Central corneal thickness measurement with Pentacam, Orbscan II, and ultrasound devices before and after laser refractive surgery for myopia.
OBJECTIVE
To determine the agreement in central corneal thickness (CCT) measurements between the gold standard method of ultrasound (US) pachymetry (UP-1000, Nidek) and 2 noncontact systems based on Scheimpflug imaging (Pentacam, Oculus) and scanning-slit topography (Orbscan II, Bausch & Lomb) in myopic eyes before and after laser refractive surgery.


METHODS
Noor Vision Correction Center, Tehran, Iran.


METHODS
In this prospective study, 30 consecutive patients having refractive surgery for myopia were enrolled. All 60 eyes were examined with the 3 devices preoperatively and 6 weeks after surgery; the US measurements were performed last. The Pentacam and Orbscan II CCT readings were compared with the US readings. Both the original and corrected Orbscan II readings were used in the analyses.


RESULTS
The mean CCT readings with US, Pentacam, and Orbscan II were, respectively, 555 microm, 548 microm, and 580 microm before surgery and 478 microm, 468 microm, and 474 microm after surgery. Preoperatively, the 95% limits of agreement (LoA) with US were -31 microm and +19 microm for the Pentacam device and -5 microm and +57 microm for the Orbscan II device. Postoperatively, the LoA were -40 microm and +19 microm and -51 microm and +50 microm, respectively. Corrected Orbscan II measurements gave 95% LoA of -48 microm and +6 microm before surgery and -85 microm and +5 microm after surgery.


CONCLUSIONS
Refractive surgery had a modest effect on the agreement between Pentacam readings and US measurements. With Orbscan II, the 95% LoA width nearly doubled after surgery. Although the Pentacam seems to show better agreement than Orbscan II, especially after refractive surgery, it is not advisable to use the 3 devices interchangeably in every clinical situation.
Hashemi
Hassan
H
Farabi Eye Hospital, Department of Ophthalmology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Mehravaran
Shiva
S
D000328:Adult; D001837:Body Weights and Measures; D003315:Cornea / Q000473:pathology*; D048988:Corneal Surgery, Laser; D019781:Corneal Topography / Q000379:methods; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation; D005260:Female; D006801:Humans; D008297:Male; D009216:Myopia / Q000601:surgery*; D010781:Photography / Q000379:methods; D011184:Postoperative Period; D011300:Preoperative Care; D011446:Prospective Studies; D015203:Reproducibility of Results; D014465:Ultrasonics