p=0.009, r=0.404), which was not found between CH change and EPT.
  
  
  CONCLUSIONS
  Structural corneal alterations following cataract surgery resulted in a statistical change in CH and CCT. These two parameters responded in a different manner that clearly demarcates their different nature. On the first postoperative day, CCT increase was correlated at a statistically significant level with intraoperative EPT. This correlation was not found with CH reduction. Other factors, besides cornea oedema or phacoemulsification energy, could be responsible for this CH modification.
authors.affiliation: Ophthalmiatrion Eye Hospital of Athens, Athens, Greece. artemiskandarakis@yahoo.gr
authors.forename: Artemios
authors.initials: A
authors.lastname: Kandarakis
authors.forename: Vasileios
authors.initials: V
authors.lastname: Soumplis
authors.forename: Michalis
authors.initials: M
authors.lastname: Karampelas
authors.forename: Ioannis
authors.initials: I
authors.lastname: Koutroumanos
authors.forename: Christos
authors.initials: C
authors.lastname: Panos
authors.forename: Stylianos
authors.initials: S
authors.lastname: Kandarakis
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Karagiannis
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena / Q000502:physiology; D003315:Cornea / Q000473:pathology* / Q000601:surgery; D004108:Dilatation, Pathologic; D004548:Elasticity / Q000502:physiology*; D005260:Female; D006801:Humans; D019654:Lens Implantation, Intraocular; D008297:Male; D009929:Organ Size; D018918:Phacoemulsification; D011446:Prospective Studies; D014792:Visual Acuity / Q000502:physiology