Central corneal thickness measurements after myopic photorefractive keratectomy using Scheimpflug imaging, scanning-slit topography, and ultrasonic pachymetry.
OBJECTIVE
To compare central corneal thickness (CCT) measurements obtained with a dual Scheimpflug camera system (Galilei), a scanning-slit topographer (Orbscan II), and an ultrasound (US) pachymeter (SP-2000) after photorefractive keratectomy (PRK) for myopia.


METHODS
Ophthalmic Research Center, Labbafinejad Medical Center, Tehran, Iran.


METHODS
This prospective study enrolled patients who had PRK to correct myopia or myopic astigmatism and a postoperative follow-up of at least 5 months. The CCT was measured in a single session using Scheimpflug imaging, scanning-slit topography, and US pachymetry. Data were analyzed with paired t tests, linear regression, and Bland-Altman plots.


RESULTS
The mean CCT in the 100 eyes (50 patients) was 524.06 microm +/- 38.56 (SD) with Scheimpflug imaging, 505.92 +/- 47.35 microm with scanning-slit topography, and 496.97 +/- 42.74 microm with US pachymetry. The lower to upper 95% limits of agreement (LoA) with US pachymetry were 2.4 to 51.8 microm for Scheimpflug imaging and -22.2 to 40.1 microm for scanning-slit topography. After application of a correction factor (0.95), the mean corrected Scheimpflug CCT measurement was 497.33 +/- 36.59 microm and the lower to upper 95% LoA with US pachymetry were -25.9 to 25.5 microm. The acoustic factor for scanning-slit topography was 0.94.


CONCLUSIONS
The CCT measurements in eyes that had PRK were thicker with Scheimpflug imaging than with US pachymetry or scanning-slit topography in the late postoperative period. With application of a correction factor, the Scheimpflug measurements were closer to US pachymetry values and had better agreement than scanning-slit topography.
Faramarzi
Amir
A
Department of Ophthalmology, Ophthalmic Research Center, Shaheed Beheshti Medical University, Tehran, Iran. amirfaramarzy@yahoo.com
Karimian
Farid
F
Jafarinasab
Mohammad Reza
MR
Jabbarpoor Bonyadi
Mohammad Hossein
MH
Yaseri
Mehdi
M
D000328:Adult; D000886:Anthropometry; D001251:Astigmatism / Q000601:surgery*; D001837:Body Weights and Measures; D003315:Cornea / Q000473:pathology* / Q000601:surgery; D019781:Corneal Topography; D003941:Diagnostic Techniques, Ophthalmological; D005260:Female; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D010781:Photography; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D014463:Ultrasonography; D055815:Young Adult