Reliability of pachymetric measurements using orbscan after excimer refractive surgery.
OBJECTIVE
To assess the accuracy of pachymetric measurements using Orbscan (Bausch & Lomb, Rochester, NY) after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK).


METHODS
Prospective instrument validation study.


METHODS
Seventy-nine nonoperated normal eyes, 84 eyes after LASIK, and 50 eyes after PRK.


METHODS
Laser in situ keratomileusis or PRK.


METHODS
Central corneal thickness was measured using ultrasound and Orbscan II. The acoustic factor (AF) was adjusted, based on the results obtained in the normal eye group, to minimize the difference between ultrasound and Orbscan pachymetric values.


METHODS
Central corneal thickness as measured by Orbscan and ultrasound pachymeter.


RESULTS
Using the adjusted AF, which was 0.946, the mean difference between Orbscan and ultrasonic pachymetric measurements was 0 +/- 17, 16 +/- 28, and 68 +/- 39 microm in the normal, LASIK, and PRK groups, respectively. The difference between all groups was statistically significant (P < 0.0001).


CONCLUSIONS
Orbscan pachymetric values may be underestimated and less accurate after LASIK and PRK.
Prisant
Olivier
O
Fondation Ophtalmologique Adolphe de Rothschild, Hôpital Bichat, 25 à 29 Rue Manin, 75019 Paris, France.
Calderon
Nila
N
Chastang
Philippe
P
Gatinel
Damien
D
Hoang-Xuan
Thanh
T
D000328:Adult; D003315:Cornea / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D003941:Diagnostic Techniques, Ophthalmological / Q000592:standards*; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D054018:Lasers, Excimer; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D015203:Reproducibility of Results; D014463:Ultrasonography