Reliability of the IOLMaster in measuring corneal power changes after hyperopic photorefractive keratectomy.
OBJECTIVE
To test the accuracy of the IOLMaster (Carl Zeiss Meditec) in detecting corneal power changes after hyperopic photorefractive keratectomy (PRK).


METHODS
Forty-five consecutive eyes that underwent hyperopic PRK with the SCHWIND ESIRIS excimer laser, ranging from +0.75 to +7.00 diopters (D) (mean: +3.84±1.56 D), were analyzed. Data included pre- and postoperative (1, 3, and 6 months) fogging refraction and automated keratometry (K). Statistical analysis was performed to determine the correlation between the changes in refraction at the corneal plane and the changes in keratometry.


RESULTS
The mean difference between the changes in refraction and the measured corneal changes was +0.27±1.19 D (range: -1.91 to +4.28 D) (P=.18) at 1 month; +0.56±0.97 D (range: -1.00 to +2.96 D) (P=.006) at 3 months; and +0.67±0.80 D (range: -0.73 to +2.31 D) (P=.00002) at 6 months. Based on these results, we suggest using the regression formula found at 6-month follow-up (y=0.8074 x + 0.092) to better calculate the effective corneal power. Comparison between the data obtained with IOLMaster measurements and equivalent K readings from the Holladay report obtained with the Pentacam (Oculus Optikgeräte GmbH) shows good agreement (R(2)=0.9).


CONCLUSIONS
Automated keratometry provided by the IOLMaster underestimates the effective refractive changes after hyperopic PRK, and a correcting factor is needed to calculate the corneal power in these cases.
Rosa
Nicola
N
Centro Grandi Apparecchiature, 2nd University of Naples, Italy. nicola.rosa@unina2.it
De Bernardo
Maddalena
M
Borrelli
Maria
M
Filosa
Maria Luisa
ML
Minutillo
Emma
E
Lanza
Michele
M
D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000503:physiopathology*; D003941:Diagnostic Techniques, Ophthalmological / Q000295:instrumentation*; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000503:physiopathology* / Q000601:surgery*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D015203:Reproducibility of Results; D014792:Visual Acuity / Q000502:physiology