Purpose: To assess the repeatability and reliability of IOLMaster (Carl Zeiss Meditec, Inc., Dublin, CA) axial length and keratometry measurements (K readings) with a soft contact lens on normal eyes. The method is designed for eyes with corneal irregularities or after endothelial keratoplasty.
Methods: Biometry was performed on 20 healthy right eyes of volunteer subjects with mean age, 27.3 +/- 4.9 years; axial length, 24.77 +/- 1.04 mm; and K reading, 43.48 +/- 1.69 D. Axial length and keratometry were measured and repeated with -0.5 D SofLens38 (Bausch & Lomb, Rochester, NY) and Acuvue2 (Johnson & Johnson, New Brunswick, NJ) soft contact lenses. Repeatability and reliability were evaluated. Contact lens thickness was measured directly by corneal optical coherence tomography (OCT).
Results: Axial lengths increased 59 +/- 10 microm with SofLens38 and 134 +/- 13 microm with Acuvue2, and these changes correlated with the OCT contact lens thicknesses (P = 0.995). The axial length variability remained constant (P = 0.18), measuring 24 +/- 10 microm for SofLens38 and 23 +/- 8 microm for Acuvue2 compared with 20 +/- 7 microm with no lens. K readings of 43.08 +/- 1.66 D with SofLens38, 42.79 +/- 1.57 D with Acuvue2, and 43.48 +/- 1.69 D with no lens corresponded to differences of -0.40 +/- 0.12 D with SofLens38 and -0.69 +/- 0.19 D with Acuvue2. The K-reading variability increased slightly from 0.04 to 0.09 D with either lens.
Conclusions: Low-power soft contact lenses enable reliable and repeatable IOLMaster axial length and K-reading measurements. Correcting for the measurable lens thickness and lens effects, a <0.5-D error in the Sanders-Retzlaff-Kraff (SRK) II power formula is predicted.