Comprehensive anterior segment normal values generated by rotating Scheimpflug tomography.
OBJECTIVE
To identify normal values for tomographic parameters that are considered useful in screening patients for refractive surgery.


METHODS
Private center, Albany, New York, USA.


METHODS
Database study.


METHODS
A Pentacam HR Scheimpflug system was used to examine 1 randomly selected eye of patients to determine normal values of 21 parameters considered the most clinically applicable for surgical screening. Normality of data was evaluated using the Kolmogorov-Smirnov test. Statistical analyses were performed using the Student t test to compare means and the 2-paired sample Wilcoxon signed-rank test. Results are displayed in 95.0% and 97.5% confidence intervals (CIs).


RESULTS
The study evaluated 341 adults. High-end outliers at the 97.5% CI were 46.1 diopters (D) for flat keratometry (K), 47.4 D for steep K, 3.4 D for astigmatism, 3.8 μm for anterior chamber depth, 4 μm for front apical elevation, 5 μm for front elevation at the thinnest point, and 12 μm for front elevation in the central 4.0 mm. Respective posterior elevation values were 7 μm, 13 μm, and 25 μm, with a progression index maximum of 1.53 and mean of 1.19, difference between apical and thinnest pachymetric reading of 7 μm, a maximum K of 48.2 D, and an inferior-superior ratio of 1.44 D. Low-end outliers were a maximum Ambrósio relational thickness of 335 and a mean of 425, minimum pachymetry of 479 μm, thickness at the apex of 481 μm, and central 4.0 mm corneal volume of 6.31 mm(3).


CONCLUSIONS
Scheimpflug-derived corneal tomography identified key refractive surgery parameters that may be useful in screening refractive surgical patients.
From the University of Arizona College of Medicine at South Campus (Gilani), the Department of Ophthalmology and Vision Science (Harvey), University of Arizona, and the Southern Arizona Veterans Administration Healthcare System (Belin), Tucson, Arizona, and Albany TLC Laser Eye Center (Cortese), Albany, New York, USA; the Department of Ophthalmology (Ambrósio, Lopes, Ramos), Federal University of São Paulo, São Paulo, and Rio de Janeiro Corneal Tomography and Biomechanics Study Group (Ambrósio), Rio de Janeiro, Brazil.
Fatimah
F
Gilani
Michael
M
Cortese
Renato R
RR
Ambrósio
Bernardo
B
Lopes
Isaac
I
Ramos
Erin M
EM
Harvey
Michael W
MW
Belin
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000869:Anterior Eye Segment / Q000033:anatomy & histology*; D048988:Corneal Surgery, Laser; D016208:Databases, Factual; D003941:Diagnostic Techniques, Ophthalmological; D004108:Dilatation, Pathologic / Q000175:diagnosis; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000175:diagnosis / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000175:diagnosis / Q000601:surgery; D012016:Reference Values; D012189:Retrospective Studies; D014054:Tomography; D055815:Young Adult