Corneal Anterior Power Calculation for an IOL in Post-PRK Patients.
OBJECTIVE
After corneal refractive surgery, there is an overestimation of the corneal power with the devices routinely used to measure it. Therefore, the objective of this study was to determine whether, in patients who underwent photorefractive keratectomy (PRK), it is possible to predict the earlier preoperative anterior corneal power from the postoperative (PO) posterior corneal power. A comparison is made using a formula published by Saiki for laser in situ keratomileusis patients and a new one calculated specifically from PRK patients.


METHODS
The Saiki formula was tested in 98 eyes of 98 patients (47 women) who underwent PRK for myopia or myopic astigmatism. Moreover, anterior and posterior mean keratometry (Km) values from a Scheimpflug camera were measured to obtain a specific regression formula.


RESULTS
The mean (±SD) preoperative Km was 43.50 (±1.39) diopters (D) (range, 39.25 to 47.05 D). The mean (±SD) Km value calculated with the Saiki formula using the 6 months PO posterior Km was 42.94 (±1.19) D (range, 40.34 to 45.98 D) with a statistically significant difference (p < 0.001). Six months after PRK in our patients, the posterior Km was correlated with the anterior preoperative one by the following regression formula: y = -4.9707x + 12.457 (R² = 0.7656), where x is PO posterior Km and y is preoperative anterior Km, similar to the one calculated by Saiki.


CONCLUSIONS
Care should be taken in using the Saiki formula to calculate the preoperative Km in patients who underwent PRK.
*MD Department of Medicine and Surgery, University of Salerno, Salerno, Italy (all authors).
Maddalena
M
De Bernardo
Stefania
S
Iaccarino
Michela
M
Cennamo
Luisa
L
Caliendo
Nicola
N
Rosa
D000328:Adult; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D055095:Optics and Photonics; D018918:Phacoemulsification; D018903:Photorefractive Keratectomy; D011184:Postoperative Period; D012029:Refraction, Ocular / Q000502:physiology*; D012189:Retrospective Studies; D055815:Young Adult