Optical Biometry and Lens Power Calculations in 500 Phakic Patients: Axial Length and Corneal Curvature in the Fellow Eye

OBJECTIVE: In eyes with severe corneal pathology, biometric measurements of the corneal curvature (K) can be challenging. The aims of this study were to test whether K mean values from the fellow eye can be used as substitute in lens power calculations and to determine if similarity in axial length (AL) in a patient’s two eyes implies similarity also in the corneal curvature. METHODS AND ANALYSIS: A retrospective study of optical biometry measurements in 500 adults (1000 phakic eyes) that was scheduled for cataract surgery. Inclusion criteria were complete recordings of all parameters in both eyes and a signal-to-noise ratio of at least 10. Similar AL was defined as less than 0.3 mm difference between the patient’s two eyes. RESULTS: The IOL power calculated with K mean from the fellow eye was 0.39 D (standard deviation (SD) 0.57) different from the calculation with both AL and K mean from the correct eye. The difference was larger than 1.0 D in 26 (5%) eyes. In patients with similar AL in their two eyes (n = 372), the interocular difference in K mean was 0.43 D (SD 0.67 D), compared to 0.45 D (SD 0.49 D) for the patients with an AL difference of 0.3 mm or more (n = 128) (p = 0.81). CONCLUSION: Lens calculations with keratometry values from the fellow eye as substitute yielded quite similar results as calculations with the correct values. Hence, this seems to be an acceptable approach in patients with incomplete keratometry recordings. Similarity in AL between a person’s two eyes did not imply more similar corneal curvatures.